FMDS0711 BELT CONVEYORS.pdf

FM Global Property Loss Prevention Data Sheets

7-11 January 2012 Page 1 of 12

BELT CONVEYO CONVEYORS RS

Table of Contents Page 1.0 SCOPE .............. ............................. .............................. ............................. ............................. .............................. ............................. ............................. .............................. .............................. ................. 2 1.1 Changes ......... ................... .................... .................... .................... ..................... ..................... .................... .................... .................... .................... .................... ..................... ................... ........ 2 2.0 LOSS PREVENTION RECOMMENDATIONS ............... ............................. ............................. .............................. ............................. ............................. ............... 2 2.1 Construction and Location ......... ................... .................... ..................... ..................... .................... .................... .................... .................... .................... ..................... ........... 2 2.2 Occupancy ......... ................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................... ............... ..... 2 2.3 Protection .......... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................... .................... ............... ..... 2 2.3.1 General ......... ................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................... .......... 2 2.3.2 Indoor Conveyors .......... .................... .................... .................... .................... ..................... ..................... .................... .................... .................... .................... .............. .... 3 2.3.3 Outdoor Conveyors .......... .................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ........... 3 2.3.4 Specialty Conveyors .......... .................... .................... .................... .................... .................... ..................... ..................... .................... .................... ................... ......... 7 2.3.5 Explosion Protection .......... .................... .................... .................... .................... .................... ..................... ..................... .................... .................... ................... ......... 8 2.3.6 Manual Protection ........... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................... ............ .. 8 2.4 Utilities .......... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................... .................... .................... .......... 9 2.5 Operation and Maintenance ......... ................... .................... .................... .................... ..................... ..................... .................... .................... .................... ................... ......... 9 2.6 Ignition Source Control .......... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... ............... ..... 9 3.0 SUPPORT FOR RECOMMENDATIONS ............... .............................. .............................. ............................. ............................. .............................. .................... ..... 10 ................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... ............. ... 10 3.1 Belt Flammability ......... 3.1.1 General .......... .................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... .................. ........ 10 3.1.2 Laboratory-Scale Testing .......... .................... .................... .................... .................... ..................... ..................... .................... .................... .................... ............ .. 10 3.2 Major Factors Affecting the Need for Fire Protection ...................................................................... 10 4.0 REFERENCES ....................................................................................................................................... 11 4.1 FM Global .......... .................... .................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... ............. ... 11 4.2 Other .......... .................... .................... .................... ..................... ..................... .................... .................... .................... .................... .................... .................... ..................... ..................... ............ 12 APPENDIX APPEND IX A GLOSS GLOSSARY ARY OF TERMS TERMS ....................................................................................................... 12 APPENDIX B DOCUMENT REVISION HISTORY ...................................................................................... 12

List of Figures Fig. 1a. Decision Decision tree to determine need for automatic automatic sprin sprinkler kler protection protection for outdoor conveyors ............ 4 Fig. 1b. Decisi Decision on tree to determine need for automatic automatic sprin sprinkler kler protection protection for outdoor conveyors ............ 5 Fig. 2a. Suggested locations for automatic sprinklers in various outdoor conveyor arrangements of combu combustibl stible e or nonco noncombust mbustible ible construction construction (The occup occupancy ancy is assume assumed d to be noncombusti noncom bustible, ble, apart from the belt or conve conveyed yed product) .......................................... ........................... .............................. ................... .... 6 Fig. 2b. Suggested locations for automatic sprinklers in various outdoor conveyor arrangements of combu combustibl stible e or nonco noncombust mbustible ible construction construction (The occup occupancy ancy is assume assumed d to be noncombusti noncom bustible, ble, apart from the belt or conve conveyed yed product) .......................................... ........................... .............................. ................... .... 6

List of Tables Table 1. Automatic Sprinkler Spacing for Enclosed and Partially Enclosed Indoor Conveyors ................... ..................... .. 3

©2009 Factory Mutual Insurance Company. All rights reserved. No part of this document may be reproduced, stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.

