The cold test is basically the last link to ensure good quality and avoid any fault. It is the initial inspection to assess whether the design and installation of the system can meet the technological requirements, which is very critical.
After cooling, run the leak check in the system carefully and comprehensively. Check whether the equipment and pipes are deformed, communicate with the design unit in time if any deformation exceeds the requirements of the specifications and instructions, make careful analysis according to the situation, and confirm whether to make corrections to the parts with the largest deformation.
After cooling, perform a comprehensive check on the system supports. If there is deformation, make timely reinforcement and modification.
Fastening of cryogenic connections is often neglected. Even if no leakage is found during the leak detection, considering that the huge difference between construction temperature and operating temperature will cause thermal expansion and contraction of fasteners, it is recommended to tighten all cryogenic fasteners after cooling to improve the safety and reliability of operating conditions.
After the whole system is inspected, whether to adopt non-destructive testing, pressure test or a second cold test should be decided according to the number of leakage points and the amount of modification.
How to improve the cooling effect in the cold test? First, the cooling should be thorough, to guarantee the frost thickness. The cooling time should not be shortened. In addition, try to avoid running the test during dry and high temperature seasons, because the air can be too dry or the temperature too high, the system is not easy to frost (especially argon system), affecting the effect. It is recommended to humidify properly in the cold box to improve the cooling effect under such conditions.
Also attention should be paid to safe removal of the racks/supports set up for the test. The system shall not be damaged during the disassembly works which is recommended to be carried out when the system is still holding pressure. In case of any fault detected, the fault shall be coorected immediately to avoid any damage.