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A Comparison of 'Standard' Methods for the Determination of Maximum Experimental Safe Gap (MESG).
Proceedings of the International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, National Materials Advisory Board, Publication NMAB-447 1987:83-108
Methods for determining the maximum experimental safe gap (MESG) for inflammable gases and vapors were discussed. Definitions used in determining MESGs were reviewed. The MESG has been defined as the minimum value of the safe gap when a combustible mixture is tested in a standard apparatus with a varying internal ignition position. The major types of apparatus used in determining MESGs were 8 liter (l) and 20 milliliter (ml) spherical vessels in the United Kingdom and Germany, and the Westerberg apparatus used by Underwriters' Laboratories in the United States. MESGs obtained for 124 compounds utilizing 8l or 20ml spherical vessels were tabulated. The smaller a MESG value the greater the burning velocity. MESGs obtained with the Westerberg apparatus frequently differ from those obtained with spherical vessels. The differences are attributed to the small receptor vessel of the Westerberg apparatus which results in the external atmosphere being confined into a volume smaller than the primary explosion vessel. The effect of variables such as primary ignition, initial stages in ignition, and fluid flow on results obtained with the Westerberg apparatus were discussed.
Combustible-gases; Explosive-atmospheres; Risk-analysis; Industrial-safety; Explosion-prevention; Laboratory-testing; Laboratory-techniques; Equipment-design;
Proceedings of the International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, National Materials Advisory Board, Publication NMAB-447
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division