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Overpressure of an Explosion-Proof Enclosure

Country: ---

Location: ---

Incident Date: 15 May 2017   Time: ---

Type of Activity: ---

Cause: Pressure release

Function: ---

What happened?:

An analyzer engineer was fatality injured when the engineer removed the cover on an explosion-proof enclosure as part of a routine task. The threaded cover, weighing ~12 lbs. and measuring 14 inches in diameter, was forcefully propelled from the enclosure as the engineer unscrewed it, inflicting a fatal head injury. The force was caused by pressure inside the enclosure from leaking sample gas or instrument air components. The enclosure was not equipped with an external indicator to determine the pressure inside the enclosure and had no means to relieve internal pressure.

Corrective Actions and Recommendations:

  • Recognize the potential hazard of trapped pressure in explosion-proof electrical enclosures from all sources of energy entering the enclosure
  • Identify explosion proof enclosures which are susceptible to trapped pressure scenarios and do not have pressure indication or pressure relief protection
  • Work with equipment manufacturers to develop a mitigation plan that addresses the trapped pressure situation while still maintaining the electrical certification of the identified enclosures


Figure 1: Re-enactment of cover removal

Figure 2: Example of Explosion-Proof Enclosure

Safety Alert number: 288
IOGP Safety Alerts


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