How Do Cryogenic Valves Work?

Cryogenic valves are specially designed to ensure stable operation at extremely low temperatures (e.g. -40°C to -253°C). Its core working principles and main designs are as follows:
1.Core principles of work
The cryogenic valves works by extending the valve stem to isolate the cryogenic zone, using cryo-resistant materials and special sealing design to accommodate the characteristics of cryogenic media (e.g. shrinkage, brittle, leakage, etc.). Specifically:
Stem extension design
Cryogenic valves extend the valve stem beyond the cryogenic zone to move key components such as packing boxes and actuators to avoid direct contact with cryogenic media, resulting in material embrittlement or seal failure. For example, the valve stem length of a cryosphere valve is usually 30%-50% longer than a normal sphere valve to ensure that the filling works at room temperature.
Cryogenic material selection
The body, valve cover and disc are made of cryo-resistant materials such as:
Stainless steel (e.g. 304L, 316L): suitable for low temperatures above -196°C.
Cryogenic carbon steel (e.g. LCB, LC3): suitable for low temperatures ranging from -46°C to -101°C.
Nickel based alloys (e.g. Inconel 718): suitable for ultra-low temperatures of -253°C hydrogen systems).
Special sealing design
The cryogenic valve has a two-way sealing structure that combines soft seals (e.g. PTFE, PCTFE) and hard metal seals (e.g. cobalt-coated alloys) to ensure zero leakage at low temperatures. For example:
Cryogenic ball valve: valve seat adopts precision grinding, redundant spring load seal, realize zero leakage in both directions.
Cryogenic gate valve: The gate valve has a Sealing surfaces on both sides, and the valve seat is made of medium pressure or external pressure to ensure the reliability of the seal.
2. How different types of cryogenic valves work
Cryogenic ball valve
On and off: Turn the ball 90° on and off.
Low temperature adaptability:
The valve seat is made of low temperature resistant materials such as stainless steel or polytetrafluoroethylene (PTFE) to avoid low temperature shrinkage and seal failure.
Stem clearance is less than1.0mm to reduce fluid residue and prevent temperature freezing.
The valve seat seat and spherical relief hole can release cavity pressure and avoid sealing failure caused by dielectric expansion at low temperature.
Cryogenic Gate Valve
Method of opening and closing: The gate moves perpendicular to the valve seat to open or close completely.
Low temperature adaptation:
The gate is designed to be flexible to compensate for the material's shrinkage at low temperatures and ensure sealing.
A pressure relief hole is arranged on the side of the air inlet to prevent the pressure of the middle cavity from rising abnormally.
The top length of the cover is determined according to working temperature to ensure a reliable valve stem packing seal.
Low Temperature stop valve
Method of opening and closing: The disc moves along the seat center line, and the disc and valve seat cover are cut or adjusted.
Low temperature adaptation:
There is no relative sliding between the disc and the valve seat sealing surface, reducing wear and extending service life.
The stem axis is perpendicular to the valve seat cover to ensure uniform force on the the sealing surface when opening and closing.
Suitable for low temperature systems requiring flow regulation (such as air separation equipment).
Cryobutterfly valve
Opening and closing method: butterfly disc rotates around the shaft to control media flow.
Low temperature adaptability:
Friction sealing principle is adopted to achieve seal by contact between friction plate and sealing ring.
Pneumatic drive principle, realize remote automatic control, improve system reliability.
Suitable for large caliber cryogenic pipeline (such as LNG tank outlets).
Cryogenic check valve
Opening and closing method: automatic opening and closing of disc according to media flow to prevent medium backflow.
Cryogenic adaptability:
check valve: Disc rotates around hinge mechanism for low flow.
Lift check valve: Disc slips along the vertical center line of the valve body, suitable for high pressure small aperture situations.
Disc is made of stainless steel or carbide to ensure a low temperature seal.
Low Cryogenic pressure Relief Valve
How it works: By adjusting the opening of the valve core opening, reduce the high-pressure cryogenic medium to the set pressure.
Cryogenic adaptability:
Double pressure control design: internal low pressure exhaust pressure is controlled at the saturation vapor pressure corresponding to the refrigerant tripoint and automatically opened or closed to maintain pressure stability.
Determine the high pressure control range according to the heat transfer of the system to avoid damage to the equipment due to pressure fluctuations.
3. Special design of cryogenic valves
Cold Loss Design
Cryogenic valves reduce cold loss and improve system efficiency by extending the valve stem and reducing liquid residue. For example, a cryosphere valve with a valve stem clearance of less than1.0mm may reduce media residue.
Fire Safety Design
Cryogenic valves are equipped with fireproof graphite gaskets and electrostatic devices to ensure sealing integrity in high temperature or electricity environments. For example, one brand of Italian cryogenic ball valves uses a redundant sealing structure of fireproof soft seats and metal hard seats to achieve zero leakage in both directions.
Explosion-proof design
Cryogenic valves are suitable for flammable, explosive media (e.g. LNG, liquid hydrogen) and must be explosion proof (e.g. ATEX, IECEX). For example, the antistatic device of the cryogenic ball valve can output static electricity and prevent sparks from causing explosions.