Cryogenic valves are primarily intended for very cold applications. The term “low temperature” refers to temperatures below -50°C.
Valves used in low temperature conditions require that the structural materials used can maintain good ductility, and the matching seals, gaskets, etc. can also adapt to these extremely cold conditions.
Industries related to liquefied and compressed natural gas, as well as liquid oxygen, nitrogen or helium, rely on these special valves to deliver cryogenic liquids and gases frequently, safely and reliably.
Generally, cryogenic valves need to use the pressure generated by the flow of liquid to push the valve to the open state, so that the medium can pass through. When the pressure of the flowing liquid drops, the valve closes again, creating a sealed space to prevent fluid leakage from the valve.
Special cleaning needs and concerns
Cryogenic valves require the valve manufacturer to use specialty solvents to remove grease and any organic contamination from the valve to keep the valve clean. Ultrasonic cleaning is usually used.
Some cleaning gases, such as oxygen or chlorine, require very high levels of cleanliness to ensure that no organic material or fiber breakage remains on the valve after cleaning is complete. Cleaned and certified valves are placed in double-sealed polyethylene bags to ensure that the valve has been stored in a clean environment until installed and used.
Operators should conduct a thorough inspection when installing cryogenic valves. This is critical to ensure that no oil or grease is accidentally introduced into the valve. Some specialty lubricants can be used in low temperature environments, and their presence or not should be determined by the specific application requirements.
As mentioned earlier, cryogenic valves must avoid fiber breakage. Generally speaking, fibers longer than 1/8 inch are not allowed on the valve. In many cases, fibers or broken ends of any length are not allowed to stick to the valve. This type of debris presents a risk of hazard in the oxygen system. Professionals in many industries use backlight testing to detect the presence of fibers.
Finally, inspectors should regularly check cryogenic valves and oxygen systems for internal and external leaks. Leakage inside the valve can be prevented by properly installing the valve and ensuring a reliable seal design. Cryogenic conditions require robust and stable seals to ensure long-lasting and reliable equipment operation. External leakage is also a serious concern, and end-welded designs are generally used. Available on the valve in the form of butt-weld or socket-weld ends.