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| Liquid Oxygen Storage Unit at Industrial Plant |
Where do cryogenic temperatures start?
Wikipedia, in a description of "cryogenics" that references the field of physics, states that "It is not well-defined at what point on the temperature scale refrigeration ends and cryogenics begins, but scientists assume it starts at or below −150 °C (123 K; −238 °F)." Oxygen, hydrogen, helium, methane, nitrogen, fluorine, and LNG are all considered cryogenic liquids, having boiling points below -150°C at atmospheric pressure. Other fluids, though not considered cryogenic by the definition above, can be solid candidates for the application of cryogenic valves for reasons related to valve performance and durability in low temperature applications.
What valve design features apply to cryogenic service?
Most cryogenic service valves share a basic common set of design features that will provide basic service performance with cryogenic fluids. One manufacturer, PBM Valve Solutions, includes the following special features in their line of ball valves for cryogenic service.
- Cleaned for oxygen service, or other high purity application.
- Special seat and graphite seal material.
- Special stem packing accommodates broad temperature and pressure ranges found in cryogenic applications.
- Fire safe version available.
- Temperature range 400°F/205°C to -320°F/-200°C with ANSI 300# Class rating.
- Available with extended ends to eliminate requirement to disassemble valve for installation.
- Vented balls, used to relieve pressure in the valve body, are keyed to the stem for precise assembly.
- Extended bonnet.
- Range of available handles or actuators for manual or automatic operation.
- Stem can be installed 45° to 90° from horizontal plane.
The video below provides further illustration of the special design features of industrial process control valves applied for cryogenic fluids. More product details and help solving any industrial process control challenge, are available from CTI Controltech.
