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Cryogenic Test means with a professional test in which valves and other equipment are exposed to extremely low cryogenic temperatures (representatively liquid nitrogen temperature of -196°C) to inspect their operational performance, sealing integrity, and material reliability under actual cryogenic situations.
It is a confirmation process that simulates whether equipment can act reasonably under the ultra-low temperature circumstances.
I. Why Make Cryogenic Testing?
Universal valves may get through tests at room temperature, but when it is an exposure to cryogenic environments (e.g., LNG at -162°C), the following problems can happen:
Material Cold Embrittlement: Common carbon steel turns to be brittle and may burst under stress.
Seal Leakage: Shrinkage and hardening of the seal rings cause internal or external leakage.
Movement Sticking: Valve stems and discs undergo clearance variations because of contraction, potentially causing seizure.
Structural Distortion: Different materials have different coefficients of thermal contraction, which may result in damage.
Cryogenic testing is used to identify these problems ahead of time and guarantee that valves are safe and dependable under authentic cryogenic conditions.
II. Typical Test Process (taking Valves as an Example)
1. Pre-treatment
Firstly, the valve is subjected to shell strength tests and sealing tests at room temperature (reference data).
Thoroughly dry the interior of the valve (to stop residuary moisture from freezing and damaging the valve).
2. Cooling
Put the valve into the cryogenic test container.
Inject liquid nitrogen (-196°C) slowly to make the entire valve a steady cryogenic temperature.
Control the cooling rate to prevent heat shocking.
3. Temperature Stabilization
Maintain the valve at cryogenic temperature for an adequate period (in general several hours) to ensure uniform inside and outside temperature.
4. Low-Temperature Operational Test
Perform complete open-close cycles (usually 3-5 times) on the valve at cryogenic temperature.
Measure the operating torque and check for any jamming or abnormal resistance.
5. Low-Temperature Sealing Test
With the valve in the closed position, introduce helium or nitrogen gas from one side to monitor whether the leakage rate verifies the specification requirements (such as standards like J-30, BS 6364, ISO 28921, etc.).
6. Heat-up and Recovery
After the test is finished, allow the valve to spontaneously come back to room temperature and conduct a normal temperature sealing test again to make sure that there is no residual damage.
