arpm_manual_2.pdf

ARPM: IP-1 Revised: 2011 • Replaces: RMA 1989 Edition

CONVEYOR AND ELEVATOR BELT HANDBOOK © 2011 by the Association for Rubber Products Manufacturers, Inc. Published in the United States of America RMA First Edition 1973 RMA Second Edition 1980 RMA Third Edition 1989 ARPM Fourth Edition 2011

7321 Shadeland Station Way, Suite 285, Indianapolis, IN 46256 Phone: 317-863-4072 Web: www.arpminc.org

Association for Rubber Products Manufacturers

INTRODUCTION PREFACE Conveyor and elevator belts are made to precise specifications and standards to service many useful functions. A better understanding of the complexities involved in manufacturing belting and the standards that are applied to it will be helpful in selecting the proper belt for the intended use and in obtaining good service after installation. Belting covered in this Handbook includes conveyor belting, used to transport bulk or packaged, boxed and bagged materials, and bucket elevator belting. The belting may be made of natural and synthetic rubbers as well as plastics, such as vinyl, with carcasses of textile fabrics, which are woven, nonwoven, solid woven, or stitched; fabric cords; or of steel cables. This handbook is intended for the general guidance and reference of persons interested in the selection and use of conveyor and elevator belting, but readers are urged to consult individual manufacturers for specific information and recommendations.

ACKNOWLEDGMENT The Association for Rubber Products Manufacturers is the national trade association of the non-tire rubber manufacturing industry in the United States. ARPM represents manufacturers of finished rubber products (excluding tires), and their related suppliers. This publication is provided as a public service, and reference for users of conveyor belt products by U.S. manufacturers of conveyor belt products, including: Airboss Compounding Rubber (NC) Fenner Dunlop Americas (Pittsburgh, PA) Garlock Rubber Technologies (Paragould, AR) Price Rubber Corp. (Montgomery, AL) Veyance Technologies Inc. (Fairlawn, OH)

© 2011 by Association for Rubber Products Manufacturers, Inc. 7321 Shadeland Station Way, Suite 285 Indianapolis, IN 46256 317-863-4072 www.arpminc.org Published in the United States of America RMA First Edition 1973 RMA Second Edition 1980 RMA Third Edition 1989 ARPM Fourth Edition 2011

IP:1 2011 Conveyor and Elevator Belt Handbook

2


TABLE OF CONTENTS Page PREFACE..................................................................................................................................................................................................2 ACKNOWLEDGMENT...........................................................................................................................................................................2 CHAPTER 1 - MATERIALS...................................................................................................................................................................4 CHAPTER 2 - ELASTOMER CHARACTERISTICS........................................................................................................................11 CHAPTER 3 - TEXTILE BELT TYPES AND MANUFACTURING METHODS..........................................................................18 CHAPTER 4 - TEXTILE BELT CHARACTERISTICS AND BELT RATINGS.............................................................................23 CHAPTER 5 - TEXTILE BELT TOLERANCES................................................................................................................................35 CHAPTER 6 - TEXTILE BELT TEST METHODS............................................................................................................................36 CHAPTER 7 - SPLICING CONVEYOR AND ELEVATOR BELTS................................................................................................40 CHAPTER 8 - STEEL CORD BELT TYPES AND MANUFACTURING METHODS..................................................................51 CHAPTER 9 - STEEL CORD BELT CHARACTERISTICS & BELT RATINGS..........................................................................53 CHAPTER 10 - STEEL CORD BELT TOLERANCES......................................................................................................................56 CHAPTER 11 - STEEL CORD BELT TEST METHODS..................................................................................................................58 CHAPTER 12 PART A - SPLICING FABRIC CORD CONVEYOR BELTS..................................................................................61 CHAPTER 12 PART B - SPLICING STEEL CORD CONVEYOR BELTS.....................................................................................75 CHAPTER 13 - BELT MONITORING.................................................................................................................................................91 CHAPTER 14 - OPERATION AND MAINTENANCE......................................................................................................................96 CHAPTER 15 - STORAGE OF BELTING........................................................................................................................................112 CHAPTER 16 - GLOSSARY OF CONVEYOR BELTING TERMS...............................................................................................113 CHAPTER 17 - USEFUL TABLES.....................................................................................................................................................130 APPENDIX............................................................................................................................................................................................136


3


CHAPTER 1

MATERIALS

INTRODUCTION The purpose of this chapter is to present general descriptions of the construction elements of conveyor belts and the materials which are presently available to produce belts for the various materials conveyed with suitable strength for the tensions and other conditions encountered in service. Conveyor belts are sometimes classified as Light and Heavy Weight belts. Light Weight = RMBT* < 160 PIW Heavy Weight = RMBT > 160 PIW *RMBT = Rated Maximum Belt Tension, in pounds per inch width (PIW) Light weight belting generally is used in very diverse applications such as food and tobacco products, agricultural products, wood products, baggage and packaging handling, metal stampings, and materials handling in the textile, printing, paper processing, postal, and electronics industries. Heavy weight belting generally conveys heavy and/or coarse abrasive materials like mineral ore, rock, sand, gravel, coal, and cement. In general, most conveyor belts consist of three elements: a top cover or conveying surface; a carcass; and a bottom cover, or pulley surface. In light weight belting there is a great diversity among the top cover or conveying surfaces used such as smooth or rough covers and raised patterns; whereas heavy weight belting often has smooth top covers. Custom fabrications with light weight belting are also more common, including attaching of cleats or V guides or hole punching, for example. The elements may also be grouped under several general classifications such as: elastomers; fabrics (woven or non-woven); spun; filament, or monofilament yarn or cord; and steel cords. A rubber or plastic elastomer is a compounded material that returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress less than the yield point. A fiber is a unit of matter having a length at least 100 times its diameter and which can be spun into a yarn. A steel cord, when used as the tension member, is usually multiple strands of steel wire twisted together. Yarn is a generic term for continuous strands of textile fibers or filaments. A fabric is a planar textile structure produced by interlacing yarns, fibers, or filaments. A fabric may be composed of yarns of cotton, glass, nylon, polyester, steel or other materials. A fabric may be made from one material or a combination of materials.

RUBBER/PLASTIC ELASTOMERS Polymers are mixed with various chemicals to obtain reinforcement and develop the physical properties of the resulting elastomer necessary for meeting service conditions. Since it is not the purpose for this Handbook to discuss compounding ingredients or methods of compounding, discussion of polymers will be restricted to the general properties of the basic polymers. A wide choice of polymers is available. They can also be blended together to obtain many combinations with intermediate properties. Elastomeric compounds are used for the top and bottom covers or surfaces of conveyor belting and for bonding together components of the belt carcass. The elastomeric covering on belts is there to provide protection for the carcass and/or provide a specific property. The coverings are applied by several processes, depending on the material (rubber vs. thermoplastic) or thickness of the covering. It is possible to classify elastomers to some extent by the basic polymer used. They are listed in Table 1-1 with a brief description of their general properties.


4


Table 1-1. Rubber/Plastic Polymers Used in Belting

Common Name

ASTM Designation D 1418-10

Composition

General Properties

Acrylic

ABR

Acrylate-butadiene

Excellent for high temperature oil and air. Poor water resistance. Poor cold flow resistance.

Brominated Butyl

BIIR

Bromo-isobuteneisoprene

Similar properties as Butyl except that it can be more readily adhered to or used in combination with other polymers.

Butyl

IIR

Isobutene- isoprene

Excellent resistance to heat. Very good resistance toozone and aging. Good resistance to abrasion.

Chlorinated Butyl

CIIR

Chloro-isobuteneisoprene

Similar properties BIIR.

EPDM

EPDM

Ethylene-propylenediene terpolymer

Excellent resistance to heat, ozone, and aging. Very good resistance to abrasion.

Ethylene Propylene

EPR

Ethylene-propylene

Same properties as EPDM.

Hydrin*

CO

Polychloromethyloxirane

Excellent oil and ozone resistance. Good flame resistance and low permeability to gases. Fair low-temperature properties.

Hydrin*

ECO

Ethylene oxide andchloromethyl-oxriane

Excellent oil and ozone resistance. Fair flame resistance and low permeability to gases. Good lowtemperature properties.

Hypalon*

CSM

Chloro-sulfonyl-polyethylene

Excellent ozone, weathering, and acid resistance. Good abrasion and heat resistance. Good oilresistance.

Hytrel*

PET

Polyethylene Terephthalate

Thermoplastic with excellent abrasion and cutresistance. Good chemical resistance. Limited temperature range.

Natural Rubber

NR

Rubber, Natural

Excellent resistance to cutting, gouging, and abrasion. Good elasticity and resiliency. Good low temperature flexibility.

Neoprene*

CR

Chloroprene

Good ozone and sun-checking resistance. Goodresistance to petroleum-based oils and to abrasion. Also good flame resistance.

Nitrile

NBR

Nitrile-butadiene

Excellent resistance to vegetable, animal and petroleum oils.

Polybutadiene

BR

Butadiene

A general purpose synthetic rubber. Generally used inblends with natural or styrene-butadiene rubber. Provides excellent abrasion resistance and high resiliency. Excellent low temperature flexibility.

Polyisoprene

IR

Isoprene, synthetic

Same properties as natural rubber.

SBR

SBR

Styrene-butadiene

Excellent abrasion resistance and good resistance to cutting, gouging, and tearing.

Silicone

VMQ

Modifiedpolysiloxanes

Excellent high and low temperature resistance. Can be made to give fair oil resistance. Poor physical properties at room temperatures.


5


Table 1-1. (continued) Rubber/Plastic Polymers Used in Belting

Common Name Common Name

ASTM Designation Designation ASTM D 1418-10 D 1418-10

Composition Composition

General Comments General Comments

Urethane

AU

Polyester Urethane

Excellent abrasion, cut and tear resistance. Good oil resistance.

Urethane

EU

Polyether Urethane

Excellent abrasion, cut, and tear resistance. Good oil resistance.

Vinyl

PVC

Polyvinyl Chloride

A thermoplastic material which has good resistance to abrasion. Excellent flame resistance. Good resistance to animal and vegetable oils. Limited temperature range.

Viton*

FKM

Fluorocarbon

Excellent high temperature and chemical resistance properties.

Teflon*

see manufacturer

Polymers

*Trade Names

TEXTILES Many types of textiles are used in conveyor and elevator belting. Their use is based on their physical properties, such as strength, elongation, dynamic fatigue resistance, aging resistance, mildew resistance, heat resistance, and other special properties depending on service requirements. For special applications, consult the manufacturer. Yarns used for belt textile reinforcement are classified as either spun or filament depending on whether the base fiber is in staple (3/4 - 2 1/2 in long single fiber) or endless filament form. A spun yarn is made by twisting relatively short lengths of staple fiber together to form a continuous yarn, called a single’s yarn. When two or more of these single’s yarns are twisted together, the result is a plied yarn. When two a more plied yarns are twisted together, the result is cable cord. The tensile strength, elongation, and thickness of a yarn of any fiber type can be changed by varying twist, size and number of single’s yarns included. Spun yarns may be made from natural or synthetic fibers. Spun yarn sizes are designated by the number of “hanks” of yarn it takes to weigh one pound. In the cotton system, one hank is 840 yards (770 m) long. One pound of a 12’s cotton yarn is: 12 x 840 yd (770 m) = 10,080 yd (9217 m) long A filament yarn is produced by extruding synthetic materials through an orifice in a continuous process. A single filament is called a monofilament. A number of small “filaments” are combined to form a multifilament yarn, which is normally called a filament yarn. Filament yarns are stronger than the same-size spun yarns of the same synthetic material. Filament yarns are designated by a denier number which is the weight in grams of 9000 meters of yarn, or a decitex number, which is the weight in grams of 100 meters of yarn.. Thus a 1650 denier yarn will weigh 1650 grams per 9000 meters. Table 1-2 provides information on some of the fiber yarns used in belting fabrics or cords.


6


Table 1-2. Some Materials Used in Belting Reinforcement Common Name

Composition

General Comments

Cotton

Natural Cellulose

Only natural fiber used to any great extent for belting. High absorption of moisture. Susceptible to mildew attack and loss of strength.

Glass

Glass

High strength. Very low elongation. Used in high temperature applications.

Kevlar*

Aramid

Very low elongation and very high strength. Does not melt but does decompose at high temperature.

Nomex*

Aramid

Very high strength, low elongation. Excellent high temperature properties.

Nylon

Polyamide

High strength and high elongation, with good resistance to abrasion, fatigue, and impact. Moderate moisture absorption. High resistance to mildew.

Polyester

Polyester

High strength, low elongation. Good abrasion and fatigue resistance. Low moisture absorption. Excellentresistance to mildew.

Steel Cord

Steel

Very high strength, very low elongation. Superiortroughing characteristics. Excellent heat resistance. Good fatigue and abrasion resistance.

*Trade Name

TEXTILE REINFORCEMENTS Textile fabrics are the most commonly used materials for reinforcing plies in conveyor and elevator belting. Textile fabrics are also used for conveyor belt “breakers” plies. Fabric properties are governed by the yarn material and size and by the fabric construction and weave. Fabric is made of warp yarns, which run lengthwise, and filling (weft) yarns, which run crosswise, as the fabric is woven, usually at right angles to each other. Non-woven fabric is a mat of fibers bonded together chemically and/or needle-punched, usually to a single-ply of woven scrim. The most common, and least complicated, fabric pattern used for flat belts is the plain weave, Figure 1-1. In this construction the warp and filling yarns cross each other alternately. A belt with two or more of these plies of fabric is known as a multi-ply belt. Other common constructions used to a lesser degree include broken twill, Figure 1-2 and Leno weave, Figure 1-3, which has an open mesh and is usually used for a breaker fabric. Solid woven, Figure 1-4, consists of interwoven multiple layers of warp and filling yarns. Straight warp weave, Figure 1-5, contains basic tension-bearing warp yarns which are essentially straight, that is, without crimp. Also, binder warp yarns are interwoven with the filling yarns to provide mechanical fastener holding strength. Some of the most commonly used belting fabrics known by their major fiber content are: Cotton - A fabric with cotton in both the warp and filling yarns. Cotton-Synthetic - A fabric with cotton warp yarns and synthetic filling yarns or a fabric with cotton/synthetic blended warp and/or filling yarns. The synthetics most commonly used are nylon, and polyester. Polyester - A fabric with polyester fiber warp yarns and filling yarns. Nylon - A fabric with nylon fiber warp and filling yarns.


7


Polyester-Polyester – A fabric with polyester warp and filling yarns. Polyester-Nylon - A fabric with polyester warp and nylon filling yarns. Solid woven fabrics are composed of spun and/or filament yarns. The spun yarns commonly used may be either cotton or synthetic or combinations thereof. The filament yarns are usually nylon or polyester.

Figure 1-1. Plain Weave

Figure 1-2. (Broken) Twill

Figure 1-3. Leno Weave


8


Figure 1-4. Solid Woven

Figure 1-5. Straight Warp Weave


9


STEEL REINFORCEMENTS Steel Cord Steel cord is used in belting where the properties of steel cord reinforcement are better able to satisfy the requirements of the service conditions. Steel cord is used to obtain high strength, excellent length stability, low bending stresses and, in some cases, to provide superior troughing characteristics. The wires, or filaments, used in conveyor belt steel cords are usually made of high carbon steel and have a surface finish to facilitate adhesion to the surrounding rubber, and provide protection against corrosion. Common constructions are 7 x 7, Figure 1-6, and 7 x 19, Figure 1-7, although many other constructions are possible. Steel cords used in conveyor belts are specially manufactured from high carbon steel to meet the high strength requirements demanded of these belts. The cord is fabricated from strands of wires, or filaments, twisted together. This gives the cord good flexibility and fatigue resistance when subjected to cyclic loading and bending around pulleys. Two common constructions are illustrated in Figures 1-6 and 1-7. In order to protect the steel from corrosion, zinc or brass coatings are applied to the wire before drawing it to the final filament size. Zinc is the most commonly used coating. Typically, the minimum zinc coating expressed in grams per square millimeter is 60 times the filament size in millimeters.

Figure 1-6. 7 x 7 Construction

Figure 1-7. 7 x 19 Construction

During belt manufacture, the steel cord is encapsulated in a special core rubber that normally has properties different to the belt covers. It is important during manufacture that the core rubber penetrates right to the center of the steel cord as this stops adjacent filaments from contacting one another and fretting during bending and stretching of the cord in service. Once embedded in the core rubber, the cord strength increases by up to 5% and it becomes less likely to suffer from corrosion caused by water penetrating the cord. The effectiveness of the rubber penetration can be determined by a special test (AS 1333) which measures if there is any loss in air pressure along the cord when air is applied to one end of the cord at 14.5 psi (1 bar), and maintained for 1 minute on a 16 in long belt sample. 5% is the maximum acceptable pressure loss. Core rubber to cord adhesion should be adequate to maintain the belt and its splices’ integrity during its normal service life. Due to the very specialized nature of this cord and the difficulties in manufacturing cord to achieve these properties, there are only a few manufacturers in the world producing steel cord for conveyor belts. Other Wire Components Several other forms of wire are used in belting for special purposes, such as rip resistance and transverse stiffness. A variety of wire structures are used, some of which include: (1) steel filling leno weave breakers, (2) straight warp steel fabrics.


10


CHAPTER 2

ELASTOMER CHARACTERISTICS HEAVY WEIGHT CONVEYOR BELT RUBBER COVER CHARACTERISTICS AND CLASSIFICATIONS

Elastomeric covers for general purpose conveyor belts with textile/cord reinforced carcasses will be defined as either Grade 1 or Grade 2. The properties, test values and minimum requirements described below can serve as a guideline for acceptable performance in most general purpose applications. It is recognized however that there is no direct correlation between test results and the performance of the belt in service. The test values as outlined are recognized as obtained from new or factory condition belting. Reference Documents ASTM D 378

Standard Test Methods for Rubber (Elastomeric) Belting, Flat Type

ASTM D 412

Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers -- Tension

CONVEYOR BELT RUBBER COVER GRADES General Purpose Rubber Covers ARPM Grade 1- Will consist of natural or synthetic rubber or blends which will be characterized by high cut, gouge, and tear resistance and very good to excellent abrasion resistance. These covers are recommended for service involving sharp and abrasive materials, and for severe impact loading conditions. ARPM Grade 2- The elastomeric composition will be similar to that of Grade 1 with good to excellent abrasion resistance in applications involving the conveying of abrasive materials, but may not provide the degree of cut and gouge resistance of Grade 1 covers. When covers are tested in accordance with ASTM D 412, the tensile strength, elongation at break shall comply with the requirements of Table 2-1, for the grade of cover, as appropriate. The tensile strength and elongation at break values are not always sufficient in themselves to determine the suitability of the belt cover for a particular service. The values in Table 2-1 should only be specified for conveyors or materials with a known history of performance, and where it is known that compliance with the value will not adversely affect other in-service properties. Covers for Special Applications Belt covers may be required to perform in various environments e.g. high heat, exposure to fluids, abrasive conditions, high ozone concentrations, low temperature exposure and noise generation limits. Cover and Ply Adhesion When belting is tested in accordance to ASTM D 378, the adhesion for covers and between adjacent plies should not be less than the values given in Table 2-2. Table 2-2 applies to continuous filament carcass.

ABRASION RESISTANCE As per RMA’s description and classification for both Grade 1 and 2 belt covers; both of these cover types will provide good to excellent abrasion resistance. There are several specific tests used by manufacturers to determine the relative abrasion resistance of different cover formulations. The most common is ISO 4649 (DIN 53516). While there are no specific U.S. industry limits, maximum or minimum, for test results from abrasion test for General Purpose (ARPM Grades 1 & 2) Belt Covers; there is enough data to suggest acceptable abrasion values.


11


A customer preparing to purchase a conveyor belt for abrasion service should, therefore, proceed as follows: 1. Describe as accurately as possible the conditions under which the belt will operate, the nature and composition of the material being carried, the range of particle size, loading conditions, and tons per hour being handled. In those instances where a replacement belt is being ordered, indicate in as complete detail as possible the construction of the belt being replaced and describe the nature of its failure. 2. Point out any condition which might accelerate cover wear, such as excessive heat, moisture, or the presence of oil or other solvents in the installation. Table 2-1. Properties of Covers Grade

Minimum Tensile Strength (p.s.i.)

Minimum Tensile Strength (MPa)

Minimum Elongation at Break (%)

Maximum Volume Loss (mm3) ISO 4649 Part B

1

2500 p.s.i.

17 MPa

400%

125 mm3

2

2000 p.s.i.

14 MPa

400%

175 mm3

Table 2-2. General Purpose Rubber Cover and Ply Adhesion Adhesion between adjacent plies Adhesion between cover & ply 30 lbs/in

5 kN/m

1/32 in (0.8 mm) ≤ Cover Thickness ≤ 1/16” (1.6 mm) 16 lbs/in

3 kN/m

Covers greater than 1/16” (1.6 mm) 30 lbs/in

5 kN/m

COVER THICKNESS Top Cover Thickness The major function of a heavy weight belt cover is to protect the strength-bearing carcass from wear or damage during the life of the belt. In a light weight belt, the cover functions also to provide the required degree of sanitation in food contact applications or the desired friction characteristics, or the required surface characteristics for incline/decline conveying. The cover thickness required for a specific belt is a function of the material conveyed and the handling methods used. Increased cover thickness is required as the conditions become more severe: e.g. material abrasiveness, maximum lump size of material, material weight, height of material dropped onto the belt, loading angle, belt speed, frequency of loading, etc. The following table shows the suggested minimum belt cover thicknesses for favorable conditions. Wear rates with identical material under adverse loading conditions have been observed to be as much as 6 times the wear rate under favorable conditions. Grade 1 - Top Cover Thickness Grade 1 covers should be considered for heavy crushed material over 3 in (75 mm) and when large lumps occur if cut or gouge resistance is the main design criteria. Consult the manufacturer for cover thicknesses. Grade 2 - Top Cover Thickness (Table 2-3) Table 2-3. Guide for Minimum Top Cover Thicknesses Under Favorable Conditions for Grade 1 and Grade 2 Belting Note: Cover thicknesses are nominal values subject to manufacturers’ tolerances.

Table 2-3 Class of Material

Examples

Minimum Thickness in

mm

Package handling

Cartons, food products

Light or fine, non-abrasive

Wood chips, pulp, grain, bituminous coal, potash ore

1/16

1.5

Fine and abrasive

Sharp sand, clinker

1/8

3

Heavy, crushed to 3 in (75 mm)

Sand, gravel, crushed stone

1/8

3

Heavy, crushed to 8 in (200 mm)

ROM coal, rock, ores

3/16

5


Friction Surface Friction Surface

12


Steel Cord Belt Covers Cover Carcass Dimensions: To protect the steel cords from impact, abrasion, and water or any other environmental factors, which could cause a loss of strength, during the entire service life of the belt, a minimum thickness of rubber must encapsulate the cords. This cover thickness is usually dictated by the service conditions, but should never be less than 5/32 in (4.0 mm). Failure to respect these limits may lead to uneven, accelerated cover wear or cord damage which would result in reduced belt life. Table 2-4 indicates the minimum thickness “F” above and below the cords that is required for this protection.

Figure 2-1. Protective covering for cords during the entire belt life. (A = 2F + D) Amount of top cover used for the service life of the belt. Amount of bottom cover used for the service life of the belt. Diameter of the cord. Rubber encapsulating the steel cords and especially compounded for compatibility with the cover rubber and bonding to the steel cords. F = Thickness of rubber to protect the cords during service. This protective rubber is not part of the top or bottom wear covers used to estimate belt tonnage.

A= B= C= D= E=

Table 2-4. Guide for Minimum Protective Rubber “F”

Cord Diameter

Minimum Thickness “F” (above & below cords)

mm

mm

in

4.1 5.6 8.3 9.5

3.5 3.9 5.8 5.8*

0.137 0.157 0.228 0.228

* This value has been lowered from the calculated 6.6 mm as a result of favorable field experience. For thickness of covers “B” and “C” consult belt manufacturer. Note: Minimum thickness of protective rubber “F” should not be less than 3.5 mm or 0.7 times the cord diameter, whichever is greater.For larger diameter cords contact manufacturer.


13


Pulley Cover Thickness The major function of a pulley cover is the same as that of a top cover: to protect the carcass material. In addition, field studies of conveyor power have shown that energy is lost by the pulley cover as it passes over each idler roll. This is called rubber indentation loss and can account for over 60% of the total belt drive power. Special pulley cover rubbers have been developed called “Low Rolling Resistance (LRR)” covers to reduce the amount of power lost. Further details can be obtained from individual belt manufacturers.. Since a pulley cover is not subjected to the severe conditions imposed upon a conveyor cover, its thickness does not need to be equal to top cover. See below section “Cover Thickness Ratio”. Table 2-5. Suggested Minimum Pulley Cover Thickness for Grades 1 & 2 Belting Minimum Thickness

Operating Conditions in

mm

Slider bed package conveyors

bareback or friction surface

bareback or friction surface

Abrasive materials

1/32

1

*Impact loading

3/32

2.5

* Increased cover thickness helps protect the carcass; however, if impact is severe, the complete system design, including carcass construction, top cover thickness, and impact rolls in the conveyor, must be considered. Note: Cover thicknesses are nominal values subject to manufacturers’ tolerances.

Cover Thickness Ratio The thickness of the cover on conveyor belting must be selected on the basis of the service conditions to which the belting is to be subjected. The ratio of the thicknesses of the top and bottom covers must also be considered. This factor becomes increasingly important with conveyor belting where the carcass is thinner than those of comparably rated multi-ply conveyor belts. A large cover thickness ratio, such as greater than 4:1, where one cover, the top, is much thicker than the other, the bottom - may cause a conveyor belt to assume a permanent transverse curl or cup, wherein the edges of the belt curl up on the carrying run and down on the return run. In its more severe state, this curl can adversely affect the training of the belt, especially on the return run. When the curl has progressed to the point that only the edges of the belt contact the return idlers, training of the belt is virtually impossible. The transverse belt curl that results from a large cover thickness ratio is a result of the shrinkage that occurs in rubber compounds after vulcanizing. With a large cover thickness ratio, the shrinkage force of the thicker cover dominates, causing the belt to curl toward the thicker cover. Multi-ply type belts, with their relatively thick and transversely stiff carcass, tend to resist the curl forces, but thin belt carcasses offer less resistance. Although transverse curl may occur in any size of conveyor belt, it is most likely to cause operational problems in narrower belts, up to 36 in (900 mm) wide. To a lesser degree, it can cause problems with 48 in (1200 mm) widths. With the wider belts, the belt weight usually forces the center of the belt down into contact with the return idlers, thus allowing normal training action to occur. Generally, a maximum ratio of 4:1 for multi-ply and 2:1 for single-ply belting is recommended. Cover thickness ratio specifications vary among manufacturers of conveyor belting. Individual belting manufacturers should be consulted for their specific recommendations on cover thickness ratios for belting.

POLYVINYL CHLORIDE (PVC) CHARACTERISTICS PVC is a resin produced from polymerizing vinyl chloride. The term PVC in the belting trade is generally applied to the elastomeric material that results from the resin having been mixed with various liquids and powders and heat treated to change the mixture into a usable elastomeric condition. The mixture of PVC, liquids, and powders may be used in the form of a liquid plastisol for saturating and top coating fabric or as a film to laminate and top coat fabric. The PVC elastomer is thermoplastic. It hardens and stiffens with reduced temperature and softens and becomes more flexible with elevated temperatures. PVC belting operates well in the range of 20 to 180°F over conventional size pulleys. With special handling, operation down to - 30°F is possible. General purpose PVC belting becomes hard and cracks when subjected to certain hydro-carbons and oils, which cause a softening and swelling action on general purpose rubber. PVC can be compounded to prevent the deleterious effect of those hydrocarbons and oils. PVC can be compounded to promote good flexibility at -40ºF and to improve flame propagation resistance. PVC elastomers are resistant to acids, alkalies, strong oxidizing agents and strong chlorinated cleaning agents. IP:1 2011 Conveyor and Elevator Belt Handbook

14


SPECIAL SERVICE BELT COVERS AND SPECIFIC CHARACTERISTICS Belting can be designed to operate in various conditions and environments. No one belt type will handle all conditions well. Specific environments that require special service belts include: static conductive, flame/fire resistance (MSHA), high (and low) temperature, oil service, high temperature and oil service, high temperature abrasion, etc. Specific test protocols are used to determine the elastomer’s response to these conditions and environments. An abbreviated listing of these tests are offered in Table 2-6 for reference in regards to belt recommendations. Table 2-6. Test Protocols for Special Service Belt Covers Condition

Test Method

Friction (Coefficient)

ASTM D 1894 -- Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Filmand Sheeting

Flame Resistance

ASTM D378 13.1 (MSHA -- 30 CFR: part 14) ASTM D378 13.2 Heat Resistance

Heat Resistance

ASTM D 865 -- Standard Test Method for Rubber-Deterioration by Heating in Air (Test Tube Enclosure)

Heat Resistance

ISO 4195-1 -- Conveyor belts -- Heat resistance -- Part 1: Test method; ISO 4195-2 -- Conveyor belts -Heat resistance -- Part 2: Specifications

Low Temperature

ASTM D 2136 -- Standard Test Method for Coated Fabrics -- Low Temperature Bend Test

Low Temperature

ASTM D 2137 -- Standard Test Methods for Rubber Property -- Brittleness Point of Flexible Polymersand Coated Fabrics

Oil Service / Chemical

ASTM D 471 -- Standard Test Method for Rubber Property -- Effect of Liquids

Ozone

ASTM D 1149 -- Standard Test Method for Rubber Deterioration -- Surface Ozone Cracking in a Chamber

Tear Resistance

ASTM D 624 -- Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers

RECOMMENDATIONS FOR OIL SERVICE BELTING Various levels of oil service may be required from belt products. These service levels may or may not involve elevated temperatures. The ARPM classifies belting (or cover formulations) to meet either MOR/VOR (Moderate / Vegetable Oil Resistant). Service requirements or EOR (Extreme Oil Resistance) service requirements based on the following test criteria. Table 2-7. %Volume Swell (ASTM D 471) 70 hr @ 100°C Oil Resistance

ASTM #1 Oil

ASTM #3 or #903 Oil

MOR / VOR Moderate / Vegetable Oil Resistant

15% Max.

140% Max.

EOR / SOR Extreme Oil Resistance

5% Max.

30% Max.

MOR / VOR - Belting is designed to resist swelling and deterioration from vegetable based oils as well as light (napthenic / paraffin / low aromatic) petroleum oils. EOR / SOR - Belting is designed for use in extremely oily environments, especially where polar aromatic materials are expected to be encoutered. Depending on temperature requirements and manufacturers’ recommendations, this class of belt may be suitable in “Hot Asphalt” applications. Additionally, in coal fired power generation facilities where the fuel is being enriched with petroleum waste oils or fuel / diesel oils, this may be the belt type required. Consult the manufacturer for recommendations when abnormal conditions are anticipated. Most of the cover formulations for belting meeting these classifications will be comprised of, or contain a certain percentage of, one or more of the following polymers: CR (Polychloroprene / Neoprene), NBR (Nitrile), PVC, Urethane (AU / EU), CPE (Chlorinated Polyethylene) or other oil resistant types listed in Table 1-1.


15


HIGH TEMPERATURE SERVICE CLASSIFICATIONS Belting designed and manufactured to handle elevated temperatures in service will be classified by type depending on the belt cover characteristics when tested to ASTM D 865 at the specified times and temperatures. Table 2-8. High Temperature Testing (ASTM D 865) Time 70 hr - Test Temperature

Retained Tensilefrom original

Retained Elongation from original

Hardness pt. change

ARPM-HR Class 1

212°F (100°C)

-25% (max.)

-50% (max.)

+20 (max.)

ARPM-HR Class 2

257°F (125°C)

-30% (max.)

-50% (max.)

+20 (max.)

ARPM-HR Class 3

302°F (150°C)

-40% (max.)

-60% (max.)

+20 (max.)

ISO 4195 is referenced as another testing and classification tool. While the classifications and value limits are similar between these tests, they differ in both time of exposure (70 hr vs. 168 hr) and method of sample preparation. ISO 4195 calls for the entire belt sample to be exposed, with test specimens to be cut / prepared from the exposed belt samples. ASTM D 865 allows for test specimens to be prepared before exposure. The correlation between these methods has not been determined and differences are expected, since the mass of ASTM sample is small relative to the dimensionally large ISO sample size. Hence the shorter time of exposure per the ASTM / ARPM protocol. While these tests and classifications do not validate product usefulness or acceptability in specific environments, they are used as tools by the industry to more narrowly define criteria for applications involving elevated temperatures. It must be noted that temperature alone may not be the overriding / determining factor in product suitability. Certain conveyed materials may degrade various elastomers at test temperatures that the elastomers may be expected to perform based on test conditions. Consult the belt manufacturer for specific recommendations.

FLAME RESISTANCE SERVICE CLASSIFICATIONS WARNING: All belting will burn when adequately ignited Table 2-9. Flame Resistance Testing (ASTM D865) Belt Designation ARPM-HR Class 1 ARPM-HR Class 2

Sample Size (Qty.) 60” x 9” (3) 1524 mm x 229mm 6” x 0.5” (4) 152mm x 13mm

Method (Time) ASTM D378 13:1 Burner (5 min) ASTM D378 13:2 Bunsen Burner (1 min)

Pass Criteria Some undamage belt in each sample Flame out average < 1 min No afterglow after 3 min

A wide variety of flame tests for conveyor belts exists throughout the world. The standard used in a particular country is usually dictated by a national or local governing body. For general flame resistant conveyor belting, the selection of the most suitable quality may be made by the ARPM-FR class designations. ARPM-FR Class I Based on the December 31, 2008 U.S. Mine Safety & Health Administration’s (MSHA), CFR Title 30 Section 14, “Requirements for the Approval of Flame-Resistant Conveyor Belts”, also known as the Belt Evaluation Laboratory Test or “BELT” test, this new ARPM-FR standard provides a flame resistance quality that is currently mandated by MSHA in the USA for underground coal mines. This belt quality is appropriate for belts that require flame resistance and which are included in the December 31, 2008 CFR, Title 30, Mineral Resources, Section 14, which primarily applies to conveyor belts used in underground coal mines. The test procedure is described in ASTM D 378 Section 13.1 and employs 60 in x 9 in sized belt test samples. Following the original MSHA guidelines, the acceptance criteria for three belt samples tested to this ARPM-FR Class I standard is each tested sample must exhibit an undamaged portion across its entire width.


16


ARPM-FR Class II Based on the pre - December 31, 2008 U.S. Mine Safety & Health Administration’s (MSHA), CFR Title 30 Section 18.65, “Requirements for the Approval of Flame-Resistant Conveyor Belts”, also known as the “2G” test, this new ARPM-FR standard provides a basic flame resistance quality that was formerly mandated by MSHA and was used successfully in the USA for many years. This belt quality is appropriate for belts, such as above ground belts, that require flame resistance and which are not included in the December 31, 2008 Code of Federal Regulations, Title 30, Mineral resources, Section 14, which primarily applies to conveyor belts used in underground coal mines. The test procedure is described in ASTM D 378 Section 13.2 and employs 6 in x 0.5 in sized belt test samples.Following the original MSHA guidelines, the acceptance criteria for belt samples tested to this ARPM-FR Grade II standard is defined as the tests of four specimens cut from any belt sample shall not result in, either duration of flame exceeding an average of 1 minute after removal of the applied flame, or the continuation of visible glowing of a specimen after flaming has ceased (afterglow) exceeding an average of 3 minutes duration. ARPM-FR Class Test Responsibility Each belt manufacturer is responsible to ensure tests are conducted to the appropriate ARPM-FR class specification on each belt order claiming the ARPM-FR class quality. Tests may be witnessed at any time by the customer or his representative to ensure compliance to the test standard. Marking A ARPM-FR class conveyor belt must be permanently and legibly marked with the appropriate ARPM-FR class designation (and/or MSHA approval number for ARPM-FR Class I) for the service life of the product. The marking must be at least 0.5 in (1.27 cm) high and placed at intervals not to exceed 60 ft (18.3 m) repeated once every foot (.3 m) across the width of the belt. Records of the initial sale of each belt order having the ARPM-FR class marking and actual test conditions and test results must be retained for at least 5 years.

POLYURETHANE (PU) CHARACTERISTICS Polyurethane is generally characterized as a cut and abrasion resistant polymer with excellent mechanical properties in the range of about -65 to 212°F (-54 to 100°C). There are both thermosetting and thermoplastic grades used in belting, and polymer back bones that enhance oil resistance or water resistance. The thermoplastic grades are easily spliced in belt constructions, and food contact polyurethane compounds are available. General When it is the user’s opinion there is a potential fire hazard, he should consult the belt manufacturer and consider whether belting manufactured to the above specifications is suitable for the application. In each installation, consideration should also be given to the following: a. b. c. d. e. f. g. h. i. j.

Fire detection systems Automatic fire suppression systems Slip and sequence interlock systems Sprinklers at transfer points to reduce flammable dust Belt lateral alignment controls Elimination of combustible materials near the conveyor belt Conductive paths to ground for static electricity including conductive grease in bearings Chute probe or level indicators at transfer points Fire retardant, static electricity conducting drum lagging, skirts, scrapers, and chute lining Heat sensors for conveying pulley bearings.