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1.0 SCOPE This data sheet covers fire, explosion, and miscellaneous exposures to vertical, horizontal, and inclined belt conveyors made of rubber or plastic. Conveying systems within manufacturing plants or warehouses (indoor conveyors) are included in this data sheet. Conveyors in sub-grade tunnels, surface systems, elevated galleries, and intermediate buildings (outdoor conveyors) are also included. Vertical bucket elevators conveying grain and other combustible materials are covered in Data Sheet 7-75, Grain Storage and Milling . Conveyor belts located in underground metal, non-metal, or coal mines are covered in Data Sheet 7-12, Mining and Ore Processing. 1.1 Changes January 2012. Terminology related to ignitable liquids has been revised to provide increased clarity and consistency with regard to FM Global’s loss prevention recommendations for ignitable liquid hazards. 2.0 LOSS PREVENTION RECOMMENDATIONS 2.1 Construction and Location 2.1.1 Use noncombustible belts. If this is not possible, use fire retardant belts if operating parameters allow them to be used. 2.1.2 Provide the following risk improvement measures for indoor conveyor belts: 2.1.2.1 Provide noncombustible covers if an enclosure is needed for quality control or other purposes. 2.1.2.2 Do not position one conveyor above another (either parallel or crossing over). Doing so will create areas that are shielded from the automatic sprinklers at the ceiling. 2.1.2.3 Do not run conveyors through fire walls. If conveyors do run through fire walls, refer to Data Sheet 1-23, Protection of Openings in Fire Subdivisions, for guidance on how to protect the penetrations. 2.1.3 Provide the following risk improvement measures for outdoor conveyor belts: 2.1.3.1 Use noncombustible enclosures and insulation for conveyor galleries, tunnels, or buildings. 2.1.3.2 Cover combustible exposed insulation on interiors of conveyor galleries, tunnels, or buildings with FM Approved fire retardant coating or replace with noncombustible insulation. Refer to Data Sheet 1-57, Plastics in Construction , for guidelines on protection of foamed plastic insulations. 2.1.3.3 Place warning markers and clearance signs on elevated galleries in high traffic areas, or under which large mobile equipment might pass, to prevent impact to exposed steel supports. 2.1.3.4 Minimize the potential for collapse by designing the conveyor system to Data Sheet 1-54, Roof Loads for New Construction . Provide employee training to help staff recognize and facilitate removal of unusual accumulations of spilled materials, snow, or ice inside or on roofs of galleries and buildings. 2.1.3.5 Protect conveyor systems against natural hazards such as landslide, flood, surface water runoff, and ground subsidence. 2.2 Occupancy 2.2.1 Do not store combustibles under indoor conveyor belts that are more than 4 ft (1.2 m) wide unless a noncombustible barrier and automatic sprinkler protection suitable for the hazard is provided below the conveyor. 2.2.2 Conduct regular inspections of conveyor galleries to ensure there is no buildup of debris beside or under the conveyor. Good housekeeping will help reduce the possibility of ignition due to friction from a buildup of debris underneath or beside the conveyor belt. 2.3 Protection 2.3.1 General 2.3.1.1 Provide automatic sprinkler protection over indoor and outdoor conveyor belts unless they meet all of the following criteria:

©2009 Factory Mutual I nsurance Company. All rights reserved.

Belt Conveyors

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The conveyor belt has a fire propagation index (FPI) of 7 or lower, as determined by testing per ASTM E2058. The material being conveyed is noncombustible. The enclosure housing the conveyor belt is of noncombustible construction. No combustibles are present near or under the conveyor belt.

