GRUPO GLORIA
YURA S. A. SPECIFICATION No. DESING CRITERIA FOR CHAIN AND BELT BUCKET ELEVATORS
Approved: REVISION 0
FEBRERO 2010
CHAIN ND BELT BUCKET ELEVATORS Bucket Elevators are used when plant structures or equipment are located too close to allow an inclined conveyor to be used to elevate material from its point of origin to its destination. A.
Application
1.
B.
Bucket Elevators can handle essentially any dry material, but have restrictions in regard to lump size and damp material stickiness. Design
1.
Design capacity shall be equal to operating capacity X 1.25.
2.
The bucket filling shall be maximum 60 % at operating capacity and maximum 75% at design capacity (with respect to water line) for fine dust like raw meal, cement and pulverized coke and coal For granular material with minimum size of 3 mm (1/8”), the filling of bucket shall be 75% maximum at operating capacity and 100 % at design capacity (with respect to water line).
3.
Use the lower material density when selecting the equipment size. For cement with 4000 Blaine and greater, use cement density of 0.60 tons/m3 (37.5 lbs/ft3). As a reference, for other materials densities, see Table “Materials typical characteristics”.
4.
Use the higher material density and buckets at 100% full of material when calculating the brake horsepower (BHP). WARNING; for capacity purposes, do not consider that the elevator could operate at 100% full.
5.
Elevators shall be of the centrifugal type, unless otherwise approved by owner.
6.
Elevators type according to material transported: Chain bucket elevator for granular material up to 100 mm (4”) and up to 250° C (480 °F).Temperature. a)
Belt bucket elevator for fine material of 25 mm (1”) or less and up to 120° C (250 °F).temperature.
b)
7. Speed by type of discharge: a)
Centrifugal discharge; 1.1 to 2.0 m/sec. (225 to 400 fpm).
b)
C.
D.
E.
Continuous discharge (Gravity); Use for granular material of 50 mm (2”) and greater, abrasive, hot, or very soft materials. The speed to consider shall be of 0.50 to 0.81 m/sec. (100 to 150 fpm).
8.
Centrifugal discharge belt bucket elevator is preferred due to higher capacity and less maintenance.
9.
For bucket elevators to feed the preheater use backstop brake on the axis of the drive pulley. In all the others bucket elevator applications the backstop brake can be installed in the high-speed shaft of the reducer.
10.
When a double transmission is used the brake must be located in an extension of the high speed shaft of the reducer on the opposite side of the inspection doors.
12.
The foot pulley shall be floating type.
13.
Transmission service factor SF = 1.5 minimum.
Buckets 1.
Perforated buckets shall be specified when handling powdered material such as kiln feed, raw meal, dust, mill product and cement. Perforated buckets increase the carrying capacity by releasing the air from materials which tend to become aerated.
2.
If it is required that the lead edge of the bucket be heat treated, the supplier will indicate so in the data sheet.
Pulleys. 1.
All pulleys of the elevator must be machined on the face, if these are made from a seamed pipe.
2.
The crown of the pulleys must be conical and may vary from 1/16" to 1/8" per foot of length of the face.
3.
The pulleys in general must have as a minimum a face length equal to the width of the belt plus 50 mm (2"). according to the CEMA norms.
4.
All the pulleys of the elevator must have rigid type hubs. Unless another type of fastening is indicated.
5.
All pulleys and shafts of the elevator, once assembled must be statically balanced.
Sprockets. 1.
The Sprockets must be of the segmented type, either of two or three sections, depending of supplier’s recommendations.
F.
G.
2.
The material for the fabrication of the sprockets and hubs must be selected by the supplier.
3.
Sprockets shall be mounted on the shaft with compression hubs and bushings. The Driver sprocket shall have a minimum of 17 teeth. One of the sprockets shall have an uneven number of teeth to prevent a repetitive contact between the chain and sprocket teeth.
4.
All the sprockets of the elevators and shafts, once assembled, must be strictly balanced and the teeth must be heat treated, indicating clearly the type of treatment done and the hardness at each 1/16" of depth.
SHAFTS
1.
Shafts 6” (150mm) diameter and greater shall be forged carbon steel, SAE 4140; those smaller than 6” (150mm) diameter shall be hot rolled carbon steel ground and polished, SAE 1045 or approved equal.
2.
