Compressed gases liquefied

When pressure relief devices are intended primarily for protection against overpressure due to external fire or heat, have no permanent supply connection, and are used for storage at ambient temperature of non-refrigerated liquefied compressed gases, they are excluded from requirements of Par. UG-125c (1) and C (2), with specific provisions. See ASME code [1] for detailed references and conditions. 

Flaring A process that is used with high vapor pressure liquids or liquefied compressed gases for the safe disposal of the product. Flaring is the controlled burning of material in order to reduce or control pressure and/or to dispose of a product. 

Venting Venting is the process that is used to deal with liquids or liquefied compressed gases where a danger, such as an explosion or mechanical rupture of the container or vessel, is considered likely. The method of venting will depend on the nature of the hazardous material. In general, it involves the controlled release of material to reduce and contain the pressure and diminish the probability of an explosion. 

However, unlike non-liquefied compressed gases, the vapor pressure of liquefied propellants decreases significantly with decreases in temperature, such that below a certain temperature, the flash evaporation process is sufficiently retarded to give poor aerosol formation. For the propellants commonly used in MDIs, unacceptable aerosol formation is likely to occur below 0°C. 

Propane and butane are two conunon flammable liquefied compressed gases. Propane has a flammable range of 2.4 to 9.5% in air, and butane 1.9 to 8.5% in air. Propane and butane have boiling points of 44°F and 31°F, respectively. Both materials are above their boiling points under ambient temperature conditions in many parts of the country year-round. This makes the materials highly dangerous when a leak or fire occurs, especially if there is a fire with flame impingement on the container. The vapor density of propane is 1.56, and butane is 2.07. Thus, both propane and butane vapors are heavier than air. 

To prevent frostbite or burns when handling cold substances (liquefied compressed gases or liquids with a boiling point below 20° C) or hot substances (e.g. molten sulfur). If the substance can penetrate or damage the skin, a glove material incorporating rubber or plastic must be found which is sufficiently resistant to the substance. 

At gas manufacturing facilities a checklist or operating procedures should be posted or available to guide those who fill containers. Procedures will vary depending on the type of cylinder and product (for example, high pressure compressed gas cylinders versus liquefied compressed gases). The checklist questions to answer should include ... 

Handling Bulk Shipments of Liquefied Compressed Gases... 

Factors contributing to the safe handling and unloading of liquefied compressed gases include ... 

In addition to single-unit railroad tank cars, a number of other vehicles are used to transport liquefied compressed gases. The following terms are commonly used when referring to such vehicles and may be encountered in regulations or other literature on this subject. 

Fig. 7-1. Tank cars for liquefied compressed gases have similar valve arrangements.

Liquefied compressed gases are usually transferred from single-unit tank cars by means of a liquid pump or pressure differential from a vapor compressor. All equipment must be designed for the particular gas being transferred. Methods for obtaining the pressure differential required and the gases to which the method may be applied are as follows ... 

Fluorocarbons listed in this handbook (except for tetrafluoromethane) are liquefied compressed gases and are stored and shipped under their own vapor pressures in cylinders, portable tanks, cargo tanks, multi-unit tank car tanks, and tank cars. 

The methylamines (monomethylamine, di-methylamine, and trimethylamine) are colorless, flammable and toxic gases at normal room temperatures and atmospheric pressure in their anhydrous form. They have a distinct and disagreeable fishy odor in concentrations up to 100 ppm. In higher concentrations they have an odor like ammonia, which they resemble and from which they are derived. They are easily liquefied and are shipped in their anhydrous form as liquefied compressed gases. They are highly soluble in water and in alcohol, ether, and various other organic solvents. 

The quality of the insulation depends among other factors significantly on the quality of the vacuum. Despite good insulation, stored liquefied compressed gases are subject to heat penetration which makes the cryogenic content evaporate slowly. The insulation quality and thus the thermal flow are described by the evaporation rate. It is indicated in percent per day, based on the maximal filling capacity of the vessel. 

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