2.3.1.2 Provide automatic sprinkler protection over conveyor belts where they enter a building or pass through a fire wall. Refer to Data Sheet 1-23, Protection of Openings in Fire Subdivisions, for guidance. 2.3.2 Indoor Conveyors 2.3.2.1 Interlock indoor conveyors to shut down automatically on sprinkler water flow or fire detection if continuing operation could spread fire to other areas. Fire spread to other areas will overtax the sprinkler system. 2.3.2.2 Protect open conveyors with ceiling sprinklers in accordance with the applicable occupancy-specific data sheet. 2.3.2.3 Provide automatic sprinklers below conveyors unless they meet the following criteria: •

The conveyor is less than 4 ft (1.2 m) wide.

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The conveyor belt is at least 70% open, or the conveyor is a roller type that is at least 50% open.

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There are no combustibles located beneath the conveyor.

2.3.2.4 Provide automatic sprinkler protection for enclosed or partially enclosed conveyors longer than 30 ft (9.0 m) shielded from overhead automatic sprinkler systems in accordance with Table 1. (Conveyors could be enclosed or partially enclosed by metal or plastic dust covers. Conveyors can also be shielded from ceiling sprinklers by other conveyors.) If flexible fire sprinkler connectors are used, ensure they are FM Approved. Table 1. Automatic Sprinkler Spacing for Enclosed and Partially Enclosed Indoor Conveyors Belt Width 2 ft (0.6 m) to 6 ft (1.8 m) > 6 ft (1.8 mm)

Style of Sprinkler Pendant Sidewall Pendant Sidewall

Sprinkler Spacing 12 ft (3.7 m) 12 ft (3.7 m) 12 ft (3.7 m) 12 ft (3.7 m)

Sprinkler Location Along the center line of the belt Along one side of the belt Along the center line of the belt Staggered along both sides of the belt (i.e., sprinkler heads on one side are spaced 24 ft [7.4 m] apart)

2.3.2.5 Provide automatic sprinkler protection over multiple parallel conveyors that are less than 2 ft (0.6 m) apart horizontally, regardless of the width of the conveyor belts. 2.3.2.6 Ensure the maximum sprinkler coverage does not exceed 100 ft 2 (9 m2) with sprinklers no more than 12 ft (3.7 m) apart for conveyor belts greater than 10 ft (3.0 m) wide. 2.3.2.7 Install FM Approved quick response sprinklers with a K factor of 8.0 (115) and a temperature rating of 165ºF (74ºC). 2.3.2.8 Design the sprinkler system based on the 10 most hydraulically remote sprinklers operating with a minimum end sprinkler pressure of 14 psi (0.96 bar). The demand of the conveyor belt sprinklers does not need to be hydraulically balanced with the ceiling sprinkler system. 2.3.2.9 Design the water supply for a duration of one hour and include 250 gpm (950 L/min) hose streams. 2.3.3 Outdoor Conveyors 2.3.3.1 Provide wet-type automatic sprinkler protection as recommended in Figures 1 and 2 and Section 2.3.3.5 for captive conveyors and Section 2.3.3.6 for cross-country conveyors. Use dry type or pre-action systems in cold climates where there is the possibility of freezing.


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2.3.3.2 Provide deluge water spray systems in conveyor galleries of an unusually steep pitch where a fire may race ahead of conventional sprinklers. A conveyor meeting the criteria can be identified as one having a belt with special buckets or other devices provided to prevent conveyed material from sliding backwards down the belt. Generally, these conveyors are pitched in excess of 30 from horizontal. 2.3.3.3 Provide deluge water spray systems in conveyors where fast response or immediate large area cooling is desired due to high values, unusual potential for severe loss, or high frequency of fires. 2.3.3.4. Design the deluge water spray system to provide 0.25 gpm/ft 2 (10 mm/m) density over the entire area of the conveyor. Ensure design and coverage are in accordance with Data Sheet 4-1N, Fixed Water Spray Systems for Fire Protection , for belt conveyors.