Effective December 31, 2008, the United States changed the minimum standard for flame performance of underground coal mine conveyor testing. Until December 31, 2009 conveyor belts placed in service in underground coal mines shall be either approved under Part 14; or accepted under Part 18. Part 18, is an old MSHA standard, “Code of Federal Regulations, Title 30, Mineral Resources, Section 18.65, Flame Testing of Conveyor Belting and Hose.” Part 18 is commonly known as “2G”. Effective December 31, 2009 conveyor belts placed in service in underground coal mines shall be approved under Part 14. If MSHA determines that Part 14 approved belt is not available, the Agency will consider an extension of the effective date. Effective December 31, 2018 all conveyor belts used in underground coal mines shall be approved under Part 14. Effective December 2, 2005, in Canada, the CAN/CSA M422 M87 “Fire Performance and Antistatic Requirements for Conveyor Belting” standard was withdrawn. Formerly this standard was the minimum standard for flame performance and electrostatic conductance for underground belting which was tested in accordance with the CAN/CSA M422 M87 “Fire Performance and Antistatic Requirements for Conveyor Belting” by Energy, Mines and Resources, Canada, Canadian Explosives Atmospheres Laboratory. They formerly assigned an approval number for each different belt which number, together with other information in M422, which was branded on the belt at least once every 15m (approx. 50’). Conformance to the M422 specification about branding was enforced by Provincial Regulatory Agencies.


17


CHAPTER 3

TEXTILE BELT TYPES AND MANUFACTURING METHODS

INTRODUCTION This chapter describes types of textile belting in terms of carcass types and of edge protection. This will be followed by a description of belt cover designs and textile belt manufacturing methods.

BELT CARCASS TYPES The belt carcass primarily provides resistance to tension forces that build up in the conveyor system. Also it provides strength to resist belt tear and loading impact and for load support, troughing, mechanical fastener holding ability, and resistance to wrinkling or edge cupping. Textile Fabric Carcass - (See Figure 3-1) The textile fabric carcass may have one or more plies of fabric bonded by elastomeric compounds to both themselves and to the belt cover. Belt strength and load support characteristics depend on the fabric construction and the number of plies used. Flexibility/ stiffness are functions of the fabric construction and number of plies of fabric, and skim and cover thicknesses and their elastomeric properties. The elastomeric compounds in heavy weight belting are often thermosetting. Light weight belting is reinforced in some constructions by one or more plies of fabric like the heavy weight belting or in other constructions by solid woven or interwoven fabric or by non-woven fabric which generally has a woven scrim component. The individual plies in light weight belting often have monofilaments in the weft to impart transverse stiffness, and the elastomeric materials in the plied constructions are predominantly thermoplastic.

Figure 3-1. Textile Fabric -- Multi-Ply Belt Shown with Three Fabric Plies and Cut Edges* * Refer to Glossary for definition of cut and slit edges.. Solid Woven Carcass Solid woven belting consists of a single ply carcass made up of multiple layers of warp and filling yarns interwoven. The carcass is usually impregnated and/or coated with thermoplastic compounds.

BELT EDGE PROTECTION - MOLDED EDGES Molded (Capped) Edge Belting Historically all conveyor belting was made with molded (capped) edges (Figure 3-2). Molded edges were necessary to protect the cotton fiber in the carcass against mildew or chemical action. Thus the carcass, in addition to being covered, was encapsulated around the edge with the elastomeric compound of the covers, and molded into a square capped edge. It must be recognized this was only a temporary expedient; since, when the covers were cut, gouged or worn to the fabric and the molded edges were torn or worn off, the absorption of water and chemicals would occur. With the availability of nylon and polyester fabrics, cut edge belting is now commonly used. In light weight belt applications capped edges are used in applications where improved edge protection is required. For example: food processing to eliminate edge fraying and subsequent absorption of fluids.


18


Figure 3-2. Multi-Ply Belt Shown with Four Plies of Reinforcing Fabric, A Breaker Ply, Covers and Rubber-Capped Edges Cut/Slit Edge Belting The general use of nylon and polyester yarn for conveyor belt carcasses has eliminated the concern for protecting the belt carcass with molded edges. The nylon and polyester fibers are resistant to mildew attack and the polyester to most chemicals. Thus most belting is now supplied with slit edges.

CARCASS PROTECTION Breaker Before the use of nylon and polyester carcass fabric, breaker plies of open texture leno weave cotton or nylon yarn were frequently used between the carrying cover and the belt carcass. It was believed a breaker ply improved the adhesion of the cover. The breaker ply next to the carcass improved cover cut and gouge resistance and provided material loading impact resistance. Breaker plies are used where severe impact conditions exist. Sometimes a breaker fabric in a molded edge is wrapped around the fabric edge to provide edge protection.

BELT COVER DESIGNS For most applications, conveyor belts have a smooth top and/or bottom cover made of elastomeric compound suitable for the material to be conveyed. There are, however, some special purpose belt surface finishes described in the following. Bareback Surface The outer surface of the top or bottom of the fabric of a bareback belt has neither an elastomeric compound cover nor is it impregnated with an elastomeric compound. A bare fabric surface provides a low coefficient of friction. A slider bed package conveyor with the bareback surface down against the slider bed or the bareback surface up in connection with a diverter bar are examples of bareback surface applications. Friction Surface The outer top and/or bottom surface of the fabric of a friction surface belt has a light impregnation of elastomeric compound. Brushback Surface Certain friction compounds may be buffed to further reduce the coefficient of friction while retaining the elastomeric compound in the interstices of the fabric. Bareback, brushback and friction surface belts can be provided with a cover on one side of the belt. Impression (Rough Top) Surface Impression belts have an embossed profile in a cover made by curing the elastomeric cover against a mold, fabric, or stamped metal or by embossing a thermoplastic cover. Impression belts are often used to convey material on inclines and declines where slippage may occur. Cleated, Flanged (Sidewall) or Ribbed Top Surface Cleats, flanges or ribs in transverse, longitudinal, continuous or intermittent, and of angular, straight or curved design may be molded onto or affixed to the cover. They improve the ability to carry coarse material on incline and decline applications. The height and spacing of the cleats, flanges or ribs depend on the size of the material to be conveyed.


19


BELT MANUFACTURING METHODS SINGLE AND MULTI-PLY BELTS Drying Cotton and spun synthetic yarn fabrics must be heated before they are frictioned so the friction rubber can be properly impregnated into the interstices of the fabric. Also the cotton, rayon, and nylon spun yarn fabrics must be thoroughly dried to remove moisture which in the belt curing operation could cause blisters between the plies of fabric or under the covers. Textile Fabric Treatment Generally, most multi-filament textiles (nylon, polyester, etc.) require an RFL treatment to ensure adequate adhesion in service. RFL is an industry term designating a treatment mixture of resorcinol formaldehyde latex (RFL), whereby the woven textile is dipped in the emulsion and dried under specific temperature and tension conditions. This process is used for most rubber based belting (Natural, SBR, NBR, CR, EPDM, etc.). For thermoplastic type belt, the treatment can involve acylics, polyurethane, PVC or other treatment for the respective textile reinforcements. Rubberizing (Skimming, Bank Coating, and Frictioning) The fabric is impregnated with a suitable elastomer by “frictioning” and/or “skim coating” on 3-roll or 4-roll calenders. Frictioning forces the pre-softened rubber compound into the interstices of the fabric by the wiping action of two calender rolls running at different surface speeds. In skim coating the calender roll speeds are essentially the same, and a thin layer of rubber compound is laid on the fabric. During the calendering operations, uniform tensions are maintained on the fabric to prevent undesirable distortion. Carcass Building Calendered plies of fabric are laminated and consolidated by squeezing between two rolls of a building unit. Depending on equipment design, from two to five plies can be laminated in a single pass through the unit. Uniform tension is maintained on each ply to ensure maximum efficiency during service. Longitudinal seams (ply splices) result when it is necessary to use more than one strip of fabric to make the full ply width. The seam is made by bringing the two edges together and, if necessary, placing a rubber cord over the joint so that a void does not occur when vulcanizing the finished belt. Longitudinal seams are generally made during the laminating pass through the building unit. Seams shall be at least 4 in from the edge, separated by 12 in within the ply and be removed from the idler junction area. Number of seams are limited by belt width. Tranverse seams (ply splices) result when the fabric length is less than the full length of the finished belt. The ends of the two or more pieces are prepared by cutting on a 20° to 45° bias angle. The ends are then butted against each other and if necessary, a strip of rubber compound is placed over the joint to prevent a void from forming during subsequent manufacturing operations. The preparation of the bias cut ends is done during the actual laminating operation at the carcass building machine, which results in a good matching of the two ends being joined. Transverse seams shall be at an angle between 26.5° and 70°, shall be separated by at least 50 ft, and be at least 50 ft from the end of the belt. No transverse seams are allowed in the outer plies. Belt Covers The elastomeric covering on belts is there to provide protection for the carcass, and/or provide a specific property. These coverings are applied by several processes, depending on the material (rubber vs. thermoplastic) or thickness of the covering. For rubber belting covers are either extruded or calendered. Extruded rubber sheets of specific widths and thickness are then laminated or press plied onto the carcass. similarly, thermoplastic covers can also be extruded and laminated. For most thin belt covers (i.e. pulley “side” covers), less than 1/8 in (3.2 mm), application is performed at a calender unit where the elastomeric compound is “skimmed” onto the textile. This process can accommodate some thermoplastic materials as well as rubber. PVC covers are also applied with roll or knife coating processes.


20


Release Coating After applying the last cover, a light coat of release agent, is applied to one or both surfaces of the belt. This is done to prevent the unvulcanized belt from sticking in the roll before cure and to help in stripping the belt from the press surface after cure. After release coating and before curing, the cover is usually perforated with fine pricker needles to help release gases that may be present withing the body of the belt. These holes are completely sealed during the vulcanization operation. Curing The belt is vulcanized in either a flat platen press (index cure) or a rotary press (continuous cure). In either case, curing is done at a temperature in the range of 280-320°F (140-160°C) while under pressure. Edge irons or rings are set at the desired belt width to retain and/or mold the rubber covered edges. Since it is essential that a small excess of material be present to create proper pressure during cure, a small overflow of cover occurs at the side retaining irons. This is removed by trimming or buffing as the cured belt comes from the press. Slab belts which are slit to width have the entire edge cut away during a subsequent operation. Tension is generally applied to the belt during cure so that the elongation of the finished product is within acceptable limits. Branding of the belt with the manufacturer’s name, grade or type of belt, and date of manufacture is generally accomplished by placing a metal stencil on the uncured belt at regular intervals. This produces an embossed label cured onto the surface. Slitting Slab belting is slit to the final width after it is cured. Full-width rubberized fabric is used to build the carcass.

SOLID-WOVEN RUBBER BELTS Carcass The woven fabric is generally treated with a special bonding adhesive which is applied by passing the fabric through a bath containing the adhesive. (See “Dipping.” under Single and Multi-ply Belts above.) Rubberizing The dried carcass is then impregnated by frictioning and/or coating on a calender. (See “Rubberizing” under Single and Multi-ply Belts above.) Covering, Dusting, and Curing These steps are essentially the same as for Single and Multi-ply Belts above.

SOLID-WOVEN PVC BELTS Textile Fabric Treatment The single- and multi-ply fabric is impregnated with PVC plastisol during and/or following weaving. Covering and Fusing The carcass is first passed through a plastisol dip tank for impregnation and cover application and then into a heated oven where plastisols are fused to the consistency required to meet service conditions. The PVC compound can alternatively be calendered into a film or sheet which can then be applied to the carcass. If smooth cover surfaces are required, fusing may be accomplished in flat or rotary presses. If rough top, cleated or ribbed top cover surfaces are required, embossing of the cover may be done immediately following the fusion process.


21


SINGLE AND MULTI-PLY THERMOPLASTIC BELTS Single and multi-ply PVC belts may be produced by dipping and/or top coating the carcass fabric with PVC plastisols, which provide the elastomeric binding layer between plies and the top cover surface. Fusion of the PVC compounds is done by heating to temperatures of approximately 350-380°F (177-193°C), and the surfaces of the belting are smoothed or embossed to provide the required textures and finish. Single and multi-ply polyurethane belts may be produced by coating the carcass with a film or sheet of compound from a hot melt coater or extruder or spraying operation and then cooling or by building a laminated construction using films or sheets of compound that are later heated in a flat or rotary press. Pre-treating the carcass is done to enhance adhesion of compounds. There are some extruded single-ply thermoplastic belts made with Hytrel or polyurethane, with no textile reinforcement.


22


CHAPTER 4

TEXTILE BELT CHARACTERISTICS & BELT RATINGS

INTRODUCTION The tension rating for a belt is the recommended maximum safe working stress that can be applied to the belt. Belt tension is commonly referred to as the force applied to the belt per unit of belt width, such as Pounds per Inch width (PIW), or Kilo Newtons per Meter width (kN/m). Textile fabrics are frequently rated for their maximum safe working stress which is expressed as the force applied per ply of fabric per unit width of the belt. There is variation among manufacturers about the following information that relates to number of plies of fabric, belt carcass thickness, minimum pulley diameter, troughability, etc., to the belt maximum safe working stress because of differences in materials and manufacturing methods. Some key differences which exist are: 1.The fiber, polyester and/or nylon, used for the fabric. 2.Recommended safe working strength for the fabric used. 3.Ratio of belt breaking strength to belt maximum safe working stress (safety factor). These factors also affect the belt carcass thickness, belt weight, minimum pulley diameter, troughability, load support with different angle idlers, transition distance, impact resistance, etc. Thus, it is essential to confer with the belt manufacturer about the belt proposed for each application.

CONVEYOR BELT AND SYSTEM TENSION CALCULATIONS Conveyor systems will take on a variety of configurations relative to drive location, elevation or descent of the load, idler and pulley type and condition, and other factors too numerous to detail in this handbook. Belt manufacturers or conveyor engineering companies should be consulted for belt (system) recommendations. The Conveyor Equipment Manufacturers Association (CEMA) provides a Handbook for in-depth system analysis and tension calculations. International Standard ISO 5048 and the German standard DIN 22101 also provide detailed methods for system tension calculations. The tables below provide an example of the basic information on multi- and single-ply fabric belt tension ratings. This information is for illustrative purposes only. Information on a specific belt construction can be provided by the belt manufacturer. The data in the following tables apply if the following service conditions occur: Mechanical Fastener Splice 1.Pulley diamters recommended by the belt manufacturer and fastener manufacturer are used. 2.No abnormal conditions, such as heat or chemicals, are exposed to the belt that will reduce the belt fabric strength or change the flexibility of the belt fabric. 3.Recommended fasteners are properly applied. 4.Across the line starting tension is limited to not greater than 150% of the splice rating. Step phase or soft starting is preferred. Vulcanized Splice 1.Pulley diameters recommended by the belt manufacturer are used. 2.Automatic take-up with adequate take-up travel. 3.Splices are made strictly in accordance with the belt manufacturer’s specifications. Where an adverse environmental condition or some special belt application exists, it is critical that the belt fabric ply tension rating be reduced by some factor recommended by the belt manufacturer. Some of the special conditions are: 1.Continuous excessive ambient temperature. 2.Exposure to deleterious chemicals. 3.Holes punched in the belt.


23


Elevator Belt Tension Recommendations Elevator tension ratings may require modification under certain adverse environmental conditions. In such cases the rating in the following tables should be multiplied by an environmental factor of 0.75. Adverse environmental factors for elevator belts include: 1.Elevated temperatures in the belt reinforcing fabric due either to high ambient temperatures or to conveying hot materials. 2.Abrasion of surface plies which are not protected by an elastomeric cover, such as friction surface belting in abrasive service. 3.Chemical service detrimental to the carcass fiber.

Safety Factors Conveyor belt operating tensions are chosen as a small percentage of the belt’s breaking strength. This provides spare strength for (1) temporary higher transient loads such as during starting and stopping, (2) handling unusual system loads such as misalignments or frozen idlers, and (3) loss of strength due to materials’ aging and other degradation factors. The ratio of original belt strength to operating tension is called the belt’s Safety Factor. Traditionally, the conveyor industry has used safety factors around 10:1 for fabric belts and around 6.7:1 for steel cord belts, however, higher and lower factors are common. It is recommended to contact the belt manufacturer for a safety factor recommendation for a specific application. In recent years, studies have linked a belt’s safety factor to its dynamic splice strength and tests have been developed to measure the dynamic strength of the splice. There are now international standards, such as DIN 22110, that define how the dynamic splice strength can be measured. There are also standards, such as DIN 22101, that provide a method to calculate the safety factor for a belt. A general guideline is that fabric belt splices have a dynamic splice efficiency of 35% of the belt’s breaking strength and steel cord belt have 45%. In practice, many conveyor belts deteriorate due to abuse or accidental damage and historical data should always be considered when selecting a safety factor. Other factors that should be considered when selecting a belt’s safety factor include the effects of a catastrophic belt break. For example, personnel safety, loss of production, clean up cost, repair time, accessibility of the belt for repair, and availability of repair labor and materials. There are examples where a critical conveyor belt has broken due to loss of strength from accidental damage combined with a high peak transient load. Such events can cost millions of dollars of lost production. The recent availability of cord monitoring systems for conveyor belts offers improved capability of accidental damage surveillance in steel cord belts. When used correctly, such systems offer additional safeguards for the operation of belts with lower safety factors.


24


Table 4-1. Typical Ratings CONVEYOR Working Strength (PIW) Number of Plies Approximate Carcass Thickness (in) Approximate Carcass Weight (lb/sq. ft)

220 2 .12

250 2 .146

330 3 .16

375 3 .20

400 2 .182

440 4 .220

500 4 .254

600 3 .258

750 3 .27

800 4 .265

1000 4 .28

1000 5 .335

1200 6 .38

.70

.81

.94

1.12

1.02

1.3

1.39

1.42

.135

.125

.141

.165

.188

16 14

24 20

24 20

24 20

22 24

30 20

30 24

36 24

42 30

Minimum Pulley Diameter (in) (% of rated max. belt tension) 81-100% 16 16 18 18 61-80% 14 14 16 16 41-60%

10

10

12

14

12

18

18

18

20

16

20

20

24

To 40%

10

10

12

12

10

16

16

16

18

14

18

18

20

18 24 18 24 30 24 36 24 30 24 30 36 30 36 30 36 30 36 42 36 42 Maximum Belt Width (in) for Empty Troughing

36 30 36

42 36 42

48 42 48

NR 42 48

TROUGHABILITY Idler Troughing Angle˚ 20˚ 35˚ 45˚

Minimum Belt Width (in) for Empty Troughing 14 18 24

18 24 30

48 48

54 48

60 60

72 60

60 54

72 66

84 72

84 72

84 72

72 72

84 72

84 84

84 84

81-120

42

42

54

54

48

60

72

72

72

72

72

84

84

Over 120

36

36

48

48

42

54

60

60

60

60

60

72

84

0-40

42

48

54

60

54

60

72

72

84

72

72

84

84

41-80

36

42

48

60

48

60

60

60

72

60

66

72

84

81-120

36

42

48

54

48

54

60

60

72

60

60

72

84

Over 120

30

30

42

42

36

48

54

54

60

54

54

60

72

0-40

36

48

48

60

54

54

72

72

72

72

72

84

84

41-80

36

36

42

48

42

48

54

54

60

54

72

72

84

81-120

30

30

42

48

42

48

54

54

60

54

72

72

84

Over 120

NR

NR

36

36

30

42

48

48

54

48

54

54

72

81-100% tension

18

18

20

20

18

30

30

30

36

22

30

36

42

61-80%

16

16

18

18

16

24

24

24

30

20

24

30

36

Up to 60%

12

12

14

14

14

20

20

20

18

20

24

30

36

Spaced Industrial 100 lb/cu. ft

6

7

7

8

9

10

11

10

11

9

10

11

12

Spaced Continuous

5

6

7

8

9

10

11

12

14

9

12

14

16

Material Weight (lb/cu. ft) 20˚ 0-40 41-80

35˚

45˚

ELEVATOR Minimum Pulley Diameter

Maximum Pulley Projection

Note 1: These are typical values only, please consult your belt manufacturer for specific product values. Note 2: Table 4.1 includes expanded product ratings. IP:1 2011 Conveyor and Elevator Belt Handbook

25


Table 4-2. Typical Ratings - Straight Warp Conveyor or Elevator Rubber Belting CONVEYOR Single-Ply Straight Warp Fabric Working Strength (PIW) 190 220 275 Approx. Carcass Gauge (in) .078 .103 .125 Approx. Carcass Weight .038 .049 .056 (PIW) Factor (lb)

390 .131

385 .157

440 .165

440 .195

Double-Ply Straight Warp Fabric 550 660 800 1000 1250 .234 .250 .281 .320 .328

.064

.067

.072

.105

.114

.120

1500 .359

.134

.148

.165

.172

Minimum Pulley Diameter (in) Depending on Fastner Splice Selected Working Tension 81-100%

16

16

18

20

24

24

24

30

30

36

42

42

42

61-80%

14

14

16

18

20

20

20

24

24

30

36

36

36

Up to 60%

12

12

14

16

18

18

18

20

20

24

30

30

30

Minimum Belt Width (in) for Empty Troughing 14 18 18 18 24 24 24 20 24 24 24 30 30 30 24 24 24 24 36 36 36 Maximum Belt Width (in) for Load Support

30 36 42

30 36 42

30 36 42

30 36 42

TROUGHABILITY Troughing Angle 20˚ 35˚ 45˚

12 14 16

14 20 24

36 30

42 36

54 42

60 48

60 48

66 54

84 84

84 84

84 84

84 84

84 84

84 84

84 84

Over 120 lb/cu. ft

30

36

42

48

48

54

60

66

84

84

84

84

84

41-80 lb/cu. ft

30

36

42

54

54

60

84

84

84

84

84

84

84

81-120 lb/cu. ft

24

30

36

42

48

48

84

84

84

84

84

84

84

Over 120 lb/cu. ft

24

30

36

42

42

48

54

60

66

84

84

84

84

41-80 lb/cu. ft

30

36

42

48

48

54

60

66

84

84

84

84

84

81-120 lb/cu. ft

24

30

36

42

42

48

54

60

84

84

84

84

84

Over 120 lb/cu. ft

18

24

30

36

36

42

48

54

60

66

84

84

84

Material Weight (lb/cu. ft) 20˚ 41-80 lb/cu. ft 81-120 lb/cu. ft

35˚

45˚

ELEVATOR Minimum Pulley Diameter Working Tension 81-100%

16

16

18

20

24

24

30

30

30

36

42

42

42

61-80%

14

14

16

18

20

20

24

24

24

30

36

36

36

Up to 60%

12

12

14

16

18

18

20

20

20

24

30

30

30

Maximum Bucket Protection Space Industrial

6

7

8

9

9

9

11

11

13

13

14

15

16

Continuous Industrial

6

7

8

9

9

9

11

11

13

13

14

15

16

Note 1:These are typical values only, please consult your belt manufacturer for specific product values. Note 2: Table 4.2 includes expanded product ratings.


26


Belt operating tension is not the only belt characteristic to be considered when selecting belt design for an application. Other important items exist that effect how the belt will perform on a given system. The importance of these characteristics is presented below.

ELONGATION Most new conveyor belts will exhibit some permanent stretch very early in their service life, as a result of the normal cyclic tensile forces exerted by the conveyor system on the belt. This length change will vary among belt constructions, but it is generally much less than one percent of the original relaxed length of the belt. The conveyor take-up system must compensate for this length change as well as the normal belt elongations which are proportional to belt tensions in the elastic region of the stress strain curve. Table 3-3. Recommended Minimum Take-Up Travel (percentage of the distance between centers of the convenor*) Type of Take-Up and Carcass Material (warp)

Percent of Rated Tension 100%

75%

50% or less

Nylon

4.00%

3.00%

2.00%

Polyester

2.50%

2.00%

1.50%

Nylon

3.00%

2.50%

1.50%

Polyester

0.00%

1.00%

1.00%

Manual Take-Up**

Automatic Take-Up

*For belts installed at average empty running, take-up position 90% of the travel, and drive location at or near the high tension end of the conveyor. **Only short endless feeder belts and the like would normally be vulcanized on conveyors with a manual take-up.

TROUGHABILITY AND LOAD SUPPORT In order to achieve the desired carrying capacities of bulk materials without spillage over the edges, most conveyor belts are operated in a troughed configuration where the trough is usually formed by a 3-roll idler system as indicated by Figure 4-1 below. The angle of the troughing rolls will usually range from 20° to 45°.

Figure 4-1. Belt Troughing In-Line Idler When the belt is running empty, it must have sufficient lateral flexibility to retain contact with the center roll. Failure to do so will usually cause the belt to wander from side to side, and considerable edge damage may result. Conversely, when the belt is running fully loaded, it must have sufficient lateral stiffness to support the load and bridge the gap between the center and troughing rolls. If the belt is too flexible in this regard, it will tend to crease into the idler gap and fail prematurely at that point. This potential problem can be reduced by using offset troughing idlers. With offset idler systems the load support may be liberalized (consult belt manufacturer).


27


LIMIT OF IDLER GAP BETWEEN CARRYING IDLERS FOR TROUGHED BELT CONVEYORS The Association for Rubber Products Manufacturers has established the following limit for gap between carrying idlers for troughed conveyors.(ARPM IP-1-2) The limits provided serve as a guideline for acceptable performance of conveyor belts in the idler junction area, preventing junction failure. Reference Document: ISO 1537 -- Continuous mechanical handling equipment for loose bulk materials -- Troughed belt conveyors (other than portable conveyors) -- Idlers Limit for gap between in-line positioned troughed carrying idlers: The maximum gap between the carrying idlers will be 3/8 in (10 mm).

Figure 4-2. Overlap and Offset Dimension for staggered (or off-set) troughed carrying idlers: A minimum overlap between the carrying idlers will be 3/8 in (10 mm).

Figure 4-3. End View A maximum offset dimension of the idler in the running direction will be: Idler diameter plus 3/16 in (5 mm).

Figure 4-4. Top View


28


From the foregoing it is apparent that there are two extremes of lateral belt flexibility to be considered in making a belt selection, and these are generally referred to as minimum and maximum ply design. Reference to manufacturers’ published tables is recommended, especially when the belt selection will be at or near either the minimum or maximum ply extreme, because of belt design variations and the fact that there are often two or more fabrics available with differing trough characteristics. The ability of the belt to trough may be measured by using a standard test method (ASTM D 378). In this test, the troughability of the belt is defined as the ratio F/L where F is the natural drop height at the center of a 6 ft (1.8 m) long belt sample freely suspended at its edges and L is the belt sample width. Table 4-4 provides a guideline for the minimum values of F/L required to ensure that a belt will trough correctly in the listed troughing idlers. Table 4-4*. Three Identical Idler Rollers -- Minimum Required Values of the Ratio of Deflection (F) to the Belt Width (L)

Inclination of side idler rollers 20°

0.08

25°

0.10

30°

0.12

35°

0.14

40°

0.16

45°

0.18

50°

0.20

55°

0.23

60°

0.26

* referenced from ISO 703 Several belt constructions made from two or more plies of synthetic fabrics are widely used and are generally referred to as multi-ply constructions. Because of the wide variety of fabric strengths, constructions, and other factors offered in these types of belt, it is necessary to consult the various manufacturers for specific data. Tables showing typical belt selection data are in Chapter 5.

TRANSITION DISTANCE ON THREE EQUAL LENGTH IDLER ROLLS FOR TEXTILE BELTS A. General In changing the troughed belt to a flat section at the head pulley or the flat belt to a troughed section at the tail pulley, edge tension is increased as the edges are stretched between the last idler and the pulley. This tension mal-distribution can be kept within safe limits by maintaining a proper transition distance between the last trough idler and the pulley to minimize the stretch induced into the belt edges. At the head (high tension end), the purpose is to avoid excessively high edge tensions. At the tail (low tension end), excessive edge tensions rarely will be encountered. If the transition is too short, however, an excessive difference between edge and center tensions can overcome lateral belt stiffness, pull the belt down into the trough, and buckle it longitudinally along the bottom roller. B. Recommended Terminal Pulley Location The vertical position of the terminal pulley with respect to the troughing idlers is of great importance in determining the minimum transition distance since this position determines the vertical drop of the belt edge. The higher the pulley location with respect to the idlers the shorter will be the minimum required transition distance. Figures 4-5 and 4-6 illustrate two terminal positions commonly used. Figure 4-5 usually is recommended from a belt standpoint; it places the pulley so that the belt edge will be lowered (or raised) approximately one-half the trough depth and requires much less transition distance than Figure 4-6 while still maintaining a troughed section across the belt width. Figure 4-6 is used occasionally where belt tension is low, lumps are large, and belt speed is high to minimize impact forces at the discharge pulley.


29


Figure 4-5. Half-Trough Transition

Figure 4-6. Full-Trough Transition C. Minimum Recommended Transition Distances The transition distances required to maintain proper edge and center tension relationships are a function of the elastic modulus or stretched characteristic of the belt carcass, the rated belt tension, and the vertical drop or rise of the belt edge through the transition. Using the elastic modulus of various belt fabrics from 1500 to 10,000 pounds per ply inch it is possible to develop a transition distance suitable for all fabric belts (Tables 4-5 and 4-6) since the maximum and minimum requirements do not vary too widely.

Table 4-5. Minimum Transition Distance with Terminal Pulley at Approximately One-Half Trough Depth Idler (deg)

Percent ofrated tension

Fabric belts

Steel cord belts

20°

More than 90 60 to 90 Less than 60

0.9w 0.8w 0.6w

2.0w 1.6w 1.0w

35°


1.6w 1.3w 1.0w

3.4w 2.6w 1.8w

45°


2.0w 1.6w 1.3w

4.0w 3.2w 2.3w


30


Table 4-6. Minimum Transition Distance with Terminal Pulley at Full Trough Depth Idler (deg)

Percent ofrated tension

Fabric belts

Steel cord belts

20°


1.8w 1.6w 1.2w

4.0w 3.2w 2.8w

35°


3.2w 2.4w 1.8w

6.8w 5.2w 3.6w

45°


4.0w 3.2w 2.4w

8.0w 6.4w 4.4w

Note 1: The above transition distances are conservative and have been used in service for years. Contact the belt manufacturer if shorter distances are desired. Note 2: Steel cord belts with their very low stretch characteristics require much greater transition distances than fabric belts. These distances at times seem unreasonably great, but a small amount of stretch in steel cord can induce an enormous stress. In one actual case, an 18 ft (5.5 m) steel cord belt transition was lengthened approximately eight more feet when it was shown that the theoretically induced edge stress caused by edge stress in the 18 ft (5.5 m) distance amounted to approximately an additional one-half of the rated belt tension.

VERTICAL CURVES General Vertical curves in conveyor belt systems are used to join two tangent sections with different slopes.Two different types of vertical curves exist; a concave curve resulting from a negative change in grade; and a convex curve, resulting from a positive change in grade. Each application needs to be evaluated to determine the correct curve radius in order to avoid problems during operation.

Figure 4-7. Vertical Curves Concave Vertical Curves A concave vertical curve should be designed with sufficient radius to allow the belt to follow the path of the troughing idlers under all conditions. The lack of a correct concave curve is immediately apparent, as the belt will lift off the idlers. Especially during startup, if the belt tensions are too high, the belt will lift off the idlers in the curve area. On the other hand, very low tension could result in excessive edge sagging and possible load spillage. In rare cases, it might also be necessary to verify that the tension at the center of the belt does not exceed the tension rating of the belt. This center tension should be limited to 115% of the rated belt tension. Convex Vertical Curves Unlike concave curves,convex vertical curves can be improperly designed and still permit belt operation at the expense of belt life. Three main items need to be investigated when designing convex curves; edge tension, center tension, and idler pressure. In a convex curve, the belt edges have a greater tension than the center of the belt. It is important to limit this tension to 115% of the rated belt tension. If the tension at the center of the belt becomes too low, the belt can buckle. To avoid this condition, a minimum of 5% of the rated belt tension should be maintained in the center of the belt.


31


Convex curves can also be restricted by the idler pressure. When going through a convex curve, the belting is forced downward onto the idlers.Convex curve limitations from the idler pressure standpoint are not created by the belt but by idler requirements. As a result, the idler manufacturer should be consulted if this appears to be the limiting factor. If the manufacturer permits a greater loading, then the radius can be reduced accordingly. Otherwise, the only other solution is to reduce idler spacing to live with the desired radius. Short convex curves can cause idler junction failure as the belt will be forced in the idler gaps. Idler junction failure will be dependent on the idler gaps, fabric type, belt rigidity, curve radius and edge / center belt tension.

PULLEY DIAMETERS Pulley diameters are important to belt performance. Pulley diameters which are too small for a given belt construction, could result in damage to the belt carcass or premature splice failure.As a belt travels around a pulley, a bending stress is induced as the outer fabric plies must elongate and inner plies must shrink. This extra stress is dependent on the diameter of the pulley, the thickness of the belt, and the elastic constant of the material. It is important to the integrity of the belt that this stress is kept within safe limits. Minimum recommended pulley diameters can be obtained from the belt manufacturer for a given belt application based on the belt construction and system tension.

IMPACT RESISTANCE Loading bulk material on a conveyor belt creates some impacting force on the belt. This occurs since the material is dropped from some height above the belt surface and the forward speed of the belt may be different than that of the material when it contacts the belt. Fine materials, regardless of weight per unit volume, do not present a problem on impacting the belt because the force is spread over a relatively large surface area. Cover damage due to gouging is minimal and carcass bruising is normally very low in operations involving fine materials. Lumpy materials can cause appreciable impact on the belt. The heavier the lump, the greater height of fall, and the greater its angular velocity when it contacts the belt, the greater will be the energy tending to rupture the belt. When the material strikes the belt directly over a support such as an idler, damage to the carcass can result from the crushing action of the lump against the idler-supported belt. Lumpy material having sharp corners and edges can cause cover nicks, cuts, and gouges. The heavier the lump, the greater height of fall, and the greater its angular velocity at the time of contacting the belt, the more extensive will be the damage to the cover. Sharp, pointed lumps can even penetrate the cover into the carcass and in rare instances completely penetrate through the belt. To minimize impact damage, every effort should be made to provide good loading conditions for the material handled. (See Chapter 14 on loading and discharge). Given full information regarding the material conveyed and the loading conditions, the belt manufacturer can provide a belt that will embody the necessary elements to resist the damaging effects of impact. The selection of a cover grade and thickness, the type of textile fiber, fabric design, and number of plies can be varied depending upon the severity of the impact conditions. The maximum fabric ratings shown in this chapter are based on the use of impact idlers and good design of loading and transfer areas. The impact energy equals the lump weight factor (Tables 4-7 and 4-8) times the equivalent free fall.


32


Equivalent Free Fall Calculation Equivalent free fall is: H f + Hr (sin2 Δ) Where:

H f = total free fall, ft (m) Hr = vertical height on loading chute slope, ft (m) Δ = angle in degrees that chute slope makes with the horizontal

Figure 4-8. Equivalent Free Fall and Location of Values H f and Hr Lump Weight Factor The following tables are a close approximation of the weight of a lump based on cubic lump and slab breakage characteristics: Table 4-7. Lump Weight Factor in Pounds Densitylb/ft3

Lump Size (in) 2

3

4

5

6

7

8

9

10

12

14

16

18

50 75 100

0.4 0.6 0.7

1.3 1.9 2.6

3.0 4.5 5.9

5.8 8.6 12.0

10 15 20

14 21 28

21 31 41

30 44 59

40 61 81

70 105 140

100 149 199

148 222 296

211 316 421

125 150 175

0.9 1.1 1.3

3.2 3.8 4.5

7.4 9.0 10.4

14.0 17.0 20.2

25 30 35

35 42 49

52 62 73

74 89 104

101 121 142

175 210 245

248 298 348

371 444 518

527 632 737

Table 4-8. Lump Weight Factor in Newtons* Densitykg/m3 800 1200 1600 2000 2400 2800

Lump Size (mm) 50

75

100

125

150

175

200

225

250

300

350

400

450

6812

14 21 27

26 38 53

45 68 90

62 93 124

93 137 182

133 196 263

178 271 360

312 466 622

445 613 882

657 990 1313

931 1401 1872

33 40 46

62 76 90

111 133 156

156 186 218

231 274 323

329 396 461

449 539 631

777 931 1088

1102 1323 1548

1646 1980 2303

2372 2813 3273

15 17 21

* Newtons, rather than kilograms, have been used to simplify calculations.


33


COEFFICIENT OF FRICTION A coefficient of friction is the ratio of the force required to slide a belt over its supporting structure to the normal force holding the belt to the supporting structure. The static coefficient of friction uses the force needed to start the belt into motion from rest, and the kinetic coefficient of friction uses the force to keep the belt in motion. Where reference is made to a coefficient of friction of belting, generally the kinetic coefficient is meant, unless specified otherwise. This important belt characteristic affects the suitability of belting in specific applications. Generally, very low coefficients of friction are required on the bottom surface for slider bed conveyors to minimize power requirements, and low coefficients of friction are desired on the top surface of belting in applications involving plowing off conveyed objects toward the belt edges. A higher coefficient of friction on the top surface is generally desired when the top surface is used to drive carrying rollers. Very low coefficients of friction are in the range of 0.15 to 0.25 typically. Untreated textile products have a coefficient of friction against steel of approximately 0.20. Friction surfaces of belting have coefficients of friction against steel of about 0.40 to 0.50, and belt covers have quite high coefficients of friction, from about 0.8 to values even greater than 1.0 depending on the formulation.

STATIC CHARGE DISSIPATION In some belting applications the generation of static electrical charges can be very detrimental to safety. This is especially true where static electrical discharges can ignite explosive mixtures of flammable materials such as dust from coal, grain, or wood. The ability of the belt to help dissipate these static charges is a very important characteristic in these applications. The establishment of a properly bonded grounding path from the belt through the conveyor to an earthing point is an important consideration. ASTM D 257 -- Standard Test Methods for DC Resistance or Conductance of Insulating Materials and ISO 284 -- Conveyor belts -Electrical conductivity -- Specification and test method, currently establishes 300 megohms (3 x 10 8 ohms) as the maximum electrical resistance for belting. It is recommended that belting used in underground mines and in grain elevators meet this specification. There are belting applications in the electronics industry and in ammunition plants that require an even higher level of electrical conductivity, perhaps in the 10 4 to 10 6 ohms range. Although no national or international standard currently exists for this level of performance, there are belting products that can be specifically designed to meet these requirements.


