Cryogenic Service Valves
Cryogenic Gate Valves are specially engineered and designed for piping systems used in the storage and transport of liquefied gasses such as LNG and liquid nitrogen and oxygen. The main structural feature of these valves is an extended bonnet with an enclosed vapor chamber to isolate packing from the cryogenic fluid and thereby allow packing to function properly. PK Vlave Cryogenic designs and liquid nitrogen testing facilities go much further to assure proven performance in this most demanding application.
Materials suitable for working condition must be adopted for low temperature valves. Especially in petrochemical industry, the types of fluids to be processed are different according to each section even in the same plants. At the same time, the temperatures used are also different. A full consideration must be paid to the selection of material.
Body And Bonnet
As for the materials constituting the low temperature valves, special consideration must be paid to the materials used at pressure parts as in the case of body and bonnet.
|BODY MATERIAL||SERVICE TEMPERATURE||BOLT||NUT|
|CARBON STEEL(GRADE LCB)||-50℉||-46℃||A320 GR. L7||A194 GR. 4|
|C-1/2Mo(GRADE LC1)||-75℉||-59℃||A320 GR. L7||A194 GR. 4|
|2 1/2NI(GRADE LC2)||-100℉||-73℃||A320 GR. L7||A194 GR. 4|
|3 1/2NI(GRADE LC3)||-150℉s||-101℃||A320 GR. L7||A194 GR. 4|
|TYPE 304(GRADE CF8)||-425℉||-254℃||A320 GR. B8||A194 CR. 8|
|TYPE 304(GRADE CF3)||-425℉||-254℃||A320 GR. B8||A194 CR. 8|
|TYPE 316(GRADE CF8M)||-425℉||-254℃||A320 GR. B8||A194 CR. 8|
|TYPE 316L(GRADE CF3M)||-425℉||-254℃||A320 GR. B8||A194 CR. 8|
Following the body and bonnet, selection of materials for main parts such as stem, seat ring, and gland is very important. We adopt austenite stainless steel.
Teflon or other plastic packing protecting from shinkage by large cloumn of insulating gas.
Stellite 6 for all medium and high pressure application prevents seizing and galling
Bolt and Nut
Material for bolts at low temperatures requires especially strength. Therefore, rigidity at low temperature is demanded and brittleness at low temperature of steel material can be improved generally by heat treatment. We use it according to ASTM standard.
Table of Liquefied Gasses
|NATURAL GAS, LNG||-270℉||-168℃|
|CARBON DIOXIDE, CO2||-314℉||-192℃|
ASTM : A351-CF8, CF8M, CF3, CF3M or Equivalent
UNIT : NPS
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