Fig. 1a. Decision tree to determine need for automatic sprinkler protection for outdoor conveyors


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Fig. 1b. Decision tree to determine need for automatic sprinkler protection for outdoor conveyors


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Fig. 2a. Suggested locations for automatic sprinklers in various outdoor conveyor arrangements of combustible or noncombustible construction (The occupancy is assumed to be noncombustible, apart from the belt or conveyed product)

Fig. 2b. Suggested locations for automatic sprinklers in various outdoor conveyor arrangements of combustible or noncombustible construction (The occupancy is assumed to be noncombustible, apart from the belt or conveyed product)


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2.3.3.5 Protect outdoor captive conveyor systems as follows: 2.3.3.5.1 Provide automatic sprinklers throughout all floors of intermediate transfer, splice, or junction buildings of combustible construction, when sprinklers are also needed for the connecting conveyors. 2.3.3.5.2 Install sprinklers under barriers where solid barriers are more than 4 ft (1.2 m) wide. 2.3.3.5.3 Separate multiple tiers of conveyors when automatic sprinklers are needed per Figure 1. 2.3.3.5.4 Provide sprinkler protection where dust-tight enclosures are used to prevent or minimize dust liberation from belt conveyors; provide sprinklers inside the enclosures per Figure 2. Provide sprinklers at the ceiling of the tunnel, gallery, or building housing the enclosed conveyor only if construction is combustible, or if other combustibles, such as grouped electrical cables, are present. 2.3.3.5.5 Where space inside the enclosures is limited, arrange piping on the exterior, and extend sprinklers through sealed openings. Provide inspection and maintenance hatches for each sprinkler. 2.3.3.5.6 Base sprinkler design for horizontal conveyors and inclined conveyors with a pitch of less than 10°on the operation of the 10 most hydraulically remote sprinklers. 2.3.3.5.7 Base sprinkler design for inclined conveyors with a pitch of 10°or greater on the operation of the 15 most hydraulically remote sprinklers. 2.3.3.5.8 Ensure a minimum end sprinkler pressure of 14 psi (0.96 bar). Limit sprinkler spacing on lines to 12 ft (3.7 m). Use FMApproved sprinklers with a K factor of 8.0 (115) and a temperature rating of 165°F (74°C). 2.3.3.5.9 Where two or more parallel rows of sprinklers are provided over parallel conveyor belts in wide galleries, design the sprinklers to provide a density of 0.25 gpm/ft 2 (10 mm/min) over 2000 ft 2 (186 m2). 2.3.3.5.10 Protect sprinklers, piping, and detectors against impact damage from oversized pieces of conveyed material. 2.3.3.5.11 To prevent collapse of a gallery due to water weight from sprinkler discharge, provide adequate drainage via floor openings or by conveyor pitch. 2.3.3.5.12 Ensure there is sufficient water supply to accommodate 250 gpm (950 L/min) hose streams. 2.3.3.6 Provide the following protection for cross-country (overland) conveyors systems: 2.3.3.6.1 For totally enclosed systems, provide automatic sprinklers per Figure 1 and Section 2.3.3.5 above. An alternative would be to partially or completely remove the enclosure and protect as outlined below for open or partially open conveyor systems. 2.3.3.6.2 For open or partially open conveyor systems, protect as follows: a) Provide and maintain fire access roads that run parallel to the conveyor system and maintain a mobile water tank with a pump and hose attached. Ensure the tank has a minimum capacity of 7500 gal (28,400 L). This will provide approximately one hour supply for manual firefighting response. Alternatively, provide standard fire hydrants at approximately 350 to 500 ft (91 to 152 m) intervals along the system. b) Provide FM Approved heat or products of combustion detection devices inside transfer, splice, or drive houses. Arrange detectors to sound an alarm and stop the conveyor belt. c) Replace combustible weather hoods and intermediate buildings with noncombustible or fire-resistive alternatives. 2.3.3.6.3 Interlock the belt to shut down on sprinkler water flow or heat detector signal. 2.3.3.6.4 Base water supplies on a duration of one hour, and include 250 gal/min (950 L/min) for hose streams. 2.3.4 Specialty Conveyors 2.3.4.1 Protect Vertical Bucket Elevators as follows: A. Provide automatic sprinkler protection at the top of the vertical bucket elevator shaft where the enclosure is noncombustible. If the enclosure is constructed from combustible materials, provide additional automatic sprinkler protection along the shaft (i.e., treat it as a vertical shaft with combustible sides).


