Maximum experimental safe gap

There is a maximum safe gap measured experimentally which will prevent the transmission of an explosion occurring within a container to a flammable mixture outside the container. Critical and maximum experimental safe gaps for a number of materials in air are listed in Lees (1980, pp. 491-492). These quenching effects are important in the design of flame arresters and flameproof equipment. 

Britton, L. G. 2000a. Using Maximum Experimental Safe Gap to Select Flame Arresters. Process Safety Progress, 19(3), 140-145. 

Lunn, G. A. 1982a. An Apparatus for the Measurement of Maximum Experimental Safe Gaps at Standard and Elevated Temperatures./. Hazardous Materials, 6, 329-340 (1982). 

Phillips, H. 1981. The Differences between Determinations of Maximum Experimental Safe Gap.y. Hazardous Materials, 4(3), 245-256. 

Phillips, H. 1987. A Comparison of Standard Methods for the Determination of Maximum Experimental Safe Gap (MESG). Proc. International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, pp. 83-108. Publication NMAB-447. National Materials Advisory Board, Washington, DC. 

FPN No. 2) The gas subdivision in (a), (b), and (c) above is based on the maximum experimental safe gap, minimum igniting current, or both. The test apparatus for determining the maximum experimental safe gap is described in lEC Publication 79-lA (1975) and UL Technical Report No. 58 (1993). 

FPN No. 3) The classification of mixtures of gases or vapors according to their maximum experimental safe gaps and minimum igniting currents is described in lEC publication 79-12 (1978). 

The upper hemisphere can be adjusted by a fine-pitch thread to defined values w for the gap. The exterior volume V equals nearly 2.5 litres. In both volumes, a and V, the same gas-air mixture normally with T = +20°C and a total pressure of 1.0 105Pa is present. After ignition in a, an MESG value (maximum experimental safe gap) can be found by varying w, so that the flame cannot pass from a to V. These MESG values (ensuring the nontransmission of the flame) show a parabolic function versus the gas concentration c (Fig. 1.3). 

Figure 1.2 Test apparatus for ascertainment of maximum experimental safe gap according to IEC Standard 60079-1 A. a = interior sphere with a volume of 20 cm3...

Figure 1.3 Dependence of the maximum experimental safe gap (MESG) on the gas concentration c in air.

A) 1975-01 Part 1 Construction and verification test of flameproof enclosures of electrical apparatus First supplement Appendix D Method of test for ascertainment of maximum experimental safe gap... 

Figure 6.77 MESG (maximum experimental safe gap) values of gas-air mixtures versus power density cr (according to Table 6.26).

Sintered metals show a strong correlation between open porosity and effective gap. (The effective gap weS of a flameproof component is the highest MESG (Maximum Experimental Safe Gap) value of combustible gas mixtures (see Section 1.2.2), for which that component ensures flameproofness. For gas mixtures with MESG < wen, flame transmission occurs.) (see [19]). 

The maximum experimental safe gaps of precompressed hydrogen-air mixtures... 

Lunn, G. A. An apparatus for the measurement of maximum experimental safe gaps at standard and elevated temperatures, Journal of Hazardous Materials 6,1982,329-340... 

Lunn, G. A. The maximum experimental safe gap the effects of oxygen enrichment and the influence of reaction kinetics, Journal of Hazardous Materials 8,1984,261-270... 

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