What Is A Cryogenic Valve?

Cryogenic valves is a valve designed, manufactured and used in cryogenic conditions (usually operating at temperatures from -40°C to -196°C or lower). Its core function is to control the flow, pressure and direction of the media reliably under extremely low temperature environment, while ensuring sealing performance and structural stability. Below is a detailed analysis of cryogenic valves:
1.Definition and core characteristics of cryogenic valves
Temperature range
The operating temperature of cryogenic valves is generally below -40°C, as follows:
Ordinary cryogenic valves: -40°C to -100°C (e.g. storage temperature of LNG LNG is approximately -162°C);
Ultra-low temperature valves: Temperatures below -100°C (e.g. liquid nitrogen, liquid hydrogen, liquid helium, etc.).
Design challenges
Low temperatures can lead to material shrinkage, seal hardening and lubricating oil failure. Therefore, cryogenic valves need to address the following key issues:
Thermal expansion and cold shrinkage compensation: prevent valve body deformation or leakage due to temperature change;
Reliability of sealing: ensure that the sealing material remains elastic at low temperature;
Material adaptability: choose materials with low temperature brittleness and corrosion resistance;
Operational stability: avoid valve stem jamming or actuator failure due to low temperature.
2. Core design elements of cryogenic valves
neck structure
The valve cover is extended to keep the stuffing box away from the cryogenic medium and prevent the stuffing box from hardening at low temperature and causing leakage.
The long neck is usually filled with insulation material or vacuum insulated to reduce cold loss.
Cryo-specific materials
Body material: e.g. LCB (-46°C), LC3 (-101°C), CF8 (304 stainless steel, -196°C), CF3 (316L stainless steel, -196°C), Inconel alloys;
Sealing materials: polytetrafluoroethylene (PTFE), nylon, flexible graphite, etc.
Gaskets and fillings: use low-temperature flexible materials such as modified PTFE or expanded graphite.
Leak-proof structure
Double seal design (e.g. valve seat, disc double seal);
Bellows seal structure (suitable for high pressure or ultra-low temperature conditions);
Welding connection replaces flange connection to reduce leakage points.
Antifreeze and lubricants
The stem surface is hard chrome plated or self-lubricating material (e.g. polyetheretherketone PEEK);
The actuator is equipped with a heating device or insulating sleeve to prevent freezing at low temperature.
3. Main types of cryogenic valves
Cryogenic ball valve
Control switch, rotary ball 90 degrees, suitable for quick opening and closing scenarios;
Advantages: good sealing, small flow resistance, long life;
Uses: LNG terminal, liquid oxygen/liquid nitrogen storage tanks, etc.
Cryogenic gate valve
Control switch by lifting gate, suitable for all open or all closed condition;
Advantages: minimal flow resistance, erosion resistance the sealing surface;
Purpose: cryogenic pipeline cutoff, large storage tank inlet import and export.
Low Cryogenic stop Valve
Adjust flow by raising the disc for throttling or precise control;
Strengths: Simple structure, reliable sealing;
Purpose: cryogenic experimental equipment, chemical process control.
Cryogenic butterfly valve
By rotating butterfly plate to adjust the flow rate, suitable for large caliber, low pressure occasion;
Strengths: Small size, light weight, easy to operate;
Purpose: cryogenic ventilation system, air separation equipment.
Cryogenic check valve
Automatically prevent medium backflow and protects equipment safety;
Purpose: LNG pump outlet, cryogenic compressor inlet and export. Cryogenic safety valve
Automatic release of pressure when overpressure occurs to prevent system from exploding;
Uses: cryogenic storage tanks, pressure vessels.
IV. INTRODUCTION Application of cryogenic valves
Energy industry
LNG production, transport, storage (e.g. LNG terminal, petrol station);
Liquid hydrogen, liquid helium and other new energy storage and transportation.
Chemical industry
Process control of low-temperature ethylene, propylene, ammonia, etc.
Air separation unit (air separation into oxygen, nitrogen, etc.).
Scientific research and medical treatment
Cryogenic experimental equipment (e.g. superconducting magnets, particle accelerators);
Liquid nitrogen cryotherapy, cryopreservation of biological samples.
Aerospace
(a) Transportation and control of rocket propellants (e.g. liquid oxygen and liquid hydrogen);
Satellite cryogenic fuel system.
V. Selection and maintenance of cryogenic valves
Selection points
The material is selected according to the temperature, pressure and corrosion of the medium.
Select valve type according to flow requirement (e.g. ball valve, gate valve, etc.);
Consider the type of actuator (manual, pneumatic, electric, hydraulic).
Notes on maintenance
Periodically inspect the wear and tear of the sealing cover;
Avoid frequent opening and closing, resulting in valve seat damage;
The actuator should be preheated before operating in a low temperature environment (for example, pneumatic valves require dry air feed).
VI. INTRODUCTION Development trend in cryogenic valves
Material innovation
Development of alloy materials (such as nickel-based alloys) that are more cryogenic and brittle resistant;
Study of new sealing materials (such as nano-composite sealing materials).
Intelligence
Integration of sensors and actuators to achieve remote monitoring and automatic adjustment;
Using Internet of Things technology to predict valve life and failure.
Environmental protection requirements
Reduce valve leakage rate (if ISO 15848 standard met);
Reduce the environmental impacts of volatilization from low temperature media (e.g. LNG valves need to meet TA-Luft standards).
Cryogenic valves is the core equipment of the cryogenic industry. Their design and application require a combination of materials, structures and processes. With the rapid development of new energy, aerospace and other fields, the technical requirements for cryogenic valves will be constantly improved, and in the future they will be developed in the direction of high reliability, long life and intelligence.