Cryogenic valves play an important role in LNG (Liquefied Natural Gas) applications. Quality inspection is a very important process for the
cryogenic valves. The details of the quality inspection of these
valves are as follows.
Preparation for quality inspection of cryogenic valves
1. Remove the stain on
the cryogenic valve, wipe it clean, and assemble it in an environment free of dust and oil stains.
2. Tighten the bolts to the preset torque value and tensile force value, and record the values.
3. Connect the valve with a proper thermocouple, so as to monitor the temperature of the valve during the whole test.
Pressure-bearing test at low temperature
1. Install
the cryogenic valve in the test container and ensure that the valve packing is at the top of the container without vaporized gases.
2. Do the initial system verification testing at room temperature and the maximum test pressure of the valve seat with the specified gas medium to ensure that
the cryogenic valve is in a suitable state and then start the test.
3. Immerse
the cryogenic valve in liquid nitrogen for cooling. The liquid level at least covers the joint between the valve body and the bonnet. Nitrogen is always supplied to the valve during the whole cooling process. During this process, the temperature of the valve is monitored by thermocouples installed at appropriate positions.
According to the above steps, obtain the corresponding data through quality inspection to determine whether the batch of
cryogenic valves meet the design requirements.
