Method for dismounting tank top system of thin oil sealing-type dry-type gas tank

The invention relates to a method for dismounting a tank top system of a thin oil sealing-type dry-type gas tank. The method comprises the following steps: installing a tank top support on an upper most section of post; dismounting connecting pieces of tank top trusses and posts; using tank top supporting posts to support the tank top system; and then falling the tank top system and a piston system down to the bottom of the gas tank by using a buoyancy lift method; then, supporting the tank top system by using a tank top central bearing bracket; and finally dismounting the tank top system byhoisting equipment. The method does not need heavy hoisting equipment, only needs less frocks and equipment to dismount superhigh long-span truss structure; and the method has the advantages of fast construction speed, convenient operation, high safety and reliability and low construction cost; the method can be widely used for dismounting the tank top system of thin oil sealing-type dry-type gastanks.