Hazards of Vacuum

Stanley M. Englund/ M S / Ch E / Fellow American Institute of Chemical Engineers Process Consultant, The Dow Chemical Company (retired). (Section Editor, Section 16 Introduction Hazard Analysis Storage and Handling of Hazardous Materials Reactive Chemicals Combustion and Flammability Hazards Hazards of Vacuum Hazards oflnei t Gases)... 

Dust Explosions Static Electricity Hazards of Vacuum Hazards of Inert Gases Gas Dispersion... 

Walter L. Frank, P.E., B.S.Ch.E. Senior Consultant, ABS Consulting Fellow, American Institute of Chemical Engineers (Hazards of Vacuum, Hazards of Inerts)... 

Causes of Vacuum Hazards The design for the internal pressure condition of vessels is usually straightforward and well understood. The design for external pressures is more difficult. The devious ways in which external pressure can be applied can often be overlooked. 

Generally a safe equipment. But in the event of vacuum leakage which, although remote, may cause a fire hazard and X-rays. X-ray warning and proper shielding may be essential... 

Because these machines require internal lubrication of the sliding-vane surface, no extreme effort is made to arrange special bearing and shaft seals, except that a gas seal of the conventional mechanical design is usually used to prevent gas from escaping to the outside or to prevent air inleakage in the case of vacuum service. For hazardous or... 

Sodium Tetraperoxo-Moiybdate (2 ), MoNa2Og Explosive decompn under vacuum H.M. Castrantes et al, "Fire and Explosion Hazards of Peroxy Compounds , ASTM... 

A small amount of hydrazine hydrate was present in the reaction mixture at this point, but a safety evaluation indicated the final reaction mixture had a very low thermal potential (AH = 15.3 J/g). This poses a minimum thermal hazard for vacuum distillation. 

Maintenance errors. One common error is the failure to remove an isolation blind in a vent line when returning a vessel to service. Even a thin sheet of plastic placed over an open nozzle may be sufficient to allow a vessel-damaging vacuum to De produced (BP, Hazards of Trapped Pressure and Vacuum, 2003). 

Lees (Loss Prevention in the Process Industries, 2d ed., Butter-worths, London, 1996), BP (Hazards of Trapped Pressure and Vacuum, 2003), and Kletz (What Went Wrong —Case Histories of Process Plant Disaster, Gulf Publishing Company, 1989) include additional case histories providing valuable lessons about how equipment failures and human errors can combine to inflict vacuum damage. 

Potential hazards associated with electron beam vacuum melting of metals include the possibility of ignition of metal aerosols or condensate films in the event of sudden loss of vacuum at elevated temperatures. 

EngrgProgr 43,667-90(L947)(Continuous vacuum crystallization of AN) 86)C.Field, ChemEngrg 54,146-7(1947)(The product that could not explode) 86a) J. Whet stone A.W. Holmes, IndChem 23,717-23( 1947)(Explosion and fire hazards of AN) 87)J.C.Holtz ... 

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