Liquefied flammable gases

When reading an accident report, look for the things that are not said. For example, a gland leak on a liquefied flammable gas pump caught fire and caused considerable damage. The report drew atten-... 

Gases Flammable gases are usually very easily ignited if mixed with air. Flammable gases are often stored under pressure, in some cases as a hquid. Even small leaks of a liquefied flammable gas can form relatively large quantities of gas, which is ready for combustion. 

Many leaks have been discussed under other headings, including leaks that occurred during maintenance (Chapter 1), as the result of human error (Chapter 3), or as the result of overfilling storage tanks (Section 5.1). Other leaks have occurred as the result of pipe or vessel failures (Chapter 9), while leaks of liquefied flammable gas are discussed in Chapter 8 and leaks from pumps and relief valves in Chapter 10. 

The release of a flammable gas or the vaporization of a liquefied flammable gas can lead to different types of fire scenarios dependent on the release mechanism and the point of ignition. Figure 5-2 on page 53 illustrates the different outcomes expected from a gas release. If ignition of a gas release does not occur immediately at the origin of the release, then a gas cloud can develop (the same situation can also occur above flammable liquid spills). A delayed ignition of the gas cloud can result in a flash fire in which the premixed (fuel and air) gas cloud burns rapidly, typically in a matter of seconds. 

NFPA 45, 2.2.1.5 4.3.2.1 For the purposes of determining laboratory fire hazard classification and the use of tables 2.2.1(a) and (b) quantities of liquefied flammable gases shall be treated as if they were Class I flammable liquids (see definition) that is, 4L (l.lgal) of liquefied flammable gas is to be considered equivalent to 4L (1.1 gal) of Class I flammable liquid. 

Instantaneous release of a pressure liquefied flammable gas (BLEVE) ho a ... 

A flammable liquid is one that at atmospheric pressure gives off a flammable vapour at a temperature of 32 C and a liquefied flammable gas is one which,... 

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