Stress and Corrostion Analysis on the Roof Plates of 10.000m³ Dome Roof Tanks

The 10, 000m³ dome roof tanks, mainly installed in the intermediate stations for long distance pipeline systems, have typical roofs of plate-frame structure. Alternating stress can be seen on roof plates when the tank is under loading and unloading operation with a pressure change of oil vapour in it. After over ten years of service. such roof is subjected to severe corrosion and even etched holes distributed mostly in a ring belt between the inner and outer up-right columns. The stress and deformation of the roof plates under tank loading and unloading are analyzed and calcuated by means of finite element method. It is concluded that in the zone of a ring-belt 10m from the central column (between the inner and outer columns) are found the highest siresses, the biggest alternating stress amplitude due to loading/unloading operation. and most severe stress corrosion. This tallies with the actual case, and concludes in turn that stress corrosion is the main reason for the roof plate damages. This conclution is of directive function to the corrosion control of such tanks.