NFPA 499 Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 499 化学工艺区易燃粉尘的分类及电气安装危险性分类推荐做法
1.1 Scope.
1.1.1 This recommended practice applies to those locations where combustible dusts are produced, processed, or handled, and where dust released into the atmosphere or accumulated on surfaces could be ignited by electrical systems or equipment.
1.1.2 This recommended practice provides information on specific combustible dusts whose relevant combustion properties have been sufficiently identified to allow their classification into the groups established by NFPA 70, National Electrical Code (NEC), for proper selection of electrical equipment in hazardous (classified) locations. The tables of selected combustible materials contained in this document are not intended to be all-inclusive.
1.1.3 This recommended practice also applies to chemical process areas. As used in this document, a chemical process area could be a chemical process plant, or it could be a part of such a plant. A chemical process area could be a part of a manufacturing facility where combustible dusts are produced or used in chemical reactions, or are handled or used in operations such as mixing, coating, extrusion, conveying, drying, and/or grinding.
1.1.4 This recommended practice does not apply to agricultural grain-handling facilities except where powdered grain is used in a chemical reaction or mixture.
1.1.5 This recommended practice does not apply to situations that could involve catastrophic failure of, or catastrophic discharge from, silos, process vessels, pipelines, tanks, hoppers, or conveying or elevating systems.
1.1.6 This recommended practice does not address the unique hazards associated with explosives, pyrotechnics, blasting agents, pyrophoric materials, or oxygen-enriched atmospheres that might be p
resent.
Maximize safety in Class II hazardous (classified) locations by accurately determining combustibility hazards according to the latest criteria in the 2008 NFPA 499.
NFPA 499 Classification of Combustible Dusts and of Hazardous Locations for Electrical Installations in Chemical Process Areas contains detailed guidelines and diagrams that serve as useful tool for professionals who perform hazardous (classified) area classification as specified by NFPA 70® National Electrical Code® for the purpose of selecting and installing electrical equipment that will not be an ignition source in environments where combustible dusts are produced, processed, or handled. This Recommended Practice also provides extensive data on physical properties of selected materials, including specific Class II, Division dust group information.
Consistent with the 2008 NEC®, the 2008 NFPA 499 includes the following updates to help reduce hazards
· Changes were made to the scope to specify that explosives, pyrotechnics, and blasting agents have unique hazards that are not addressed by the recommendations of the document.
· Revisions to Table 4.5.2 on composition and ignition temperature of combustible materials covered in this table were made to correlate with information contained in other industry documents.
(Softbound, 23 pp., 2008)