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B. Design the automatic sprinklers to deliver a minimum end sprinkler pressure of 14 psi (0.96 bar), using a sprinklers with a K factor of 8.0 (115) or greater. C. Refer to Data Sheet 7-75, Grain Storage and Milling and Data Sheet 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fires if the bucket elevator transports grain or other combustible products that may present an explosion hazard. 2.3.4.2 Protect Serpentine (pipe) conveyors systems with automatic sprinkler protection as outlined in section 2.3.3.6. 2.3.4.3 Protect air-supported conveyor systems as follows: 2.3.4.3.1 Provide an interlock to stop the belt in the event of losing one or more compressors. 2.3.4.3.2 Provide automatic sprinkler protection for air-supported conveyors per Section 2.3.3.6 where practical. 2.3.4.3.3 Do not install grouped electrical cables, gas piping, or similar combustibles within the conveyor framework. 2.3.5 Explosion Protection 2.3.5.1 Design conveyor transfer points to minimize generation of dust. Most dust generated during conveyor operations occurs when material is being transferred from one belt to another. Provide the following at these locations: A. A hood discharge chute designed so the material transferred does not impinge directly against the side of the chute. B. A spoon loading chute so material is discharged onto the lower belt in the same direction and at the same speed as the belt. C. A settling enclosure with a passive dust-control system over the lower belt. 2.3.5.2 Tightly enclose conveyors handling combustible dust and / or provide collection systems to exhaust dust fines where conveyor transfer points are not properly designed. 2.3.5.3 Avoid the use of sub-grade tunnels for combustible dusts that present an explosion hazard. 2.3.5.4 Use damage-limiting construction for conveyor galleries, buildings, or enclosures handling combustible dusts per Data Sheet 1-44, Damage-Limiting Construction . 2.3.5.5 Refer to Data Sheet 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fires, for recommendation on the arrangement of explosion protection for combustible dusts. 2.3.6 Manual Protection 2.3.6.1 Provide (in easily accessible locations) either of the following manual protection options for indoor conveyors: A. Small water hose stations with combination nozzles (solid stream and spray) for mop-up operations after a fire. This is the preferred option for manual protection. B. Portable fire extinguishers rated for the occupancy in accordance with Data Sheet 4-5, Portable Extinguishers, l ocated within 50 ft (15.2 m) of the conveyor. For conveyors on mezzanines, provide extinguishers at readily accessible locations on the mezzanine level. 2.3.6.2 Provide standard yard hydrant protection for outdoor conveyor systems captive to a plant site. 2.3.6.3. Provide FM Approved 1.5 in. (38 mm) hose stations for outdoor cross country conveyor systems. Locate the hose stations at suitable intervals inside totally or partially enclosed housings where size permits personnel access. Small hose connections can be made to wet-system sprinkler piping as long as the hose demand is added at the point of connection. Where freezing is a concern, feed hose stations from dedicated dry-pipe valves or from normally shut, drained systems.


