How to Avoid Tank Wall Depression of Steel Arch-roof Tanks

Two 5000m³ diesel oil tanks were subject to wall depressed during oil loading and unloading operation. Qualitative and quantitative analyses on the variation of oil-air space pressure within the tank are conducted to deal with this problem. Data processing is carried out based on the theory of short barrel pressured vessel. The result displays that tank wall is depressed at the time when the internal and/or external pressure differential of tank is higher than the critical unstable pressure of tank, which is the major cause of tank wall's depression. Some countermeasures against the wall's depression are provided in the paper.