Storage tanks are the basic equipment for storing and transporting materials in the chemical industry. In order to avoid safety hazards in storage tanks, storage tanks should be inspected regularly for safety. Tank inspection is divided into external inspection, internal inspection and comprehensive inspection. Tank cycle inspection is based on the technical conditions of use of the equipment to determine, - in general, external inspection at least - once a year, internal inspection at least once every 3 years, comprehensive inspection at least once every 6 years. If the use of the storage to reach more than 15 years, then every two years, it is necessary to carry out an internal and external inspection, if the use of up to 20 years, then every year at least one internal and external inspection.

Tank inspection should be done before the preparatory work, the tank will be cleaned of internal materials, and other equipment separated and clearly marked, the residual gas in the tank for replacement cleaning process, and analysis to achieve safety standards, open all the manholes, remove the internal parts, remove the inner wall dirt, cut off the tank power.

External inspection: test the tank's anti-corrosion layer, insulation and equipment nameplate is intact, safety accessories, control devices are complete, sensitive and reliable; the external surface has no cracks, deformation, local overheating and other phenomena; take over the weld, pressurized components have no leakage, fastening bolts are intact, the foundation has no sinking, tilting and other abnormalities.

Internal inspection: the internal surface and manhole take over the tank there is no corrosive wear phenomenon, weld, head transition zone or other stress concentrations where there are no cracks; internal and external surfaces of the tank corrosion and other phenomena, there should be suspected parts of multiple wall thickness measurement. Measured wall thickness, such as less than the design of small wall thickness, should be re-approved strength, and whether to continue to use and allow high working pressure recommendations; tank wall decarburization, stress corrosion, intergranular corrosion and fatigue cracks and other defects, metallographic testing and surface hardness determination, and inspection reports.

Comprehensive inspection: the main weld or shell for damage free inspection, sampling length of 20% of the total length of the weld; after passing the internal and external inspection, 1.25 times the design pressure of the tank for hydrostatic testing and tank design pressure for gas-tight test. In the above test process, the tank and each weld without leakage, as well as the tank without visible abnormal deformation is qualified.