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2.4 Utilities 2.4.1 Do not use conveying systems to transport utilities such as grouped electric cables, flammable gases, and ignitable liquids. If unavoidable, protect cables as recommended in Data Sheet 5-31, Cables and Bus Bars . Provide shutoffs for gases and liquids at locations external to the conveyor. 2.5 Operation and Maintenance 2.5.1 Where a history of longitudinal belt ripping exists, provide anti-rip detection devices to shut off drive power and minimize further damage. An alternative is to use high tear-resistant belts. 2.5.2. Provide sufficient spare belting, drives, rollers, etc. to repair the longest belt at the plant, or ensure spares can be delivered within 24 hours from an offsite location. 2.5.3 Provide belt alignment interlocks for all styles of conveyor belt (e.g., horizontal conveyors, vertical bucket conveyors) to shut down the conveyor if the belt misaligns. 2.5.4 Maintain all bearings per manufacturer’s recommendations and keep them free of dust, product, and buildup of lubrication material. 2.5.5 Have regular thermographic scans conducted on known or frequent ignition zones, such as conveyor drive pulleys and drums, to identify potential problems. 2.5.6 Clear weeds, brush, and trees from underneath and at least 25 ft (7.6 m) from both sides of the conveyor system. Remove combustible yard storage and limit the proximity of unprotected combustible buildings. Remove and relocate ignitable liquid operations, such as storage tanks, pumping stations, and tank truck unloading or loading facilities, from under or near conveyor systems. 2.5.7. Prevent fueled vehicles from being staged or parked under conveyor systems. 2.5.8. Develop preventive maintenance programs to reduce the potential of other common ignition sources, such as friction, overheated bearings or drive machinery, misalignment of belts or drivers, etc. 2.5.9. Ensure all variable speed drive motors are operated within the frequency range recommended by the manufacturer. 2.6 Ignition Source Control 2.6.1 Provide interlocks to shut down the feed system where heated materials are discharged onto belts if the material exceeds a safe temperature or if the belt or cooling system shuts down. 2.6.2 Provide motion-sensing switches or other devices to detect a slipping or jammed conveyor. Interlock the motion sensors to shut off drive power when the belt stops or slows down more than 20% of normal speed. Interlock contributing conveyors so no operating conveyor can discharge material to a stopped downstream conveyor. 2.6.3 Use the FM Global Hot Work Permit System for all hot work activities near the conveyors. Refer to 10-3, Hot Work Management, for further details. 2.6.4 Prohibit smoking around all combustible conveyor belts or conveyor belts that transport combustible materials. 2.6.5 Protect and arrange gas-fired space heaters in conveyor systems as recommended in Data Sheet 6-20, Space Heaters . 2.6.6 Interlock drive motors to shut down on detection of overload, over current condition, or if the belt slows down more than 20%. 2.6.7 Arrange electrical equipment in conveyor systems handling combustible dusts as recommended in Data Sheet 5-1, Electrical Equipment in Hazardous Locations , or appropriate jurisdictional electrical codes for hazardous locations. 2.6.8 Install magnetic tramp metal separators at rail car and truck dump hoppers and on conveyors ahead of grinding or pulverizing operations when the material being conveyed is combustible.


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3.0 SUPPORT FOR RECOMMENDATIONS 3.1 Belt Flammability 3.1.1 General Although the conveyed product and the structure may be noncombustible, loss history demonstrates that the belt itself presents sufficient combustible loading to spread the fire without other fuel contribution. Conveyor belts are manufactured of natural and synthetic rubber or plastic, such as polyvinyl chloride (PVC), acetal, polyethylene, polypropylene and nylon. They are often reinforced with fibers for strength. Outdoor belts usually are formed in laminated layers and may have, for example, a PVC base for flexibility with a rubber top layer to allow for product adhesion under incline conditions. Belt conveyors, whether made of natural or synthetic rubber or plastics, generally are assumed to be capable of self-sustained fire propagation whether or not other combustibles are present. For this reason, automatic sprinkler protection has been recommended for most installations regardless of the conveyor material’s claimed fire or flame retardancy, or of the combustibility of materials conveyed. The use of fire-retardant belts is encouraged. They are typically harder to ignite when exposed to a low-energy ignition source, thereby reducing the frequency of fire. 3.1.2 Laboratory-Scale Testing The following is a comparison between a non-fire-retardant belt and a belt advertised as a flame-retardant conveyor belt. Heat of combustion: The heat of combustion of both belts was determined by oxygen bomb calorimetry. The non-fire-retardant belt was 9,720 Btu/lb The fire-retardant belt was 9,755 Btu/lb Parallel Panel Test: Tests were conducted with two vertically mounted 6 in. by 18 in. (152 x 457 mm) panels of each material, spaced 1 ⁄ 2 in. (13 mm) apart. Both conveyor belts were exposed by a Bunsen Burner flame between the panels at the bottom. •

