Inspection items for cryogenic storage tanks

The inspection of cryogenic vacuum storage tanks is divided into external inspection, internal inspection and multi-sided inspection. The periodic inspection of the cryogenic storage tank shall be determined according to the technical use conditions of the storage tank.
 
Generally, external inspections are performed at least once a year, internal inspections are performed at least once every 3 years, and multi-faceted inspections are performed at least once every 6 years. If the service life of the low-temperature storage tank reaches more than 15 years, internal and external inspections are required every two years, and if the service life is 20 years, internal and external inspections are performed at least once every year.
 
Internal inspection
1. Whether the inner surface and manhole take over the storage tank are corrosive and abraded, and whether there are cracks in the weld seam, the head transition area or other places with stress concentration;
2. When there is corrosion on the inside and outside surfaces of the tank, multiple wall thickness measurements should be performed on its parts. If the measured wall thickness is less than the design wall thickness, the strength verification should be carried out again, and suggestions on whether it can continue to be used are put forward;
3. When the inner wall of the tank has defects such as decarbonization, stress corrosion, intergranular corrosion, and fatigue cracks, metallographic examination and surface hardness measurement shall be performed, and an inspection report shall be submitted. External inspection
1. Check whether the anti-corrosion layer, insulation layer and equipment nameplate of the cryogenic liquid storage tank are intact, and the safety accessories and control devices are complete, sensitive and reliable;
2. Whether there are cracks, deformations, and local overheating on the outer surface;
3. Take over the welds, pressure components for leaks, whether the fastening bolts are intact, and whether the foundation sinks or tilts abnormally.
 
Multifaceted inspection
1. Non-destructive inspection of the main weld or shell, with a spot check length of 20% of the total weld length;
2. After passing the internal and external inspections, perform a hydraulic test at 1.25 times the design pressure of the storage tank and an airtight test at the design pressure of the storage tank. During the inspection, the tank and all welds were leak-free, and no visible abnormal deformation of the tank was qualified;
 
After the inspection of the low-temperature storage tank is completed, a report on the inspection of the storage tank shall be made, indicating the problems and reasons that can be used continuously or can be used but need to be repaired and cannot be used.