Liquid to gas, expansion

The growing technology provided experience in coping with the more conventional cryogenic hazards associated with material s brittleness, with cold flesh "burns," and with liquid to gas expansion in confined spaces. 

Gases may also be liquefied. Liquefaction takes advantage of a gas s abihty to be liquefied by pressure or cooling, or a combination of both. Liquefied gases have a large liquid-to-gas expansion ratio. This allows a larger quantity of gas to be shipped as a liquid compared to a gas. It is much more economical to ship a compressed gas as a liquid. 

Passage of thionyl chloride through a flexible metal transfer hose which was contaminated with water or sodium hydroxide solution caused the hose to burst. Interaction with water violently decomposes the chloride to hydrogen chloride (2 mol) and sulfur dioxide (1 mol), the total expansion ratio from liquid to gas being 993 1 at 20° C, so very high pressures may be generated. 

The potential hazard associated with expansion of liquid to gas is substantial for hydrogen, as it is for other cryogenic fluids. Careful attention must be given to the location of relief devices in liquid hydrogen handling systems. 

Knowledge of the Hazards. Adequate knowledge of each of the hazards associated with handling hydrogen in any form allows all needed safety practices to be fully implemented. These hazards have been identified as related to flammability, expansion from liquid to gas in confined spaces, improper materials of construction, cold "burns," and breathing atmospheres con-... 

The foam expansion ratio or its reciprocal value the foam liquid volume fraction, called also relative or volume density of a foam, is used as a basic parameter characterizing the liquid to gas ratio in the foam. 

Cryogenic fluids (hquified gases) are characterized by extreme low temperatures, ranging from a boiUng point of -78.5 C (-109 F) for carbon dioxide to -269.9 C (-453.8 F) for an isotope of hehum, e. Another common property is the large ratio of expansion in volume from liquid to gas, fixrm approximately 553 to 1 for carbon dioxide to 1438 to 1 for neon. Table 4.13 contains a more complete summary of the properties of cryogenic fluids. 

There are two general methods available for producing the cellular core of SF mouldings (see PST 2). One method relies on the chemical decomposition of a blowing agent at elevated temperatures - the chemical blow method. The other method involves the formation of gas cells due to a physical change such as from liquid to gas to the expansion of a compressed gas - the physical blow method . 

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