Cryogenic equipment

Structural Properties at Low Temperatures It is most convenient to classify metals by their lattice symmetiy for low temperature mechanical properties considerations. The face-centered-cubic (fee) metals and their alloys are most often used in the construc tion of cryogenic equipment. Al, Cu Ni, their alloys, and the austenitic stainless steels of the 18-8 type are fee and do not exhibit an impact duc tile-to-brittle transition at low temperatures. As a general nile, the mechanical properties of these metals with the exception of 2024-T4 aluminum, improve as the temperature is reduced. Since annealing of these metals and alloys can affect both the ultimate and yield strengths, care must be exercised under these conditions. 

Nickel Steel Low-carbon 9 percent nickel steel is a ferritic alloy developed for use in cryogenic equipment operating as low as —I95°C (—320°F). ASTM specifications A 300 and A 353 cover low-carbon 9 percent nickel steel (A 300 is the basic specification for low-temperature ferritic steels). Refinements in welding and (ASME code-approved) ehmination of postweld thermal treatments make 9 percent steel competitive with many low-cost materials used at low temperatures. 

The low-temperature properties of metals have created some unusual problems in fabricating cryogenic equipment. 

Most of the measurements described in the fifth section have been carried out using a low-power dilution refrigerator. This apparent constraint obliged the authors of the experiments to look for original configurations which are fully discussed in the text. We avoided to make a list of the suppliers of cryogenic equipments as happens in most books, since this type of information is at present easily obtained through internet. 

Because of its low price and no toxicity, it finds a lot of applications (see Chapter 14). In particular, because of its high latent heat of evaporation, it is commonly used in the precooling of cryogenic equipments (see Chapter 5). 

Chart Applied Technologies—Division of world s largest cryogenic equipment manufacturer. 

G. Applications of SLA to the design, evaluation and optimization of cryogenic equipment/processes (116 to 140). 

G. Applications of Second Law Analysis to the Design, Evaluation and Optimization of Cryogenic Equipment/Processes... 

Cryogenic equipment (advanced superconducting machines and processes exposed to liquid helium at -268°C and liquid nitrogen at —196°C)... 

The technique remains highly specialized due to the use of expensive electro- or superconducting magnets and cryogenic equipment. 

Large institutional and commercial refrigerators, freezers, and cold storage areas, including cryogenic equipment and gas tanks, are insulated with polystyrene or polyurethane foams. Polystyrene foam is popular where cost and moisture resistance are important polyurethane is used for spray application. Polystyrene foam is also used in load-bearing sandwich panels for low-temperature applications. 

Insulation suited to cryogenic equipment are characterized by multiple small spaces or pores that occlude more or less stagnant air of comparatively low thermal conductivity. Table 8.19 lists the most common of these materials. In application, vapor barriers are provided in the insulating structure to prevent inward diffusion of atmospheric moisture and freezing on the cold surface with resulting increase in thermal conductivity and deterioration of the... 

Cryogenic equipment (-200°F) employs insulants with fine pores in which air is trapped. 

Use Superconducting and magnetic alloys (with tin and titanium), cermets, missiles and rockets, cryogenic equipment, ferroniobium for alloy steels. 

The cryogenic equipment is all contained in an insulated structure termed a coldbox to minimize the impact of heat leak into the process. 

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