Dusts, hazard class

The dust hazard class, Rst, vessel volume and strength, and the relieving pressure of the vent closure are the key components of the relief determination using the nomographs [27]. Although stated by Ref. [27] to be non-exact... 

The dust hazard classes for deflagrations are given in Table 7-28, with data in Tables 7-28 and 7-30A, B, C, D, and E. 

From Table 7-30C, lignite is dust hazard class 1, with = 151 bar-m/sec. 

Material Median particle size, pm Minimum explosive concentration g/m= p max bar ga (dp/dt)max> ba r/sec Ksi bar-m sec Dust Hazard Class... 

SpGr = specific gravity of fluid, relative to water =1.0 St = dust hazard class St St = stainless steel SSU = viscosity Saybolt universal seconds °S = degrees of superheat, °F T = absolute inlet or gas temperature, degrees... 

Dusts, particle sizes, 225 Dusts, hazard class, 521-523 Explosion characteristics, 524 Efficiency, centrifugal pumps, 200 Ejector control, 380 Ejector systems, 343, 344, 351 Air inleakage, table, 366, 367 Applications, 345 Calculations, 359-366 Chilled water refrigeration, 350 Comparison guide, 357, 375 Evacuation lime, 380, 381 Charts, 382 Example, 381 Features, 345... 

ElecU ical Equipment in Hazardous (Class.) Locations, Gases, Vapors, Dusts 49VM... 

Hazard Classes and Ks( Values for Selected Types of Dusts... 

Do NOT wash away into sewer. Sweep spilled substance into containers if appropriate, moisten first to prevent dusting. Carefully collect remainder, then remove to safe place. Personal protection P3 filter respirator for toxic particles. Unbreakable packaging put breakable packaging into closed unbreakable container. Do not transport with food and feedstuffs. EU Classification Symbol T, N R 21-25-36/38-48/23/25-50/53 S 1/2-35-36/37/39-45-60-61 Note A, 1 UN Classification UN Hazard Class 6.1 ... 

Collect leaking liquid In sealable containers. Sweep spilled substance into containers if appropriate, moisten first to prevent dusting. Carefully collect remainder, then remove to safe place (extra personal protection self-contained breathing apparatus). UN Classification UN Hazard Class 6.1 ... 

The second option permits selection of approved equipment. However, not only must it be approved for the hazardous class, but, also, for the specific type of vapor, dust, or fiber involved. 

Before being milled on an industrial scale, each pigment has to pass a test concerning its sensitivity to dust explosion. There are standardized milling regulations for each hazardous class. 

In its NEP, OSHA points out that for workplaces not covered by 1910.272, but where combustible dust hazards exist within dust control systems or other containers, citations under section 5(a)(1) of the OSH Act (the General Duty Clause) may generally be issued for deflagration (fire) or explosion hazards. National Fire Protection Association (NFPA) standards should be consulted to obtain evidence of hazard recognition and feasible abatement methods. Other standards are applicable to the combustible dust hazard. For example, if the workplace has a Class II location, then citations under 29 CFR 1910.307 may be issued to those employers having electrical equipment not meeting the standard s requirements. 

Each plant or laboratory should adopt definite rules and procedures for electrical installations and work. All installations should be in accordance with the National Electrical Code (NEC) for the type of hazard, eg, Class I flammable gas or vapor Class II organic, metallic, or conductive dusts and Class III combustible fibers and the degree of process containment, eg, Division 1 open and Division 2 closed (67). Regardless of the flammability of the materials in the installed operations, changes in procedure involving use of such materials often occur, sometimes without concurrent alteration of the electrical installation. 

A recent U. S. Bureau of Mines report also rates the metal powders, with the rather surprising result that aluminum dust is classed with seemingly more hazardous metal powders such as magnesium and thorium in the most susceptible group.Another report discusses the prevention of such ignition by the use of powdered additives with inerting properties. 

Experimental data on dust explosibility enable the classification of dust into dust explosion hazard classes. Such a classification applied in different countries is presented in Table 56.2. The determination of the dust explosion hazard... 

Are flammable gases, vapours, liquids or solids (dust) present To which ignition group and hazard class do they have to be assigned ... 

Experimental data on dust explosibility enable the classification of dust into dust explosion hazard classes. Such a classification applied in different countries is presented in Table 48.3. The determination of the dust explosion hazard class is required not only to assess dust explosion risk, but also to define statutory requirements as well as to assist in the identification of protective measures for different hazard classes. (Table 48.4), presents a selected data for dust explosivity [16-21]. 

In addition, there is a non-IDLH class based on oxygen level between 19.5 and 21 percent, but classified as hazardous due to the presence of nuisance dusts or vapors below the IDLH level, but not greater than the protection factor of air-purifying respirators or low concentration of toxic or flammable substances. 

FPN No. 1) For additional information on the properties and group classification of Class I materials, see Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations, NFPA 497M-1991, and Guide to Eire Hazard Properties ofElammable Liquids, Gases, and Volatile Solids, NFPA 325—1994. 

Class II Locations. Class If locations are those that are hazardous because of presence of combustible dust. Class If locations shall include those specified in (a) and (b) below. 

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