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NFPA 655: Standard for Prevention of Sulfur Fires and Explosions
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What is NFPA 655?
NFPA 655: Document Scope

1.1 Scope. 1.1.1* This standard shall apply to the size reduction of sulfur and to the handling of sulfur in any form. A.1.1.1 Sulfur differs from most other combustible dusts found in industry in that it has relatively low melting and ignition points. Depending on purity, sulfur melts at or slightly below 246°F (119°C). The ignition temperature of a dust cloud is 374°F (190°C); the ignition temperature of a dust layer is 428°F (220°C). Dilution of sulfur with inert solids is not effective in raising the ignition temperature. Sulfur is handled and processed in the liquid and vapor states in some cases. The liquid is highly combustible, and the vapor is explosive when mixed with air in the proper proportions. The finely divided sulfur produced during size reduction and size reduction is the most hazardous from an explosion standpoint. Also, mixtures containing finely divided elemental sulfur can be just as hazardous if the sulfur is present in sufficient quantity. Some explosion and fire hazards also accompany the handling and processing of sulfur in bulk in coarse sizes due to the fine dust present. 1.1.2 This standard shall not apply to the mining of sulfur, recovery of sulfur from process streams, or transportation of sulfur. 1.1.3 The owner/operator shall be responsible for implementing the requirements in this standard. 1.1.4 This standard shall be used in conjunction with the requirements of NFPA654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. Where conflicts exist, the requirements of NFPA 655, Standard for Prevention of Sulfur Fires and Explosions, shall apply.

This standard establishes requirements to eliminate or reduce explosion and fire hazards encountered in the crushing, grinding, and pulverizing of bulk and liquid sulfur, and to the safe handling of sulfur in any form. Official document scope
What does NFPA 655 address?
Criteria provide safety guidance on handling sulfur in bulk, handling liquid sulfur at normal handling temperatures, handling liquid sulfur and sulfur vapor at temperatures above 309 F (154 C), fugitive dust control and housekeeping, training and procedures, and inspection and maintenance. NFPA 655 is to be used in conjunction with NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and handling of Combustible Particulate Solids.
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