Abstract: Oil tank overhaul is carried out in Weigang Pumping Station in order to eliminate the floating roof blockage and increase the capacity factor. Based on the result analysis on floating roof offset, blockage treatment program of floating roof is worked out, which involves in releasing the internal stress of central drains, adjusting the offset of slide way and treating the deformation of tank shell by means of water loading testing. The specific treatment procedure is to change the fixed structure of two central drains into a soft connection, adjusting the gap between the floating ladder and the slide way, reducing the level size of upper and lower clamps of primary seal and making a cold calibration on the deformation location in tank shell. Through the overhaul, the goal in eliminating the blockage of oil tank is achieved.