34


CHAPTER 5

TEXTILE BELT TOLERANCES

The width tolerances listed in Table 5-1 are the commercially accepted standards of the conveyor belt manufacturing industry. Tighter tolerances may be specified by agreement between the individual manufacturer and his customer. Table 5-1. Belt Width Tolerances Molded Edge Width Tolerance

Belt Widths

Slit Edge Width Tolerance

in

mm

in

mm

Up to 24 in (600 mm)

± 1/4

±6

± 3/16

±5

24 in (600 mm) up to 36 in (900 mm)

± 3/8

± 10

± 3/16

±5

36 in (900 mm) or greater

± 1%

± 1%

± 1%

± 1%

Zero Plus or Zero Minus Tolerances If a customer specifies a zero plus or a zero minus tolerance, the full tolerance still applies to the belt. For instance, if a customer requests a 26 in slit edge belt with a minus zero tolerance, the tolerance will read 26 in + 3/8, 0, but if molded edge + 3/4, 0. This method of tolerancing is being used for clarity and simplicity and takes no stand on pricing of belt based on plus tolerances. Tolerances on Lengths The permissible tolerances for the lengths of conveyor belts, measured loose, are given in Tables 6-2 and 6-3 and as specified in ISO 251. a) For endless belts, so delivered and mounted: Table 5-2. Endless Belts Length ft (m)

Tolerance in (mm)

over

up to (inclusive)

--

49 (15)

± 2 (± 50)

49 (15)

66 (20)

± 3 (± 75)

66 (20)

--

± 0.5% of the size in meters

b) For open belts:

Table 5-3. Open Belts Belt Delivery Condition

Tolerance (maximum permissible difference between the delivered length and the ordered length)

As one length

+ 2.5%, - 0.0%

In several lengths

for each single length ± 5%

for the sum of all lengths + 2.5%, - 0.0%

Note: The lengths of conveyor belts are not standardized.


35


CHAPTER 6

TEXTILE BELT TEST METHODS TEST METHODS

Below are the list of the tests against various standards. ASTM International ASTM D 378

Standard Test Methods for Rubber Elastomeric Belting, Flat Type Included are tests for: Measurements of Dimensions Physical Properties of Elastomeric Covers Immersion Tests Adhesion Tests Breaking Strength and Modulus Testing Flame Test for Belting Carcass Tear Test Troughability Test Breaking Strength of Mechanical Fastenings (Static Test Method) Elevator Belt Bolt Holding Strength Test

ASTM D 2228 Standard Test Method for Rubber Property - Relative Abrasion by Pico Abrader Method ASTM International standards can be obtained at www.astm.org. Canadian Standards Association CAN/CSA-M422-M87 -- Fire Performance and Antistatic Requirements for Conveyor Belting CSA standards can be obtained at www.csa.ca. International Organization for Standardization (ISO) ISO 251

Conveyor belts with textile carcass -- Widths and lengths

ISO 252

Conveyor belts -- Adhesion between constitutive elements -- Test methods

ISO 282

Conveyor belts -- Sampling

ISO 283

Textile conveyor belts -- Full thickness tensile strength, elongation at break and elongation at the reference load -Test method

ISO 284

Conveyor belts -- Electrical conductivity -- Specification and test method

ISO 340

Conveyor belts -- Laboratory scale flammability characteristics -- Requirements and test method

ISO 433

Conveyor belts -- Marking

ISO 433

Conveyor belts -- Marking (Amd 1)

ISO 505

Conveyor belts -- Method for the determination of the tear propagation resistance of textile conveyor belts

ISO 583

Conveyor belts with a textile carcass -- Total belt thickness and thickness of constitutive elements -- Test methods

ISO 703

Conveyor belts -- Transverse flexibility (troughability) -- Test method

ISO 1120

Conveyor belts -- Determination of strength of mechanical fastenings -- Static test method

ISO 1537

Continuous mechanical handling equipment for loose bulk materials -- Troughed belt conveyors (other than portable conveyors) -- Idlers

ISO 3684

Conveyor belts -- Determination of minimum pulley diameters

ISO 3684

Conveyor belts -- Determination of minimum pulley diameters (Amd 1)


36


ISO 3870

Conveyor belts (fabric carcass), with length between pulley centres up to 300 m, for loose bulk materials -Adjustment of take-up device

ISO 4195

Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods

ISO 4195

Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods (Cor 1)

ISO 5284

Conveyor belts -- List of equivalent terms

ISO 5284

Conveyor belts -- List of equivalent terms (Cor 1)

ISO 5285

Conveyor belts -- Guidelines for storage and handling

ISO 5293

Conveyor belts -- Determination of minimum transition distance on three idler rollers

ISO 5293

Conveyor belts -- Determination of minimum transition distance on three idler rollers (Cor 1)

ISO 9856

Conveyor belts -- Determination of elastic and permanent elongation and calculation of elastic modulus

ISO 10247

Conveyor belts -- Characteristics of covers -- Classification

ISO 10247

Conveyor belts -- Characteristics of covers -- Classification (Amd 1)

ISO/TR 10357

Conveyor belts -- Formula for transition distance on three equal length idler rollers (new method)

ISO 14890

Conveyor belts -- Specification for rubber or plastics covered conveyor belts of textile construction for general use

ISO 14890

Conveyor belts -- Specification for rubber or plastics covered conveyor belts of textile construction for general use (Cor 1)

ISO 15147

Light conveyor belts -- Tolerances on widths and lengths of cut light conveyor belts

ISO 16851

Textile conveyor belts -- Determination of the net length of an endless (spliced) conveyor belt

ISO 18573

Conveyor belts -- Test atmospheres and conditioning periods

ISO 21178

Light conveyor belts -- Determination of electrical resistances

ISO 21179

Light conveyor belts -- Determination of the electrostatic field generated by a running light conveyor belt

ISO 21180

Light conveyor belts -- Determination of the maximum tensile strength

ISO 21181

Light conveyor belts -- Determination of the relaxed elastic modulus

ISO 21182

Light conveyor belts -- Determination of the coefficient of friction

ISO 21183-1

Light conveyor belts -- Part 1: Principal characteristics and applications

ISO 21183-2

Light conveyor belts -- Part 2: List of equivalent terms

ISO 22721

Conveyor belts -- Specification for rubber- or plastics-covered conveyor belts of textile construction for underground mining

ISO Standards can be obtained at www.ansi.org. German DIN Specifications Many DIN specifications are used internationally and most are available in English. 22101

Continuous conveyors - Belt conveyors for loose bulk materials - Basis for calculation and dimensioning

22102-1

Conveyor belts with textile plies for bulk goods; dimensions, specifications, marking

22102-2

Conveyor belts with textile plies for bulk goods; testing

22102-3

Conveyor belts with textile plies for bulk goods; permanent joints

22109-1

Conveyor belts with textile plies for coal mining - Part 1: Mono-ply belts for underground applications; dimensions, requirements


37


22109-2

Conveyor belts with textile plies for coal mining - Part 2: Rubber - belts with two plies underground applications; dimensions, requirements

22109-4

Conveyor belts with textile plies for coal mining - Part 4: Rubber - belts with two plies for above applications; dimensions, requirements

22109-5

Conveyor belts with textile plies for coal mining; branding

22109-6

Conveyor belts with textile plies for coal mining - Part 6: Testing

22118

Conveyor belts with textile plies for use in coal mining; fire testing

22121

Conveyor belts with textile plies for coal mining - Permanent joints for belts with one or two plies; dimensions, requirements, marking

DIN standards can be obtained at www.din.ne, or through ANSI at www.ansi.org.

BOW OF CONVEYOR BELTS Bow is the concave deviation of the edge of the belt from a straight line between two points along the belt edge. (Camber is the convex phenomenon, on the other edge of the belt.) Bow is measured by unrolling at least 50 ft (15 m) and more preferably 100 ft (30 m) of the belting from a shaft-supported roll onto a flat surface, so there is no tension on the belt. Place a tape or string between two points along the belt edge. Measure the belt length between these two points, and also the distance at the mid-point of the length between the belt edge and the tape or string. The amount of bow is the ratio of the distance, midway between the above two points, between the belt edge and the tape or string, and the tape length between the two points. To express it in percent, calculate the ratio in hundredths and multiply by 100. For example the point-to-point length of 100 ft (30 m) has a bowed width of 18 in (450 mm) or 1.5 ft so 1.5/100 x 100 = 1.5% bow. Bow may not be troublesome. It may “pull out” when the belt is tensioned and operate satisfactorily. The main causes of bow are: a. Bowed filling yarns transversely across the fabric of the carcass; b. Crooked slitting of the belt into a narrower belt, and; c. Storage of a belt on its edge when the floor is damp or water and/or other liquids reach the belt edge on the floor.

RIP TEST SPECIFICATION 1. Purpose a. Test the ability of a given fabric carcass to resist ripping/tearing in the longitudinal direction once an object has become logged both in the belt and the system at the same time. 2. Sample Size a. Sample Base - Length X Width - 12 in x 10 in

1/2 “ D

b. Punch 3 - 5/8 in holes in the upper half of the sample with each hole being 2 in from the edges of the sample. c. Punch one 1 1/16 in hole in the center of the sample approximately 4 1/2 in from the end of the sample. (opposite of the 3 - 5/8 in holes) d. This is a carcass test, to eliminate variable effects of covers the covers must be removed or a line must be cut in the direction of the rip. Using a special blade that is dulled on on the end cut a vertical line through the

1 1/16 “ D 4 1/2 “

Figure 6-1.


38


top cover from the center of the 1 1/16 in hole to the bottom of the sample. Flip the sample over and cut the same line through the pulley cover. Be careful to only cut the covers - Do not cut the carcass.

1/2 in Holes

3. Sample Testing a. Testing jigs, pictured in Figure 6-2 and 6-3, are required to both fasten and rip the sample during testing. b. Sample is secured using the top three holes in a moveable jaw of lab testing apparatus and top testing jig (Figure 6-2). Top Testing JIG

c. Bottom Testing Jig (Figure 6-3) is placed into the bottom jaw of lab testing apparatus and sample is lowered until the 1 1/16 in hole of the Jig and hole on the bottom half of the sample line up.

Figure 6-2.

d. Place a 1 1/16 in diameter steel rod (Figure 6-3) through both the bottom testing jig and sample. The steel rod will facilitate the carcass rip. e. Actuate the upper jaw of the test apparatus moving the sample upward with the steel rod being held in place by the bottom jig. The steel bar will start to rip through the carcass. f. Continue test for at least 4 in and record all load peaks during the rip. The test is intended to break the fabric cords in the weft direction, document if any cords pullout instead of breaking.

1 1/16 in Hole

1 1/16 in Steel Rod

4. Results

Bottom Testing JIG

a. Report should include: i. Carcass Construction b. Recorded Results

Figure 6-3.

i. Average of load peaks during 4 in tear ii. Documentation of any anomalies during test. (cord pullout)

Note: Information regarding the Impact Test Procedure will be available at a later date.


39


CHAPTER 7

SPLICING CONVEYOR AND ELEVATOR BELTS

INTRODUCTION This chapter is intended to serve as an introduction to splicing methods in general use. Belt users should consult belt and fastener manufacturers for more specific detailed information.

CONVEYOR BELT SPLICES USING MECHANICAL FASTENERS A mechanical splice, while it does not afford the strength or permanence of a vulcanized splice, is typically used in the following conditions: 1. Belt tensions are low enough to meet the requirements for the belt under its mechanical splice rating. 2. Available downtime is only adequate for mechanical splicing. 3. Belt ends must be joined in cramped locations where vulcanized splices would be difficult to make. 4. The conveyor is an extensible or portable type which is frequently knocked down and moved. (Note: Typically mechanical fasteners offer a safety factor of 4:1) When initial belt stretch on new belt is intended to be cut out before a vulcanized splice is made, it is common, particularly on a long-center conveyor requiring more than one splice, to make the last joint with fasteners and run the belt for a period of time. Then replace the mechanical splice with the final vulcanized splice. This procedure helps to set the belt to the conveyor idlers and other equipment. It also helps to remove initial stretch, thereby ensuring against the premature necessity of shortening the belt with a vulcanized resplice. When following this break-in procedure, sufficient length must be reserved to provide for the final vulcanized splice. Metal Plate Fasteners 1. Double Plate Bolted Fasteners Splices using double plate bolt fasteners are made with pairs of rigid metal plates bridging the joint on the top and bottom sides of the belt and fastened through the belt with bolts and nuts. The splice is prepared by punching or drilling bolt holes at the proper interval across the belt and distance from the belt ends. Proper spacing is best achieved by using metal templates sold by the manufacturer for each belt width and size of fastener. Fastener plates are also made with prongs which are forced into the belt as the nuts are tightened. For ordinary service, steel plates are used. Special stainless steel and alloy plates are available for use where increased resistance to corrosion, abrasion, anti-sparking, and nonmagnetic qualities are required. Templates and applicator tools are purchased from the fastener manufacturer according to the size of the fastener used. The fastener size is governed by the thickness of the belt and the diameter of the smallest pulley involved. For belt covers over 1/8 in (3 mm) thick, fastener plates should be countersunk below the surface of the cover by buffing off an appropriate amount of cover. This results in the most efficient anchoring of fasteners and permits the use of the smallest size fastener possible. Special countersinking equipment and advice are available from fastener manufacturers. For general use, the joint for a splice made with double plate fasteners is prepared squarely across the belt at 90° to the belt centerline. The joint may also be made on a 45° angle for smoother pulley contact. Plates applied on a 45° angle will operate over pulleys 25% smaller in diameter than those on a 90° splice. The number of fasteners required on a 45° angle joint is approximately a third more than on a 90° joint. In applying the fasteners on a 45° splice, the plates are installed at right angles to the joint. Tension on the belt thus tends to tighten the joint. 2. Drive-on Plate Fasteners Although drive-on plate fasteners are sometimes used to make belt splices, they are better for making quick, temporary repairs. They are fabricated with sharp teeth or rivets that are driven through the belt from the top surface on each side of the joint and clinched over on the bottom surface.


40


HINGED FASTENERS Hinged fasteners are attached to each belt end separately. The ends are then brought together and joined by inserting a flexible hinge pin, or spindle. Hinged fasteners are of the greatest value in conveyors which must be knocked down frequently or varied in length. Joined ends may be separated by releasing tension on the belt and removing the hinge pin. Hinged fasteners are widely used in extensible coal conveyors. They are not recommended for service involving rock or other service where abrasive fines are a factor because abrasive particles cause premature failure of hinge pins and fastener loops. It is also difficult to prevent the sifting of fines through a hinged fastener joint. a. Bolted Double Plate Hinged Fasteners These fasteners are attached to the belt in the same manner as double plate bolted fasteners, using templates and applicator tools sold by fastener manufacturers. b. Wire Hook Fasteners These fasteners are furnished in the form of wire hooks with ground points. The hooks are supplied mounted on cardboard “combs”. They must be applied to the belt with special crimping machines which are made by the fastener manufacturer. These fasteners come in various sizes and wire diameters for belt thicknesses ranging from approximately 1/16 in (2 mm) to 5/8 in (16 mm). c. Riveted Plate Hinged Fasteners These consist of formed metal plates which extend from the top belt surface, around the cut end, and onto the bottom surface. The plates are made with countersunk holes to allow passage of pointed rivets. Installation is accomplished by hammering rivets through the plates and belt and peening the rivet ends into the countersunk holes of the plates tightly onto the belt. A hinge pin is then inserted. d. Drive-on-Hinged Fasteners This type of fastener comes packaged in various lengths corresponding to common belt widths and in a range of sizes for belts 1/16 in (2 mm) to 5/8 in (16 mm) thick. The only tool needed for application is a hammer. The fastener is slipped over the end of the belt and anchored by driving the prongs or teeth through the belt. This type of fastener is widely used for package handling, post office belting, food processing, etc.

VULCANIZED CONVEYOR BELT SPLICES A vulcanized splice is stronger than a conventional joint made with fasteners. In addition, vulcanized splices have the following advantages over mechanical fasteners: 1. Longer service life. 2. Greater protection against penetration of the belt carcass by moisture and fines. 3. Uninterrupted surfaces which do not score pulleys or idlers. This is due to their being flush with the top and bottom covers. Vulcanized splices will operate smoothly under belt cleaners and other conveyor parts with close clearance, such as skirt boards and deflectors. 4. Elimination of the hazard of damage to the belt which can result from partial fastener failure in a mechanical joint which can break or wear out from abrasion. Bent or broken fasteners can damage the belt by snagging conveyor parts with close clearance and in passing over pulleys and idlers. 5. Avoidance of the problem of fines sifting through to decking or return run. 6. Greater length of service uninterrupted by mechanical splice failure in belts carrying hot materials. Localized conduction of heat by the metal fastener into the belt carcass around the metal fasteners can result in splice failure due to excessive heat degradation of the belt fabric.


41


SPLICE PROCEDURE OVERVIEW While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but not limited to, the following basic steps: 1. Determine the proper belt for the service intended. 2. Determine the belt’s intended direction of travel (DOT). Most cases the bottom fill / keyway leads in the direction of travel. Finger splices and flex steel splices will have the outside fingers or cords pointing opposite direction of belt travel. 3. Determine the belt length required for the installation with the take-up in its recommended position for the type of belt. 4. Cut the belt ends allowing enough length for the splice. 5. Prepared the belt ends to match into a smooth, efficient joint. 6. Uncured cement and compounds, specified by the belt manufacturer, are applied to the prepared ends. 7. Cure the entire splice in a portable press under heat and pressure. Storage of Hot Splicing Materials When unvulcanized splice materials are stored under unfavorable conditions their physical and/or chemical characteristics change. Eventually these changes will render the unvulcanized splice materials unsuitable for use. These effects result in changes in the curing behavior and/or in the cured physical properties of the splice materials. The harmful effects of these factors can be minimized by a careful choice of the following storage conditions. In case of doubt, consult the supplier of the conveyor belt splice material about the storage conditions. 1. Materials stored in non-refrigerated conditions will shorten shelf life. Materials stored in refrigerated conditions will increased shelf life Acceptable refrigerated storage temperature is at 55°F (12.8°C). Do not allow the materials to freeze. Allow refrigerated materials to warm before use to and allow condensation to disappear. 2. The relative humidity should preferably be below 60% for long-term storage. Damp conditions should be avoided since long-term exposure to moisture can influence the curing and crosslinking behavior of the materials. 3. Sunlight and artificial light which has a substantial content of ultraviolet light can adversely affect the stability of unvulcanized rubber. Depending on the grade and the time span of exposure, chain rupture and/or crosslinking may occur. In view of this, exposure to light should be restricted to a minimum. 4. Where possible, unvulcanized rubber should be protected from excessive air circulation and should not be stored near electrical equipment (motors) that could be a source of ozone. For this reason it is advisable to keep the splice material boxes closed and sealed. 5. Unvulcanized rubber should be stored in an area which meets the usual standards of cleanliness, even though the rolls are individually wrapped in polyethylene sheeting. Avoided direct contact with foreign materials of any kind. It is recommended that the material be kept in its original packaging until the moment it is used. 6. Splice materials should not be stored for any longer than the specified shelf life. It is therefore recommended that the FIFO (first in - first out) stock rotation system be used.


42


Tools and Equipment (Fabric Belt) Instructions for the proper use of splicing tools may be part of a designed splice training program. Safety Glasses Work Gloves Tape Measure Angle Square Plumb Line White Marking Pencil or Soft Crayon Claw Hammer Duplex Nails Smooth Face Roller - 2 x 2 in Corrugated Face Stitcher - 1/8 x 2 in Needle Face Roller - 2 x 2 in Electric Stripping Cable Winch Stainless Steel Stripping Frame or Grip Tongs Wetstone Hand Dust Brush Rotary Wire Brush & Buffer

Pincers Ply Lifter Offset Knife Rubber Knife - 6 in Long Bevel Point Knife - 4 x 1 in Curve V-Trim Knife - 2 1/4 x 3/4 in Mill Knife Single Ply Knife (cutting depth matching the fabric gauge) Heavy Duty Scissors Belt Clamps Come-a-longs H.D. C-Clamps Screw Clamps Edge Bars (1/16 in thinner than belt) Fabric Belt Vulcanizing Press Electric Handheld Thermometers with Leads

SPLICING CONDITIONS Work Place The quality and durability of a hot splice begins with a clean work place. The careful use and application of the splicing products are essential. Follow the approved safety practices for the locale in which the service is being conducted. Conveyor Belt The belt ends to be spliced must be dry and clean to ensure a reliable splice. If necessary, dry the belt using the pre-heated lower part of the vulcanizing press, before any further preparation work. Ambient Conditions The influence of humidity, e.g. formation of condensation water (due to temperature falling below the dew point), must be absolutely avoided. Avoid loss of heat due to wind. Extreme cold may have a negative affect on splicing materials. During extreme cold conditions a splicing tent with heating devices may be needed. 1. Set-up a tent to protect the working area against adverse ambient conditions (sunshine, cold, rain, wind, dust). 2. It is possible to warm-up the splice area of the belt using the pre-heated lower part of the vulcanizing press. Do not to allow the temperature to rise above 150°F (66°C) Use of Thermocouples with Leads Vulcanizing press temperatures should be verified with thermocouples allowing a minimum of one lead per heating zone (top and bottom platens). Thermocouples allow the control of the cure temperature during the cure cycle. Documentation During the splicing operation all irregularities and special conditions have to be recorded. During the actual cure cycle the curing temperature of each thermocouple and the curing pressure must be recorded at defined intervals. The heat-up and cool-down of the vulcanizing press is also recorded.


43


GENERAL PREPARATION Center Lining the Belt Ends On both belt ends establish and mark 1. the belt center line; 2. the perpendicular square line; 3. the belt cover transition lines. Establish and mark the centerline of the belt by measuring across the width of the belt at three points in length of each belt end at a distance of approximately 12 in (304 mm). At least three center markings on each belt end must be outside the splice area. The establishment of the centerline is easiest when done with two rulers. The three center markings on each belt end are then connected by means of a chalk line which represents the belt centerline or by holding stationary the measuring tape at 0 in on one belt edge while sliding the tape on the opposite belt edge until an easily divided number is aligned with the belt edge. This centerline ensures exact alignment of the belt ends, which is indispensable for straight belt running. The centerline outside the splice area must be durable enough to remain evident throughout the entire splicing operation. Destroyed or missing belt edges must be considered. The width of the belt edge is established by measuring the width of the belt at suitable areas of the undamaged belt ends. Figure 7-1. Establishment of the Centerline (Step 1)

Establish a perpendicular square line across the upper belt end at the end of the splice area. On narrow belts this can be done by placing a metal square onto the center line. On wide belts it is recommended to establish the square lines as follows: Near the end of the splice area select a point A on the center line. Mark points B and C on the center line equidistant to point A (AB=AC).

Figure 7-2. Establishment of the Centerline (Step 2)

Now describe a circle with the same radius around points B and C by means of a plumb line and a pen. The points of intersection of both circles must still be on the belt. These intersections are points D and E.

A line drawn between these two points will be perpendicular to the belt edges and forms the square line, which should pass point A for additional control. This square line will be the starting point from which the splice will be laid out. Figure 7-3.


44


FABRIC BELT SPLICING PROCEDURES Conveyor belt splices should be performed by only trained and qualified personnel. This is extremely important when splicing is done on the actual conveyor system. The splice is prepared on the bottom platen of the vulcanizer with two tables on each end. The two tables are to be the same height as the bottom plate of the vulcanizer. Position the belt ends to be spliced on the bottom platen with the tables at each end supporting the belt ends in place. Be certain the conveyor belt lays even and straight without tension. The belt ends have to be aligned in the direction of the conveyor belt in such a way that they overlap each other on the lower part of the vulcanizing press and that the belt center lines are exactly superimposed. A 22 degree bias cut (0.4 x belt width) will favorably influence the durability of a splice. Most splices require the bottom fill/key way to lead in the belt’s intended direction of travel. For descending conveyors that require restraint, the top fill /keyway may lead in the belt’s intended direction of travel. Dimensions of Fabric Hot Splices Multi-ply belts may be joined with a diagonal stepped splice. To make this splice both belt ends are cut to form a matching series of steps that permit each ply in one end to be aligned to the corresponding ply in the other end.

Step Lengths The recommended step lengths vary for different types of fabric and among manufacturers. The manufacturer will provide the specified step and overall splice length. For precise splicing procedures contact the belt manufacturer for accurate specified splice training. Use only the tools required. When cutting the covers and or ply joints/seams, do not damage “nick or cut” the adjacent plies. The following procedure does not represent all manufacturers preferred splicing techniques.

Preparation of the lower part of the belt Fold back the upper part of the belt.

Step 1: Make a bias cut on the lower belt part. Fold back the lower part of the belt and draw a line parallel to the bias cut on the pulley side at the belt end. Also mark the belt rubber edges to be preserved.

Figure 7-4. Step 1


45


Step 2: Cut the rubber cover with a dull and rounded tip Mill Knife held at an angle (of approximately 45°), without damaging the top fabric ply.

Step 3: Using pincers, strip the rubber cover (thus preparing the future joint gap). Fold back the lower part of the belt again and mark the splice length (according to the chart), step length. Cut the rubber cover along this line with a dull tipped Mill Knife held at an angle of approximately 45°. Avoid damaging fabric plies!

Figure 7-7. Step 4 Steps 4 & 5 (See Figure 7-7 and 7-8): Remove the rubber cover strip and detach this ply using a ply lifter. Strip the upper ply and rubber cover using the grip tongs. Mark the subsequent fabric plies according to the step length. Cut them and detach these plies using a ply lifter and strip them off using grip tongs. The last fabric ply has to be retained.

Figure 7-8. Step 5

Preparation of the upper part of the belt Superimpose the belt ends ensuring correct alignment. Secure both parts against dislocation (e.g. with clamps). Exactly transfer the cut edge of the top fabric ply of the lower part to the upper part. Transfer the subsequent fabric steps of the lower part to the upper part (make the marks with a marking crayon on both edges of the belt).


46


Cut off the excess length of the upper part put on the lower part. Draw a line on the carrying side from the cut. Cut the rubber cover along the line with a Mill knife held at an angle of 45°, without damaging the top fabric ply. Strip off the rubber cover with pincers (thus preparing the joint gap). Fold back the upper part of the belt, secure it and prepare the pulley side just as the carrying side of the lower part. (Step the fabric plies)

Dry Fit of Splice Ends (See Figure 7-10) Superimpose the two belt ends. Check if the joints and fabric steps match exactly. Rectify, if necessary. Make sure that the edges of the two belt ends are correctly aligned.

Figure 7-10. Dry Fit of Splice Ends

Joining of the splice Carefully buff the cut edges of the rubber covers and the surface of the rubber edges with a buffing tool (e.g. a rotating wire brush). Buff the intermediate rubber and remove any un-even spots. When buffing, do not scorch or smear the rubber nor leave shiny spots on it. Round the edges of the fabric steps, without damaging the fabric (e.g. protect it with a thin tin plate). Carefully remove the buffing dust with a dry brush. Thoroughly stir the required quantity of splicing cement before use. Attention: The splicing cement should remain covered until use and then recovered to reduce thickening.

Step 1 (See Figure 7-11): Apply one even coat of the splicing cement to the whole splicing area and the joint gaps of both belt ends. Use a brush with short bristles. Let the splicing cement dry until it is just a little sticky (check with the back of your finger). Note: The drying time will be shorter, if the conveyor belt is warmed up by the means of the preheated lower part of the vulcanizing press.

Figure 7-11. Step 1


47


Step 2 (See Figure 7-12): Cover the fabric steps of the lower belt part with uncured tie gum rubber. Stitch the rubber to avoid air entrapment. Cut the tie gum rubber flush with the belt edge. Remove the protective foil. Step 3: Cover the belt edges and fabric steps with an approximately wide strip of uncured tie gum rubber.

Figure 7-12. Step 2

Step 4: For the joint gap on the pulley side cut to size an exactly fitting filler strip consisting of a strip of uncured tie gum rubber, breaker fabric and uncured cover rubber. The applied filler strip must be slightly thicker than the rubber cover of the belt.

Step 5 (See Figure 7-15): Superimpose the upper and lower belt ends, aligning them exactly using the center line of each belt and avoiding air entrapment. The splicing areas have to match exactly.

Figure 7-13. Step 3

Do overlap fabric steps which are on the same level. Stitch or roll the whole splicing area from the center outwards.

Step 6 (See Figure 7-16): Apply one strip of uncured tie gum rubber and breaker fabric to the joint gap on the carrying side, then fill the gap with uncured cover rubber and tightly stitch together. Trim excess filling flush with the belt surface using an offset knife. Apply a strip of uncured rubber cover to the filled joint gap. Stitch thoroughly and cover both joints with release paper.

Figure 7-15. Step 5

Vulcanizing the splice Apply steel or aluminum edge bars to either belt edge and press them against the edges of the splice, using tightening clamps mounted outside of the area of the vulcanizing press. Note: The edge bars are to be approximately 0.060 in (1.5 mm) thinner than the belt.

Figure 7-16. Step 6


48


Figure 7-17. Splice Preparation for Vulcanization Cover the whole splicing area with Release Paper. Level out uneven surface areas using as many layers of Pressure Compensation Cloth (Artificial Silk) as needed, especially if areas of the belt cover is worn. Apply and position the upper heating platens. Position the upper cross arms, making sure that the two extreme cross arms are located outside of the splicing area. The heating platens have to cover an area which is on either side at least 4 in (100 mm) longer than the splice length and at least 2 in (50 mm) wider than the belt width. Secure the upper and lower cross arms and generate pressure and heat according to the operating instructions of the vulcanizing press: After the curing cycle, switch off the curing system (unplug the press to cut off the power supply). Let the conveyor belt cool down under pressure to a temperature specified by the belt manufacturer. Water-cooling can also speed up the cool down process. Release pressure only after the press has cooled to the specified cool down temperature. Then unlock the cross arms. Remove the upper cross arms, heating platens and Compensation Cloth and/or Release Paper. Detach the edge bars and remove them. * Note: Cure temperature must be verified during the curing cycle (i.e. heat-up, cure, cool-down). ** Note: The curing time begins when each thermocouple achieves the specified curing temperature. Final Measures 1. Check for correct vulcanization. React and note any abnormalities found while examining the finished splice. 2. Remove material overflow (with knife, buffing tool) and cut even the belt edges. 3. Identify the splice according to the DIN 22102 Part 1: a. Date of splicing (month/year) b. Splice company identification c. ID abbreviation of vulcanizing machine d. Number of the splice 4. The conveyor belt can be put back into operation, after the splice has cooled down to ambient temperature. 5. Complete the splice report.

ELEVATOR TEXTILE BELT SPLICES Operating conditions peculiar to elevator belts make joint requirements slightly different than those for conveyor belts. Elevator belts can operate with joints that are not flush, and on the bucket side they need not even be flat. Because the take-up in elevator belts is usually shorter than is necessary for conveyor belts, there may be a need for more frequent shortening and re-splicing of the belt than is necessary for conveyor belts. For elevator belt installations it is therefore desirable to use a relatively simple joint that can be made in a confined space.


49


Types of Joints 1. Lap Joints Lap joints are one of the two most frequently used elevator belt joints. They are not generally recommended for belts having more than about six or seven plies of fabric because of their tendency to pound on the pulley. The belt ends are lapped over each other and secured usually with elevator bucket bolts. The length of the overlap must be at least equal to the belt width or two bucket spacings, whichever is greater. In attaching the buckets on the lap, the bucket projection is increased by the extra thickness of belt. It is recommended that buckets with lesser projection be used in the lap area so that the projection is the same all along the belt. The direction of the lap is usually with the leading edge of the joint on the bucket side. The cut end of the belt on the pulley side will, thus, trail over the pulleys rather than run against them. The ends of the laps should be cut off as closely as possible to the last row of bolts to minimize collecting material in the joint. 2. Butt Strap Joints This type of joint is the other most frequently used joint. It is generally recommended for thick belts. The ends of the belt are butted together. A separate piece of belting of sufficient strength and flexibility and as wide as the elevator belt is bolted over the butted joint on the bucket side. This separate piece of belt is the “strap”. The length of the strap should be sufficient to extend under at least two buckets on each side of the joint. It may be necessary to omit a bucket at the joint to make room for a double row of bolts through the strap where the ends of the belt meet. As in the case of the lap joint, buckets on the strap should have decreased projection equal to the thickness of the strap. Thus the strap of course should be on the outside of the belt rounding the pulley. 3. Conventional Belt Fasteners Conventional belt fasteners may be used for elevator belts to provide a smooth joint, but they are not recommended where the belt is stressed beyond 50% of its rating. 4. Vulcanized Splices Vulcanized splices in elevator belts offer the same advantages as in conveyor belts. They are recommended for large, highly stressed belts where adequate take-up and access to the belt exists. 5. Oil Well Splices This type of splice is illustrated in the sketch in Figure 7-17. The clamps used to bolt the belt ends come in a variety of shapes and designs, but in all cases the belt ends are bent 90° on a relatively short radius.



50


CHAPTER 8

STEEL CORD BELT TYPES AND MANUFACTURING METHODS

INTRODUCTION This chapter describes steel cord belting with references to its major components of steel cord, cover rubber, inside rubber and if specified a breaker. This will be followed by a description of belt cover compounds, steel cord belt manufacturing methods, and special considerations in field applications.

BELT CARCASS Purpose The belt carcass primarily provides resistance to tension forces that build up in the conveyor system from frictional resistance and vertical changes in loading. Also it provides the strength to resist belt tearing and impact damage and still allow flexibility for load support. Splicing is a critical part of the carcass design and will be discussed separately. Steel Cord Carcass (see Figure 8-1.) The steel cord carcass is made up of three major components: top cover, insulation gum, steel cord bottom cover and in some cases a breaker in one or both covers. The belt strength or rating is determined by the cord diameter and pitch. The top and bottom covers protects the steel cords, the insulation gum penetrates and adheres to the steel cords which then provide corrosion resistance. Top Cover Insulation Gum

Steel Cord Bottom Cover Figure 8-1. Steel Cord Belt Components

BELT EDGE PROTECTION - MOLDED EDGES Molded (Capped) Edge Belting All steel cord belts have molded edges which are necessary to protect the steel cords against corrosion and damage from rubbing contact against the conveyor structure. Cut/Slit Edge Belting Steel cord belts are manufactured to width and unlike fabric belts are not slit to narrower widths widths. If a steel cord belt were manufactured in a wide width and slit into narrow widths, the belt would have a tracking issue with each belt section tending to run toward opposite edges of the conveyor system.

CARCASS PROTECTION Breaker Depending on the application and customer desire, some steel cord belts are specified with a breaker in the top and/or pulley cover. The breaker aids in abuse resistance by reducing the impact, slitting and gouging of the covers and also offers some limited protection to the cords.


51


BELT MANUFACTURING METHODS Belt Covers The elastomeric covering on belts is there to provide protection for the carcass, and/or provide a specific property. These coverings are applied by several processes, depending on the material or thickness of the covering. The belt insulation compound is calendered or extruded to the correct width and gauge and laminated onto the cover which has been previously produced in the same manner. The lamination rolls for both the top and bottom covers are then forwarded to the belt building operation. Steel Cords The carcasses of steel cord belts are most often composed of galvanized plated steel cords uniformily spaced across the belt width. Although other constructions are available for special applications, most manufacturers typically use a 7 x 7 or 7 x 19 construction for the best combination of strength vs flexibility. Belt Building The total number of cords required for the belt width are threaded from spools containing long lengths of cord through a device that controls cord tension. The cords then travel through sizing combs to control the cord pitch. The rubber covers are then cold compacted onto the previously tensioned cords with time and pressure. Belt Covers with Breakers Depending on the applications, some customers may specify a breaker be placed within the top cover and/or bottom cover for added protection against the abuse of impact, cover cutting and gouging. Below details the fabric process. Textile Fabric Treatment Generally, most multi-filament textiles (nylon, polyester, etc.) require an RFL treatment to ensure adequate adhesion in service. RFL is an industry term designating a treatment mixture of resorcinol formaldehyde latex (RFL), whereby the woven textile is dipped in the emulsion and dried under specific temperature and tension conditions. This process is used for most rubber based belting (NR, SBR, NBR, CR, EPDM, etc.) Release Coating Before entering the curing press, a light coat of release agent is applied to both surfaces of the belt. This is done to prevent the unvulcanized belt from sticking to the press surface after cure and is generally applied as a dust, liquid for fiber. Before release coating and before curing, the cover is usually perforated with fine pricker needles to help release gases that may be present within the body of the belt. These holes are completely sealed during the vulcanization operation. Curing The belt is vulcanized in a flat platen press (index cure) with a temperature in the range of 280-320°F (140-160°C) while under pressure. Edge irons are set at the desired belt width to retain and/or mold the rubber covered edges. Since it is essential that a small excess of material be present to create proper pressure during cure, a small overflow of cover occurs at the side retaining irons. This flashing or rind is removed by trimming or buffing as the cured belt exits the press and is inspected in preparation for packaging. Samples from both ends of the belt are cut and tested in the QA laboratory prior to releasing the belt for shipment. Branding of the belt with the manufacturer’s name, grade or type of belt, and date of manufacture is generally accomplished by placing a metal stencil on the uncured belt at regular intervals. This produces an embossed label cured onto the surface.


52


CHAPTER 9

STEEL CORD BELT CHARACTERISTICS & BELT RATINGS INTRODUCTION

The tension rating for a belt is the recommended maximum safe working stress that can be applied to the belt. Belt tension is commonly referred to as the force applied to the belt per unit of belt width, such as Pounds per Inch width (PIW), or Kilo Newtons per Meter width (kN/m). There is variation among manufacturers about the information in the following paragraphs that relates to certain system design items such as the minimum pulley diameter, troughability, and maximum safe belt working stress to mention a few because of differences in materials and manufacturing methods. As a direct result other belt parameters are effected such as the number of cords in a belt, belt weight, minimum pulley diameter, troughability, belt modulus, transition distance, impact resistance, etc. Thus, it is essential to confer with the belt manufacturer about the belt proposed for each application.