Limit combined bending and torsion stress, including keyways, to 8000 PSI (55 MPa) maximum, and 10,500 PSI (72 MPa) for shafts without keyways
3.
Turned down shafts shall be tapered between diameters.
4.
All drive hubs shall be keyed with keys and keyways conforming to latest ASTM Standards.
Access and Maintenance 1.
Hinged access doors shall be specified for both sides of the elevator. One set of these doors shall be in the boot section for access to the tail shaft assembly. The second set shall be in an intermediate level for pinning elevator belt and for raising the tail pulley assembly.
2.
The doors or registers for inspection in the boot must be of the hinged type with quick lock and a seal to prevent spill of material, as well as in the body and header of the elevator.
3.
A removable panel adjacent to the intermediate level address doors, on the up-coming belt side, shall be provided for bolting the buckets to the belt.
4.
Three inspection doors will be specified; one for viewing the head pulley or sprocket area, one for viewing the bucket discharge and elevator outlet lip, and one for viewing the inlet feeding into the buckets.
5.
A trolley hoist beam shall be provided above the head section for removal of the head casing, lifting of the head shaft, the head belt or sprocket, and the elevator belt or sprocket in operating position. The trolley hoist beam shall not be type to handle the lifting forces to remove a fallen and jammed elevator belt. It is assumed that the lifting forces, required for breaking loose a jammed belt, will be provided from the upper casing itself or from a structural framing member provided for that
purpose above the elevator. Beam should be able to take full load of elevator. 6.
H.
Backstops 1.
I.
J.
When the elevator is not located within or adjacent to a compatible structural flooring system, the elevator shall be specified to include an access platform at the head section along with the hoisting system and access ladder. The platform shall be provided with handrail and the ladder with safety cage if required.
All Bucket Elevators shall be specified with backstops, either mounted on the head shaft, or integral with the gear reducer if the reducer is shaft mounted.
Inching Drives 1.
Shall be provided for maintenance purposes on those bucket elevators that the process depends on for continuous operations (such as cement mills, kiln feed) and shall be provided with stop-start station at the intermediate platform use for maintenance and inspection.
2.
Creep speed = 0.15 m/sec
3.
When a double transmission is used the backstop brake must be placed on an extension of the low speed shaft of the reducer on the opposite side of the register doors.
Couplings 1.
Design a.
K.
(30 feet/min)
Couplings shall be a steel grid design, Falk Steelflex type or Owner approved equal.
Elevator belt. 1.
The width of the belt will be such that the buckets may be fixed to it adequately, and must be at least 25.4 mm (1") wider that the length of bucket selected.
2.
The belts will be of the flat type covered with rubber of 0.993 Kg. (35 ounces) minimum unless the supplier recommends another type.
3.
The minimum work strength of the belt will be of 5.72 Kg./cm. in width and per ply (32 Lb./in./ply.).
4.
The quality of the cover will have a minimum strength to tension of 245 Kg./cm.2 (3500 Lb./in.2).
5.
L.
Elevator Chains 1.
M.
The Joint of the belt will be of the vulcanized type, when the belt is of the textile type, when due to tension and temperature a belt with steel cable is used an appropriate joint mechanism will be used.
The equipment must have a central chain or two chains at the sides of the buckets, as required. b.
The chain speed will be that appropriate for the material being handled and the capacity indicated in the data sheet.
c.
The chain must be selected by the supplier and must also specify the material, thickness, treatment and hardness of each element.
V-Belts 1.
Design a. b. c. d. e. f. g.
N.
V-Belts shall be of standard cross-section (A-B-C-D-E or 5V-8V wherever practical. The preferred reduction ratio shall be 4.0 to 1, with 6.0 to 1 being the maximum. Sheaves shall be mounted on the shaft with compression hubs and bushings. All V-Belt drives shall be enclosed with an expanded metal guard. V-Belts must be in matched sets. Minimum number of belts for any drive shall be two. Where possible, multiple belts shall be 'OPTI' type. Motor sheaves must be at least the minimum pitch diameter recommended by the sheave or the motor manufacturer, whichever is greater. The motor manufacturer must approve the motor sheave size where permissible limits are not tabulated.
Bearings and Pillow Blocks 1.
All bearings shall be heavy duty with series per AFMBA standards. Use fully self-aligning cast iron split pillow blocks.
2.
A minimum L-10 life rating of 50,000 hours is required.
3.
