Cryogenic service

W. Broadway, "A Pressure Sensitivity and Temperature Response Butterfly Valve for Cryogenic Service," paper presented at Energy Technology Conference and Exhibition, Houston, Nov. 5—9,1978. 

There are many design features and styles of safety relief valves, such as flanged ends, screwed ends, valves fitted internally for corrosive service, high temperature service, cryogenic service/low temperatures, with bonnet or without, nozzle entrance or orifice entrance, and resistance to discharge piping strains on body. Yet most of these variations have little, if anything to do with the actual performance to relieve overpressure in a system/vessel. 

Lowe, R. E. (1987) Chem. Eng., NY 94 (Aug. 17th) 131. Plate-and-fin heat exchangers for cryogenic service. 

Carbon steels Acceptable Not acceptable Too brittle for cryogenic service... 

NOTE This resuits in a higher joint integrity and shouid be considered for critical and cryogenic services. 

Caution. Only stainless steel (i.e., 316 SS) or aluminum pressure vessels approved for cryogenic service should be used. The use of lecture bottles of mild steel must be avoided, since such lecture bottles lose their strength at cryogenic temperatures. 

Gaskets for flanged connections in cryogenic service are readily available and compatibility with LNG is not a problem. 

Because of the uncertain reliability of balanced bellows spring valves on cold and cryogenic services, POSRVs have offered a good alternative for these applications for more than 35 years now. 

The mistake which is made here, because of lack of specific SRV test specifications for cryogenic service, is that test specifications from line valves are simply transposed or used on SRVs. 

However, the European normalization committee is in the process of looking at the issue and is working on the EN-13648-1 Cryogenic vessels -Safety devices for protection against excessive pressure - Part 1 Safety valves for cryogenic service. The tendency is to go to a much more reliable test as described hereafter which will simulate the real process conditions to a greater degree. 

This method of testing an SRV on cryogenic service has become more and more popular since the mid-1980s when it was first developed. 

While conventional spring-loaded SRVs can provide an acceptable level of reliability, particularly when fitted with a soft seat of proven design, the balanced bellows spring-loaded SRV can create a highly hazardous situation and should therefore be avoided on cold or cryogenic services. 

Cryogenic Service Valves designed to minimize heat absorption for throttling liquids and gases below 80 K are called cryogenic service... 

Adequate predictions of thermal conductivity for pure metals can be made by means of the Wiedemann-Franz law, which states that the ratio of the thermal conductivity to the product of the electrical conductivity and the absolute temperature is a constant. High-purity aluminum and copper exhibit peaks in thermal conductivity between 20 and 50 K, but these peaks are rapidly suppressed with increased impurity levels and cold work of the metal. The aluminum alloys Inconel, Monel, and stainless steel show a steady decrease in thermal conductivity with a decrease in temperature. This behavior makes these structural materials useful in any cryogenic service that requires low thermal conductivity over an extended temperature range. 

Cryogenic service is usually defined as temperatures below -100°C (-150°F). Properties of some cryogenic fluids are listed in Table 2.73. Valve materials for operation at temperatures down to -268°C (-450°F) include copper, brass, bronze, aluminum, 300-series stainless steel alloys, nickel, Monel, Durimet, and Hastelloy. The limitation on the various steels falls between 0° and -150°F (-17 and -101°C), with cast carbon steel representing 0°F (-17°C) and 3.5% nickel steel being applicable to -150°F (-101°C). Iron should not be used below 0°F (-17°C). 

Instruction manual for PLC-180A PLC-180LP, from Cryogenic Services Inc.,... 

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