CONVEYOR BELT AND SYSTEM TENSION CALCULATIONS Conveyor systems will take on a variety of configurations relative to drive location, elevation or descent of the load, idler and pulley type and condition, and other factors too numerous to detail in this handbook. belt manufacturers or conveyor engineering companies should be consulted for belt (system) recommendations. The Conveyor Equipment Manufacturers Association (CEMA) provides a Handbook for in-depth system analysis and tension calculations. ISO 5048 and DIN 22101 also provide detailed methods for system tension calculations. The tables below provide an example of the basic information on steel cord reinforced belt tension ratings. This information is for illustrative purposes only. Information on a specific belt construction can be provided by the belt manufacturer. The data in the following tables apply if the following service conditions are met: Vulcanized Splice 1. Pulley diameters recommended by the belt manufacturer are used. 2. Automatic take-up with adequate take-up travel. 3. Splices are made strictly in accordance with the belt manufacturer’s specifications. Where an adverse environmental condition or some special belt application exists, it is critical that the belt tension rating be reviewed with the belt manufacturer. Some of the special conditions are: 1. Continuous excessive ambient temperature. 2. Exposure to deleterious chemicals. 3. Reduced safety factors. Table 9-1. Steel Cord Belt Standard Specifications Belt Tension Minimum Ultimate Tension Rating

ST800 ST1000 ST1250 ST1600 ST2000 ST2500 ST3150 ST3500 ST4000 ST4500 ST5000 ST5400

PIW 4568 5710 7138 9136 11420 14275 17987 19985 22840 25695 28550 30835

kN/m 800 1000 1250 1600 2000 2500 3150 3500 4000 4500 5000 5400

Operating Tension

PIW 686 856 1070 1370 1712 2140 2697 2996 3424 3852 4280 4623

kN/m 120 150 187 240 300 375 472 525 600 675 750 810

Cord Diameter (Nominal)

in 0.142 0.142 0.205 0.205 0.205 0.205 0.315 0.315 0.362 0.394 0.433 0.433

mm 3.61 3.61 5.21 5.21 5.21 5.21 8.00 8.00 9.19 10.01 11.00 11.00

Cord Pitch (Approximate)

in 0.688 0.547 0.855 0.666 0.533 0.450 0.768 0.690 0.792 0.805 1.098 1.023

mm 17.48 13.89 21.72 16.92 13.54 11.43 19.51 17.53 20.12 20.45 27.89 25.98

Belt Modulus

PIW 329000 411000 514000 657000 822000 1030000 1290000 1440000 1640000 1850000 2050000 2220000

kN/m 57617 71977 90015 115058 143954 180381 225914 252183 287208 323985 359010 388782

Tension ratings are available in addition to those shown above. Other cord diameters may be substituted according to individual requirements. Operating tensions are based on a 6.676:1 safety factor. Cord pitch based on 48 in belt. IP:1 2011 Conveyor and Elevator Belt Handbook

53


Table 9-2. Steel Cord Belt Thickness

Table 9-3. Steel Cord Belt Weight

Table 9-4. Cover Compound

ARPM 1

ARPM 2

Cover Weight per 1/32 in (lb/ft2)

0.18

0.19

Approximate Belt Weight = Carcass Weight + Cover Weight Minimum pulley cover requirement 5/32 in Table 9-5. Steel Cord Belt Standard Classifications

Snubs are defined as having 6 in or less belt contact and tension less than 50% of belt rating. Pulley sizes for belts are determined by face pressure on the pulley and/or the pulley-to-cord diamteter ratio. All pulleys must be flat as crowned pulleys will cause excessive center tension in the high modulus steel cord product. Contact belt manufacturer for belt tensions higher than 4623 PIW.


54


Table 9-6. Recommended Transition Distances, Minimum Transition Distance: One-Half Trough Depth Idler

% of Rated

Transition Length W = Belt Width

20

More than 90

60 to 90

Less than 60

2.0W

1.6W

1.0W

35

More than 90

60 to 90

Less than 60

3.4W

2.6W

1.8W

45

More than 90

60 to 90

Less than 60

4.0W

3.2W

2.2W

Table 9-7. Recommended Transition Distances, Minimum Transition Distance: Full Trough Depth Idler

% of Rated

Transition Length W = Belt Width

20

More than 90

60 to 90

Less than 60

4.0W

3.2W

2.8W

35

More than 90

60 to 90

Less than 60

6.8W

5.2W

3.6W

45

More than 90

60 to 90

Less than 60

8.0W

6.4W

4.4W

Belt operating tension is not the only belt characteristic to be considered when selecting a belt design for an application. Other important items exist, that effect how the belt will perform on a given system. The importance of these characteristics are presented below.

ELONGATION Most new conveyor belts will exhibit permanent stretch very early in their service life, as a result of the normal cyclic tensile forces exerted by the conveyor system on the belt. This length change will vary among belt constructions, but it is generally much less than one percent of the original relaxed length of the belt. The conveyor take-up system must compensate for this length change as well as the normal belt elongations which are proportional to belt tensions in the elastic region of the stress strain curve. The initial take-up position is that which the take-up finds after the clamps have been removed and the belt run empty a few belt revolutions to produce a natural tension distribution. Table 9-8. Recommended Initial Take-Up Position Belt Type

Percent available for length increase

Percent available for length decrease

Steel cord

1/4

Splice length



55


CHAPTER 10

STEEL CORD BELT TOLERANCES INTRODUCTION

Information in this chapter is referenced from ISO 15236-1, 15236-2, 15236-3, and 15236-4.

BELT THICKNESS The belt thickness (s 1) is obtained by adding the actual cable diameter and the top cover and pulley cover thicknesses. The thickness tolerances are shown in Table 10-1. Table 10-1. Belt Thickness Tolerances Belt Total Thickness

Tolerance

15 mm

± 10%

≥ 15 mm

+ 10%, - 5%

In both cases, the thickness cannot be - 1.5 mm from the dimension of S 1.

BELT WIDTH The width tolerances listed in Table 10-2 are the commercially accepted standards of the conveyor belt manufacturing industry. Tighter tolerances may be specified by agreement between the individual manufacturer and his customer. Table 10-2. Belt Width Tolerances Type of Belt

Unit

500

630

800 1000 1250 1400 1600 1800 2000 2250 2500 2800 3150 3500

4000 4500 5000 5400

Min. breaking strength KNmin.

N / mm

500

630

800 1000 1250 1400 1600 1800 2000 2250 2500 2800 3150 3500

4000 4500 5000 5400

Max. cord diameter dmax.

mm

3.0

3.0

3.7

Min. breaking load of the cord Fbsmin.

kN

7.6

7.6

10.3 12.9 18.4 20.6 26.2 25.5 25.5 26.2 39.7 39.7 50.0 55.5

63.5 75.0 90.3 96.0

4.2

4.9

5.0

5.6

5.6

5.6

5.6

7.2

7.2

8.1

8.6

8.9

9.7

10.9 11.3

Cord pitch t

mm

14.0 11.0 12.0 12.0 14.0 14.0 15.0 13.5 12.0 11.0 15.0 13.5 15.0 15.0

15.0 16.0 17.0 17.0

Min. thickness of covers smin.

mm

4.0

6.5

Belt width, B in mm

Tolerance in mm

500

+10 / -5

33

42

39

39

34

34

31

650

+10 / -7

44

54

51

51

45

45

41

46

52

56

41

46

41

41

41

39

36

N/A

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

5.0

5.0

5.5

6.0

7.0

7.5

8.0

Number of cords n N/A N/A N/A N/A N/A N/A N/A

N/A N/A N/A N/A

800

+10 / -8

54

68

64

63

55

55

50

57

64

69

51

57

51

51

51

48

45

45

1000

±10

68

84

80

80

68

68

63

71

80

86

63

71

63

64

63

60

56

57

1200

±10

86

110

97

97

82

82

76

85

96

104

76

85

76

76

76

72

67

68

1400

±12

96

124

114

113

97

97

90

100

112

122

89

99

89

89

89

84

79

79

1600

±12

111

142

130

130

111

111

103

114

129

140

102

114

102

102

102

96

90

90

1800

±14

125

160

147

147

125

125

116

129

145

159

116

128

116

116

116

108

102

102

2000

±14

139

177

164

163

140

139

130

144

162

177

129

143

129

129

129

121

114

114

2200

±15

153

195

180

180

154

154

143

159

179

195

142

158

142

142

142

133

126

126

2400

±15

167

213

197

197

168

168

156

174

195

213

156

173

156

156

156

146

137

137

2600

±15

181

231

214

213

182

182

170

189

212

231

169

188

169

169

169

158

149

149

2800

±15

196

249

230

230

197

197

183

203

229

249

182

202

182

182

182

171

161

161

3000

±15

210

267

247

247

211

211

196

218

245

268

196

217

196

196

196

183

173

173

3200

±15

224

286

264

263

225

225

210

233

262

286

209

232

209

209

209

196

184

184

N/A = Not applicable because of troughability


56


Zero Plus or Zero Minus Tolerances If a customer specifies a zero plus or a zero minus tolerance, the full tolerance still applies to the belt. For instance, if a customer requests a 2000 mm wide belt with a minus zero tolerance, the tolerance will read 2000 mm + 28, - 0. This method of tolerancing is being used for clarity and simplicity and takes no stand on pricing of belt based on plus tolerances.

BELT LENGTH Tolerances on Lengths The permissible tolerances for the lengths of conveyor belts, measured loose, are given in Table 10-3. Table 10-3. Belt Length Tolerances

Belt Delivery Condition

Tolerance (maximum permissible difference between delivered and ordered lengths)

For a belt delivered in one complete length

+ 2.5%, 0%

For belt delivered in several lengths

± 5% for each single length, subject to an overall tolerance for the sum of all lengths of + 2.5%, 0%

Note: The lengths of conveyor belts are not standardized.

BELT EDGE The edge width may not be smaller than 15 mm.


57


CHAPTER 11

STEEL CORD BELT TEST METHODS TEST METHODS

Below are the list of the tests against various standards. ASTM International ASTM D 257

Standard Test Methods for DC Resistance or Conductance of Insulating Materials

ASTM D 378

Standard Test Methods for Rubber Elastomeric Belting, Flat Type Included are tests for: Measurements of Dimensions Physical Properties of Elastomeric Covers Immersion Tests Adhesion Tests Breaking Strength and Modulus Testing Flame Test for Belting Carcass Tear Test Troughability Test Breaking Strength of Mechanical Fastenings (Static Test Method) Elevator Belt Bolt Holding Strength Test

ASTM D 430

Standard Test Methods for Rubber Deterioration - Dynamic Fatigue

ASTM D 2228 Standard Test Method for Rubber Property - Relative Abrasion by Pico Abrader Method ASTM International standards can be obtained at www.astm.org. Canadian Standards Association CAN/CSA-M422-M87 -- Fire Performance and Antistatic Requirements for Conveyor Belting CSA standards can be obtained at www.csa.ca. International Organization for Standardization (ISO) ISO 34-1 pieces

Rubber, vulcanized or thermoplastic -- Determination of tear strength -- Part 1: Trouser, angle and crescent test

ISO 252

Conveyor belts -- Adhesion between constitutive elements -- Test methods

ISO 282

Conveyor belts -- Sampling

ISO 284

Conveyor belts -- Electrical conductivity -- Specification and test method

ISO 340

Conveyor belts -- Laboratory scale flammability characteristics -- Requirements and test method

ISO 433

Conveyor belts -- Marking

ISO 433

Conveyor belts -- Marking (Amd 1)

ISO 703

Conveyor belts -- Transverse flexibility (troughability) -- Test method

ISO 1120

Conveyor belts -- Determination of strength of mechanical fastenings -- Static test method

ISO 1183-1

Plastics -- Methods for determining the density of non-cellular plastics -- Part 1: Immersion method, liquid pyknometer method and titration method

ISO 1537

Continuous mechanical handling equipment for loose bulk materials -- Troughed belt conveyors (other than portable conveyors) -- Idlers

ISO 3684

Conveyor belts -- Determination of minimum pulley diameters

ISO 3684

Conveyor belts -- Determination of minimum pulley diameters (Amd 1)


58


ISO 4195

Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods

ISO 4195

Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods (Cor 1)

ISO 4649

Rubber, vulcanized or thermoplastic -- Determination of abrasion resistance using a rotating cylindrical drum device

ISO 5284

Conveyor belts -- List of equivalent terms

ISO 5284

Conveyor belts -- List of equivalent terms (Cor 1)

ISO 5285

Conveyor belts -- Guidelines for storage and handling

ISO 5293

Conveyor belts -- Determination of minimum transition distance on three idler rollers

ISO 5293

Conveyor belts -- Determination of minimum transition distance on three idler rollers (Cor 1)

ISO 7590

Steel cord conveyor belts -- Methods for the determination of total thickness and cover thickness

ISO 7622-1

Steel cord conveyor belts -- Longitudinal traction test -- Part 1: Measurement of elongation

ISO 7622-2

Steel cord conveyor belts -- Longitudinal traction test -- Part 2: Measurement of tensile strength

ISO 7623

Steel cord conveyor belts -- Cord-to-coating bond test -- Initial test and after thermal treatment

ISO 8094

Steel cord conveyor belts -- Adhesion strength test of the cover to the core layer

ISO 9856

Conveyor belts -- Determination of elastic and permanent elongation and calculation of elastic modulus

ISO 10247

Conveyor belts -- Characteristics of covers -- Classification

ISO 10247

Conveyor belts -- Characteristics of covers -- Classification (Amd 1)

ISO/TR 10357

Conveyor belts -- Formula for transition distance on three equal length idler rollers (new method)

ISO 15236-1

Steel cord conveyor belts -- Part 1: Design, dimensions and mechanical requirements for conveyor belts for general use

ISO 15236-2

Steel cord conveyor belts -- Part 2: Preferred belt types

ISO 15236-3

Steel cord conveyor belts -- Part 3: Special safety requirementsfor belts for usein underground installations

ISO 15236-4

Steel cord conveyor belts -- Part 4: Vulcanized belt joints

ISO 18573

Conveyor belts -- Test atmospheres and conditioning periods

ISO Standards can be obtained at www.ansi.org.

German DIN Specifications Many DIN specifications are used internationally and most are available in English. DIN EN 12385-2 Steel wire ropes -- Safety -- Part 2: Definitions, designation and classification DIN EN 13827

Steel cord conveyor belts -- Determination of the Lateral and Vertical Displacement of Steel Cords

DIN EN 20284

Electrical conductivity of conveyor belts -- Specification and method of test

DIN 22101

Continuous conveyors - Belt conveyors for loose bulk materials - Basis for calculation and dimensioning

DIN 22131 P1

Steel cord conveyor belts for hoisting and conveying; dimensions, requirements

DIN 22131 P2

Steel cord conveyor belts for hoisting and conveying; marking

DIN 22131 P3

Steel cord conveyor belts for hoisting and conveying; testing

DIN 22131 P4

Steel cord conveyor belts for hoisting and conveying; belt joints; dimensions; requirements

DIN EN 28094

Steel cord conveyor belts -- Adhesion strength test of the cover to the core layer

DIN 53504

Testing of rubber -- Determination of tensile strength at break, tensile stress at yield, elongation at break and stress values in a tensile test


59


DIN 53505

Shore A and Shore D hardness testing of rubber

DIN 53509 P1

Determination of resistance of rubber to ozone cracking under static strain

DIN 53509 P2 DIN 53515

Testing of rubber -- Determination of resistance to ozone cracking -- Part 2: Reference method for determining ozone concentration in laboratory test chambers Determination of tear strength of rubber, elastomers and plastic film using graves angle test piece with nick

DIN 53516

Testing of rubber, elastomers; Determination of abrasion resistance

DIN standards can be obtained at www.din.ne, or through ANSI at www.ansi.org. Australian (AS) Specifications AS 1333

Conveyor belting of elastomeric and steel cord construction AS standards can be obtained at www.standards.org.au.


60


CHAPTER 12 - Part A

SPLICING FABRIC CORD CONVEYOR BELTS

INTRODUCTION This chapter is a brief summary for splicing Fabric Reinforced Belting. Belt users and/or splicing companies should consult the belt’s manufacturer for more specific detailed splicing information and/or belt splice training. THE FABRIC REINFORCED CONVEYOR BELT: The conveyor belt and conveyor structure are typically matched to ensure the expected operating conditions and tensions do not exceed the belt’s limitations. The conveyor belt type and manufacturer must be known to accurately select the specified splice design, the specified cure data and splicing materials. Contact the belt’s manufacturer with any questions or concerns. FABRIC REINFORCED CONVEYOR BELT SPLICES Vulcanized and/or Mechanical splices are typically used to join fabric belts. The fabric belts are generally designed with a 10:1 safety factor. It is considered impossible to maintain the same safety factor in the splice area. However vulcanized splices are designed Table 12:1

Maximum Tensile Strength kn N/mm

630 to 3150 200 to 2000 315 to 3150 800 to 3150 800 to 1600 1000 to 5400 <100 - >5400

Splice design According to:

Relative Reference Fatigue Strength:

DIN 22102-3 Finger Splice DIN 22102-3 With intermediate tension carrier DIN 22102-3 Stepped Splice DIN 22121 DIN 22121 With intermediate tension carrier (B) DIN 22129-4 Based On DIN 22129-4

0.35 0.35 0.30 0.35 0.30 0.45 0.45

Currently, the mechanical splices provide an approximate 4:1 safety factor as advertised. and tested to exceed the typical running tensions of the belts. DIN 22101 – 2002 – 08 Specifies the following: The values for textile belt are reference values, most of which are derived from proven use in practice. When determining the minimum tensile strength of a belt, the reference fatigue strength actually demonstrated for a particular belt type and a particular splice implementation can always be used. FABRIC REINFORCED CONVEYOR BELT SPLICE TESTING: SPLICE EFFICIENCY: Splice efficiency can be measured in two ways, (1) Static, (2) Dynamic. Static Splice Efficiency Defined as the measured force required to break a splice expressed as a percentage of the theoretical breaking strength of the belt. In addition to the peak force, the time for the splice to separate is sometimes also recorded. This is typically performed either by clamping each belt end on either side of a splice in a suitable fixture and measuring the force to pull the splice apart, or by making an endless belt loop with a single splice then measuring the force to pull the loop apart using a suitable fixture. Dynamic Splice Efficiency Defined in DIN 22110 Part 2 for fabric belt splices For fabric belt splices, the DIN standard describes a 6-pulley, constant speed test machine where an endless length of belt with one or more splices and/or fastener joints is subject to a constant tension (commonly expressed as a percentage of the nominal breaking strength of the belt). The splice is subject to multiple bend reversals on each cycle which accelerates its failure on the test. The DIN standard only specifies that the time to failure at a given test load is recorded. However, based on a series of tests at different loads a “splice efficiency” of the fabric belt splice (or fasteners) can be determined as that IP:1 2011 Conveyor and Elevator Belt Handbook

61


maximum percentage of the nominal belt breaking strength at which the splice will achieve a pre-determined life (hours) on the test machine. Fabric belt splices may also be tested to DIN - 22110 Part 3, as described for steel cords belt splices. However, fabric belt testing to DIN 22110 Part 3 has proved problematic due to the relatively high extension of low tension fabric belts and the limited allowance for belt stretch on machines primarily designed to conduct the test on steel cord belts. Ambient Conditions during splicing Efforts to achieve and maintain tolerant ambient temperatures and/or conditions during splicing must be made. In extreme cold temperatures, the shelter and a portable heater may be used to maintain a warmer environment and to eliminate cold winds from adversely affecting outer edges of the platen temperatures. Store all splice materials in a cool dry place out of direct sunlight. Splice Work Shelter: The quality and durability of a vulcanized splice begins with a clean work place. A shelter may be required to protect the splice and surrounding work environment from contamination (such as dirt, dust & moisture). The work area consists of the lower part of the press (traverses and heating platens) and approximately 10 - 12 ft (3 - 4 m) long work tables at either end of the press. The heating platens must be flush with the surfaces of the work tables and be at least 4 in. (100 mm) to 6 in (152 mm) longer than the splice on each end and at least 4 in (100 mm) wider than the belt on each side. Storage of Splicing Materials When unvulcanized splice materials are stored under unfavorable conditions their physical and/or chemical characteristics change. Eventually these changes will render the unvulcanized splice materials unsuitable for use. These effects result in changes in the curing behavior and/or in the cured physical properties of the splice materials. The harmful effects of these factors can be minimized by a careful choice of the following storage conditions. In case of doubt, consult the supplier of the conveyor belt splice material about the storage conditions. a. Materials stored in non-refrigerated conditions will shorten shelf life. Materials stored in refrigerated conditions will increase shelf life. Acceptable refrigerated storage temperature is typically 45°F-55°F (12.8°C-7.0°C). Do not allow the materials to freeze. Allow refrigerated materials to warm before use to allow condensation to disappear. b. The relative humidity should preferably be below 60% for long-term storage. Damp conditions should be avoided since long-term exposure to moisture can influence the curing and cross linking behavior of the materials. c. Sunlight and artificial light which has a substantial content of ultraviolet light can adversely affect the stability of unvulcanized rubber. Depending on the grade and the time span of exposure, chain rupture and/or cross linking may occur. In view of this, exposure to light should be restricted to a minimum. d. Where possible, unvulcanized rubber should be protected from excessive air circulation and should not be stored near electrical equipment (motors) that could be a source of ozone. For this reason it is advisable to keep the splice material boxes closed and sealed. e. Unvulcanized rubber should be stored in an area which meets the usual standards of cleanliness, even though the rolls are individually wrapped in polyethylene sheeting. Avoided direct contact with foreign materials of any kind. It is recommended that the material be kept in its original packaging until the moment it is used. f. Splice materials should not be stored longer than the specified shelf life. It is therefore recommended that the FIFO (first in – first out) stock rotation system be used. Tools and Equipment typically used for making a Fabric Belt vulcanized splice: 1. The splicing procedure may require a number of tools and equipment which may vary with the preference of the splicer that uses them. 2. Proper use of the needed splicing tools may be part of a designed splice training program. 3. Belt ends may be stripped by one of the following methods, which requires special individual tools: 4. The following list is considered a partial list of tools and may not include all tools used. a. Thermocouple unit & wires b. Buffer c. Sharpening Stone d. Square e. Awl f. Measuring Tape g. Foxtail Brush


62


h. Stanley Knife i. Dull rounded tip knife for cutting the rubber covers j. Single ply knives k. Ply Prodders l. Porcupine roller m. 4” Flat roller n. 1/16” stitcher roller o. Tuggers p. Straight edge, squares and chalk lines q. Ply Pullers / Pinchers r. Ply Clamps / pulling device 5. Practice the safety requirements associated to the tools and equipment used. 6. The vulcanizer must be capable of achieving and maintaining the specified temperature and pressure during the cure cycle and be large enough to adequately cure the splice in one cure. 7. The platens must have cool down capability. A minimum of 130o F (54.4o C) is typically required before releasing the cure pressure. 8. Steel edge guides must be secured along the edges of the splice and adjoining belt edge. The edge bars must approximately .063” (1.5 mm) less than the overall belt gauge and extend out each end of the bottom platen a minimum of six inches (150 mm). 9. Use thermocouples to monitor and maintain an accurate cure temperature throughout the cure cycle. A minimum of one thermocouple per heating element is typically specified. Thermocouples are used to accurately maintain the specified cure temperature throughout the cure cycle. By doing so, achieving the desired optimum cure is greatly enhanced while reducing the risk of over and/or under cured splice gums. Most belt manufacturers typically require one thermocouple per heating zone (top & bottom platens) Thermocouple lead wire. See fig. 12:1

Fig. 12:1

SPLICE PROCEDURE OVERVIEW Refer to the belt manufacturer for the detailed specified splice design, splicing procedures/best practices, and the specified splicing materials. The flowchart on pages 17, 18, and 19 show the basic steps required to splice a steel cord belt. Vulcanized Fabric Belt splicing generally involves, but may not be limited to the following basic steps: a. Determine the proper belt for the service intended. b. Determine the belt’s intended direction of travel (DOT). In the majority of splices the bottom cover fill will lead into the belt’s direction of travel or the outside fingers will point in the opposite direction of the belt’s intended travel when on the conveyor system. c. Determine the belt length required for the installation with the take-up in its recommended position for the type of belt. d. Cut the belt ends allowing enough length for the splice. e. Prepared the belt ends to match into a smooth, efficient joint. f. The splicing materials, specified by the belt manufacturer, are applied to the prepared ends. g. Cure the entire splice in a portable press under specified time, heat and pressure. h. The splice shall be cured in a single cure. i. The press platens shall have cool down capabilities.


63


Documenting the splice All pertinent information regarding the actual splicing must be documented. The pertinent information may include but not be limited to the following: a. Date & Location b. Splice company and lead splicer identification c. Cured splice identification / branding d. Weather conditions e. Belt manufacturer and belt condition f. Specified the step length or finger dimensions used in the splice g. Bias Length h. Actual cure time, cure temperature, & cure pressure used i. Number of heating elements and thermocouples used j. Splice material manufacturer and type – include expiration dates k. Breakers used (top and bottom) include type l. Time the splice cure begins m. The temperature and pressure of each thermocouple at defined intervals. n. Cool down method o. Time cool down begins p. Actual cool down temperature reached before releasing cure pressure q. Post cure buffing, trimming and inspection completed r. Date & Time belt is released for production s. Comment section for any abnormality that may have occurred during the building and/or curing of the splice. t. Any quality issues found during the post cure inspection 10.0: Do’s and Don’ts of Fabric Belt Splicing: 1. Do use the splice materials specified by the belt’s manufacturer. 2. Properly store and maintain the splice materials as specified by the manufacturer. 3. Do document the splicing procedure used – the curing procedure used – the splice materials used. 4. Do not use splice materials that have exceeded the shelf life as specified by the manufacturer. 5. Do allow all solvent and cemented areas to dry completely before continuing. 6. Do not knick, cut, or damage adjacent fabric plies when stripping the belt ends. 7. Do not allow ply seams / joints to overlap or to be butted tightly 8. Do allow a gap of approximately 1/32” (0.8 mm)at all ply seams / joints. 9. Do place a noodle over each ply seam gap. 10. Do use the specified breaker fabrics when directed. 11. Do follow the splicing procedures as specified by the belt’s manufacturer. 12. Do follow the curing rules specified by the bet’s manufacturer. 13. Do post cure requirements: a. Inspect the splice for abnormalities such as:  Blisters  Gum Blows  Ply Blows  Porosity  Wavy / uneven splice b. Buff the flash from the fill area to crate a smooth transition from the belt to the splice. c. Straight edge the splice even with the belt’s edges and trim accordingly d. Document any abnormalities that may have occurred during the splicing and / or the post cure procedures. 11.0: Drawing the Master Line: The Master Line: This is normally the first of the marks to be made on the belt on each of the two ends. The mark is drawn straight across the belt width at a distance from the belt end and equal to the distance of the total splice length. Three typical methods of locating and squaring the Master Line are as follows: a. Square and straight edge  From the belt end, measure back into the belt the length of the splice.  Use a square and straight edge to draw the master line.  Check the master line by laying the square on the opposite belt edge. See fig. 12:2.


64


Fig. 12:2 b. Triangulation  From the belt end, measure back into the belt the length of the splice. Mark the belt edge.  Measure and mark approximately 24” along the belts edge on each side of the mark.  From each of the 24” marks, measure equal diagonal lengths to the opposite belt edge and mark.  Draw the master line.  This method is common on belts 72” (1800 mm) or wider. See fig. 12:3.

Fig. 12:3 c. Swinging Arc  Accurately mark a point at the center of the belt’s width.  Measure from this point and make a mark at each edge near the belt end. These two diagonal marks must be exactly equal  From each of the two diagonal marks measure back into the belt the total splice length.  Draw the master line. See fig. 12:4.

Fig. 12:4 Drawing the Bias, Steps and/or Fingers: The bias can typically be made to match the bias angle of most vulcanizers. The most common bias angles are 20 o and 22 o. To get the 20 o bias, multiply the width of the belt x .036. To find the 22obias multiply the belt width x .40. From the Master Line the Bias Line and all steps and finger can be marked and drawn. See fig. 12:5


65


Fig. 12:5

13.0: Fabric Belt Splice Designs: Fabric vulcanized splices are typically made on a 22 o bias. The 22 o bias matches most vulcanizers. The bias angle may be adjusted if warranted. Multiply the belt’s width x .40 to find a 22 o bias angle. As with any fabric belt splice, the splice design is intended to reduce as much shear and stress as possible. There are three well known types of vulcanized fabric splices commonly used: 1. The Bias Step Splice: See fig. 12:6 2. The Bias Step Splice with Fingers: See fig. 12:7 3. The Full Carcass Finger Splice: See fig. 12:8 Detailed splice procedures and or splice training can generally be achieved by contacting the belt’s manufacturer. Bias Step Splice: Two belt ends being spliced together

Fig. 12:6

While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but is not limited to, the following basic steps: Building the Bias Step Splice: 1. Maintain a clean work area and environment 2. Properly maintain and store the splicing materials 3. Build a proper size splicing shelter (if needed) 4. Splicing dimensions are on a 220 bias 5. The top and bottom fill strips are 4” (200 mm) long 6. Top cover and bottom cover skive cuts are at an approximate 45o angle. Refer to fig 12:6 7. Cover skives and approximately 1” of the adjoining belt cover must be buffed 8. Make all step length cuts according to the specified instructions of the belt’s manufacturer.


66


9. Center line the belt ends, 10. Dry fit the belt ends and make stationary. 11. Apply one even coat of cement to the carcass / exposed fabric of each belt end. Allow the cement to dry completely before proceeding. 12. Clean all splicing materials with the specified solvent during installation 13. Build the splice as specified by the belt’s manufacturer. See Do’s and Don’ts of Splicing in this document. Bias Step Splice with Fingers Install the fingers as required in the steps. Use caution when cutting the fingers as to not damage the adjacent plies. Finger splices generally require designated cutting blades to cut the fingers. Noodles will be used to fill all voids around the fingers and in the splice. Center Line Direction of Travel

Cover Skive Finger

DOT

1st. Ply Dimensions

4” 2nd. Ply

Fingers at the ends of each ply 3rd. Ply

Fig. 12:7

All cuts and fingers are on a 220 bias angle

While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but is not limited to, the following basic steps: Building the Bias Step Splice with fingers: 1. Maintain a clean work area and environment 2. Properly maintain and store the splicing materials 3. Build a proper size splicing shelter (if needed) 4. Refer to the belt’s manufacturer for specified splice dimensions. Finger length and transition lengths will vary according to the belt type and/or the belt’s PIW rating. Splicing dimensions are on a 220 bias. 5. Draw out the splice on the belt ends. 6. Make the required cover skive cuts. Cover skive cuts are at an approximate 450 angle 7. Cover skives and approximately 1” of the adjoining belt cover must be buffed 8. Center line the belt ends. 9. Strip belt ends 10. Extend the center line from the belt through the full length of the exposed carcass. 11. Draw & cut out the fingers - Outside fingers must point opposite the belt’s direction of travel. 12. Dry fit the belt ends and make stationary. 13. Apply one even coat of cement to the carcass / exposed fabric of each belt end. Allow the cement to dry completely before proceeding. 14. Install the bottom cover fill strip composite 15. Clean all splicing materials with the specified solvent during installation. 16. Build the splice as specified by the belt’s manufacturer. See Do’s and Don’ts of Splicing in this document.


67


Full Carcass Finger Splice

Fig. 12:8

While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but is not limited to, the following basic steps: Building the Full Carcass Finger Splice: This picture shows the centerline on the carcass and the fingers marked to be cut. The opposite belt end to be spliced to this belt end will have the opposite fingers removed. Outside finger point opposite the belts direction of travel. See fig. 12:9 Fig. 12:9

1. 2. 3. 4.

Maintain a clean work area and environment Properly maintain and store the splicing materials Build a proper size splicing shelter (if needed) Refer to the belt’s manufacturer for specified splice dimensions. Finger length and transition lengths will vary according to the belt type and/or the belt’s PIW rating. Splicing dimensions are on a 220 bias. 5. Cover skives and approximately 1” of the adjoining belt cover must be buffed 6. Center line the belt ends. 7. Draw the splice on the top cover of each belt end. 8. Remove the top and bottom covers. 9. Cover skive cuts are at an approximate 450 angle 7 10. Extend the center line from the belt through the full length of the exposed carcass. 11. Draw & cut out the fingers – Cut approximately 1/32” (0.8 mm) outside the drawn lines when cutting fingers. This will create a gap between the fitted fingers of each belt end. Outside fingers must point opposite the belt’s direction of travel. 12. Dry fit the belt ends and make stationary. 13. Apply one even coat of cement to the carcass / exposed fabric of each belt end. Allow the cement to dry completely before proceeding.


68


14. Build the bottom cover composite. The composite will consist of: a. Bottom cover b. Breaker fabric. The breaker fabric must be long and wide enough to completely wrap the carcass. c. Inside gum 15. Clean all splicing materials with the specified solvent during installation. 16. Use the porcupine roller after each laminate to remove all possible trapped air. 17. Position the bottom cover composite 18. Build the splice as specified by the belt’s manufacturer. See Do’s and Don’ts of Splicing in this document. GENERAL SPLICE PREPARATION Center Lining the Belt Ends On both belt ends establish and mark 1. Establish and mark the centerline of the belt ends to be spliced by measuring across the width of the belt at three points in length of each belt end and outside the splice area at a distance of approximately 12 in (304 mm). 2. The centerline ensures exact alignment of the belt ends, which is indispensable for straight belt running. 3. The perpendicular square line; This square line will be the starting point from which the splice will be laid out. 4. The following three methods are general used to achieve a true straight line: a. Square & Straight Edge – Typically used on new belt with straight edges b. Triangulation – This method is typically used on the wider belts (72” and greater) c. Swing Arch – Can be used on any belt 5. The belt’s cover transition lines. The transition distance is typically defined by the belt’s manufacturer and is a line drawn perpendicular to the square line. Aligning the belt ends Accurate belt end alignment is required to ensure the belt runs straight on the conveyor system. Misaligned splices can also create additional stress on the cords and or fill rubber within the splice. Align the lower part of the vulcanizing press (traverses and heating platens). Accurately count the number of cables of each belt end and mark the center cable. Align the belt ends under consideration of: a. splice length, b. the belt’s center cables and the carcass center line on each belt end c. mark correct alignment with a chalk line. Now the center lines on both belt ends must form one straight line. d. The distance of the reference lines on both belt edges must be equal distances approximately the overall splice length. e. Secure both belt ends with clamps. See fig. 12:10

Fig. 12:10

Best practices generally used to build a bias step fabric belt vulcanized splice or the bias step fabric belt vulcanized splice with fingers: Refer to the belt’s manufacturer for specific detailed splicing instructions a. Determine the appropriate splice design.


69


a. Determine the appropriate splice design. The appropriate splice design will match the belt, the conveyor system, and expected dynamic operating parameters. Refer to the belt’s manufacturer for proper splice design and materials. b. Lay out the splice and strip each belt end. c. If the splice is the bias step fabric belt vulcanized splice, the bottom fill strip will lead in the belt’s direction of travel. If the splice is the bias step fabric belt vulcanized splice with fingers, the bottom fill strip will lead and the outside fingers must point opposite the belt’s direction of travel. d. Strip the belt ends. Use caution and DO NOT damage the adjacent plies when cutting. If the adjacent plies are damaged the splice must be stepped back or redone. The damaged area must be removed from the splice. e. Buff the 45o cover skives and one inch of the adjoining cover f. Apply one even coat of cement to the fabric only g. Allow all cement and solvent applications to dry completely before continuing. h. Install thermocouples on bottom platen (minimum of one per heating zone) i. Cover the bottom platen with release paper j. Center line and stabilize belt ends k. Dry Fit belt ends. Make necessary adjustments. Each ply seam / joint must have an approximate 0.031” (0.8mm) gap. Do not fit the ply seams/joints tightly together or allow them to overlap. l. Verify the belt’s center line and stabilize belt ends m. Install inside gum to the bottom of the splice carcass section n. Place noodles over each ply seam joint and or around each finger o. Install bottom cover fill composite p. Position top side of the splice q. Install top cover fill composite r. Install thermocouples on top cover (minimum of one per heating zone) s. Install steel edge guides and balance guides t. Install release paper over the splice u. Install top of press v. Secure edge guides and wedges if necessary w. Cure the splice following the manufacturers recommended curing specifications. x. Document cure (cure temperature and pressure of each thermocouple at defined intervals) y. After the cure cycle has been completed - Cool the platens to at least 130o F. while maintaining the cure pressure. z. Release pressure and remove the top platen of the press after the press has cooled to a minimum of 130o F. aa. Inspect and trim the splice bb. Buff any flash from the splice located on the adjacent belt covers. A smooth and even transition from the belt to the splice is required. Best practices generally used to build a bias full carcass finger fabric belt vulcanized splice: Best practices for the traditional full carcass finger splice typically include: a. Mark out the specified dimensional fingers at each belt end. b. Install Thermocouples on the bottom platen at each heating element used. c. Install the bottom cover composite on the bottom section of the vulcanizing press; d. Cut the specified dimensional fingers to length and width. e. Apply one even coat of the specified cement to the bare fabric carcass and fingers to promote adhesion to the rubber; f. Lay down the fingers in the defined direction of travel. Outside fingers will point opposite the direction of travel. g. Fill all voids between and around each finger and within the splice with noodles. h. Wrap the complete carcass fingers with the specified breaker fabric. i. Install the top cover gum followed by completion of the press assembly; j. Install thermocouples on the top cover composite of the splice at each heating element location used. k. Install and stabilizing the proper edge guides l. Vulcaniz the splice. Curing the Fabric Belt Splices: 1. Use a minimum of one thermocouple per heating element/zone. 2. The vulcanizer must be large enough to cure the splice in one cook. The platens are to be at a minimum 4” – 6” longer each end and 4” – 6” wider each side of the splice. 3. The vulcanizer must be capable of achieving and maintaining the specified curing pressure throughout the cure and cool down cycles.