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Standard belt: Ignition occurred in 5 s with flames reaching the tops of the panels in 55 seconds. After about 65 seconds, the sample was noted to begin melting and dripping. The burner flame was removed after 2 minutes. Flame continued to propagate. The sample melted and dripped into a large liquid pool fire. Flame retardant belt: Ignition occurred in 5 seconds with flames reaching the tops of the panels in 75 seconds. The burner flame was removed after about 2 minutes and flaming extinguished with no melting or dripping of the material noted. A propane torch was then applied to the belt for periods of 33 and 30 seconds. Melting, dripping, and deformation did occur, especially during the second attempt, but after removal of the torch after each attempt, the flaming extinguished. After the third application of the torch for 20 seconds, the flaming continued, slowly propagating up the sample. The sample melted and dripped into a liquid pool as observed with the “standard” conveyor belt.

Fire Propagation Index (FPI) Test: A test of a non-fire-retardant belt resulted in an FPI of 14.9. The test for the flame retardant belt resulted in an FPI of 11.4. The fire propagation index (FPI) used to classify electric cables has also been successfully used to classify conveyor belting. During conveyor belt tests using the FM Approvals 500 kW small-scale flammability apparatus, excellent agreement was found between the small-scale FM Approvals’ tests and tests conducted by the US Bureau of Mines (USBM) large-scale fire gallery in the 1980s. Based on the results of this study, conveyor belt samples were able to be classified as propagating or non-propagating. The propagating conveyor belts have been classified as those that develop an FPI higher than 7 on the flammability apparatus and for which flame propagates rapidly followed by entire sample destruction in MSHA large-scale fire gallery tests. The non-propagating types are those for which the FPI is 7 or less, and for which flame did not propagate beyond the ignition region in MSHA large-scale fire gallery tests. 3.2 Major Factors Affecting the Need for Fire Protection Major factors influencing the need for special fire protection for conveyors are as follows:


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The belt itself provides sufficient combustible loading to spread a fire. Major fires have spread on belts as narrow as 2 ft (0.6 m) wide and on systems carrying noncombustible materials such as limestone, iron ore, and metal cans. While not as common as single-tier systems, multiple-tier arrangements represent greater vertical combustible loading as well as a more favorable burning configuration than single-tier systems. A tier is defined as the feed and return layers of the belt. A single-tier system has two horizontal layers of belting stacked vertically; a two-tier system has four horizontal layers of belting stacked vertically. Conveyor belts emit dense, black, toxic smoke when ignited. This feature can severely hamper manual firefighting in underground or totally enclosed systems where entry and means of heat venting are limited. Ventilation (air flow) within a sprinklered tunnel or gallery does not appear to influence fire spread to a great degree. FM Global conducted air-flow studies over conveyors in coal mines to test detector sensitivity. These tests were correlated to sprinkler operation after detection by computer simulation. Fire Service response may be delayed, as many conveyors are in unoccupied areas. Fires occurring without automatic fire protection can be expected to be well developed before they are detected and the fire service responds. Accessibility and openness of the system directly influence fire spread, severity, ease of manual response, and damage. A fully enclosed system will not allow heat to be released or hose streams to be introduced from outside the conveyor system. Firefighters cannot physically fight the fire except from the ends of the conveyor, and often, dense smoke prevents effective response. A firefighting team will rarely enter an enclosed conveyor system. All of these factors combine to permit a free-burn fire that will spread rapidly with very high heat release and expose the steel structure. If this occurs, the entire structure can sag, cantilever, or collapse. Alternatively, an open or partially open system will allow heat to escape and hose streams to penetrate the fire plume. Damage can be significantly less, with structural collapse much less likely. Height of the conveyor above grade influences accessibility; incline influences the rate of fire spread. Generally, galleries or towers greater than 40 ft (12.2 m) above grade should be considered inaccessible for manual firefighting, even with substantial openings for hose stream penetration. Inclines of more than 10% allow for a faster spreading flame front. Unprotected interior exposed steel or combustible support framing on an elevated, totally enclosed structure can lead to collapse of the entire elevated portion during a fire. Intermediate buildings, such as transfer, splice, and tensioner houses, assume the same hazard as tunnels or elevated galleries of similar construction and accessibility. The presence of motorized drive equipment and more frequent personnel activities in these buildings creates more frequent ignition sources.

