This article discusses the use and possible misuse of Maximum Experimental Safe Gap (MESG) in selecting deflagration and detonation flame arresters (DDAs). Gas mixtures having low autoignition temperatures or unusually wide flammable ranges might not behave as predicted on the basis of MESG, especially under restricted-end deflagration conditions. When applied to DDA selection the Westerberg apparatus might prove to give a more reliable ranking of gas sensitivity than the IEC apparatus. If credit is taken for inert gases using the new MESG combination formula in NFPA 497 an incorrect DDA could be selected. An outline is given for a possible test program to elucidate the effect of gas mixture MESG on DDA performance.

Using maximum experimental safe gap to select flame arresters

The explosion-suppression performance of mesh aluminum alloys and spherical nonmetallic materials on hydrogen-air mixtures

Additive influence on maximum experimental safe gap of ethylene-air mixtures

Britton discovered that with increased “net heat of oxidation” (ΔHox), the maximum flame temperatures of CH and CHO fuels in air increase linearly while flame temperatures at the lower flammable limit (LFL) decrease linearly. Maximum flame temperature is a major factor determining the combustion rate of optimum fuel-air mixtures and relationships were found between ΔHox and “optimized” flammability parameters such as minimum ignition energy. The LFL is the fuel concentration needed to attain the lower limit flame temperature; since less fuel is needed to attain a smaller flame temperature, the LFL varies inversely with ΔHox. Simple expressions derived between ΔHox and parameters commonly used in process safety were previously published in this journal. The commercially available computer program “CHETAH™” now solves these expressions and outputs the flammability parameters plus the internally generated thermodynamic data used in the solutions. This article updates the original expressions together with new findings and explanatory material. © 2014 American Institute of Chemical Engineers Process Saf Prog 33: 314–328, 2014

Using CHETAH to estimate lower flammable limit, minimum ignition energy, and other flammability parameters

Effects of mesh aluminium alloys and propane addition on the explosion-suppression characteristics of hydrogen-air mixture

An apparatus for the measurement of maximum experimental safe gaps at standard and elevated temperatures

The maximum experimental safe gap: The effects of oxygen enrichment and the influence of reaction kinetics

The influence of chemical structure and combustion reactions on the maximum experimental safe gap of industrial gases and liquids

The maximum experimental safe gap: Comparison of results from 8-litre and 20-cm3 explosion vessels

A note on the lower explosibility limit of organic dusts

G.A. Lunn

Papers

An apparatus for the measurement of maximum experimental safe gaps at standard and elevated temperatures

The maximum experimental safe gap: The effects of oxygen enrichment and the influence of reaction kinetics

The influence of chemical structure and combustion reactions on the maximum experimental safe gap of industrial gases and liquids

The maximum experimental safe gap: Comparison of results from 8-litre and 20-cm3 explosion vessels

A note on the lower explosibility limit of organic dusts