70


4. The vulcanizer should have cool down capability. Water cool down is preferred. The platens are cooled to at least 1300 F. after the cure cycle has completed. The curing pressure is not released until the platens have reached the desired cool down temperature. Do not leave the belt on a hot platen for an extended period of time. 5. Refer to the belt’s manufacturer for the specified cure time, cure temperature and cure pressure. However, the typical cure temperature is 2900 F +/- 50 F and the typical cure pressure is 100 psi. 6. Steel or aluminum edge guides are to be positioned along the entire length of the splice length. The edgeguides should extend past the ends of the bottom platen by a minimum of 6” (152mm). The edge guides are positioned tightly against the splice and belt’s edges and held in place with come-a-longs or some other clamping device.

MECHANICAL SPLICES IN FABRIC BELTING: In those cases where belt ends are joined with mechanical fasteners the first requirement for a good splice is that the belt ends be cut square. Failure to do so will cause some portion of the belt adjacent to the splice to run to one side at all points along the conveyor. New belts can usually be squared with sufficient accuracy by using a carpenters square and working from one belt edge. There are four major types of major classes of mechanical fasteners. Since the optimum performance depends on belt construction, service conditions, pulley diameters and tension it is recommended that the fastener manufacturer be contacted for proper selection. Bolted Plates: Commonly used for heavy belts handling bulk materials. The bolted plate makes a strong, durable splice with no gap to leak materials. See illustration fig. 12:11

Fig. 12:11

Hinge Plate Fasteners: Many plate fasteners use the same bolt and plate attachment to the belt ends but has a hinge connection between the two belt ends connected together with a removable pin. The Hinge Plate fastener is extensively used underground where conveyors are frequently extended or retracted. See fig. 12:12.

Fig. 12:12


71


Riveted Plate Fastener: A variation of the hinge plate-type fastener uses rivets to hold the fastener to the belt ends. See fig. 12:13 Fig. 12:13

Hook types: The Hook Type fasteners attach to the belt ends by means of hooks formed from wire or sheet steel. They are applied by forcing the hooks through the belt and clinching on the opposite side. They have a hinge pin or rocker pin joint and can be taken apart easily. They will permit leakage of material. These types are particularly suited for package conveying where there relative smoothness may be an advantage. See fig. 12:14 Fig. 12:14

Extensive testing has proven the necessity for tightening the fasteners on a periodic schedule, usually after a few hours operation, after a few days of operation and at intervals of two or three months. Inspections may indicate the necessity to re-tighten at more frequent intervals. Failure to inspect the fasteners may result to severe belt damage and or mechanical splice failure. Fasteners are available in a variety of different metals designed for special applications, which may include non-sparking, non-magnetic, and abrasion and chemical resistance. The manufacturer should be consulted for the proper recommended use of specific applications. ELEVATOR BELT SPLICING The type of splice is more critical on elevator belts than on conveyors because of limited take up travel for belt stretch plus extreme dangers and difficulties generated if a splice separates and the belt falls into the boot. The confined space makes the belt splicing difficult. Vulcanized splice: This is the most desirable splice yet the least used due to lack of available space for the vulcanizing equipment. Consult the belt manufacturer for specific installation and/or splicing procedures. There are several customary methods of joining elevator belt. They are listed below in order of preference: Butt Strap Splice: A properly designed Butt Strap Splice utilizes the bucket bolts and plate fasteners to join the belt ends. The butt strap should be an all nylon construction equal to the elevator rating and compound and should be long enough to overlap 2 to 4 buckets on each side of the belt joint. See fig 12:15.


72


Fig. 12:15

Lap Splice: Only the bucket bolts join the belt ends. The ends of the belts are overlapped a minimum of four buckets and fastened with the top row of the bucket bolts passing through both pieces of the belt. This method should not be used for belts over 5/8” (15 mm) thick. See fig. 12:16.

Fig. 12:16


73


Mechanical or Plate Fastener Splice: Only suitable for lightly tensioned applications. Plylon belts may be installed with this type of splice at their full elevator tension rating. Ratings of other fabrics require a 50% reduction. Fasteners should be chosen in accordance with the fastener manufacturer’s recommendations. OIL WELL SPLICE: This splice may be used on light duty applications where the belt gauge is thin and the tensions are low and should not be used on elevators running at more than 50% of the rated belt tension. Clamps should extend to within ½” (12mm) of the belt’s edges. See fig. 12:17.

Fig. 12:17


74


CHAPTER 12 - Part B

SPLICING STEEL CORD CONVEYOR BELTS

INTRODUCTION This chapter is a brief summary for splicing Steel Cord Belting. Belt users and/or splicing companies should consult the belt’s manufacturer for more specific detailed splicing information. 12b:1 THE STEEL CORD CONVEYOR BELT: The conveyor belt and conveyor structure are typically matched to ensure the expected operating conditions and tensions do not exceed the belt’s limitations. The conveyor belt type and manufacturer must be known to accurately select the specified splice design, the specified cure data and splicing materials. Contact the belt’s manufacturer with any questions or concerns. 12 b:2 STEEL CORD CONVEYOR BELT SPLICES Vulcanized splices are typically used for steel cord belts. Currently, mechanical fasteners do not provide the needed dynamic strength to reliably join steel cord belts. 12b:3 STEEL CABLE CONVEYOR BELT VULCANIZED SPLICES An individual splice drawing for each steel cord belt construction can generally be obtained from the belt manufacturer. Splice drawings typically detail the proper cutting dimensions, cord step lengths, and the correct rubber and cement to use. Specific instructions for “tearing down” the belt ends and “building up” the uncured splice will vary with the technician. Contact the belt’s manufacturer for specific splicing details and / or possible splice training. 12b:4 Construction and Dimensions of Steel Cable Belt Splices 12b:4.1 Splicing methods: Splices on steel cable belts in accordance with DIN 22131 can be 1-step or multi-step splices in rhombic (belt width x .4) or rectangular shape. The load ability of both the rectangular and the rhombic shaped splice is similar. 12b:4.2 Splice Construction: Cable diameter and cable pitch as well as the minimum breaking strength of a cable and the dynamic cable tear-out strength in the splice area dictate length and geometrical construction of a splice. The geometrical construction is determined by: a. number of steps; b. length of steps; c. length of transitions; d. cyclic cable laying sequence (including cut cables); e. cable pitch in the splice area (noodle thickness). The construction is also influenced by: f. distance between butted cables; g. stepping of cable ends; The gap between butted cables shall be a min. 3 times and max. 4 times the cable diameter. The cable ends are typically staggered to reduce the flexing load as the belt runs over the pulleys. Cables on the belt edges should be laid in full length in opposite running direction of the belt. Cables within the dimensions of the splice must not be cut to allow room in the splice. Using the specified splicing materials, following the specified splicing procedures and splice diagram will ensure a straight splice and will allow all cords to fit in the splice. If a steel cable belt is equipped with a breaker, a breaker should be applied in the splice area corresponding to the belt construction.


75


The breaker will be positioned approximately 2 inches (50 mm) from each cover skive. 12b:4.3 The splice length includes: a. deflection zones of cables: b. staggering of cable ends: c. minimum step length: d. distance of butted cables: 12b:5 SPLICE EFFICIENCY Splice efficiency can be measured in two ways, (1) Static, (2) Dynamic. 12b:5.1 Static Splice Efficiency: Reference the ASTM testing method Defined as the measured force required to break a splice expressed as a percentage of the theoretical breaking strength of the belt. In addition to the peak force, the time for the splice to separate is sometimes also recorded. This is typically performed either by clamping each belt end on either side of a splice in a suitable fixture and measuring the force to pull the splice apart, or by making an endless belt loop with a single splice then measuring the force to pull the loop apart using a suitable fixture. 12b:5.2 Dynamic Splice Efficiency Defined in DIN 22110 Part 2 for fabric belt splices, and Part 3 for steel cord belt splices. For steel cord belt splices DIN 22110 Part 3 describes a 2-pulley, constant speed test machine where an endless loop of belt with one splice is subjected to a cyclic tension every 50 seconds. The tension cycle is intended to approximately simulate a real life belt tension cycle but at elevated peak tensions to accelerate the test. The cycle ramps from low tension to high tension then down to the low tension again with a ramp time ratio of 5:1 for the two segments (i.e. approximately 42 seconds up, 8 seconds down). The low test tension is defined as 6.67% of the nominal breaking strength of the belt. The high test tension is defined as one of a series of at least four different maximum test loads, at least one of which is typically 50% of the nominal belt breaking strength or higher. The four test loads are used to determine four test lives, each measured in terms of the number of test cycles completed at splice failure. These points are then plotted on a type of fatigue curve, known as a Wohler curve. The Wohler curve displays, test load (y-axis), in percent of nominal belt break strength, against load cycles to failure (x-axis). The so-called relative reference fatigue strength of the splice, which is expressed as a percentage of the nominal breaking strength of the belt, is defined as the test load on the Wohler curve at which 10,000 load cycles are achieved. 12b:6 Ambient Conditions during splicing Efforts to achieve and maintain tolerant ambient temperatures and/or conditions during splicing must be made. In extreme cold temperatures, the shelter and a portable heater may be used to maintain a warmer environment and to eliminate cold winds from adversely affecting outer edges of the platen temperatures. Store all splice materials in a cool dry place out of direct sunlight. 12b:7 Splice Work Shelter: Due to the need for cleanliness and the need to protect the splice from contamination (such as dirt and dust) where possible, the splice should be made in a sheltered area. The quality and durability of a hot splice begins with a clean work place. The splicer should eliminate the possibility of contaminants entering the splice and/or the splicing materials and adhere to all local and other associated safety requirements. The entire work area should be adequately protected by the shelter from environmental influences. The work area consists of the lower part of the press (traverses and heating platens) and approximately 10 - 12 ft (3 - 4 m) long work tables at either end of the press. The splicer should install a work table and the bottom of the vulcanizing press. The heating platens must be flush with the surfaces of the work tables and be at least 4 in. (100 mm) to 6 in (152 mm) longer than the splice on each end and at least 4 in (100 mm) wider than the belt on each side. 12b:8 Storage of Splicing Materials When unvulcanized splice materials are stored under unfavorable conditions their physical and/or chemical characteristics change. Eventually these changes will render the unvulcanized splice materials unsuitable for use. These effects result in changes in the curing behavior and/or in the cured physical properties of the splice materials.


76


The harmful effects of these factors can be minimized by a careful choice of the following storage conditions. In case of doubt, consult the supplier of the conveyor belt splice material about the storage conditions. a. Materials stored in non-refrigerated conditions will shorten shelf life. Materials stored in refrigerated conditions will increase shelf life. Acceptable refrigerated storage temperature is at 45°F-55°F (12.8°C-7.0°C). Do not allow the materials to freeze. Allow refrigerated materials to warm before use to allow condensation to disappear. b. The relative humidity should preferably be below 60% for long-term storage. Damp conditions should be avoided since long-term exposure to moisture can influence the curing and cross linking behavior of the materials. c. Sunlight and artificial light which has a substantial content of ultraviolet light can adversely affect the stability of unvulcanized rubber. Depending on the grade and the time span of exposure, chain rupture and/or cross linking may occur. In view of this, exposure to light should be restricted to a minimum. d. Where possible, unvulcanized rubber should be protected from excessive air circulation and should not be stored near electrical equipment (motors) that could be a source of ozone. For this reason it is advisable to keep the splice material boxes closed and sealed. e. Unvulcanized rubber should be stored in an area which meets the usual standards of cleanliness, even though the rolls are individually wrapped in polyethylene sheeting. Avoided direct contact with foreign materials of any kind. It is recommended that the material be kept in its original packaging until the moment it is used. f. Splice materials should not be stored for any longer than the specified shelf life. It is therefore recommended that the FIFO (first in – first out) stock rotation system be used. 12b:9 Tools and Equipment (Splicing Steel Cable Belt) 1. Instructions for the proper use of the needed splicing tools may be part of a designed splice training program. Practice the safety requirements associated to the tools and equipment used. 2. Belt ends may be stripped by one of the following methods which requires special individual tools: a. Hook Knife: Requires hook knives b. Piano Wire: Requires piano wire and a tugger / pulling device pulling device c. REMA Strip: Requires a REMA Strip machine and a tugger / pulling device 3. Practice the safety requirements associated to the tools and equipment used. 4. The vulcanizer must be capable of achieving and maintaining the specified temperature and pressure during the cure cycle and be large enough to adequately cure the splice in one cure. 5. The platens must have cool down capability. A minimum of 130o F (54.4o C) is typically required before releasing the cure pressure. 6. Steel edge guides must be secured along the edges of the splice and adjoining belt edge. The edge bars must approximately .063” less than the overall belt gauge and extend out each end of the bottom platen a minimum of six inches. 7. The vulcanizer must be capable of achieving and maintaining the specified temperature and pressure during the cure cycle and be large enough to adequately cure the splice in one cure. Typical specified cure temperature is 290 +/- 50 and the specified cure pressure is 150 psi – 200 psi. Consult the belts manufacturer for accurate cure specifications. 8. Steel edge guides must be secured along the edges of the splice and adjoining belt edge. The edge bars must approximately .063” (1.5 mm) less than the overall belt gauge and extend out each end of the bottom platen a minimum of six inches (150 mm). 9. Use thermocouples to monitor and maintain an accurate cure temperature throughout the cure cycle. A minimum of one thermocouple per heating element is typically specified. Thermocouples are used to accurately maintain the specified cure temperature throughout the cure cycle. By doing so, achieving the desired optimum cure is greatly enhanced while reducing the risk of over and/or under cured splice gums. Most belt manufacturers typically require one thermocouple per heating zone (top & bottom platens) Thermocouple lead wire. See fig. 12b:1

Fig. 12b:1


77


12b:10 Documenting the splice All pertinent information regarding the actual splicing must be documented. The pertinent information may include but not be limited to the following: a. Date & Location b. Splice company and lead splicer identification c. Cured splice identification / branding d. Weather conditions e. Belt manufacturer and belt condition f. Specified number and length of steps or stages in the splice g. Number and length of steps or stages installed in the splice h. Method used to strip cords i. Heat up and pressure up procedure (steel cord splices) j. Time the splice cure begins k. Actual cure time, cure temperature, & cure pressure used l. Number of heating elements and thermocouples used m. Splice material manufacturer and type – include expiration dates n. Breakers used (top and bottom) include type o. The temperature and pressure of each thermocouple at defined intervals. p. Cool down method q. Time cool down begins r. Actual cool down temperature reached before releasing cure pressure s. Post cure buffing, trimming and inspection completed t. Date & Time belt is released for production u. Comment section for any abnormality that may have occurred during the building and/or curing of the splice. v. Any quality issues found during the post cure inspection

12b:11 SPLICE PROCEDURE OVERVIEW While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but is not limited to, the following basic steps: a. Determine the proper belt for the service intended. b. Determine the belt’s intended direction of travel (DOT). Steel Cord splices shall have the outside cords pointing opposite direction of belt travel. c. Determine the belt length required for the installation with the take-up in its recommended position for the type of belt. d. Cut the belt ends allowing enough length for the splice. e. Prepared the belt ends to match into a smooth, efficient joint. f. The splicing materials, specified by the belt manufacturer, are applied to the prepared ends. g. Cure the entire splice in a portable press under specified heat and pressure. h. Prepare the vulcanizer and cure the splice as required by the belt’s manufacturer. The splice shall be cured in a single cure under the specified cure time, cure temperature, & cure pressure. i. The press platens shall have cool down capabilities. Refer to the belt manufacturer for the detailed specified splice design, splicing procedures/best practices, and the specified splicing materials. The flowchart on pages 88, 89, and 90 show the basic steps required to splice a steel card belt. ` Steel Cord splicing generally involves, but may not be limited to the following basic steps:

12b:12 Steel cord splicing methods and splice patterns: 12b:12.1 Traditional Steel Cord Splicing Method Traditional steel cord splices are generally made by: a. Stripping the cords from the ends of the two belts to be joined; b. Installing Thermocouples on the bottom platen at each heating element used. c. Installing the bottom cover composite on the bottom section of the vulcanizing press; d. Cutting the cords to length for laying in the defined pattern; e. Cement the steel cords to promote adhesion to the rubber; f. Laying down the cords in the defined pattern with rubber strips (called “noodles”) between adjacent cords; Noodles are typically long thin strips of rubber that are made to exact dimensions during manufacture. Special attention should be given


78


g. h. i. j.

uring the cord and noodle assembly. Cord alignment and spacing should be checked regularly during cord assembly to ensure width accumulations are not occurring. Corrective measures typically involve stretching noodles longitudinally, which reduces their width, to ensure cords are aligned correctly. Laying down the top cover composite followed by completion of the press assembly; Installing Thermocouples on the top cover composite of the splice at each heating element location used. Installing and wedging the proper edge guides Vulcanizing the splice.

12b:12.2 Pre-Molded Steel Cord Splicing Method Cord alignment within splices can be well controlled using pre-molded core gum rubber panels instead of noodles. These panels are manufactured core gum rubber sheets with semi-circular grooves formed in them that corresponds to the correct cord locations within the splice. Typically the cords are stripped using a stripping machine leaving approximately .5mm of core rubber on the cord. Compared to the traditional splicing technique using noodles, the pre-molded panels offer improvements in: a. Cord alignment, b. Cord spacing and straightness. c. Possible contamination during splicing is reduced because cement is not used. d. Pre-molded panels are used in conjunction with cords that have been stripped from the belt leaving a sheath of the original rubber which has then been buffed to improve adhesion. e. Pre-mold splices are typically dynamically stronger than the conventional splicing using noodles. f. Splicing time can be reduced as much as 25% using the Pre-mold splicing method

12b:12.3 STEEL CORD SPLICE PATTERNS Steel cord splices are made by laying cords from the opposing belt ends together in such a way that all cords are separated from one another by rubber. The adhesion of the rubber to the cords from the opposing belt ends provides the means for the tension load from one belt end to be transmitted to the other belt end. The simplest manner of joining two belt ends is shown in Fig. 12b:2. Here all cords from either end are the same length and alternate cords are from alternate belt ends. This is known as a single stage or one stage splice. Figure 12b:2

One Stage Splice Even number of cords

Direction of belt travel

As the number of cords is increased in the belt, there comes a point where it is impossible to fit all cords into the splice while maintaining the required gap between cables. In order to accommodate the extra cables it is necessary to cut and butt some of them, as in Fig 12b:3. A splice pattern is chosen such that the rubber gap between all cords is at least 35% of the cord diameter.


79


Figure 12b:3

Four Stage Splice Even number of cords

Direction of belt travel

12b:13 Best practices generally used to build a steel cord splice: Refer to the belt’s manufacturer for specific detailed splicing instructions a. Determine the appropriate splice design. The appropriate splice design will match the belt, the conveyor system, and expected dynamic operating parameters. Refer to the belt’s manufacturer for proper splice design and materials. b. The hot vulcanized splicing method used will be the conventional style using noodles or the pre-mold method using inside gums. Noodles are not needed for cord spacing or alignment c. Determine the appropriate method for stripping the cords from each belt end: Hook Knife – Piano Wire – REMA Striped d. Lay out the splice and strip each belt end. e. Buff the 45o cover skives and one inch of the adjoining cover f. Prepare the exposed cords and belt ends for splicing. g. Allow all cement and solvent applications to dry completely before continuing. h. Install thermocouples on bottom platen (minimum of one per heating zone) i. Cover the bottom platen with release paper j. Center line and stabilize belt ends k. Install bottom cover composite l. Position cords in the splice in accordance to the corresponding splice diagram. Always start with the center cords. m. Fill all voids with noodles (bend zones/transitions and butt gaps) n. Install the top cover composite o. Install thermocouples on top cover (minimum of one per heating zone) p. Install steel edge guides and balance guides q. Install release paper over the splice r. Install top of press s. Secure edge guides and wedges t. Cure the splice following the manufacturers recommended curing specifications. u. Document cure (cure temperature and pressure of each thermocouple at defined intervals) v. After the cure cycle has been completed - Cool the platens to at least 130o F. while maintaining the cure pressure. w. Release pressure and remove the top platen of the press after the press has cooled to a minimum of 130o F. x. Inspect and trim the splice y. Buff any flash from the splice located on the adjacent belt covers. A smooth and even transition from the belt to the splice is required.

12b:14 GENERAL SPLICE PREPARATION Center Lining the Belt Ends On both belt ends establish and mark 1. Establish and mark the centerline of the belt ends to be spliced by measuring across the width of the belt at three points in length of each belt end and outside the splice area at a distance of approximately 12 in (304 mm).


80


2. The centerline ensures exact alignment of the belt ends, which is indispensable for straight belt running. 3. The perpendicular square line; This square line will be the starting point from which the splice will be laid out. 4. The following three methods are general used to achieve a true straight line: a. Square & Straight Edge – Typically used on new belt with straight edges b. Triangulation – This method is typically used on the wider belts (72” and greater) c. Swing Arch – Can be used on any belt 5. The belt’s cover transition lines. The transition distance is typically defined by the belt’s manufacturer and is a line drawn perpendicular to the square line. 12b:15 Prepare tools, equipment and splicing materials: Be Certain that: a. all the required tools are available and in working order b. the vulcanizer is capable of achieving and maintaining the specified cure temperature and cure pressure. c. the vulcanizer has cooling capabilities d. the specified splicing materials are available and meet manufacturing requirements e. the required curing specifications and splice design are available from the belt’s manufacturer before beginning the splice 12b:16.1 Draw the splice Dimensions on each belt end:

Figure 12b:4 12b:16.2 Cut off the rubber edges along the outer steel cables from belt transition lines to belt ends.

Figure 12b:5 12b:16.3 Cut the cover skives completely across the belt’s width and down to the cables at an angle of approximately 30o to 45o.

Figure 12b:6 IP:1 2011 Conveyor and Elevator Belt Handbook

81


12b:16.4 Remove the top cover and stripping of steel cables / Conventional manual procedure Remove the top cover from the cover skive to the belt end. The method of removing the cover may vary with individual splicing groups. It may be necessary to remove the cover in longitudinal strips approximately 8” (203mm) – 12” (305”) wide.

Figure 12b:7 12b:16.5 The cables can be stripped by: a. Hook Knife – Usually preferred method for small diameter cables and/or short splice lengths consisting of one stage and perhaps two stages. Cables should be cleaned of excess rubber prior to installation.

Figure 12b:8 12b:16.6 Piano Wire – Usually used on cords 5.2mm or greater diameter. Remove as many/much of the rubber tips from the stripped cables.

Figure 12b:9


82


12b:16.7 The bottom cover can be removed after the hook knife or piano wire cord removal procedure is completed. 12b:16.8 Coated Cords for Pre-Mold Splices: Cords will have approximately .5mm of the belt’s cured inside gum attached. This allows rubber to rubber adhesions for greater bonding and dynamic performance. Pre-Mold splices are typically used in cases where many of the same splices will be applied and or on the larger diameter cords. a. Make sure to use cutting blades corresponding to the cable diameter. b. After stripping, the result should be a nearly round cable, with rubber embedded on the cable. Stripped cables should be handled with clean gloves only and placed onto a clean surface (PE film). c. Requires buffing the cords no more than twenty four hours prior to installation. d. Carefully buff the rubber embedded cables with a grooved wire brush. Avoid overheating, shiny spots and scorching of the rubber. Buffing will automatically break the edges of cubed cable rubber. e. Cementing the cables is not necessary when using the Pre-mold Belt Splice Method f. Stripped cables should be handled with clean gloves only and placed onto a clean surface. 12b:17 Aligning the belt ends Accurate belt end alignment is required to ensure the belt runs straight on the conveyor system. Misaligned splices can also create additional stress on the cords and or fill rubber within the splice. Align the lower part of the vulcanizing press (traverses and heating platens). Accurately count the number of cables of each belt end and mark the center cable. Align the belt ends under consideration of: a. splice length, b. the belt’s center cables and the carcass center line on each belt end c. mark correct alignment with a chalk line. Now the center lines on both belt ends must form one straight line. d. The distance of the reference lines on both belt edges must be equal distances approximately the overall splice length. e. Secure both belt ends with clamps. Figure 12b:10

12b:18 Buff the transition zones On both belt ends the rubber surfaces of the transition zones must be thoroughly buffed with a rotating wire brush. Overheating, shiny spots and scorching of the rubber should be avoided. The buffing dust has to be thoroughly removed with a clean hand brush. Figure 12b:11


83


12b:19 Cleaning the cords: Cords must be cleaned and free of contaminates prior to applying cement. a. If the cords were stripped using the piano wire: The rubber tabs and pieces of rubber must be removed using a “V” knife or some similar tool. b. If cords were stripped using the hook knife: Remove as much of the thick rubber remnants as possible making the cords uniform in circumference. c. Do not use solvents or other cleaners on cords. d. If rust, dirt or debris is fund on the cables, clean the with a rotating wire brush 12b:20 Applying splicing cement Apply one even coat of splicing cement to the cables. Allow the cement to dry completely. 12b:21 Preparing the belt ends On both belt ends establish and mark a. the belt center line; b. the perpendicular reference lines; c. the belt cover transition lines. 12b:21.1 Cut off the rubber edges along the outer steel cables from belt transition lines to belt ends with a long knife 12b:21.2 Bevel cut through top cover down to the steel cables along the belt transition line using a knife held at an angle of approximately 30° to 45°. 12b:21.3 Removing the top and bottom covers and stripping the steel cables: Methods of removing the top and bottom covers will vary with the splicing crew. Covers should be removed as close to the surface of the cables as possible. 12b:21.4 Buffing the rubber embedded cables (Pre-Mold): Rubber embedded cables are generally stripped using a specific tool with specified cutting knives attached. Approximately .5 mm of embedded rubber will be left on the cables. Slightly buffing the rubber embedded cables will enhance the adhesion values. Do not buff the cables more than 24 hours prior to cable installation. Clean the cords with solvent just prior to installation. 12b:21.5 Buffing the transition Zones Using a rotating wire brush, buff the transition zones, the cover skives, and approximately one inch of the adjacent top and bottom covers. 12b:21.6 Removing the buffing dust Using a foxtail broom remove all buffing dust to prevent gum blows. 12b:21.7 One coat of cement is sufficient. Allow the cement to dry thoroughly before continuing. Use the back of your fingers when checking to see if the cement is dry. 12b:21.8 Proper belt end and cord alignment are critical to achieve a quality finished splice. 12b:22 Assembly of cover composites When possible the top and bottom cover composites may be built in the shop. The combined gauges of the materials used to build the top and bottom cover composites must be approximately 0.030” heavier than the belt’s overall gauge. Care must be taken to prevent contamination and stretch of the cover composites. The splice materials will be specified by the belt’s manufacturer to match the desired splice design and dimensions. The assembled top and bottom cover pads will be larger than the splice width and length and slightly thicker than the original belt covers. Required minimum thickness of cover pads: a. Belt width plus 6 in (150 mm) b. Splice length plus 10 in (250 mm) Cover pads generally consist of: a. Tie gum next to cables b. Breaker (if specified)


84


c. Cover gum It is not necessary to use cements between the layers of the cover pads. It is recommended to strike / wipe the surfaces with the specified solvent – Allow the solvent to dry completely then laminate. After each laminate remove all possible trapped air using the Porcupine / stitcher roller. 12b:23 Installing the bottom cover pad a. Measure and cut a bottom cover approximately 16” longer and 6” wider than the splice. b. Wipe it clean with solvent. c. Cut an equal size inside gum / tie gum and wipe it clean with solvent d. Install the inside gum / tie gum to the cover gum – matching the cleaned sides to each other e. Remove all possible trapped air using the porcupine / pricker roller. f. Carefully place the bottom cover pad in position between the belt ends and mark the location of the cover skives. g. Make a 450 skive cut along the freshly made cover skive marks on the bottom cover composite h. Position the bottom cover in place matching the cover skives of both belt ends and the bottom cover pad skive cuts. 12b:24 Matching and Laying Cables: a. Splices with odd number of cables at each belt end will generally have a butt gap joining the center cables. b. Splices with even number of cables at each belt end will generally have two long center cables. c. The center cords must be center lined and placed in the splice d. Lay the cables from the center cords to the outside cords as explained in the corresponding splice drawing. e. Check for proper cord alignment during the process of laying the cables. f. Outside cables must point opposite the belts direction of travel. g. It is very important to follow the specified splice dimensions and design when laying cables. Do not cut additional cables to allow room if cables begin to bow. h. The top and bottom covers must be stitched tightly against the top and bottom cover skives. The cover skives as well as the adjoining cover pad interface must be cut at approximately 450 angles. i. The belt’s cover skives must be buffed and cleaned. j. Strike / wipe the belt’s cover skives and the top and bottom cover pads skives with solvent before mating them together. k. Scribe / mark the step lines for laying the cables according to the specified laying scheme of the splice diagram on the tie gum of the bottom cover composite. l. The step lines can also be marked by placing noodle rubber strips onto the established lines. 12b:25 Laying the cables: The following steps are guidelines which are generally true: However it is strongly recommended to refer to and follow the instructions as detailed on the splice drawing for the particular splice being applied. a. The belt’s manufacturer will generally supply a splice drawing when requested. b. Always start in the center of the splice by accurately positioning the center cables. Continue laying cables from the center to the splice edges. c. Lay an equal number of cables at each side of the center cords checking the alignment often. d. Carefully clean all surfaces with the specified solvent to remove possible contaminants and create better green tack. e. The specified noodle rubber strip is placed edgewise between the cables. The dimensions of the noodle rubber strips are to ensure that the cables are laying straight and maintain the correct gap between them. f. Correctly using the noodle tie rubber strips will help to maintain a uniform distance between the cables, especially at the cable ends, which are exposed to the maximum rubber shearing force within the splice. g. During the laying operation continuously check that the cables are laying straight. h. When the last cables are laid, there should be sufficient space for the rubber edge. 12b:25.1 One step splices: Splices with odd number of cables in them generally will have a butt gap joining the center cables of each belt end. 12b:25.2 Two step and multi-step splices: In both cases start with the center cable of the first belt end, which, in case of a multistep splice is a long cable. This cable is deflected by half the cable pitch towards the belt center line. On the second belt end also start with the center cable, which then is deflected towards the other side of the belt center line by half the cable pitch and laid in the matching length in accordance with the cable cycle. All further cables are laid according to cable laying scheme proceeding to the edge on both sides. 12b:25.3 Even number of cables On each belt end start with the left cable of the two center cables, which are staggered towards the marked belt center line.


85


12b:25.4 Even and odd number of cables If the number of cables in each belt end is not matching, start laying the center cable of the belt with the odd number of cables onto the belt center line and then proceed according to the specified cable laying scheme. 12b:25.5 After having laid all cables mark the splice edges with a chalk line and trim excess rubber. Build up edges with excess cover stock to the upper level of the cables. The splice should now be slightly wider than the adjoining cured belt. Excess material will be trimmed later together with the top cover pad. 12b:25.6 Thoroughly and completely fill up all remaining gaps and cavities slightly above upper level of cables either manually or with an extruder gun. 12b:26 Placing the top cover pad 12b:26.1 Using the specified solvent wipe/clean the buffed top cover skive/bevel cuts of the transition zones on both belt ends as well as to the built up rubber edges and allow them to dry completely. 12b:26.2 Before placing the top cover pad onto the cables and rubber edges proceed as follows: a. check the thickness of the cover pad; b. remove the protection film from the tie rubber side. If tack is needed, using the specified solvent, wipe/clean the exposed tie rubber and the bottom surface of the top cover gum. 12b:26.3 When placing the top cover pad avoid trapping air. Press on and stitch the top cover pad vigorously from the center outwards or in direction of the butt joints respectively and firmly fit the cover pad to the belt’s cover skive. Use a porcupine roller to stitch the cover skive interface. Remaining air within the splice area can be evacuated by using an awl. 12b:26.4 Trim excess rubber at the cover skive interface with an off-set knife. 12b:26.5 Place any splice brands and/or identifying marks on the splice. 12b:27 Curing the splice 12b:27.1 Cover the complete heating area with release. Install the edge bars (edge irons) on both sides of the splice. Using come-a-longs or other types of edge clamps position the edge bars tightly against the edges of the splice and adjoining belt. The edge bars are to be approximately 1/16 in. (2 mm) thinner than the belt and 12” (305 mm) longer than the overall splice length. 12b:27.2 Install a minimum of one Thermocouple per heating element on top of the splice / belt. 12b:27.3 Assemble top platens and then place the upper traverses in line with the lower traverses. The upper heating platens also must be at least 6 in (150 mm) longer than the splice on either side and at least 3 in (75 mm) wider than the belt on each side. The arrangement or layout of the heating platens must be noted in the splice record. 12b:27.4 The press must produce and maintain the curing pressure of 180 - 200 PSI (specific surface pressure: 12 bar) throughout the cure and cool down cycles. 12b:27.5 Increase pressure while temperature rises and observe temperature on all heating platens. a. If a bladder type press is being used, pressurize the 200 psi and hold for approximately 5 minutes to check for any possible leaks, then release pressure.; b. Turn on the power to the platen heating zones. c. Apply 100 psi pressure and hold until the thermocouple readings all reach approximately 2050 F (950 C). d. Increase the cure pressure to a minimum of 180 psi and hold throughout the cure cycle. Monitor the pressure during the cure and adjust as necessary. Curing pressure must be 180 psi – 200 psi. The pressure will generally increase as the cure temperature rises. e. The cure time starts when each thermocouple has reached the specified cure temperature. f. Monitor the splice throughout the cure cycle. Document the cure temperature of each thermocouple and cure pressure at defined intervals. g. Platen temperature uniformity should be within ±5°F (±3°C) of the selected temperature. Higher deviations must be recorded. h. Apply total specific pressure when all heating platens have reached a temperature between 212°F (100°C) and 230°F (110°C). Maintain this temperature for a period of approximately 5 minutes. At this temperature range the rubber develops its optimum flowing properties. i. Continue increasing the temperature. The curing time starts when the temperature on all thermocouples has reached the specified cure temperature. The curing time depends on the belt thickness and belt type. The belt manufacturer will provide


86


the specified cure time - cure temperature - & curing pressure. j. Thermocouples with wire leads on the belt surface should be used to check the press temperature. Use one thermocouple per heating element. k. The typical specified cure temperature is 290°F ± 5°F (143°C). This temperature range must be maintained throughout the entire cure cycle. l. When curing is completed allow the heating platens to cool down to 130°F (54°C) before releasing the pressure. Do not allow the belt and/or splice to rest on a hot platen surface. 12b:28 Completing the splice a. Remove vulcanizing press, strips of cloth, release paper and inspect the splice. Check for correct vulcanization (absence of porosity or blisters, elasticity, thickness and Shore hardness). b. Trim edges, remove material overflow and make any other appearance modifications as may be necessary. c. The splice should be durably marked with a splice number. d. The conveyor belt can be put into operation after the splice has cooled down to ambient temperature. e. The splice record sheet must be completed. Any irregularities which occurred during the splicing operation are to be registered. The record sheet should be signed, distributed and a copy maintained / archived.


87


TYPICAL STEEL CORD SPLICE FLOW CHART

Section 12b:7

Tool & Equipment

Section 12b:9

Section 12b:4

Section 12b:14

Section 12b:14

Section 12b:14

Section 12b:14

Section 12b:21

Section 12b:16.5

Section 12b:16.6

Section 12b:16.8


88


TYPICAL STEEL CORD SPLICE FLOW CHART 1 Section 19.0 Page: #12 Section 12b:19

Section 11.0 Section 12b:11 Page: #11

Cord & Skive Preparation

Alignment, Cord Cleaning

& Cementing

Section

Section 16.3 12b:16.3 Page: #9

Section 12b:19 19.0 Section Page: #12

Section 12b:20 Section 20.0 Page: #12

Bottom Cover Composite

Bottom Thermocouple Installation

Section 22.0 & 23.0 Section 12b:22 & 12b:23 Page: #13

Section 9.012b:9 Section Page: #4 Section 10.3 Page: #13

Bottom Cover Installation

Cord Lay - Up

Top Cover Installation

Steel Edge Guide Installation

Top Thermocouple Installation

Section 23.0

Section Page: #1312b:23


Section 26.012b:26 Section Page: #15

Section 27.1.0 Section 12b:27.1 Page: #13

Section Section9 12b:9 Page: #4

2


89


TYPICAL STEEL CORD SPLICE FLOW CHART 2

Final Press Assembly

Cure Start-up

Final Press Assembly

Section 27.0 Section 12b:27 Page: #15 & #16

Splice Vulcanization

Monitor Cure Time & Pressure

Cool Platens To at least 130o –54oC

Release Cure pressure and Post Cure Splice Prep & Inspection

Vulcanizer Removal

Section27.0 12b:27 Section Page: #15

Section27.5 12b:27.5 Section Page: #16


Document Cure Temperature & Pressure

Section 12b:10 Section 10.0 Page: #5

Section 27.5 Section 12b:27.5 Page: #16

Section Section27.5 12b:27.5 Page: #16

Section 27.5 Section 12b:27.5 Page: #16

Splice Completion


90


CHAPTER 13

BELT MONITORING

INTRODUCTION Conveyor belts are a critical component of many mining and processing operations. The loss of a conveyor belt on a critical conveyor line will result in significant downtime and cost the operation significantly due to lost productivity. There are a number of methods that can be utilized by operations to monitor their belt in order to maximize the belts productivity. Operation monitoring sensors continually monitor the interaction between the material being conveyed, the conveyor belt and the conveyor system in order to detect situations that are considered to be out of the normal operating conditions. Included in these sensors are belt slip sensors, belt tracking or misalignment sensors, plugged chute sensors and metal detectors, to name a few. By monitoring the operation for potentially catastrophic events it is possible to minimize or avoid damage to the conveyor belt that would result in prolong downtime of the mining operation. 13:1 Operation-Based Sensors Slip Sensors Slip Sensors monitor for belts running on a frozen pulley or a pulley driving a belt that is not moving. In either case, this type of event will result is a large amount of heat from frictional forces between the pulley and the belt that can result in fire and potentially a broken belt. The slip sensors monitor the rotation of two different pulleys on the system and compare the speed differential between the two pulleys. This is typically accomplished using encoders or proximity sensors mounted on two different pulleys, normally a drive and a separate non-drive pulley. Assuming the system is functioning properly, the speed of the belt should be the same in both locations. Alignment Switches Alignment Switches are used to measure when a belt tracks off of the conveyor structure. These are used to trigger a belt stop when the belt pushes a bar attached to a limit switch beyond the limit setting for that switch. Belt tracking could also be tracked by an ultrasonic sensor; however, the fail safe characteristics of the alignment switches are the most common methodology implemented in mines. Figure 13:1: Misalignment Switch Mounted Near Edge of Conveyor Belt

Plugged Chute Switches Plugged Chute switches are used to shut the belt down if the chute becomes blocked and the load is not being carried through the process as expected. Chute switches operate under a number of different sensor types including microwave, radio-frequency type capacitance probes, ultrasonic, radar, nuclear, and laser technologies. All of these sensors are interacting in some way with the material in order to detect its presence in the chute structure when the chute is filling up due to a chute blockage.

