Maximum experimental safe gap

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Maximum experimental safe gap (MESG) is a standardized measurement of how easily a gas flame will pass through a narrow gap bordered by heat-absorbing metal. MESG is used to classify flammable gases for the design and/or selection of electrical equipment in hazardous areas, and flame arrestor devices. [1] The National Electrical Code classifies Class I hazardous locations into different groups depending on the respective MESG's of gases in the area. [2]

Examples

NEC Class I Group and Gas MESG [2]
NEC Class I GroupGas MESGExample Gas
Group A0.25 mm Acetylene
Group B≤0.45 mm (Except acetylene) Hydrogen
Group C0.45 mm < x ≤ 0.75 mm Ethylene
Group D> 0.75 mm Propane

References

  1. ↑ Enardo Flame Arrestor Technology. "Flame Arrestor Technology" (PDF).
  2. 1 2 [ dead link ] Class I: Flammable gases, vapors or liquids

http://site.ul.com/global/documents/offerings/services/hazardouslocations/CI_groups.pdf%5B‍%5D

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