An explosion hazard may also exist in a conveyor system used to handle materials that can generate combustible dusts (e.g., sulfur, coal, various grains). A small initial dust explosion can initiate secondary dust explosions that can propagate the entire length of tunnels or galleries. Fires originating at conveyor belts have been the ignition source for dust explosions in the grain industry and coal mining facilities. Other exposures to conveyors include impact damage from mobile equipment, collapse, and longitudinal ripping from sharp objects. Belts that have become separated have been known to slide down elevated galleries or tunnels, causing impact damage and presenting a challenge to cleanup operations. 4.0 REFERENCES 4.1 FM Global Data Sheet 1-23, Protection of Openings in Fire Subdivisions Data Sheet 1-44, Damage-Limiting Construction Data Sheet 1-54, Roof Loads for New Construction Data Sheet 1-57, Plastics in Construction Data Sheet 4-1N, Fixed Water Spray Systems for Fire Protection Data Sheet 4-5, Portable Extinguishers Data Sheet 5-1, Electrical Equipment in Hazardous Locations Data Sheet 5-31, Cables and Bus Bars Data Sheet 6-20, Space Heaters


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Data Data Data Data Data

Sheet Sheet Sheet Sheet Sheet


7-12, Mining and Ore Processing 7-75, Grain Storage and Milling 10-3, Hot Work Management 7-75, Grain Storage and Milling 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fires

4.2 Other ASTM International. Standard Test Methods for Measurements of Synthetic Polymer Material Flammability Using a Fire Propagation Apparatus (FPA). ASTM E2058. APPENDIX A GLOSSARY OF TERMS FM Approved: References to ‘‘FM Approved’’ in this data sheet mean the product or service has satisfied the criteria for FM Approval. Refer to the Approval Guide for a complete listing of products and services that are FM Approved. Ignitable Liquid: Any liquid or liquid mixture that is capable of fueling a fire, including flammable liquids, combustible liquids, inflammable liquids, or any other reference to a liquid that will burn. An ignitable liquid must have a fire point. APPENDIX B DOCUMENT REVISION HISTORY January 2012. Terminology related to ignitable liquids has been revised to provide increased clarity and consistency with regard to FM Global’s loss prevention recommendations for ignitable liquid hazards. October 2009. The following changes were made: 1. Added protection recommendations for indoor conveyor belts in manufacturing and warehouse settings. 2. Added protection requirements for serpentine (also called pipe) conveyors and air-supported conveyors. 3. Removed requirements for underground mines; these are covered in Data Sheet 7-12, Mining and Ore Processing . 4. Added protection recommendations for vertical bucket elevators. January 2005. Clarification of protection needed for single conveyor systems, where barriers are located between supply and return belts, was made (section 2.3.1.1). September 2004. Minor editorial changes were done for this version. Clarification was made in section 3.2, Conveyor Belt Flammability. January 2003. Minor editorial changes were done for this version. January 2000. This revision of the document was reorganized to provide a consistent format.


FMDS0711 BELT CONVEYORS.pdf

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