Infrared Technology Infrared Technology in the form of spot, line and camera sensors are often used in the coal industry to monitor the temperature of the material being carried; however, in some cases, IR cameras are also being used as a means to detect heat build in pulleys or idler rolls.


91


Metal Detectors Metal Detectors are often utilized to detect metal debris on the belt that may result in belt damage or a longitudinal rip. If a large enough piece of metallic debris is detected, the unit will shut the conveyor down to enable operations to remove the metal. In high risk areas, mines will implement electromagnets to remove as much of this metallic debris as possible out of the material being conveyed before it causes damage. Speed Monitors Speed Monitors are used to monitor the belt speed in order to ensure the belt drives are controlling the belt speed properly. Speed sensors can either be encoders that make physical contact with pulley or a non-contact proximity sensor that detects a target system mounted to the pulley (Figure 13:2). In either case, the revolution of the pulley is converted to a belt speed and this speed is used to verify that the conveyor is functioning properly. Figure 13:2 Encoder and Proximity Sensor Speed Sensors

Counter Weight Limit Switches Counter Weight Switches are set up on the system to monitor the position of the counter weight on the take-up ystem. If the counter weight goes to the low or high tension ends of the take-up, it is an indication that the tensions are too low or are exceeding the upper limit of the design. A limit switch on the counter weight will be set such that if the take-up pulley exceeds its displacement range trying to fully tension the belt, it is an indication that there is not enough tension on the system. In some cases this is one of the first indicators of a transverse belt tear having occurred on the system. Alternatively, if the belt tension forces the take-up pulley to the higher tension end of the displacement range, a limit switch on the upper limit of the displacement range will be activated resulting in a system alarm. Rip Detection Rip Detection can be achieved by several methodologies from those that monitor material spillage or belt tracking to those that involve interaction with embedded components within the conveyor belt. Material Spillage Detection Material Spillage Detection is utilized by a number of sensor systems to detect longitudinal belt rips. As the event progresses, material will spill from the belt at the event. There are several manufacturers that offer pull cord devices that detect material spillage as it falls on the conveyor or is pulled along the return conveyor. These pull cord systems require wires to be strategically placed transverse to the conveyor belts direction of travel. When material falling through the ripped conveyor belt strikes the pull cord, a relay is tripped in the device that indicates an issue has been detected in that area. Ultrasonic and laser based sensors have also been utilized in a similar fashion to detect material dropping from the belt indicating a rip is taking place. In this case, an ultrasonic or laser beam field is disturbed and the sensor alarms. Belt Width Monitoring In some systems, the width of the belt can be utilized as a means of detecting longitudinal rips. If an edge strip is taken from the edge of the belt or the belt overlaps in a center rip situation, the measurable width of the belt will be eeduced and the system will alarm. Similarly, if there is an expansion of the width of the belt, the belt width monitoring systems can detect that change and stop the belt


92


Inductive Rip Detection Induction Rip Detection has been around since the 1970’s. The principle of an inductive system is to place metallic loop antennas across the width of the belt at regular intervals along the belts length. A transmitter is used to induce electrical currents in these antennas that are then detected with a receiver as the loop passes. If the loop is good, the induced current is detected by the Receiver and a signal is sent to a control unit indicating the loop is good. A damage loop will not carry an induced current and will not be detected by the receiver. These systems normally utilizes the time between loops or the distance between loops to monitor the loops in the passing conveyor belt. If the expected time or distance between loops is exceeded due to a loop being damaged by a longitudinal rip, the system will alarm by opening a relay to stop the belt. Figure 13:3 Transmit and Receive Detector Monitor Loop Integrity

Magnetic-based Rip Protection The most recent advance in longitudinal rip detection is the magnetic based rip detection technology. Like the inductive systems, the magnetic systems utilize sensors that are installed at regular intervals along the length of the belt. The magnetic insert are composed of transverse or biased wires that cover the width of the belt. After magnetizing these inserts, the integrity of the inserts are monitored using magnetic sensor arrays and the previous record of the rip insert. Unlike the inductive loops, the magnetic insert can sustain some damage without significant effect to its magnetic signature. As a result it is considered to be more durable.

Figure 13:4 Magnetic Rip Inserts at Regular Intervals (Application Dependent)


93


Periodic and Continuous Conveyor Belt Health Measurements Conveyor Cover Wear One of the measures of the remaining life of a conveyor belt is how much of the belts top or “carry” cover is remaining. Knowing the wear rate and the amount of cover left, a mine can determine how much more life to expect out of the conveyor belt that is otherwise in good shape. Based on the loss of material between measurements at two different times, one can calculate the wear rate to see if there has been a change in wear rate and/or to predict the expected life remaining for that conveyor belt. Ultrasonic Wear Measurements: Periodic measurements using ultrasonic gauges are commonly used by site surveyors to assess how much cover wear has taken place on textile conveyor belts and steel cord belting. The ultrasonic measurement determines the gauge of rubber above the carcass by transmitting the ultrasonic wave through the material to the carcass and measuring the reflected wave to determine the gauge of the rubber cover. In fabric belts, the ultrasonic wave reflection is mainly from the first layer of fabric and these reflected waves are then detected by the ultrasonic sensor to determine the cover gauge of the belt. Similarly for steel cord belts, the ultrasonic waves will reflect off of the steel cables. It should be noted that for the best results, it is important to know the properties of the rubber you are measuring as the transmission of the ultrasonic waves through different rubber compounds will yield slightly different results. Eddy Current Wear Measurements: Similarly, periodic measurements using eddy current-based sensors can also be used on steel cord belts to measure the cover gauge. The eddy current sensor emits a high-frequency alternating-current magnetic signal. When the sensor is moved towards a conductive surface, eddy currents are generated on the surface of that conductor. The magnitude of the eddy current signal detected is dependent on the conductive properties of the steel cord and the separation of the steel cord and the sensor surface. Given that the conductive properties of the steel cord are known, the gauge of the rubber can be determined in order to give a measure of the remaining rubber gauge on the conveyor belt. Laser Wear Measurements: More recently, laser based scans have been used to accurately determine the thickness profile of the conveyor belt by measuring its thickness across the width of the conveyor belt. In essence this is done by using lasers positioned above and below the conveyor belt and doing a differential measurement to determine the overall gauge of the conveyor belt. This type of measurement is capable of giving very accurate information about the belt thickness belt; however, one must be careful that the belt is clean and that pulley cover wear is not contributing to the gauge variation of the belt. Conveyor Belt Integrity Conveyor belt integrity is often determined from conveyor belt scans. Many mine sites will have diagnostic scans of their conveyor belts completed on a regular basis in order to evaluate their potential risk of a transverse tear or splice failure. X-Ray Based Belt Scanning For many years, X-Ray scanning of conveyor belting has been utilized to determine the integrity of the conveyor belt carcass in fabric or steel cord belting. These scans are typically done periodically and require radiation restrictions to be applied where the scans are performed. During an X-Ray scan, the X-Rays penetrate the belt and are measured on the opposite side of the conveyor belting. The integrity of the material reinforcement in the belt is measured as a function of the intensity of the X-Ray image. The X-Ray image intensity will vary with variations in density of the internal components of the conveyor belt. As a result, damage to the fabric reinforcement or the steel cord reinforcements can be detected due to the density changes associated with these damage points. Magnetic-Based Belt Scanning Magnetic Scans of steel cord conveyor belts have become one of the most popular methods of scanning steel cord conveyor belts to determine the integrity of the steel cords running longitudinally. The majority of the systems rely on a permanent magnet mounting that magnetizes the cords in the conveyor belt as it passes over


94


or under the magnet. Once magnetized, a single steel cord will have a north polarity on one end and a south polarity on the opposite end. The magnetic flux lines that are emitted from these cord ends will be more per pendicular to the belt surface and hence magnetically distinct from the magnetic field of the rest of the belt. These distinct magnetic flux lines can be detected using inductive coils or solid state sensor technologies, both of which generate voltages proportional to the magnetic field strength in the region of the cord ends. With this technology, it is possible to map any cord damages that occur along any given length of belt. The fact that this sensor technology is not restrictive and can be used to monitor the conveyor belt continuously, these sensors are starting to find their way into the mainline sensor arsenal of mines. The ability to detect and minimize the risk of a transverse tear event and the ability to detect longitudinal rips is expected to become a standard in steel cord conveyor belt monitoring. Splice Monitoring Splice monitoring in textile belts has always been a challenge. Historically, the two most common systems for splice monitoring in textile belting utilize optical or magnetic markers near the edges of the splice. By comparing subsequent images of the splice to a baseline image, the quality of the splice can be determined. Primarily, the analysis is looking at splice deformation compared to the baseline image in the form of de-linearization of the splice along designed construction lines and/or the elongation of the overall splice length. X-Ray Based Splice Scanning Periodic X-Ray scanning of textile and steel cord splices has also been a method of checking the integrity of the conveyor belt splices. Like in the conveyor belt, damage to the fabric or steel cords will be visible as density changes in the belt. Variation in splice lengths and deformations can also be determined by analyzing the X-ray images and comparing them to a benchmark image of the belt. Magnetic Based Splice Scanning Steel cord splice monitoring has historically been done as part of the belt analysis on a periodic basis. Once a magnetic scan was completed the magnetic signal is reviewed for evidence of change or degradation of the magnetic intensities. In some cases, once a magnetic anomaly has been identified X-Ray images are completed to verify the magnetic results. This type of analysis has been automated more recently in order to continually monitor changes to a splice over time and to alarm if the splice quality is degrading. For the best combination of conveyor belt design and applicable sensor systems for a given application, it is recommended that the belt manufacturer is consulted.


95


CHAPTER 14

OPERATION AND MAINTENANCE BELT INSTALLATION

Belting ready for installation should be mounted on a shaft for unrolling and threading onto the conveyor. Conveyor belting can be rolled with top cover either in or out, and this should be considered when positioning the roll for threading. In some cases, such as in mines where head room does not permit maneuvering a roll, the belt may have to be pulled off the roll and reefed. Extreme care must be exercised to see that the loops have large bends to avoid kinking or placing undue strain on the belt. No weight should ever be placed on the belt when it is in a reefed position. Ideally, supports should be placed at each end where the bends occur. Another method of handling belting under such conditions is to lay the roll on a turntable with a vertical spindle. The belt must make a 90-degree twist as it comes off the turntable. New belting can be pulled onto the conveyor either by attaching it to the trailing end of the old belt which has been cut or, in the case of a new installation, by attaching it to a rope or cable which has been threaded around the idlers and pulleys. It is important to prevent damage to the new belt. It should be attached to the old belt or cable with a clamp or other device so as to distribute the pull evenly over its entire width.

COLD TEMPERATURE SERVICE The increasing use of conveyor systems in severely cold climates places demands not only on the conveyor systems, but also on the conveyor belting. Consideration should be given to the following: a. installation of creeper drives to allow a conveyor to start and turn at a very slow speed until the belting and equipment have “warmed up”. It is also common practice to keep an empty conveyor operating continually at creep speed to prevent build-up of deposits which could harm the belting; b. reduction of impact at loading points to prevent damage to a frozen belt; c. selection of belting which combines resistance to cold flex cracking and impact cracking with other desirable properties; d. selection of belting which will exhibit longitudinal and transverse cold flexibility to maintain adequate contact around pulleys and adequate troughing characteristics to ensure proper drive and tracking. It is strongly recommended that individual belting manufacturers be consulted for proper recommendations on belting destined for cold temperature service.

IDLERS Diameter The diameter of carrying idlers should conform to the following: Table 14-1. Idler Recommendations

Diameter of Idler up to 4 in (100 mm)

Conditions of Use Portable underground equipment for coal.

4 in (100 mm)

Materials 40 lb/ft3(640 kg/m3) or less. Speeds 300 ft/min (1.5 m/s) or less.

5 in (125 mm)

Materials of 100 lb/ft3(1600 kg/m3) or less. Speeds 600 ft/min (3 m/s) or less. Lumps notover 12 in (300 mm).

6 in (150 mm)

Materials over 100 lb/ft3(1600 kg/m3). Speeds 800 ft/min (4 m/s) or less. Lumps up to 18 in (450 mm).

7 in (175 mm)

Materials over 100 lb/ft3(1600 kg/m3). Speeds up to 1000 ft/min (5 m/s). Lumps over 18 in (450 mm).

Note: Idlers are also categorized by their load carrying ability. The Conveyor Equipment Manufacturers Association (CEMA) defines a range of standard idlers. IP:1 2011 Conveyor and Elevator Belt Handbook

96


Width The length of the idlers must be greater than the width of the belt to allow for transverse movement of the belt. In general, the length of the idlers shall not be less than: Table 14-2. Width Belt Width

Return Idler Length - Amount greater than Belt Width

under 36 in (914 mm)

+ 3 in (75 mm)

36 in (914 mm) to 60 in (1524 mm)

+ 4 in (100 mm)

over 60 in (1524 mm)

+ 5 in (125 mm)

Note: For information on idler gaps see Chapter 5, Troughability and Load Support. Structural Clearance The conveyor belt must have the ability to move transversely to prevent damage to the belt edges due to structural misalignment, foundation shifting, temperature changes, weather conditions, belt tolerances, etc. These conditions become more severe as the conveyor length increases. Therefore the following belt clearance must be observed: Table 14-3. Belt Structural Clearance Structural Clearance (Minimum Each Edge)

Belt Width

Under 500 ft (152 m) Centers

Over 500 ft (152 m) Centers

under 36 in (914 mm)

2 1/2 in (64 mm)

6 in (152 mm)

36 in (914 mm) to 72 in (1829 mm)

4 in (102 mm)

6 in (152 mm)

Over 72 in (1829 mm)

6 in (152 mm)

8 in (203 mm)

Table 14-4. Idler Recommendations Return Idler Type

Training Influence

Comments

2 Roll “V”

Positive

Flat

None

Acceptable with additional training idlers as needed

Flat Disc - Clustered Ends

None

Less desirable than flat but acceptable with training idlers as needed. (Cluster of 8 in (203 mm) min.)

Flat Disc - Equally Spaced

None

Not recommended

Highly recommended on conveyors over 500 ft. (152 m)

A belt is basically trained by the effect of contact between the belt surface and the face of the idlers. Misalignment in a conveyor system, misaligned idlers, or a crooked belt, will cause off-center operation, but as long as the belt surface contacts the idlers and there is not a restricting edge force, training can be controlled by adjusting idler alignment and/or use of training idlers. Usually, these adjustments are sufficient to permit acceptable belt training. Narrow disc type return idlers can cause conveyor belt training problems because they violate the basic concepts for belt training in two respects, as follows: 1. The belt edges may extend beyond the end discs on the idlers. Any degree of off-center operation due either to idler misalignment or belt crookedness results in an edge extending well beyond the end disc, sometimes to the extent that the cantilever effect eliminates or reduces belt surface contact on the face of the idler to the point that training effect is lost. At this point, the belt tends to move off the pulley until it contacts some stationary part of the conveyor structure, thus damaging the belt and/or the structure. This effect will be exaggerated with belts in which some degree of cupping or curl is present. 2. When a belt moves off-center on narrow disc type return idlers to the extent that one edge is inside the end disc, that edge may drop down enough that corrective training action will be restricted because the belt edge is trapped inside the end disc. This effect will also be exaggerated by any degree of cupping or curl in the belt (see Figure 14-1).


97


Figure 14-1. Table 14-5. Minimum Face Width of Pulleys

Conveyor Centers

Belt widths up to and including 42 in (1050 mm)

Belt widths over 42 in (1050 mm)

Under 500 ft (150 m)

Belt width plus 2 in (50 mm)

Belt width plus 3 in (75 mm)

500 ft (150 m) or over

Next larger standard face width beyond recommendation shown above.

Examples: 1. A belt 42 in (1050 mm) wide on centers of 450 ft (135 m) will use pulleys with a minimum face width of 44 in (1110 mm). 2. A belt 48 in (1200 mm) wide on centers of 450 ft (135 m) will use pulleys with a minimum face width of 51 in (1275 mm). 3. A belt 42 in (1050 mm) wide on centers of 500 ft (150 m) will use pulleys with a minimum face width of 46 in (1150 mm) since a 46 in (1150 mm) face is the next standard face width above 44 in (1100 mm). 4. A belt 48 in (1200 mm) wide on centers of 500 ft (150 m) will use pulleys with a minimum face width of 54 in (1400 mm) since a 54 in (1400 mm) face is the next standard face width above 51 in (1275 mm).

BELT TRAINING The basic rule of tracking is that the belt moves toward the end of the roll/idler that it contacts first. All conveyors require a positive training influence on the belt to maintain a centered position. This is particularly true on conveyor centers over 500 ft (150 m) where structural tolerances, weather conditions and multi-ply belt roll variations can accumulate. Usually the troughing idlers on the carrying side exert a training influence and are generally sufficient to maintain belt position. The addition of carrying side training idlers can be installed if needed for the more difficult conveyor. The return side presents the most serious condition for belt damage due to its confined position within the conveyor structure or idler hanger brackets. The typical flat return idler exerts no positive centering influence on the belt. Table 15-4 outlines the effectiveness of the different types of return idlers as to belt training. Training a belt is the procedure required to make a belt run straight when empty and also when fully loaded. If a conveyor belt is off center in the loading zone the belt will not track well down the carry side of the conveyor. It is therefore critical to have the belt centered as it goes through the areas where material is loaded on the belt. Pulleys All pulleys must be set at right angles to the direction of belt travel. Manual Take-Up This device must be such that when tension is applied to the pulley, the pulley will remain at right angles to the direction of belt travel.


98


Automatic Take-Up The track alignment must be such that the pulley(s) are maintained at right angles to the direction of belt travel. In a gravity take-up the carriage must be guided to maintain the pulley on a horizontal axis. Idlers The troughing and return idlers should be initially installed at right angles to the direction of belt travel. All tilted wing idlers must be installed with the tilt in the direction of the belt travel. Tilting of idlers should not be done on reversing conveyors as the positive training influence in one direction can cause negative training influence when the belt is run in the opposite direction. Conveyor Structure The conveyor structure must be straight and level. Side Guide Idlers Side guide idlers are not recommended for constant use in forcing belts to run straight. They may be used to assist in training a belt initially or for protection in an emergency. Reversible Belts In reversible belts all idlers should be kept at right angles to the direction of belt travel and any correction necessary made with self-aligning idlers designed for reversing operation. (See Tilted Troughing Idlers below.) Procedure for Training a Belt The normal sequence of training a belt is to start with the return run, working toward the tail pulley, and then to follow with the top run in the direction of belt travel. Start with the belt empty. For stiff belts it may be desirable to load the belt after the return run is corrected to complete the training. Adjustment is made while the belt is running and should be spread over some length of the conveyor preceding the region of trouble. The result of an adjustment may not be immediately apparent, so permit the belt to run for several minutes after the idlers have been adjusted to determine if additional adjustment is required. If the belt is over-corrected after adjustment, it should be restored by moving the same idler back and not by shifting additional idlers. If the entire belt runs to one side at a particular point(s) on the conveyor structure, the cause will probably be due to the alignment or leveling of the structure or to the idlers and pulleys in that particular area or a combination of these factors. If a section(s) of the belt runs off at all points along the conveyor, the cause is most likely in the belt itself, in the belt not being joined squarely, or in the loading of the belt. If it is in the belt, this will be due to bow, and it should correct itself after it is operated under fully loaded tension. A bowed belt rarely needs to be replaced. If a belt is not joined squarely, it is necessary to cut away the faulty joint and make a new one properly squared. Tilted Troughing Idlers Tilting the troughing idlers forward, not over 2°, in the direction of belt travel produces good alignment. If the angle of tilt exceeds 2°, excessive wear may occur on the pulley side of the belt and on the troughing idler itself due to rotation of these rolls on an axis not at right angles to the direction of belt travel. Tilted troughing idlers must not be used on reversible belts. Centering a belt as it approaches the tail pulley can be further assisted by slightly advanced and raising the alternate ends of the return idlers nearest the tail pulley. Self-Aligning Idlers Both troughing and return idlers are usually mounted on center pivots. An off-center belt causes the idlers to rotate about these center vertical pivots in such a direction as to bring the belt back to center. These should only be used on problem systems and should ideally be up to 50 ft from any terminal or bend pulleys to achieve maximum benefit. Do not use training idlers in either concave or convex vertical curves. 1. Unidirectional Self-Aligning Idlers This type of idler depends on pressure from the belt edge on a side roller mounted on an arm extended in the front of the idler. It will function only for belts running in one direction.


99


2. Nondirectional Self-Aligning Idlers This type of idler depends on pressure from the off-center belt on eccentric discs at the ends of the troughing rolls. It will function on reversible belts.

PULLEY CROWNS The purpose of a pulley crown is to create a centering force on the belt so that the belt tends to train toward the center of the pulley thereby holding the belt centrally on the conveyor. The crowned pulley is most effective when it has a long unsupported span of belt approaching the pulley. The lateral position of the belt can be influenced by the crown more easily when there is a minimum of resistance being offered by a supporting slider bed or supporting idlers. Crown-faced pulleys should never be used on systems with steel cord belting, or high modulus ply type belting. When a crowned pulley is used, the recommended amount and configuration of crown used is dependent upon the belt type and belt tension applied.

PULLEY LAGGING Drive Pulleys Drive pulleys should be lagged for the following reasons: 1. Improved coefficient of friction. This permits a belt to be driven by lower slack slide tension, resulting in lower total tension in many cases. 2. Reduction of slippage in wet conditions if grooved lagging is used. 3. Increased life for pulley and belt covers. Non-Driving Pulleys Non-driving pulleys, especially those contacting the carrying cover, should be lagged for the following reasons: 1. Partial self-cleaning. Rubber deflection minimizes material build up on pulleys. Grooving generally improves the deflection and cleaning action of lagging. 2. Increased life for pulley and belt covers. Quality of Pulley Lagging Various polymers are used for lagging, but the most common are natural rubber, SBR, neoprene and urethane. Except in very light service, the level of quality is generally equal to or greater than Grade 2 conveyor belting. Hardness recommendations for lagging are generally as follows: Drive and High Tension Pulleys* 60 ± 5 Shore A Durometer Non-Driving, Low Tension Pulleys 45 ± 5 Shore A Durometer *With some high tension steel cord belts, pulley lagging on high tension pulleys of 70 ± 5 Shore A Durometer is recommended. Types of Pulley Lagging 1. Vulcanized-on Lagging This is a material generally 1/2 in (13 mm) thick cured directly to the metal surface. Fabric reinforcement is not required. It is longer wearing with better and more uniform adhesion to the pulley than bolted-on lagging. 2. Cemented-on Lagging This is similar to vulcanized-on lagging except that the rubber is cured and supplied in sheet form. Field application using the proper self-curing cement is its big advantage over the vulcanized-on type. When properly applied, the results are comparable to vulcanized-on lagging. 3. Sprayed-on Lagging This type of lagging is applied from an airless spray gun supplied with suitable material.


100


4. Bolted-on Lagging This comes in strip or sheet form and is fabric backed with two or more plies of belt duck to hold bolts. The thickness is generally 1/8 in (3 mm) for smooth lagging and 1/4 in (6 mm) for grooved. When installed, the bolt heads must be sunk below the level of the surrounding lagging to prevent damage to the belt cover. 5. Spiral Lagging This is a lagging with a special adhesive backing which may be spiraled onto the pulley for low tension service. 6. Stretch on Sleeve Lagging This lagging is previously made as a curved sleeve and is stretched onto the pulley. 7. Grooved Pulley Lagging A grooved lagging is usually required to maintain a sufficient coefficient of friction between a drive pulley and a wet belt. The pattern of grooving most commonly used is a chevron or herringbone design with the apex at the pulley center pointing in the direction of belt travel so the pulley cover engages the groove progressively from the center to the belt edge, driving out water or slimy materials. Groove depth should leave at least 1/16 in (2 mm) or more material at the bottom on fabric-backed lagging and 1/8 in (3 mm) or more at the bottom on non-reinforced lagging. Groove widths generally range from 1/4 in (6 mm) to 3/4 in (19 mm). Center spacing of grooves is usually from 1 in (25 mm) to 2 in (50 mm) but sometimes is as little as 1/2 in (13 mm). Note: For further information on pulley lagging please refer to the current ARPM Roll Covering Handbook (ARPM IP-5).

TAKE-UP Introduction A take-up device in a conveyor belt system has three major functions: 1. To establish and maintain a minimum slack-side operating tension in the belt that will enable the drive pulley(s) to impart the necessary tractive force to the belt and will prevent excessive sag of the loaded belt between idlers. 2. To remove the accumulation of slack (elastic elongation) in the belt occurring at start-up or during momentary overloads, in addition to maintaining the correct operating tension. 3. To provide sufficient reserve belt length to permit resplicing if necessary. Types 1. Screw Take-Up (Manual) This type of take-up consists of tension pulley, usually the tail, which can be moved to tighten the belt by means of threaded rods or by steel cables which can be wound on a winch. They give no indication of the tension they establish and are adjusted by trial and error until slippage is avoided. They are unable to automatically compensate for any length changes in the belt between adjustments and they permit wide variations in belt tension. Use is generally restricted to short and lightly stressed conveyor belts up to 200 ft (60 m) center-to-center in length. 2. Automatic Take-Up This type depends on suspension of a predetermined weight (gravity) or by activation of a torque motor or by hydraulic pressure. These devices maintain a predetermined tension at the point of take-up regardless of changes in belt length resulting from load change, start-up, stretch, etc. They allow the belt to be run under the minimum operating tension and should be used on all long conveyors and moderate to highly stressed conveyors.

ASSOCIATED EQUIPMENT Decking Decking between the top and return runs will prevent spillage of excess material from falling on the return. Even though it might not be considered for the entire length, such decking is especially desirable in the loading region.


101


Plows Plows should be placed on the return run immediately in front of the tail pulley or other pulleys so material which has fallen on the return run is not carried between the belt and pulley. Plows are generally held against the belt by gravity and set at an angle of about 45° to the direction of belt travel. Screen Bars When dealing with lumpy material mixed with fines, incorporation of screen bars into the back plate of the chute allows the fines to fall through first and form a bed or cushion to help absorb the impacting force of the lumps and minimize cutting and gouging of the cover. A “V” slot cut in the bottom of the chute is another satisfactory method of allowing fines to fall on the belt before the lumps. Skirt Boards Skirt boards assist in centering and settling the load on the belt as it leaves the loading point. They are vertical or inclined slightly outward at the top and are set in from each edge by approximately one-sixth of the width of the belt. Thus, at the start, the opening is two-thirds of the width of the belt, tapering out in the direction of belt travel. The length, which should be sufficient to center and settle the load properly, is generally four to five times the width of the belt. The solid structure of the skirt board is never brought down tightly against the belt surface, but is left with a substantial clearance [approximately 1 in (25 mm) minimum] which is then closed with a sealing strip. The clearance between the skirt boards and the belt should increase in the direction of belt travel to permit freeing any trapped material. To further ensure against trapping material here, the sealing strip should be on the inside of the skirt board. Skirt boards are what may be termed “necessary evils” and, if not kept properly set and sealed, can do more damage to the belt than any other single source of abrasion or cover cutting. Vertical Take-Up Protection Plates The use of a metal plate is recommended to keep material which would have fallen into the loop from dropping down between the belt and the take-up pulley. Belt Cleaning Devices Adequate means must be provided for belt cleaning, particularly where materials are damp and/or sticky and have a tendency to build up on the pulley or idlers. Build-up of material on snub pulleys and return idlers as well as on other pulleys will cause the belt to run out of line. 1. Brushes Dry materials may be cleaned off the belt with rotating bristle or vane brushes driven at a fairly high surface speed. These brushes wear rapidly, require considerable maintenance, and are likely to fill up and solidify if used with moist, wet, or sticky materials. 2. Scrapers These are generally mounted adjacent to the head pulley. Care should be taken that they are held against the belt with only sufficient pressure to remove the material without causing damage. With sticky materials it is generally necessary to apply a scraper to the snub pulley also. 3. Water Sprays Water sprays before wiping with a scraper will do a good cleaning job on almost any material.

MAINTENANCE Lubrication of Metal Parts Provision must be made for lubrication of the driving gear, bearings, and idlers of a conveyor system, and a program of periodic checking should be adopted and followed. All lubrication should be according to the recommendations of the manufacturer of the equipment. 1. Idlers Idlers should be lubricated as frequently as is needed to keep them in good running condition. A “frozen” idler will cause excessive cover wear and may lead to crooked running resulting in edge wear or even igniting the belt when it is stopped. 2. Self-Aligned Idlers These idlers must have freedom to move and good lubrication is essential.


102


3. Excessive Lubrication Excessive lubrication should be avoided and extreme care must be taken in lubrication that oil or grease does not get on the belt and that no excess can drop or otherwise come into contact with the covers of the belt. Belt The belt itself should be checked periodically for cover cuts, gouges, abraded areas, edge wear, and carcass breaks. Both the top and bottom of the belt should be inspected. The frequency of inspection will depend on the type and severity of service. Field-made repairs of belting are discussed in detail below.

COMMON DIFFICULTIES, PROBABLE CAUSES, AND REMEDIES As important as noting the occurrence of a rip, tear, cut, or gouge are the pattern and location of a belt and/or equipment in order to determine the cause of problems and thus apply suitable remedies. Some of the more common difficulties that arise in a conveyor belt installation, the probable causes, and the remedies are given below. Problem 1:

Conveyor runs to one side at given point on structure.

Cause A: Solutions:

Buildup of material on idlers Remove accumulation; improve maintenance; install scrapers or other cleaning devices.

Cause B: Solutions:

Sticking idlers Free idlers and improve maintenance and lubrication

Cause C: Solutions:

Idlers or pulleys out-of-square with centerline of belt Readjust idlers in affected area

Cause D: Solutions:

Conveyor frame or structure crooked Straighten in affected area

Cause E: Solutions:

Idler stands not centered on belt Readjust idlers in affected area

Cause F: Solutions:

Conveyor frame or structure not level Level frame or structure in affected area

Problem 2:

Particular section of belt runs to one side at all points on the conveyor.

Cause A: Solutions:

Belt not spliced/joined squarely Remove affected splice and re-splice

Cause B: Solutions:

Bowed belt For a new belt, this condition should disappear during break-in; in rare instances, belt must be straightened or replaced; check storage and handling of the belt rolls.

Problem 3:

Belt runs to one side for long distance or entire length of the conveyor.

Cause A: Solutions:

Belt running off-center around the tail pulley and through the loading area Install training idlers on the return side prior to the tail pulley

Cause B: Solutions:

Off-center or poor loading Adjust chute to place load on center of belt; discharge material in direction of belt travel at or near belt speed.

Cause C: Solutions:

Buildup of material on idlers Remove accumulation; improve maintenance; install scrapers or other cleaning devices.

