An investigation of the maximum experimental safe gap anomaly

Abstract

summaryThe "safe gap'! is defined as the maximum gap between two close-fitting, flat, machined metal surfaces that will just prevent an explosion within a vessel from producing a propagating combustion wave in the gases that surround the vessel. At present three distinctly different apparatuses are used throughout the world to determine experimentally the maximum safe gap for different combustible gases and vapors. Unfortunately, the maximum safe gap thus determined sometimes differs widely from vessel to vessel. This report investigates the nature of the processes by which the explosion is transmitted to the surrounding media, paying particular attention to the differences from apparatus to apparatus. It is found that the time constants associated with the combustion process and with vessel exhausting are markedly different for the different vessels and that the pressure levels developed inside a vessel during the test also vary markedly from vessel to vessel. Rased on these observations, it is recommended that a more thorough theoretical and experimental investigation of the safe gap testing procedures and vessel design be made as the basis for a proper design for adequate safe gap testing of all combustible vapors and gases.

An investigation of maximum experimental safety gap of CH4H2 blended fuel at different initial pressures

“…To solve the problem in actual production, many researchers have explored the process of igniting the external combustible gases with inert hot gases. [3][4][5][6][7][8][9][10] Meanwhile, a series of standards was established to regulate the appliance of electrical equipment in factories. [11][12][13] In the earlier studies, many experiments were conducted on different devices to investigate the effect of container size and some conclusions were drawn.…”

“…To solve the problem in actual production, many researchers have explored the process of igniting the external combustible gases with inert hot gases 3–10 . Meanwhile, a series of standards was established to regulate the appliance of electrical equipment in factories 11–13 .…”

Critical slot size for deflagration initiation by hot products discharge into hydrogen–air atmospheres

“…For example, in the design of f ameproof enclosures for electrical equipment [12] the permissible gaps must be sufficiently small to ensure that, if a reactive mixture enters the enclosure and becomes accidentally ignited by an electric spark or other ignition source, the resulting jet of escaping combustion products would not initiate a def agration in the surrounding combustible atmosphere. This has led to the classif cation of f ammable gases and vapors into different groups based on the so-called maximum experimental safe gap [13,14,15].…”