SGM-SF_2017with 12/20 Revisions

15 SGM-SF 13.4.3 Pipe material 13.4.4 Exhaust Greater care is needed to help prevent water from escaping the piping. With potent concentrations, it is sometimes prudent that exhaust locations be further away from ventilation openings and people than minimally required in SGM-SF. Filtration of exhaust can even be needed. 13.4.5 Additional ASD fan requirements Advisory— Fan choices and spark resistance features must comply with the National Electric Code (NEC) for hazardous locations such as where flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. Health Advisory— It is extremely important to limit the concentration of chemicals in the airstream of an Active Soil Depressurization to well below the Lower Explosion Limit (LEL) for that gas. Failure to maintain gas concentrations below 10%of LEL could result in a fire, explosion and serious injury. Tables 13.4.5 Examples of Explosion Proof Fan Classifications Class Definitions Class I Locations: Are those in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. Class II Locations: Are those which are hazardous due to the presence of combustible dust. Class III Locations: Are those which are hazardous due to the presence of easily ignitable fibers or flyings, but in which such fibers or flyings are not likely to be in suspension in the air in quantities to produce ignitable mixtures. Division Division I Locations in which hazardous concentrations in the air exist continuously, intermittently, or periodically under normal operating conditions. Division II Locations in which hazardous concentrations are handled, processed, or used but are normally within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown. Group (Class I) Group A Atmospheres containing acetylene. Group B Atmospheres containing hydrogen, or gases (or vapors) of equivalent hazard, such as manufactured gas. Group C Atmospheres containing ethyl-ether vapors, ethylene or cyclo propane. Group D Atmospheres containing gasoline, hexane, naptha, benzine, butane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas. Group (Class II) Group E Atmospheres containing metal dust, including aluminum, magnesium and their commercial alloys and other metals of similarly hazardous characteristics. Group F Atmospheres containing carbon black, coal, or coke dust. Group G Atmospheres containing flour, starch, or grain dust. The next pages provide Lower Explosion Limits (LEL) for certain common chemicals