Cause D: Solutions:

Idlers or pulleys out-of-square with centerline of the belt Readjust idlers in the affected area

Cause E: Solutions:

Conveyor frame or structure crooked Straighten in affected area

Cause F: Solutions:

Idler stands not centered on belt Readjust idlers in affected area


103


Problem 4: Cause A: Solutions: Problem 5:

Belt tracks erratically and does not follow a pattern Belt too stiff to train Install self-aligning idlers; tilt troughing idlers forward; use more troughable belt on replacement Belt runs off at the tail pulley

Cause A: Solutions:

Belt running off-center around the tail pulley and through the loading area Install training idlers on the return side prior to the tail pulley

Cause B: Solutions:

Material spillage and buildup Improve loading and transfer conditions; install cleaning devices; improve maintenance

Cause C: Solutions:


Problem 6:

Belt runs off at the head pulley

Cause A: Solutions:

Pulley lagging worn Replace the pulley lagging

Cause B: Solutions:


Cause C: Solutions:


Cause D: Solutions:

Idler stands not centered on the belt Readjust the idlers in the affected area

Problem 7:

Belt slip

Cause A: Solutions:

Insufficient traction between the belt and pulley Lag the drive pulley; increase the belt wrap; install belt-cleaning devices

Cause B: Solutions:


Cause C: Solutions:

Counterweight too light Add counterweight or increase the screw take-up tension to value determined from calculations

Cause D: Solutions:

Material spillage and buildup Improve loading and transfer conditions

Cause E: Solutions:


Problem 8:

Belt slip on starting

Cause A: Solutions:

Insufficient traction between the belt and pulley Lag the drive pulley; increase the belt wrap; install belt-cleaning devices

Cause B: Solutions:

Counterweight too light Add counterweight or increase the screw take-up tension to value determined from calculations

Cause C: Solutions:


Problem 9: Cause A: Solutions:

Excessive belt stretch Improper belt installation, causing excessive belt stretch Pull belt through the counterweight with tension equal to at least the empty running tension; break belt in with mechanical fasteners


104


Cause B: Solutions:

Improper initial positioning of the counterweight in its carriage, causing apparent excessive belt stretch Consult conveyor belt manufacturer for the recommended initial position

Cause C: Solutions:

Insufficient counterweight travel Consult conveyor belt manufacturer for recommended minimum distances

Cause D: Solutions:

Tension too high Increase belt tonnage at same tonnage; reduce tonnage, maintain same belt speed; reduce friction with better maintenance and replacement of damaged idlers; decrease tension by increasing arc of contact or go to lagged pulley; reduce the counterweight to minimum amount

Cause E: Solutions:

Counterweight too heavy Lighten counterweight to the value required by calculations

Cause F: Solutions:

System under belted Recalculate belt tensions and select proper belt


Belt shrinks Belt absorbing moisture Put in extra piece of belt; increase tension if belt construction permits - contact conveyor belt manufacturer before increasing tension Grooving, gouging or stripping of the top cover

Cause A: Solutions:

Skirt boards improperly adjusted or wrong material Adjust the skirt board supports to a minimum of 1 in between metal and belt, with gap increasing in direction of belt travel; use skirt board rubber, not old belt

Cause B: Solutions:

Belt spanking down under load impact Install cushion idlers

Cause C: Solutions:

Material hanging up in or under the chute Improve loading to reduce spillage; install baffles; widen chute

Cause D: Impact of material on the belt Solutions: Reduce impact by improving the chute design; install impact idlers Cause E: Jamming of material in chute Solutions: Improve loading to prevent spillage or install baffles; reduce size of material or redesign chute Problem 12:

Excessive top cover wear, uniform around the belt

Cause A: Solutions:

Dirty, stuck, or misaligned return rolls Remove accumulation; install cleaning devices; use self-cleaning return rolls; improve maintenance and lubrication

Cause B: Solutions:

Cover quality too low Replace with a belt of heavier-cover gauge or higher-quality rubber

Cause C: Solutions:

Material spillage or buildup Improve loading and transfer conditions; install cleaning devices; improve maintenance

Cause D: Solutions:

Off-center loading or poor loading Adjust the chute to place the load on the center of the belt; discharge material in the direction of belt travel at or near the belt speed

Cause E: Solutions:

Excessive sag between idlers causing the load to work and shuffle on the belt as it passes over idlers Increase tension if unnecessarily low; reduce idler spacing

Problem 13:

Severe pulley cover wear

Cause A: Solutions:

Sticking idlers Free idlers, improve maintenance and lubrication

Cause B: Solutions:

Slippage on the drive pulley Increase tension through screw take-up or add counterweight; lag the drive pulley; increase arc of contact

Cause C: Solutions:

Material spillage and buildup Improve loading and tranfer conditions; install cleaning devices; improve maintenance


105


Cause D: Solutions:

Material trapped between the belt and pulley Install plows or scraper on return run ahead of tail pulley

Cause E: Solutions:

Bolt heads protruding above lagging Tighten bolts; replace lagging; use vulcanized on lagging

Cause F: Solutions:

Excessive forward tilt of trough rolls Reduce forward tilt of idlers no more than 2 degrees from vertical

Cause G: Solutions:

Cover too thin or low grade for material being handled Specify a thicker cover and/or a higher grade belt cover on replacement

Problem 14:

Longitudinal grooving or cracking of bottom cover

Cause A: Solutions:


Cause B: Solutions:

Slippage on the drive pulley Increase tension through screw take-up or add counterweight; lag the drive pulley; increase arc of contact

Cause C: Solutions:


Cause D: Solutions:

Pulley lagging worn Replace pulley lagging

Problem 15:

Covers harden or crack

Cause A: Solutions:

Heat or chemical damage Use the belt designed for the specific condition

Cause B: Solutions:

Improper storage or handling Refer to conveyor belt manufacturer for proper storage and handling instructions


Cover swell in spots or streaks Spilled oil or grease; over-lubrication of idlers Improve housekeeping; reduce quantity of grease used; check grease seals Belt breaks at or behind fasteners; fasteners pull out

Cause A: Solutions:

Fastener plates too long for pulley size Replace with smaller fasteners; increase pulley size

Cause B: Solutions:

Wrong type of fastener; fasteners too tight or too loose Use proper fasteners and splice technique; set up schedule for fastener inspection

Cause C: Solutions:

Tension too high Increase belt speed, same tonnage; reduce tonnage, maintain same belt speed; reduce friction with better maintenance and replacement of damaged idlers; decrease tension by increasing arc of contact or go to lagged pulley; reduce the counterweight to minimum amount

Cause D: Solutions:

Heat or chemical damage Use belt designed for specific conditions

Problem 18:

Vulcanized splice separation

Cause A: Solutions:

Belt improperly spliced Re-splice using proper method as recommended by conveyor belt manufacturer

Cause B: Solutions:

Pulleys too small Use larger-diameter pulleys

Cause C: Solutions:

Tension too high Increase belt speed, same tonnage; reduce tonnage, maintain same belt speed; reduce friction with better maintenance and replacement of damaged idlers; decrease tension by increasing arc of contact or go to lagged pulley; reduce the counterweight to minimum amount


106


Cause D: Solutions:

Material trapped between the belt and pulley Install plows or scrapers on return run ahead of the tail pulley

Cause E: Solutions:

Improper transition between troughed belt and terminal pulleys Adjust transition in accordance with conveyor belt manufacturer’s recommendations

Problem 19:

Excessive edge wear, broken edges

Cause A: Solutions:

Off-center loading or poor loading Adjust chute to place the load on the center of the belt; discharge material in direction of belt travel at or near belt speed

Cause B: Solutions:


Cause C: Solutions:

Belt hitting structure Install training idlers on carry and return run

Cause D: Solutions:

Bowed belt For a new belt, this condition should disappear during break-in; in rare instances, the belt must be straightened or replaced; check storage and handling of belt rolls

Problem 20:

Transverse breaks at belt edge

Cause A: Solutions:

Belt edges folding up on structure Install limit switches; provide more clearance

Cause B: Solutions:

Improper transition between troughed belt and terminal pulleys Adjust transitions in accordance with conveyor belt manufacturer’s recommendations

Cause C: Solutions:

Severe convex (hump) vertical curve Decrease idler spacing in vertical curve; increase curve radius; consult conveyor belt manufacturer for assistance

Problem 21:

Short breaks in carcass parallel to belt edge, star breaks in carcass

Cause A: Solutions:

Impact of material on the belt Reduce impact by reducing the chute design; install impact idlers; supply more impact resistant belt on replacement

Cause B: Solutions:

Material trapped between belt and pulley Install plows or scrapers on return run ahead of tail pulley

Cause C: Solutions:

Belt folding back on itself Realign idlers to center belt; remove obstructions which cause edge to fold back; install limit switches to shut off motor in extreme cases of shifting

Problem 22:

Ply separation

Cause A: Solutions:

Insufficient transverse stiffness Replace with the proper belt

Cause B: Solutions:

Pulleys too small Use larger-diameter pulleys

Cause C: Solutions:

Heat or chemical damage Use the belt designed for specific condition

Problem 23:

Carcass fatigue at idler junction

Cause A: Solutions:

Improper transition between troughed belt and terminal pulleys Adjust transition in accordance with conveyor belt manufacturer’s recommendations

Cause B: Solutions:

Severe convex (hump) vertical curve Decrease idler spacing in curve; increase curve radius

Cause C: Solutions:

Excessive forward tilt of troughed rolls Reduce forward tilt of idlers to no more than 2 degrees from vertical


107


Problem 24: Cause A: Solutions: Cause B: Solutions:

Cover blisters or sandblisters Cover cuts or very small cover punctures allow fines to work under the cover and propagate between the cover and carcass Make a vulcanized spot repair or a self-curing repair Spilled oil or grease, over lubrication of idlers; improve housekeeping; reduce quantity of grease used; check grease seals Decrease idler spacing in curve; increase curve radius

ELEVATOR BELTS The general rules set forth in Chapter 15, Storage of Belting, and in the preceding pages of this chapter are to be observed in storing, installing, maintaining, repairing, and inspecting elevator belts. The following comments apply to elevator belts only: Punching Elevator belts should be punched with the aid of a template to ensure correct location of the holes. Tension Apply only enough tension to avoid: a. Slippage at the drive pulley and; b. Belt slack at the boot pulley. Joints 1. Fastened Lap and butt joints are most frequently used. Lap joints are generally not recommended for belts having more than six or seven plies of fabric because they tend to pound considerably on the pulley. A butt strap joint is generally recommended for thick belts, in which case a separate piece of belting is laid over the joint extending under at least two buckets on each side of the joint. Plate fasteners are not recommended where the belting is stressed beyond 50% of its rating. 2. Vulcanized Vulcanized splices are recommended on large, highly stressed belts and often are the most economical when adequate take-up is available. 3. Oil Well Splice The oil well splice is sometimes used for light-duty applications where the belt gauge is thin and the tensions are low. Some users have successfully developed oil well splices that are tailored to their equipment and type of belt. The following guidelines should be adhered to: a. Do not use oil well splices on any elevators running at more than 50 percent of rated belt tension. b. Clamps should extend to within 1/2 in of belt edges. If they are too much shorter than the belt width, the belt may tend to crease around clamp ends and tear. c. Plates used to make the clamps should be heavy enough to spread the clamp pressure over as mucg belt area as possible. Thickness of 1/4 in for light belts and service to 1/2 in for heavy belts and service are generally acceptable. d. Bend as large a radius as possible. Radii more than 1in are probably rarely used but even a 1 in radius can induce enormous bending stresses in the belt. e. Form the clamps by bending steel plate rather than rounding one edge of a steel angle bar. f. Keep bolt holes as far from the ends of the clamps as possible; twice the thickness of the belt with a 1 in minimum. Less than 1 in is no doubt frequently used with success, especially in light service, but it could lead to reduced splice life. g. Install clamps tightly and then retighten at frequent intervals. The more the rubber in the belt construction, the greater the possibility of some compression set early in the splice life which could cause the clamp to loosen. This is the same procedure commonly recommended with mechanical conveyor belt fasteners.


108


Flaps Flaps made of transmission belting or conveyor belting (new or used) are useful on continuous bucket elevators to keep material from getting under the buckets as they discharge. Hot Material Where hot material is being carried, washers made from belting placed under each bucket are recommended. These washers will protect the belt from the heat of the bucket. Clearance The elevator system must be designed to provide the necessary clearance for the belt and buckets. Inspection 1. Splices Splices should be inspected frequently to see that there is no immediate danger of a failure that would allow the whole belt to fall into the boot. Such an occurrence could result in serious damage to the belt. 2. Buckets The buckets and bolts should be inspected frequently. Badly worn buckets should be replaced. Loose bolts should be retightened to seat the head in the cover properly. Badly worn bolts should be replaced. 3. Boot When handling hard, coarse materials, an accumulation of lumps in the boot should be avoided. Pieces of material not picked up by the normal passage of buckets may become jammed and tear off buckets or damage the belt. Decking installation just above the boot pulley will prevent any large particles from falling between the pulley and the belt. The take-up mechanism on a boot take-up should be kept clean to permit the required adjustment.

LOADING AND DISCHARGE Conveyors Only good loading and discharge conditions will provide the full potential service possible in conveyor belt applications. Good service is vitally dependent on these conditions. Conveyor Loading Loading points should be designed to permit loading material onto a belt in a manner resulting in the least wear or damage to the belt. Ideally, the material should be loaded in the direction of belt travel with horizontal velocity the same as belt velocity, as little vertical fall as possible, uniform flow, and impact distributed over the maximum surface wear area. Selection of auxiliary loading or feeding equipment, such as chutes, gate controlled hoppers, belt feeders, apron or pan feeders, reciprocating or vibrating feeders, must be based on the characteristics of the material, the surge control required, and so forth. This is particularly important at intermediate loading points where additional material may be introduced to an already existing load. Conveyor Discharge Discharge of conveyor belts is normally effected over the head end pulley, but it may occur over either terminal pulley on reversing conveyors. Intermediate discharge may be by fixed or movable trippers; nonabrasive material may be plowed off either or both sides of the belt. Discharge chutes must be designed to match the trajectory of the material and to accept and pass freely the type(s) of material handled. Scrapers, brushes, limit switches, interlocking controls, and so forth, must be chosen with care to prevent the belt from running through material pile-up from over-filled bins or stoppage of equipment. Elevators Belt elevators are generally of two types: (1) spaced centrifugal bucket elevators and (2) continuous bucket elevators. Either type may be vertical or inclined. Spaced centrifugal discharge elevators employ centrifugal force and gravity to effect unloading. The shape and spacing of the buckets, the relatively high speed of the belt, and the diameter of the head pulley are designed to provide satisfactory discharge by taking


109


advantage of centrifugal force acting at the center of gravity of the material in the bucket. Continuous bucket elevators have buckets installed close together and shaped so that discharge can be accomplished by gravity alone at fairly slow speeds. The discharge from one bucket slides over the flanged back of the preceding bucket. Elevator Loading Spaced centrifugal elevators are usually vertical and, when inclined, are not more than 20° to 25° from the vertical. Loading is accomplished by digging in the boot or a combination of digging and “fly-feed” from a chute feeding directly into buckets on the ascending leg. Centrifugal discharge elevators are preferred for handling fine, free flowing, or small lump material such as grain, sand, gravel, coal, finely crushed ore, sugar, or any other material which may be loaded into the spaced buckets by digging at the boot pulley and which leaves the bucket easily in discharging. Easy digging and discharge materials such as grain are handled at higher speeds and with closer bucket spacing, whereas sluggish, sticky, and large lumpy materials require lower speeds and wider bucket spacing. Continuous bucket elevators may be vertical or inclined but are normally vertical for best pick-up and discharge of materials. Loading is “fly-fed” directly from a chute into the first, second, or third bucket above the boot pulley. The belt is supported from behind and guided laterally at the loading point to ensure accurate loading from the chute. Any digging is only small amounts of spill in the boot. The speed of continuous bucket elevators is slower than that of spaced centrifugal elevators. The “V” bucket is shaped and spaced to handle abrasive materials such as coarse crushed ore, stone, or other large lumpy materials. The slow speed is also excellent for very fine, dusty materials that tend to trap air. Elevator Discharge Discharge of spaced centrifugal bucket elevators is directly affected by the shape of the bucket; the weight, size, and cohesiveness of the material; the speed of the belt; and the diameter of the head pulley. All of these factors must be related and the discharge opening located so that little or no material can spill down the back leg. Continuous bucket elevators, particularly inclined elevators, are not as critically affected by discharge variations as are spaced bucket elevators, but the same factors must be considered.

FIELD REPAIRS OF BELTING A conveyor or elevator belt represents a substantial investment both for the manufacturer and the user. To protect this investment, the belt should be repaired whenever it is damaged so that its expected service life can be realized. The user should institute regularly scheduled maintenance of belting to achieve the lowest unit operating cost. In service, repairs can be separated into three groups by the type of damage and its immediate effect on continuing operation of the belt. They are: (1) temporary repairs, (2) minor vulcanized repairs, and (3) major vulcanized repairs. 1. Temporary Repairs These repairs involve cuts or gouges in the cover that expose the carcass, thereby permitting the entrance of moisture or foreign material. The belt manufacturers can usually suggest a suitable self-curing compound. The repair will have reasonable abrasion resistance and will keep moisture and foreign material out of the carcass. These repairs can be quickly and easily made so that down time is kept to a minimum. It should be recognized, however, that self-curing (cold bond) repairs are not a substitute for vulcanized ones nor are they as long lasting. In general, repairing should be carried out in a dry area as free from dust and dirt as practical. The spot being repaired should be cleaned and dried before the application of the repair compound in order to ensure reasonably good adhesion. 2. Minor Repairs These repairs involve cuts, gouges, and stripped covers or edges that expose the carcass. Since a properly made repair requires several time-consuming steps and care to avoid cutting the carcass when preparing the area being repaired, it is necessary that they should be made during a scheduled shut-down of the operation of the belt. Specific instructions for making a repair and materials to accomplish the job are generally available from the belt manufacturer. The steps usually consist of removal of all loose cover, buffing and cleaning the exposed fabric surfaces and cover edges, application of bonding cement with appropriate drying time, and applying the cover repair compound. The repair is then completed in accordance with the instructions from the belt manufacturer.


110


It is important that repairs be made under good working conditions, moisture and dust or dirt should be prevented from contacting the area being repaired because either can cause poor adhesion or blistering of the repaired area. Work should be scheduled so that once the repair spot is cleaned, cementing, drying, and applying the new cover are done promptly to prevent contamination. 3. Major Vulcanization Repairs These repairs involve replacing at least a portion of the carcass. The severity of the injury to the carcass determines whether the belt can be allowed to run in regular service until a scheduled shutdown occurs or whether the operation should be shut down immediately to avoid drastic damage to the belt. In either case, the repair requires stepping back one or more of the carcass plies to remove the damaged area. Coated fabric is then laid into the area under repair, and finally the whole area is covered with new cover compound. Finally, the entire repaired area is finished in a heated press. Manufacturers supply proper instructions for stripping down the damaged area and inserting the new carcass members and the new cover. The necessary repair materials are available from the belt manufacturers, who will also supply in detail the proper conditions for making repairs. As with minor repairs, it is doubly important that moisture, dust and dirt be prevented from getting in or on the surface being repaired. The timing of the repair work should permit cementing, drying, and application of the repair materials in rapid sequence to prevent contamination of the clean surfaces before the whole area is sealed with new cover compound. With extensive carcass damage it is generally considered good practice to remove the damaged section and make a splice, inserting a length of new belting if required.


111


CHAPTER 15

STORAGE OF BELTING

RECEIVING AND HANDLING Generally, belting shipped from the manufacturer is in a desirable form for proper storage if it is not needed for immediate installation. Unless obvious damage has occurred during shipping, the roll of belting should be left in its original package. If there is obvious damage to belt packaging there may be damage to the belt. This should be inspected and the carrier notified for his inspection and claim adjustment. Crates or rolls of belting should never be dropped from freight cars, trucks, or other means of conveyance. They should be rolled in the same direction as the belt was originally coiled. Rolling a belt in the wrong direction tends to loosen the coils, and cause the roll to telescope which may cause damage to the belt during subsequent handling. When hoisting a belt with a chain and bar through the belt, the top coils of the belt should be protected with suitable pads or chain spreader.

STORAGE Preferably a roll of belting should be stored suspended off the floor on a bar pushed through the center of the roll. Where suspension is not possible, the roll should be stored on a dry surface, and rotated 90º every 6 months. It is particularly advisable to rotate a large roll of belting (over 25 tons) to prevent “flat spotting” (cold flow). This flow under pressure, creates a thinner belt. Although this condition may correct itself after several months of operation, it is advisable to take steps for its prevention. Belts in storage should be protected against excessive temperature and humidity, ozone, sunlight, oils, solvents, corrosive liquids and fumes, insects and rodents. Whenever possible, belts should be stored in their original shipping containers until ready for use, especially when such containers are wooden crates or are protected with cardboard and/or black polyethylene film. These containers will provide protection against the deteriorating effects of oils, solvents, and corrosive liquids, and some protection against ozone and sunlight. Even if the precautions outlined in this section are followed, it is still possible that the outside wrap of each roll may suffer excessive hardening or cracking during long-term storage. If this situation occurs, remove the outer turn of the roll to assure that optimum cover/carcass quality material is used for splicing. In the case of neoprene belting, the 40ºF (4ºC) minimum recommended temperature must be respected, since unlike other belting, excessive hardening and stiffening may result at temperatures even slightly below 40ºF (4ºC). Since this characteristic is time-temperature dependent, short-term exposure to ambient winter temperatures during normal shipment can be tolerated. Particular care should be taken to warm neoprene belting thoroughly before installation and splicing.

MOVING A ROLL OF BELTING When moving a roll of belting to and from storage, it should not be rolled any appreciable distance and then only in the direction marked on the container. Note: Reference ISO 5285 for specifics on storage and handling procedures.


112


CHAPTER 16

GLOSSARY OF CONVEYOR BELTING TERMS -A-

abrasion:a wearing away by friction. abrasion test:determination of the rate of wearing away by friction. abrasion tester:a machine for determining relative abrasion resistance. accelerated aging:intensive exposure to operating conditions to obtain an early change in physical properties of an elastomer. accelerated life test:a method designed to approximate in a short time the deteriorating effects obtained under normal service conditions. across the line starting tension: tension developed in a belt when full electrical power is applied to the drive system. adhesion:the strength of the bond between two surfaces. adhesion failure:the separation of two adjoining surfaces due to service conditions. adhesive:a material which, when applied, will cause two surfaces to adhere. adhesive coating:a coating applied to a surface to increase its bond to an adjoining surface. adhesive fabric:a fabric with a surface treatment which will bond two surfaces together when interposed between them. aftercure:a continuation of the process of vulcanization after the cure has been carried to the desired degree and the source of heat removed. afterglow:in fire resistance testing, the red glow persisting after extinction of the flame. aging:the irreversible change of properties after exposure to an environment for a period of time. air cure:vulcanization without the application of heat. air oven aging:a means of accelerating a change in the physical properties of rubber compounds by exposing them to the action of air at an elevated temperature at atmospheric pressure. ambient temperature:the temperature surrounding an object. angle of repose:the angle to the horizontal which a material assumes when dropped into a pile. angle of slide:the angle at which material begins to slide down an inclined surface. ANSI:American National Standards Institute. (www.ansi.org) antislip surface: a specially treated surface to obtain greater than normal traction. apron feed:an intermediate feed system. arc of contact: the circumferential portion of a pulley which is engaged by a belt. armored belt:a conveyor belt with crosswise insertions in the cover such as steel cables to minimize gouging or tearing of the cover by sharp objects. ARPM: Association for Rubber Products Manufacturers (www.arpminc.org) ASME: American Society of Mechanical Engineers. (www.asme.org) ASTM: International formerly American Society for Testing and Materials. (www.astm.org) atmospheric cracking:small fissures in the surface of a belt cover caused by exposure to atmospheric conditions. automatic take-up:a mechanical device to maintain proper tension in a belt automatically compensating for belt stretch or shrinkage in service. average modulus:the total change of stress divided by the total change of strain.


113


-Bbackstop:a mechanical device for preventing a loaded, inclined conveyor or elevator belt from running backwards after the belt has been stopped. Banbury mixer:a specific type of internal mixer used to incorporate fillers and other ingredients in rubber or plastic operations. bare pulley:a pulley whose face surface is not covered or lagged. bareback surface:a belt surface where the textile surface is without any coating. basic tension bearing yarns:one of the two warp systems in a straight warp fabric where the warp yarns are substantially without crimp and provide the tensile strength for the belt. basket weave: a fabric with ends of yarn side by side in both the warp and filling in a plain weave construction. bead rubber:an extruded polymeric compound used to fill the void between a butted joint of two pieces of fabric. bed:a continuous surface over which a conveyor belt may slide. belt:a flexible reinforced band placed around two or more pulleys to carry materials from one place to another. belt clamp:beams or metal plates secured transversely on both sides of belt ends to hold the ends in a desired position. belt conveyor:a mechanical system composed of suitable head, tail, bend pulleys and belt idlers or a slider bed to handle bulk materials, packages, or other objects placed directly upon it. belt cleaning device:a scraper or rotating device pressed against the belt surface to remove material stuck to the belt. belt drive:an assembly of power-driven pulley(s) used to transmit motion to a conveyor or elevator belt. belt fastener: a device for holding belt ends together. belt grade:a classification of belting according to the quality and properties of the belt cover. belt modulus:the ratio of stress to strain. belt sag:the amount of vertical deflection of a conveyor belt from a straight line between idlers, usually expressed as a percentage of the center to center spacing of the idlers. belt sag factor: a constant used to determine the amount of tension required to limit to a prescribed amount the sag of a belt between the idlers. belt slip: the action that takes place, causing a differential movement between the pulley surface and the belt. belt slope tension:see tension, slope. belt tracking switch:a limit switch actuated by the edge of a conveyor belt when the belt moves abnormally to either side of its centered path. belt turnover/twist:a system of pulleys arranged to turn a belt over. It prevents sticky material on the carrying side from building up on the return idlers. bending force:the force required to bend a belt under prescribed conditions. bend pulley:a pulley used to change direction of belt run. bias angle:the smaller included angle between the warp yarns of a fabric and the diagonal line across the warp yarns. bias laid:material laid on or wrapped around so the warp yarns are at an angle less then 90° to the longitudinal direction. binder warp yarn:one of the warp systems in a straight warp fabric interlaced with the filling yarn to provide the strength to hold mechanical fasteners. bolted plate hinge fastener:steel plates both sides and both ends of two belt ends to be fastened together (secured to the belt with bolts) with the ends of the plates constructed into a circular hole for accepting a hinge pin to secure the two ends of the belt(s) together. boot:enclosure for the loading end of a bucket elevator belt.


114


bootlegging:progressive ply delamination in belting. bottom cover: the protective cover of a conveyor belt contacting the carrying idlers. bow:(1) a curved deviation in a plane; (2) a deviation from a straight line of the filling yarn in a fabric: (3) a concave deviation from a straight line of the edge of a belt unrolled on a flat surface under no tension. brand:a mark or symbol identifying or describing a product and/or manufacturer: may be either embossed, inlaid, or printed. breaker ply:an open weave fabric used next to the carcass fabric and/or in the cover to improve the attachment of the cover to the carcass and to improve cover cut and gouge resistance. breaking strength:the tensile which a textile yarn or cable, a steel cord, or a belt is at rupture. bucket:one of the cups on an elevator belt. bucket cover:the cover of an elevator belt next to the carrying buckets. bucket elevator:belt with buckets attached. bucket projection:the distance the bucket protrudes beyond an elevator belt. buffing:grinding a surface to obtain dimensional conformance, or to prepare it for repair or splicing. buffing marks: the characteristic surface condition after a buffing operation. butt seam:a seam made by placing edge to edge the two pieces to be joined. butt strap joint:the connection of elevator belt ends with a piece of belting the width of the elevator belt placed over the butted belt ends, usually extending under at least two buckets and secured with bolts to the belt.

-Ccable yarn:two or more plied yarns twisted together. calender:a machine with three or more internally heated or cooled cylinders used to (1) continuously sheet out polymeric compound or fused PVC (2) to wipe polymeric compound into the interstices of a fabric leaving a small portion of it on the surface of the fabric, or (3) to lay a continuous sheet of compound on a fabric. calendered “rubber” sheets:continuous film of uncured elastomer produced from a calender. camber:the curvature of a belt relative to the center line (see bow). capacity:the maximum number of pieces, volume, or weight of material a belt conveyor can handle in a given time interval and belt speed. capped edge: a belt edge covered with an elastomer to protect the carcass. capped end:a belt end covered with an elastomer to protect the carcass end carcass:the tension-carrying portion of a belt comprised of one or more plies of textile fabric or cord, or steel cord bonded together with an elastomer. carcass break:a ply or plies of fabric ruptured by impact or gouging. carcass tear strength:the resistance of a belt against tearing. carcass tear test:the determination of the tension at which a belt may be torn. carrying run:the portion of a conveyor that carries the load between the loading and discharge points. catenary idler:a type of flexible belt-carrying idler with ends supported in pivoted stands. The tube or rollers sag under the weight of the load to form trough. CEMA:Conveyor Equipment Manufacturers Association. (www.cemanet.org) cement:a mixture of polymeric compound or elastomer used as an adhesive or sealant. cemented edge:a slit belt edge sealed with an application of elastomeric cement.


115


cemented end:a belt end sealed with the application of elastomeric cement. center roll:the horizontal roll between the side troughing rolls. center-to-center:the distance between the center of two pulleys or idlers. Also called centers or center distance. centrifugal bucket elevator: a type of bucket elevator having a belt which travels at sufficient speed to discharge material from the buckets by centrifugal force. checking:the short shallow fissures on the surface of a belt cover caused by action of environmental conditions. chevron:a ridge or profile arranged in a Vee shaped configuration on a belt carrying cover to stabilize material carried up an incline. chute lining:highly abrasion resistant elastomeric lining in a chute to protect the metal chute from abrasion wear. chute slope:angle relative to the horizontal a chute is inclined. cleated belt:transverse raised sections on a conveyor belt to stabilize material carried up an incline. closed belt conveyor:a moving, endless conveyor belt formed into a tubular shape by joining its edges while carrying material, and opening the edges while in motion to receive and discharge material. cluster end:a flat disc idler with several discs adjacent to each other at the ends of the idler. cohesive:tendency of a material to stick to itself. cold flexibility:the relative ease of bending following exposure to low temperature. cold flow:continued deformation under stress. compound:a mixture of a polymer(s) and other materials to give the desired chemical and physical properties in the elastomeric components of a belt. compression member:the portion of a belt beneath the pitch line as the belt bends around a pulley. compression set:the deformation in a material remaining after it has been subjected to and released from a compressive force. conductivity: the ability of a material to conduct heat, electricity, and particularly static electricity. continuous bucket elevator:a bucket elevator belt that discharges by gravity over the inverted bottom of the preceding bucket on the descending side of the elevator. control:a material or a product of known characteristics included in a series of tests to provide a basis for evaluation of other products. conveyor:a system for the continuous movement or transport of bulk materials, packages or objects along a predetermined path. conveyor belt:a belt that carries materials from one place to another. conveyor belt stretch:the increase in belt length which takes place when tension is imposed. Stretch is either elastic or permanent. Elastic stretch is a temporary change in length which varies directly with the pull. Permanent stretch is the residual change in length after tension has been removed; it generally accumulates over a period of time. cord belt: a belt with textile or steel cords for the longitudinal tension-bearing member. cord fabric:a fabric with plied or cabled yarns in the warp direction and a light weight filling yarn spaced only sufficiently to process the fabric. cotton:a natural fiber of high cellulosic content. count:in fabric, the number of warp ends, the number of filling picks, or both in a square inch of fabric. counter weight:in conveyor belting, the weight applied to the take-up assembly to maintain proper belt tension. cover:the outer component of a belt. cover splice:the transverse joint formed by connecting two lengths of cover stock. cover wear:the loss of material during use due to abrasion, cutting, or gouging. crack:a sharp break or fissure in a surface. Usually caused by strain and/or environmental conditions.


116


crazing:a cover surface with many fissures. creeper drive:an auxiliary drive, usually consisting of a small motor and speed reducer, used to keep a belt conveyor in motion at a very low speed during non-operating periods in extremely cold weather. It is used to prevent freezing of a belt and other components. crimp:in fabric, (1) the sinusoidal like curvature impressed in the warp and filling yarns when fabric is woven. The percent crimp is the ratio of distance between two points on the yarn in the fabric and of the same two points when the yarn is removed from the fabric and stretched by a standard tension. crowned pulley:a pulley with a greater diameter at the center, or other points, than at the edges. crystallization:a hardening and stiffening that occurs in some compounds due to prolonged exposure to low temperatures. cure:see vulcanization. cure temperature:the temperature at which a compounded polymer is changed into an elastomer. cure time:time required, at a given temperature, to produce optimum physical properties in an elastomer. curl:the action of the edges of a belt bending upward on the carrying run and downward on the return run. Also called cuping. cushion breaker:a leno or cord breaker imbedded in a belt cover. cut edge:the uncovered edge of a laminated product, such as a belt, created by cutting after vulcanization. cut resistance:the ability of a belt cover to withstand the cutting action of sharp objects.

-Ddate code:any combination of numbers, letters, symbols, or other methods used by a manufacturer to identify the date of manufacture. decking:a protective covering over the return run of a belt conveyor. deflector:a board or plate at an angle across the path of a belt traveling over a flat surface to transfer material off the belt. denier:a yarn sizing system for continuous filament synthetic fibers on the basis of the weight in grams of 9000 meters of the yarn. dip coat:a thin film formed on a surface by immersing the material in a suitable coating solution. dipped fabric:a cloth coated by passing it through a solution and drying. discharge:removal of material from a belt. dog leg:the abrupt deviation of belt from a straight line. double plate bolt fastener:two ends of belting joined together with a plate on both sides across both ends of the joint. drive:an assembly of electrical and mechanical parts that provide motive power to a belt. drive factor:a numerical factor used for calculating the belt minimum slack side tension required for a given driving condition and or configuration. drive-on plate fastener:two ends of belting joined with a single plate, across the top cover joint, with rivets or sharp teeth clinched over on the bottom cover side of the belting. drive-on hinged fastener: two ends of belting joined together with a pre-packaged fastener assembly having prongs for driving through the belt end. drive pulley: a pulley mounted on a drive shaft which transmits power to the belt. drive snubbed pulley:an undriven pulley located close to the drive pulley to provide a greater arc of contact around the drive pulley. drop ply:the omission of a reinforcing ply, usually the bottom or next to bottom ply, for a specified distance from both edges to improve the troughability of the belt. duck:a term applied to a wide range of medium and heavyweight woven fabrics made from cotton or synthetic fibers or a combination of both. Duck is also identified as canvas, army duck, belt duck, harvest duck, hose duck, and shoe duck. dumbbell:a test specimen with lesser width at the middle of its length than at its ends.


117


durometer:an d t iinstrument t t ffor measuring i th the hhardness d off an elastomer. l t durometer hardness:a numerical value which measures the resistance to indentation of the blunt indentor point of a durometer. dutchman:a short section of belting mechanically spliced into a length of belting and removed when the take-up allowance is exceeded. dynamometer:an apparatus capable of inducing various loads for evaluation of dynamic belting properties. dynamic fatigue:loss in properties of a material when continually subjected to flexing and or cyclic stress.

-Eedge wear:damage to the edge of a belt by abrasion. effective tension:difference between the tight side and the slack side tension at the drive pulley providing the necessary pull to move the load. elasticity:the property of an elastomer or belt when deformed to recover all or part of its original dimensions when the deforming force has been removed. elastic limit:the limiting extent to which a material may be deformed and yet return to approximately its original shape after removal of the deforming force. elastomer:a macromolecular material that returns rapidly to approximately the· initial dimensions and shape after substantial deformation by a weak stress and release of the stress. elastomeric properties: the chemical and physical properties of an elastomer. elevator belt:a belt that raises material vertically in buckets attached to the belt. elongation:extension produced by a tensile stress. embossing:raised or indented design on a surface. endless belt:a belt made endless without a joint. equivalent free fall:the calculated vertical distance material falls from the discharge point to end of a belt. extensible conveyor:an adjustable conveyor system with a loop of belting between the carrying idlers and the return idlers for changing the center distance. extration test:a test in which certain components are separated from a solid by dissolving them in a liquid solvent under suitable conditions.

-Ffabric:a planar structure produced by nonwoven or interwoven yarns, fibers, or filaments. fabric count: the number of warp ends per inch and the number of filling picks per inch. fabric design:the combination of size and numbers of fibers or yarns, in both warp and filling, and the manner in which they are processed. fabric impression:a pattern in the cover of a belt formed by contact with a fabric during processing. fabric rating:the maximum tension per ply of fabric a belt should be operated under ideal conditions. face:the outer surface of a pulley or belt. fatigue:the loss of physical properties of a material from a cyclical or continuous application of stress. feeder belt:a belt that discharges material onto another conveyor belt. fiber:a unit of matter having a length at least 100 times its diameter and which can be spun into a yarn. filament:a continuous fiber of extreme length. filler: a material mixed with a polymer to improve quality or lower cost of a compound.


118


filler seam:extruded polymeric compound used to fill the void between two pieces of belt cover or fabric. filling yarns:the transverse yarns in a fabric. finger splice:belt ends cut into mating fingers. flanged edge:in conveyor belting, an edge built up to prevent spillage. flame performance:the manner in which belting after being ignited will burn and/or self extinguish. flame test:a means, under specific conditions, for establishing the flame performance of a belt. This will not indicate the performance of the belt in any fire in which the belt may be involved. flanged pulley: a pulley with a raised rim at the edges for the purpose of keeping the belt on the pulley. flash:excess material protruding from the surface of a molded article at a parting line. flat belt:(1) a belt the cross section of which is in the general form of a rectangle; (2) a belt which operates on a smooth flat bed or straight idlers or rollers. flat press:a belt finishing press with flat platens, between which the belt is heated and compressed. flat spots:thin spots on a conveyor belt surface stored on a flat surface for a long time. flat wire braid:flattened braided wire, frequently used for armoring the belt. fleet:the lateral movement of a conveyor belt to either side of its intended path. flex cracking:a surface cracking induced by repeated bending and straightening. flexing:the bending of a belt. flex life:the relative ability of a belt to withstand cyclical bending stress. flight:(1) one of a series of belt conveyors discharging one to another. (2) a series of cleats or profiles on a belt. floating breaker:a leno or cord breaker embedded in a belt cover with a distinct layer of elastomer separating the breaker from the carcass. folded belt edge:a belt construction with the inner carcass enclosed in an envelope of a ply or plies of fabric. frequency factor:the duration of time in minutes required for one complete cycle of a conveyor belt. friction surface:the duration of time in minutes required for one complete cycle of a conveyor belt. friction:(1) the resistance to motion of a belt due to the contact between two surfaces. (2) improperly used to indicate the bond between two surfaces. friction coating:a polymeric compound applied to the surface of a fabric when the fabric interstices are filled with the polymeric compound. frictioned fabric:a fabric impregnated and lightly surface coated with a polymeric compound. fusion:an irreversible process during which a PVC compound or platisol undergoes a physical change and becomes a homogeneous mixture by the mutual solvation of the PVC resin and the plasticizers in the compound, as a result of heating to an appropriate temperature.

-Ggauge:(1) an instrument for making measurements (2) a term used to indicate a measure of thickness. glass fiber:glass extruded through a die with many fine holes into continuous filaments. gouging:the effect of sharp heavy material falling onto a conveyor belt cover to loosen or tear out pieces of the cover. grade:the ratio of incline or decline of a conveyor expressed as a percent of the vertical height to the horizontal distance. grade of belting:the quality of belting cover on the basis of gouge, cut, and abrasion resistance.


119


gravity take-up:a mechanical system that adjusts for the stretch or shrinking of a conveyor belt automatically by a weighted pulley in the system. grooved lagging:lagging with round or angular grooves to minimize material buildup on the pulley. ground finish:a surface produced by grinding or buffing.

-Hhank:a length of 840 yards of a yarn. hardness:degree of resistance to indentation. hardening:an increase in resistance to indentation. hazing:a dull finish. head:the delivery end of a conveyor belt. head-tall drive:a belt driving system using one or more powered pulleys at or near both the head and tail pulleys with each pulley independently driven. heat degradation:change in chemical and/or physical properties due to excessive exposure to heat. heavy weight belt:a belt with a rated maximum working tension equal to or greater than 160 pounds per inch width, when operating under ideal conditions. herringbone weave:the longitudinal appearance of a row of parallel lines slanting at an angle in the opposite direction to another row of slanting parallel lines. hinged fastener:a fastener attached independently to each of the belt ends designed with an opening in the end of the fastener to accept a pin through the opening to complete the joint. hinge pin:a cable or rod to join together hinged fasteners. Holland cloth:a filled sheeting (usually starch filled) with a smooth, glossy finish on both sides, used as separating medium. horizontal belt curve:the portion of a conveyor system which deviates from a straight line in the same horizontal plane as the rest of the system. horsepower:a unit of power equal to 33,000 foot-pounds per minute (746 watts). hot air cure:vulcanization by using heated air, with or without pressure. hugger belt conveyor:two belt conveyors whose conveying surfaces combine to convey loads up steep inclines or vertically. hysteresis:a loss of energy due to successive deformation and relaxation. a measurement of the area between the deformation and relaxation stress-strain curves. hysteresis loop:the configuration of the graphical plot of stress and strain from the initial application of stress to some reduced stress. The measure of hysteresis is the area under stress-strain curves of increasing and decreasing stress.

-Iidler stand:the mechanical system that supports an idler pulley. impact:the single instantaneous contact of a moving body on another body either moving or at rest. impact energy:the effective combination of force (weight of the body and height) when one body falls on another. impact force:the energy power of impact. impact idler:a belt idler having a resilient roll covering, resilient molded elastomer rings, pneumatic tires, springs or other means of absorbing impact energy at or close to the place where material contacts the belt. impact rating:the maximum rating of a belt construction based on the fabric, impact rolls, design of loading, size of material falling on the belt, relative speed of the material and the belt, etc. to withstand the energy of impact loading. impact resistance:the relative ability of a conveyor belt assembly to absorb impact loading without damage to the belt.


120


impregnation:filling the interstices of and partial absorption into the yarns of a fabric with a polymeric compound. impulse:an application of force in a manner to produce sudden strain or motion. indentation:(1) the extent of deformation by the indentor point of any one of a number of standard hardness testing instruments; (2) a recess in the surface of a belt cover. inside length:a belt length measured along its inside circumference. installation allowance:the amount by which the center distance can be adjusted so a belt can be installed without damaging. instantaneous modulus:the ratio of stress to strain at a single point on the stress-strain curve. interstice:a small opening, such as between fibers in a cord or threads in a woven or braided fabric. interwoven conveyor belt:a type of conveyor belt construction similar to that of a solid woven belt, with plies interwoven such that it is impossible to separate them. irons:strips of metal at the edges of a belt in a flat press to confine the edge elastomer for making a molded edge or to obtain uniform thickness of the edges of a slit edge belt near its edges. ISO:International Organization for Standardization. (www.iso.org)

-Jjaws:clamps to hold a specimen when applying stress to the specimen for certain tests. joint:the location where two belt ends are fastened together by either mechanical means or a vulcanized splice.