Use one fixed and one floating pillow block assembly. Provide end closing seals where shafts terminate at the bearings, and with triple labyrinth seal.
4.
Standard button-type lubrication fittings are required on all pillow blocks.
O.
POWER TRANSMISSION Various types of drive components and unique methods are required depending on the specific application of each drive. Some considerations are equipment speed, horsepower range, and thrust loads. Purchased equipment requiring a drive shall have the drive components including guards furnished with that equipment. The size and selection of these components shall be the responsibility of the supplier.
A.
B.
Motors 1.
Design
a.
Constant speed drives shall be A-C squirrel cage motors.
b.
Variable speed drives shall be used as required. The type used will be determined by the conditions of the specific application.
c.
Hydraulic motors shall be investigated for high torque and low speed applications when they appear to have an efficiency and economical advantage.
d.
Fluid couplings or other owner approved means shall be provided when connecting motors to equipment requiring a soft start unless the motor design has incorporated such characteristics.
Speed Reducers 1.
Design
a.
Generally reducers shall be SEW, Falk, Hansen, Dodge, others shall be approved by the Owner, and must be selected for class II (AGMA)
b.
Reducers shall be used based on the following sequence of choice; Reducers with drive power of up to 40 HP must be type on a shaft mounted, preferably a parallel shaft gear motor. Reducer with drive power of 50 HP, or more must be of the parallel shaft type and in no case with shafts at 90° (with the exception of critical space limitation cases).
c.
Load Classifications of Service Factors for each application are stated in the TABLE attached.
DESIGN FACTOR RECOMMENDED EQUIPMENT SPEED REDUCER (FD)
FLEXIBLE COUPLING (FD)
HYDRAULIC COUPLING (FD)
SPROCKETS & CHAIN (FD)
PULLEYS & "v" BELTS (FD)
Belt conveyor
1.50
1.25
1.40
1.30
1.30
Bucket elevator
1.50
1.25
1.40
1.30
1.40
Chain conveyor
1.50
1.25
1.40
1.30
1.40
Screw conveyor
1.50
1.25
1.40
1.30
1.40
Feeders (general)
1.50
1.25
1.40
1.50
1.50
Design factor as a function of the operation of the equipment, for 24 hrs/day and load classification (AGMA) class II,
TECHNICAL QUESTIONNAIRE FOR BELT BUCKET ELEVATORS
PLANT: ___________________________________________ EQUIPMENT No: ___________________________________ PROJECT No.: _____________________________________ The following questionnaire must be answered and returned together with the bid. 01
Name of the supplier
02
Date questionnaire is filled
03
Selected elevator
04
.01
Type
.02
Model
.03
Operating speed
.04
Material to be raised
.05
Nominal capacity
TPMH
.06
Design capacity
TPMH
.07
C. to C. distance(height)
mm
.08
Percentage fill with respect to water line
%
.09
Required power
BHP
.10
Motor power
HP
.11
Make of elevator
.12
Dimensions of cube
m/sec
mm
Header section .01
Pulley diameter
mm
.02
Fabrication material
.03
Covering material
mm
.04
Shaft dimensions
mm
.05
Type of pillow blocks
.06 05
06
07
08
Type of lubrication
Boot section .01
Pulley diameter
.02
Fabrication material
.03
Covering material
.04
Shaft dimensions
.05
Type of pillow blocks
.06
Type of lubrication
mm
mm
Belt .01
Maximum tension
Kg/cm2
.02
Total length
mm
.03
Thickness
mm
.04
Width
mm
.05
Rubber belt specifications
.06
Number of piles
.07
Make
Buckets .01
Dimensions
.02
Type and make
.03
Material
.04
Spacing
Transmission .01
Speed reducer
.02
Type and make
.03
Model
.04
Size
.05
Capacity
.06
Service factor
.07
Speed relation
.08
Type of lubrication
.09
Type of coupling High speed (make)
mm
mm
Low speed (make) 09
10
11
12
Motor .01
Power
.02
S.F.
.03
Speed
.04
Frame
.05
Voltage
.06
Amperage
.07
Frequency
.08
Make of motor
Safety devices .01
Make
.02
Type
.03
Amount
Control devices .01
Make
.02
Type
.03
Model
.04
Amount
Creep mechanism .01
Reducer type and make
.02
Reduction relation
.03
Clutch type
.04
Motor Power RPM
13
Other accessories proposed By the supplier