-Kkinking:a temporary or permanent distortion of belting caused by doubling the belt on itself.

-Llagged pulley:a pulley having its surface covered with lagging. lagging:a smooth or embossed covering on a pulley to increase friction between belt and pulley. lap:a part that extends over itself or a like part. lap joint:an elevator joint where one end of the belt laps over the other end with the leading edge on the bucket side. lap seam:a joint of polymeric compound of fabric where one end of the material laps over the other end. lateral:coming from the side. lateral misalignment:offset of pulleys, idlers, or structure from a design longitudinal reference line. leno breaker:an open mesh fabric made from coarse ply yarns, with a leno weave. leno weave:an open mesh fabric in which the warp yarns are held by the filling yarns with the filling yarns twisted around alternating warp yarns in opposite direction. life test:a laboratory procedure used to determine the resistance of a rubber article to a specific set of destructive forces or conditions. lift:the net vertical distance material is moved by a conveyor or bucket elevator. light weight belt:a belt with a rated maximum working tension of less than 160 pounds per inch width. lined bolt holes:bolt holes which have been given a protective coating to cover the exposed carcass. liner:a separator, usually cloth, plastic film, or paper, used to prevent adjacent layers of material from sticking together. live rolls:a series of rolls over which objects are moved by application of power to all or some of the rolls. live storage:(1) the storage of objects on a conveyor belt having a low coefficient of friction surface or on live rollers so the objects can accumulate while they are added to or removed at different rates; (2) the storage of material in a silo while material is being discharged or poured in at the same time; (3) an extensible conveyor with a loop of belting between the carrying and return idlers where the length of the loop is continuously decreased as the equipment at the mining face is advanced.


121


load support:the ability of a fully loaded conveyor belt to bridge the idler gap without creasing into the idler gap and carry material without excessive sag between the carrying idler pulleys. load weight:the weight of material per unit of time. loading angle:the angle to the horizontal at which material is loaded onto a conveyor belt. loading impact:the energy with which material is loaded onto a conveyor belt. longitudinal:a lengthwise direction. longitudinal seam:a joint butting two materials lengthwise in the finished product. low temperature flexibility:the ability of belting to be bent or flexed at low temperatures without loss of serviceability. lump size:the size of larger material on a conveyor belt.

-Mmaximum horsepower:the highest power requirement. maximum ply: (1) the maximum number of plies permissible that will permit for satisfactory troughability; (2) the maximum number of plies permissible to satisfactorily operate around a pulley of a given diameter. maximum safe working stress:the greatest tension at which a belt should be operated. mechanical fastener:any mechanical device used to join the ends of belting. mildew:a fungus growth. mildew inhibited:containing material to prevent or retard the propagation of a fungus growth. mill:a machine with two horizontal rolls revolving in opposite directions used for the mastication or mixing of rubber. minimum accelerating time:the least time allowed to accelerate a conveyor belt from rest to normal speed without exceeding its maximum safe working stress. minimum braking time:the least time allowed to decelerate a conveyor belt from normal speed to rest without exceeding the maximum safe working stress or causing the belt to double up on itself. minimum ply:the least number of plies that will support the load on a belt without damaging deformation. minimum pulley diameter: the smallest pulley diameter around which a belt is recommended to operate. mirror finish:a bright, polished surface appearance. modulus:a physical testing of materials, a measure of stress to strain. mold lubricant:material used to coat the surfaces of a curing press to facilitate release after vulcanization. mold mark:an indentation or embossment on the surface of a molded product caused by irregularities in the mold surface. molded edge:a belt edge formed during vulcanization by curing in a mold or against edge irons. monofilament:a single extruded strand of material. monomer:a relatively simple compound which can react to form a polymer. Mooney viscosity:a measure of the plasticity of a polymeric compound determined in a Mooney shearing disc viscometer. MSHA:Mine Safety and Health Administration. (www.msha.gov) multifilament:many extruded fine strands of material grouped together.

-Nnarrow disc idler:a flat pulley with discs attached around the pulley at certain intervals across the pulley. necking down:a localized decrease in the cross-sectional area of a product. needle punched:non-woven fabric punched with a hack latched needle to improve its strength and stability.


122


net endless length:the manufactured length necessary to provide proper initial fit and tensioning of a belt on a specified drive. nicks:cuts in the surface or edge of belting. nitrile:common name for nitrile-butadiene polymer. nominal:an approximate amount. nonwoven fabric:a mat of nonaligned fiber bonded together. Norway type elevator bolt:flat top, squared shoulder bolt for attaching elevator buckets to elevator belts. NR:abbreviation for isoprene polymer. numbered duck:fabric weight designated by numbers based on linear yard of cloth 22 in in width. nylon:common name for polyamide fiber.

-Ooffset idler:the center carrying roller which is offset and transversely lapping the troughing idlers. oil swell:the change in volume of an elastomer resulting from contact with oil. oil well splice:two ends of a belt each bent 90˚ around a steel form and bolted together through the belt and steel form. operating tensions:the tension of longitudinal sections of a belt system (tight side and slack side) when moving material, as distinguished from tension when the belt is running empty. optimum cure:the time, temperature and compression of vulcanization or of fusion at which a desired combination of properties is attained in an elastomer. outside diameter eccentricity:the degree a pulley is out-of-round with respect to its central axis. oxidation:the reaction of oxygen on a rubber product, usually evidenced by a change in the appearance or feel of the surface or by a change in other physical properties. oxygen bomb:a chamber capable of holding oxygen at an elevated pressure oxygen bomb:a chamber capable of holding oxygen at an elevated pressure which can be heated to an elevated temperature. Used for an accelerated aging test. oxygen bomb aging:a means of accelerating change in the physical properties of rubber compounds by exposing them to the action of oxygen at an elevated temperature and pressure. ozone cracking:belt cover cracks or crazing caused by exposure to ozone in the atmosphere.

-Ppackage conveyor:a conveyor which transports packaged, boxed, or bagged material. packed material:material on belting compacted as the belting moves along the system. permanent set:the amount by which an elastic material fails to return to its original form after deformation. permanent stretch: elongation permanently removed from belting when it is first used. permeability:passage of liquids or gases through a material. physical properties:a measure of mechanical characteristics of a material. pick:an individual filling yarn of a fabric. picking idler:a short-sided troughing idler for readily removing material by hand from a belt. Pierce tape:a woven mesh of steel wire or cord. pitch line:the plane within a belt which undergoes neither stretching nor compression when the belt rounds the pulley, i.e., the neutral plane of the belt structure. plain weave:the simplest type of weave with both adjacent warp and filling yarns crossing over and under each other. IP:1 2011 Conveyor and Elevator Belt Handbook

123


plasticity:(1) a measure of the resistance to shear of an unvulcanized elastomer; (2) a measurement of resistance to shear with heat history. plasticizer:a compounding ingredient which can change the physical and chemical properties and processibility of a polymeric compound. plastisol:a dispersion of a powderous polymer in a plasticizer. plied yarn:a yarn made by twisting together two or more single yarns. plows:plates across a belt to remove material lying on or sticking to the belt. ply:a layer of fabric, multiple strands of textile cord, or steel cord. ply adhesion:the force required to separate two adjoining reinforcing members of a belt. ply tensile:the ultimate breaking strength of a belt expressed in force per inch width per ply. polymer:a macromolecular material formed by the chemical combination of monomers having either the same or different chemical composition. polymerization:the process that converts monomers into polymers. porosity:the condition of containing numerous small holes or voids. portable conveyor:a conveyor system readily moved from one place to another. portable vulcanizer:a vulcanizer readily moved from one place to another, usually used for making field splices and repairs. pot life:the period of time during which a reacting polymeric compound remains suitable for its intended use after having been mixed with a reaction-initiating agent. press:a machine consisting of two or more heated plates which can be brought together and separated by hydraulic pressure or mechanical action. press cold ends:the area of reduced temperature at the press platen end. press lap:the area of overlap of one press cure length on the next. press length:the length of a belt which can be pressed at one time. press marks:irregularities in the surface of a vulcanized product caused by the press ends or by corresponding irregularities in the press surface. pricker marks:small marks in the cover of a vulcanized belt where a roll with sharp needles had penetrated the uncured belt to allow trapped air in the uncured belt composite to escape. processing:the operations in the manufacture of a belt. prong:the sharp point of a mechanical fastener that penetrates the belt. pulley:a cylinder, mounted on a central axis rod. pulley cover:(1) a covering on a drive pulley; (2) the bottom cover of a belt that contacts the drive pulley. pulley wear cover:(1) elastomeric material attached to the pulley to minimize pulley surface wear; (2) additional belt bottom cover thickness where extraordinary wear is anticipated. pulley projection:the amount a pulley face width extends beyond belt edge. pure gum compound:a natural rubber or isoprene compound containing only the ingredients necessary to process it, to protect it from aging, and to cause vulcanization.

-Qqualification inspection test:the examination of samples from a typical production run to determine conformance to a given specification for approval to become a supplier. qualification conformance inspection:the examination of samples from a production run to determine conformance to a given specification.


124


quarter turn drive:a belt system in which the axes of the adjacent pulleys are at right angles to each other to cause a 90° twist in the belt about its longitudinal axis.

-RRAC:The Rubber Association of Canada. (www.rubberassociation.ca) raised cover center:a belt cover with increased thickness along the center portion of the belt. raised edge:a flanged edge conveyor belt to minimize spillage. raised rib belt:a belt with transverse or diagonal bars or cleats on the top cover. rated conveyor belt:the manufacturer’s recommended maximum working tension for a conveyor belt. rating:the normal working tension recommended for a belt. recovery:the degree an elastomeric material returns to its original dimensions after being stressed. reefed:a belt folded back and forth on itself. reinforcement agent:an ingredient in a polymeric compound not basic to its vulcanization used to increase its chemical and physical properties. reinforcing element:the strengthening members of a belt. repair:the area of new material replacing damaged material in a belt. resin:certain materials produced by chemical synthesis. resilience:the property of recovering from mechanical force. return idler:a roll(s) that supports a belt on its return run. return run:the part of a conveyor system where the belt returns to the tail. reversion:the softening of vulcanized rubber when heated excessively. It results in a deterioration in physical properties. (Extreme reversion may result in a tackiness.) ribs:transverse configurations on the carrying side of a belt to facilitate carrying material on an incline. riveted plate joint:a mechanical fastener with rivets projecting through a plate on both sides of the belt. RMBT:Rated Manufacturers Belt Tension. rosin:the hard amber-colored material of the residue from the distillation of oil of turpentine. rotary press:a vulcanizing machine consisting of a rotating, heated drum with a flexible steel band partially encircling the drum, which continuously advances a material while under pressure and heat between drum and band. rough top:a belt made with projections in the carrying surface to improve the ability of the belt to carry material on inclines. rubber cement:a mixture of polymeric compound or elastomer used as an adhesive or sealant. rubberized:coated with rubber compound. run:the distance or route covered by a conveyor.

-Ssaddle:an additional short length of belting added to an existing belt. safety factor:the ratio of the maximum stress that a belt or a belt splice can withstand to the maximum stress recommended for it by the manufacturer. The ratio of breaking strength to rated working tension. safe working strength:the manufacturer’s recommended maximum working tension for a conveyor belt operating in ideal conditions. sag:the amount of vertical deflection of a conveyor belt from a straight line between idlers, usually expressed as a percentage of the spacing between idlers.


125


sag belt tension:the minimum tension in any portion of the carrying run of a belt necessary to prevent excessive sag of the belt between idlers. sample:a piece of material removed for evaluation. scraper:a device for cleaning the surface of belting. screw take-up:a take-up for a conveyor system in which movement of a pulley-bearing block is accomplished by means of a screw. See also take-up. seam:the place where two edges of fabric or elastomer are adjacent to each other to form a single ply or layer. seaming strip:a strip of polymeric material laid over and/or in a seam to fill any voids between the adjacent plies of material. self-aligning idler:an idler having a belt-activated swivel mechanism to control the side movement of an operating conveyor belt. selvage:the lengthwise woven edge of a fabric. Also called selvedge. semi-cure:a partial or incomplete cure. service condition:all the conditions of operation to which a conveyor or elevator belt is exposed. service factor:the amount by which the normal rating of a unit is altered to compensate for specific service requirements. service test:a test in which the product is evaluated under actual service conditions. set:the amount of deformation remaining after complete release of the load producing the deformation. shadowing:a bas-relief or outline of a reinforcement which appears on a cover after vulcanization. shelf storage life:the period of time prior to use during which a product retains its intended performance capability. singles yarn:the product from aligning and twisting together fibers or twisting together filament fibers. skim:a thin layer of polymeric compound applied to a fabric. skirt board:in a conveyor system, the vertical or inclined plates located longitudinally and closely above the belt to confine the conveyed material. skive:a cut made on an angle to the surface of a material to produce a tapered or feathered edge. slab belting:belting made in wide widths and long lengths for later slitting into narrower widths and cutting into shorter lengths. slack side tension:the lessor of the tensions in a belt on an operating conveyor. Usually immediately following the drive pulley. slider bed:a stationary surface on which a belt slides. slip:the action that takes place, causing a differential movement between the pulley surface and the belt. slip and sequence system:an interlocking belt conveyor system that stops the system when the speed of the conveyor belt drive ulley exceeds a certain speed of the conveyor belt. slit edge:the square finished edge of a belt after trimming to width. slope belt:a conveyor belt used to carry material along an inclined flight. snub pulley:a pulley adjacent to a drive pulley that increases the arc of contact on the drive pulley to increase the effectiveness of the drive. solid woven belt:a type of conveyor belt wherein the carcass is a single ply consisting of multiple layers of warp and filling yarns interwoven. The carcass usually is impregnated and/or coated with polymeric compound. specification:detail description of specific requirements. specimen:a piece cut from a sample of belting to test. splice:methods for joining the ends of belting together without using a mechanical fastener. splice angle:the angle at which belting is spliced. spread coat:to apply a thin coat of material over a surface determined by means of a knife, bar, or doctor blade.


126


spring take-up:a mechanical device on both sides of the conveyor system where a variable force spring is secured to the conveyor structure and to the tail pulley block for the purpose of maintaining a uniform tension in the belt. spun yarn:a yarn produced from short fibers by aligning and twisting them together. stacker:a conveyor adapted to piling or stacking bulk material, packages, or objects. stamped metal:perforated metal sheet used for making a rough top design on a conveyor belt. standard:a quality level set for the results from a belt test. staple fiber:the short fibers from which a spun yarn is made. starting tension:the tension necessary to accelerate a belt from rest to normal operating speed.

-Ttack:having a property of temporary adhesion. tail end:the end of a conveyor, usually near its loading points. tail pulley:the belt pulley near the loading end of the conveyor system. take-up:(1) removal of slack or stretch in a belt; (2) an assembly of structural and mechanical parts to maintain proper belt tension. take-up pulley:a pulley which can move in space due to gravity, a spring, or other forces in order to maintain relatively constant tension in a specific strand of a belt. take-up travel:the distance the take-up can move during the belt operation. tandem drive:a belt driving system employing two adjacent powered pulleys. tape line measurement-maximum length:the inside circumference of a belt measured around the pulley surfaces when the take-up idler(s) are moved out to where they take up all the belt slack their movement permits. tape line measurement-minimum length:the inside circumference of a belt measured around the pulley surfaces when the take-up idler(s) are moved in for the installation of the shortest belt possible. tex:a yarn size system defined as the weight in grams of 1000 meters of yarn. tear down:the removal of a ply of fabric in a multi-ply fabric belt to prepare the stepped down configuration for a stepped splice. tear propagation:continuation of tear. telescoped roll:at the outside end of a roll of belting, turns of the belting progressively loosened and moved outward from the remainder of the evenly wound turns of the belting. template:a pattern to guide the punching of holes or cuts in belt ends. tension, maximum:the highest tension occurring in any portion of the belt in a conveyor or elevator belt during its operation. tension ratio:in an operating belt system, the ratio of the larger to the smaller tension as the belt approaches and leaves a driving or driven pulley. tension, slope:the tension in an inclined belt caused by the weight of the material being elevated in addition to the belt weight and independent of friction and other sources of tension. tension, take-up:the amount of tension in each of the runs of belting approaching and leaving the take-up pulley, the total of which is the force exerted by the take-up device. tensile strength:the maximum force, stress, applied to a specimen at rupture. tension rating:the maximum safe working stress for a fabric or belt recommended by the belt manufacturer. tension, tight side:in an operating conveyor system, the greater of the tensions as the belt approaches and leaves the drive pulley. tension, working:the maximum working tension for a fabric or belt recommended by the manufacturer. terminal position:the maximum working tension for a fabric or belt recommended by the manufacturer. terminal pulley:the pulley at or near the discharge end of a conveyor belt system.


127


textile:a general term applied to yarn, cord, non-woven, or woven fabric made from a fibrous material. tie gum:a thin sheet of unvulcanized rubber inserted between plies in vulcanized repairs of splices. tilted troughing idlers:used for belt training. time cycle:the duration of time, in minutes, required for one complete cycle of a conveyor belt. tire bead wire:steel wire placed in or beneath the top cover to minimize rips in the belt by objects that penetrate the belt. tolerances:the limiting values for a dimension. top cover:the material conveying surface of a conveyor belt. top cover wear:loss of the elastomer due to abrasion. traction:the friction between a drive pulley and the conveyor belt. training:the process of adjusting idlers, pulleys, and loading conditions to insure the belt runs straight. training idler:an idler mounted on a mechanical device, actuated by the belt moving sidewise to make the belt run straight. trajectory:the arc made by material freely discharged from a conveyor system. transition distance:the distance between the last fully troughed idler and the flat driving or discharge pulley. transition idler:a troughed belt idler having a lesser degree of trough than the previous carrying idlers. transverse:a crosswise direction of a belt. transverse cord breaker:a cord fabric laid in the top cover at right angles to the belt edges. transverse seam:the joint, across the belt, of two ends of a fabric ply in the belt or cover material. tripper:a fixed or moveable mechanism at some intermediate place in the conveyor system to discharge material from the belt. troughability:the property of a belt that permits it to conform to the contour of troughing idlers. troughability index:the ratio of the deflection of a freely supported transverse section of a belt to the distance between the freely supported ends. troughed belt:a belt operating in a conveyor system with inclined side idlers to cause the belt edges to turn up and increase the amount of material carried while minimizing side spillage of the material. troughing angle:the angle troughing idlers are to the horizontal extension of the flat carrying idler. troughing idlers:an idler system which supports a belt in a troughed configuration. Usually it consists of a center horizontal roll with an inclined roll on each side. See also catenary idler. twill weave:a fabric woven with the appearance of diagonal lines. twist:the rotation of a belt on its longitudinal axis. A 180˚ twist is used as a means of inverting a belt through the zone of the twist.

-Uultimate elongation:maximum elongation at rupture. ultimate strength:the force required to rupture a specimen. uncured:not vulcanized. undercure:a less than optimal state of vulcanization which may be evidenced by tackiness or inferior physical properties.

-Vvertical curve:the portion of a conveyor belt where the angle of incline increases. viscosity:the flow property of a material. vulcanization:a process over a range in temperature during which a polymeric compound, through a change in molecular structure (e.g., crosslinking) becomes less plastic and causes changes in the physical and chemical properties of the resulting elastomer.


128


vulcanized splice:a joint in a belt made by means of vulcanization. vulcanized splice step length:the longitudinal distance between steps in the splice.

-Wwarp:the lengthwise yarns in a woven fabric. weathering:surface deterioration, evidenced by cracks and crazing of an elastomer, during outdoor exposure. weave:a fabric pattern description denoting a specific relationship of warp and filling yarns at specific locations in the fabric. weft:another term for the filling yarns in a fabric. winged pulley:a pulley with radial vanes extending from a supporting structure to the center shaft to minimize trapping material that otherwise would build up and damage the belt. wire hook fastener:a mechanical fastener consisting of wires capable of being driven through the belt end and bent back into the belt by a special tool device. wires:metal in the form of a fine flexible rod. wire tire cord:fine wires twisted together. woven fabric:a flat structure composed of two series of interlacing yarns of filaments, one parallel to the axis of the fabric and the other transverse. wrap:arc of contact. woven wire carcass:a belt with woven wire fabric.

-Yyarn:a generic term for continuous strands of textile fibers or filaments. yarn number:the number of hanks in a pound of spun yarn. yield point:the stress in a material at which a substantial increase in strain occurs with a minimum increase in stress. Young’s modulus:stress per unit strain for perfectly elastic material.


129


CHAPTER 17

USEFUL TABLES

CAPACITY OF TROUGHED CONVEYOR BELTS WITH EQUAL ROLL IDLERS Short Tons (2000 lb) per hour, TPH, with: [Metric Tonnes, 1000 kg (2204 lb) per hour, t/h, with:] (a) Belt speed at 100 ft per minute (0.50 m/s) (b) Material at 100 lb per cubic ft (1600 kg/m 3) (c) Based on edge distance, e = 0.055W + 0.9 in (20 mm) Surcharge Angle*

Belt Width

0˚

5˚

10˚

20˚

25˚

30˚

in

mm

TPH

t/h

TPH

t/h

TPH

t/h

TPH

t/h

TPH

t/h

TPH

t/h

14 16 18 20

350 400 450 500

15 21 27 34

13.6 19.0 25.4 30.8

18 25 33 42

16.3 22.7 29.9 38.1

22 29 38 49

20.0 26.3 34.5 44.5

28 38 50 64

25.4 34.5 45.4 58.2

32 43 56 72

29.0 39.0 50.8 65.3

34 48 63 80

30.8 43.6 57.2 72.5

24 30 36

600 750 900

52 86 125

47.2 78.0 113.0

63 105 155

57.2 95.3 141.0

74 120 180

67.2 109.0 164.0

96 87.2 155 141.0 230 209.0

110 176 260

99.8 160.0 236.0

120 195 290

109 177 263

42 48 54 60 66 72

1050 1200 1350 1500 1650 1800

175 235 300 375 455 550

159 213 272 340 413 499

210 280 360 450 550 655

191 254 327 408 499 594

250 330 420 525 640 770

227 300 381 476 581 700

360 480 610 760 930 1115

327 435 554 690 845 1011

400 530 680 845 1030 1230

363 482 617 767 935 1115

320 425 545 680 830 995

290 386 494 617 753 902

IDLER CONVERSION FACTORS

20˚ Idlers 35˚ Idlers 45˚ Idlers Flat Rolls

1.00 1.59 1.87 0

1.000 1.470 1.690 0.185

1.00 1.39 1.55 0.32

1.00 1.27 1.37 0.53

1.00 1.22 1.30 0.56

1.00 1.19 1.25 0.62

*Surcharge angle is that angle which the material makes with the horizontal while being conveyed.

Example:

Width Trough Angle Speed

English Units 48 in 45˚ 500 fpm

Material Surcharge Angle

130 lb/ft3 25˚


SI Units 1200 mm 45˚ Belt 2.5 m/s 2080 kg/m3 25˚

130


CONVERSION FACTORS FOR CONSTANT EDGE DISTANCE Capacity with e = 2 in (50 mm) (Commonly used for slumping materials) Multiply TPH (t/h) as above by the following conversion factors: Belt Width, in 14 (mm) (350) Factors 0.85

16 (400) 0.91

18 (450) 0.96

20 (500) 1.0

24 (600) 1.05

30 (750) 1.095

36 42 48 54 60 66 72 (900) (1050) (1200) (1350) (1500) (1600) (1800) 1.13 1.155 1.175 1.19 1.195 1.205 1.215

CAPACITY OF TROUGHED CONVEYOR BELTS WITH LONG CENTER ROLL IDLERS Short Tons (2000 lb) per hour, TPH, with:

(a) Belt speed at 100 ft per minute (0.50 m/s)

[Metric Tons, 1000 kg (2204 lb) per hour, t/h, with:]

(b) Material at 100 lb per cubic ft (1600 kg/m3) (c) Based on edge distance, e = 0.055W + 0.9 in (20 mm)

Belt Width 0˚ in 24 30 36 42 48

mm 600 750 900 1050 1200

5˚

TPH t/h TPH t/h 82 74.5 95 86.2 105 95.2 130 118.0 130 118.0 165 150.0 150 136.0 200 182.0 160 145.0 220 200.0

35˚ Long Center Rolls Surcharge Angle 10˚ 20˚ TPH t/h TPH t/h 105 95.2 110 99.9 145 132.0 175 159.0 185 168.0 235 213.0 225 204.0 295 268.0 260 236.0 355 322.0

TPH 125 195 260 330 405

30˚ t/h 113 177 236 300 368

TPH 140 210 290 370 450

t/h 127 191 263 336 408

45˚ Long Center Rolls Surcharge Angle

Belt Width 0˚ in 24 30 36 42

mm 600 750 900 1050

TPH 97 130 160 180

t/h 88 118 145 163

10˚ TPH t/h TPH t/h 104 110 99.9 115 150 150 136.0 165 191 190 173.0 210 227 225 204.0 250

48 54 60

1200 1350 1500

200 360 390

182 327 354

260 430 485

Example:

25˚

5˚

Width Trough Angle Belt Speed Material Surcharge Angle


236 390 440

295 475 540

268 432 490

English Units 48 in 45˚ LC 500 fpm 130 lb/ft3 25˚

20˚ TPH t/h 130 118 190 172 255 232 300 272

TPH 140 210 280 355

t/h 127 191 254 322

TPH 150 225 305 395

t/h 136 204 277 358

345 526 617

430 640 755

390 582 685

485 700 830

440 635 752

380 580 680

25˚

30˚

SI Units 1200 mm 45˚ LC 2.5 m/s 2080 kg/m3 25˚

131


RULES AND VALUES FOR INTERCONVERSION OF ENGLISH UNITS AND SI UNITS Widths of Conveyor Belting

SI Units

English Units

The standard widths of conveyor belting in SI units and their agreed full-inch equivalents as given in ISO 251 are as follows:

The standard widths of conveyor belting in inches and their agreed rounded equivalents in SI units are as follows: in

mm

mm

in

10 12 14

250 300 350

300 400 500

12 16 20

16 18 20

400 450 500

600 650 800

24 26 32

24 26 30

600 650 750

1000 1200 1400

40 48 56

36 42 48

900 1050 1200

1600 1800 2000

64 72 80

54 60 72

1350 1500 1800

84

2100

Thicknesses of Conveyor Belting English Units Fractional in 1/32 1/16 3/32 1/8 5/32 3/16 1/4 5/16 3/8 1/2 5/8 3/4 1

mm 1 2 2 3 4 5 6 8 10 13 16 20 25

SI Units mm 1 2 3 4 5 6

Fractional in 1/32 1/16 1/8

8 10 13

5/32 3/16 1/4 5/16 3/8 1/2

16 20 25

5/8 3/4 1

Lengths of Conveyor Belting English Units Specified lengths of conveyor belting are rounded to the next highest whole number of feet. For conversion to SI units: Multiply belt length in feet by factor 0.304 8; Round to the next highest whole number; The result is belt length in meters.


132


SI Units Specified lengths of conveyor belting are rounded to the next highest whole number of meters. For conversion to English units: Divide belt length in meters by 0.304 8; Round to the next highest whole number; The result is belt length in feet. Factors for Test Data and Application Engineering Conversion factors which are exact are in bold type; the other factors given are much more than sufficiently accurate for conveyor belting work. All factors may therefore be rounded off at a level which provides sufficient accuracy for the data involved, or full factors may be used and the converted results rounded as outlined under Rounding of Converted Values on page 135.

CONVERSION UNITS To Convert FROM English units TO SI units MULTIPLY by the Factor. To convert TO English units FROM SI units DIVIDE by the Factor. Quantity

English Unit

Acceleration

SI Unit

Metric Symbol

Factor

foot per second per second meter per secondper second

m/s2

0.304 8

Area

square footsquare inch

square metersquare centimeter

m2cm2

0.092 903 04 6.451 6

Capacity

bushel, U.S. dry bushel, Canadian gallon, U.S. gallon, Canadian

cubic decimeters (liters) cubic decimeters (liters) cubic decimeters (liters) cubic decimeters (liters)

dm3 dm3 dm3 dm3

35.239 07 36.368 72 3.785 412 4.546 09

Density

pound per cubic foot

kilogram per cubic meter

kg/m3

16.018 46

Energy

foot pound-force horsepower hour kilowatt hour

joule megajoule megajoule

J MJ MJ

1.355 818 2.684 52 3.6

Force

pound-force pound-force

newton* kilogram-force

N kgf

4.448 222 0.453 592 37

Force Per Unit Width

pound per inch width pound per inch width

kilonewton per meter* kilogram-force per centimeter

kN/m kgf/cm

0.175 127 8 0.178 58

Length

foot inch inch milemil (0.001 inch) yard

meter millimeter centimeter kilometer millimete rmeter

m mm cm km mm m

0.304 8 25.4 2.54 1.609 344 0.025 4 0.914 4

* Metric units that should not be used with SI. ** Care must be taken in the interpretation of the word “tonne” in French texts of Canadian origin where the meaning may be “a ton of 2000 pounds.”


133


Conversion Units (continued) Quantity

English Unit

SI Unit

Metric Symbol Factor

Mass

ounce (avoirdupois) pound (avoirdupois) slug ton, short (2000 lb.) ton, long (2240 lb. UK)

gram kilgram kiogram **metric tonne (1000 kg) **metric tonne (1000 kg)

g kg kg t t

Mass Per Unit Area

ounce per square yard pound per square foot pound per square inch

gram per square meter kilogram per square meter kilogram per square meter

g/m2

tex tex

milligram per meter gram per kilometer

Mass Per Unit Length Moment of Inertia of Mass

Momentum Power

Pressure or Stress (Force Per Unit Area)

Torque (Moment of Force) Velocity (Speed) Volume horsepower

28.349 523 0.453 592 37 14.593 9 0.907 184 74 1.016 046 908 33.905 7 4.882 43 703.069 6

kg/m

2

kg/m2

1.000 1.000

mg/m g/km

pound foot squared (WR2 ) kilogram meter squared kilogram centimeter squared pound inch squared

kg.m2 kg.cm

0.042 140 1 2.926 4

pound foot per second

kilogram meter per second

kg.m/s

0.138 255

horsepower, horsepower, metric (cheval vapeur)

kilowatt kilowatt

kW kW

0.746 0.735 499

pound-force per square inch (psi) pound-force per square inch (psi) pound-force per square inch (psi)

kilopascal (kilonewton per square meter) megapascal *kilogram-force per square centimeter

kPa MPa

6.894 757 0.006 895 0.070 307

pound-force foot pound-force inch foot per minute foot per second mile per hour mile per hour cubic foot cubic foot cubic yard

newton meter newton meter meter per second meter per second meter per second kilometer per hour cubic meter cubic decimeter (liter) cubic meter

2

kgf/cm2 N.m N.m m/s m/s m/s km/h

1.355 818 0.112 985 0.005 08 0.304 8 0.447 04 1.609 344

m3

0.0283 28.31685 0.764555

dm

3

m3

*Metric units that should not be used with SI.


134


Rounding of Converted Value Standard Rounded Equivalents. Standard rounded equivalents for belt dimensions are found on page 132.

ROUNDING OFF DATA Numerical Range of Converted Values Equal to orgreater than

Round tothe nearest

But less than

0.0050

0.0250

0.0001

0.0250

0.0500

0.0005

0.050

0.250

0.001

0.250

0.500

0.005

0.50

2.50

0.01

2.50

5.00

0.05

5.0

25.0

0.1

25.0

50.0

0.5

50

250

1

250

500

5

500

2 500

10

2 500

5 000

50

5 000

25 000

100

25 000

50 000

500

50 000

250 000

1 000


135


APPENDIX

CONVEYOR ANALYSIS DATA SHEET

Conveyor Analysis Data Sheets provide a standardized format for the orderly collection of data which best characterize a particular conveyor installation. These data can then be used to develop a specific recommendation with regard to the conveyor belt construction deemed to be most suitable for the application described. The following pages show a typical Conveyor Analysis Data Sheet for both English and Metric units.


136


CONVEYOR ANALYSIS DATA SHEET English Units DATE: ____________________________________________________________________________________________________ CUSTOMER: ______________________________________________________________________________________________ LOCATION: ______________________________________________________________________________________________ SKETCH OF CONVEYOR PROFILE: __________________________________________________________________________ REPRESENTATIVE: ________________________________________________________________________________________ Material ___________________ Wt./Cu. ft______lb Max. Lump Size ____in % Fines____________________________ Max. Temp. ______ ˚F Avg. Temp. ______ ˚F Oil Condition ______________________ Abrasion: Slight Moderate Extreme Other Conditions ________________________________________________ Total Belt Length ______ft Belt Width ______in Capacity: Max. T.P.H. ________________ Avg. T.P.H. ________________ Belt Speed ______F.P.M. Indicate whether Conveyor is: Horizontal Incline or Decline Horizontal: give HorizontalC-C __________ft Incline (or Decline): give HorizontalC-C __________ft or Contour C-C __________ft and Vertical C-C __________ft or Angle or Slope __________˚ Drive: No. Drive Pulleys__________ Location: Tail Return Run Head Arc of Contact______˚ Wrap: Lagged Bare Motor Type _______________________________________________Motor H.P. ____________________________ Type of Starting __________________________________________________________________________________ Idlers: Idler Angle__________Spacing: Carrying________ft________in Return________ft________in Diameter: Carrying________in Return________in Type: High Grade Roller Brg. Standard Antifriction Special Type, Describe __________________________________________________ Loading Point:Type______________________________________________Spacing__________ft__________in Takeup: Screw Gravity or Automatic Takeup Travel__________ft__________in Takeup Location__________________________________ Actual Takeup Weight_______________________________lb Splice: Vulcanized Splice Pulley Diameters: Tripper_____________in Loading Conditions:

Mech. Fastener, Type __________________________________________ Drive__________in Takeup_________in

Drive Snub__________in Head__________in Head Snub__________in Takeup Bend_________in Tail___________in

From______________________________Loading Point _________________________________ _ Total Vertical Drop__________ft (made up of__________ft Free Fall and __________ft of Vertical Height on Loading Chute at__________˚ angle to horizontal)

Discharge: End Plow Tripper, Lift__________ft Other (Describe)____________________________________ To ________________________________________ Previous Conveyor Belt:

Width__________in Fabric______________________________________Plies ____________ Quality__________Top Cover___________in Pulley Cover________________________in Manufacturer________________________________________Life __________________________ Pattern of Belt Failure: Ply Separation Carcass Breaks Cover Worn Off Other, Specify __________________________________________

Profile Sketch—Refer to back of sheet as applicable.


137


SKETCH OF PROFILE-CONVEYOR IDENTIFICATION English Units Simply give diagram number for a conveyor of similar profile.

Diagram No.

Otherwise, make special sketch. Where required, supply dimensions:

C tail to curve ____________ft D tail to drive ____________ft R


138


CONVEYOR ANALYSIS DATA SHEET Metric (SI) Units DATE: ____________________________________________________________________________________________________ CUSTOMER: ______________________________________________________________________________________________ LOCATION: ______________________________________________________________________________________________ SKETCH OF CONVEYOR PROFILE: __________________________________________________________________________ REPRESENTATIVE: ________________________________________________________________________________________ 3 Material ___________________ m

__________kg. Max. Lump Size ____mm % Fines __________________________ Max. Temp. ______ ˚C Avg. Temp. ______ ˚C Oil Condition ______________________ Abrasion: Slight Moderate Extreme Other Conditions _____ ___________________________________________

Total Belt Length ______m Belt Width ______mm Capacity: Max. t/h ________________Avg. t/h __________________________ Belt Speed ______m/s Indicate whether Conveyor is: Horizontal Incline or Decline Horizontal: give HorizontalC-C __________m Incline (or Decline): give HorizontalC-C __________m or Contour C-C __________m and Vertical C-C __________m or Angle or Slope __________˚ Drive: No. Drive Pulleys__________ Location: Tail Return Run Head Arc of Contact______˚ Wrap: Lagged Bare Motor Type _______________________________________________Motor kW ______________________________ Type of Starting __________________________________________________________________________________ Idlers: Idler Angle__________Spacing: Carrying________mm Return________mm Diameter: Carrying________mm Return________mm Type: High Grade Roller Brg. Standard Antifriction Special Type, Describe __________________________________________________ Loading Point:Type______________________________________________Spacing__________mm Takeup: Screw Gravity or Automatic Takeup Travel__________mm Takeup Location__________________________________ Actual Takeup Weight_______________________________kg Splice: Vulcanized Splice Pulley Diameters: Loading Conditions:

Mech. Fastener, Type __________________________________________ Drive__________mm Takeup_________mm

Drive Snub__________mm Head__________mm Head Snub_________mm Takeup Bend_________mm Tail___________mm Tripper___________mm

From______________________________Loading Point __________________________________ Total Vertical Drop__________m (made up of__________m Free Fall and __________m of Vertical Height on Loading Chute at__________˚ angle to horizontal)

Discharge: End Plow Tripper, Lift__________m Other (Describe)____________________________________ To ________________________________________ Previous Conveyor Belt:

Width__________mm Fabric______________________________________Plies ____________ Quality__________Top Cover___________mm Pulley Cover_______________________mm Manufacturer________________________________________Life __________________________ Pattern of Belt Failure: Ply Separation Carcass Breaks Cover Worn Off Other, Specify __________________________________________

Profile Sketch—Refer to back of sheet as applicable.


139


SKETCH OF PROFILE-CONVEYOR IDENTIFICATION Metric (SI) Units Simply give diagram number for a conveyor of similar profile.

Diagram No.

Otherwise, make special sketch. Where required, supply dimensions:

C tail to curve ____________m D tail to drive ____________m R


140

arpm_manual_2.pdf

Recommend Documents