Abstract: Propylene, a kind of petroleum gas easy to liquify or gasify under pressure or heat, can be transported as liquid depending on the gaseous pressure in tank.In Fushun where spherical tank is required to have an operation pressure ranging from 0.9 to 1.4Mpa, the boosting system for liquified propylene tank must be started to pressurize when temperature drops to 11℃ or less.The original boosting system has the following drawbacks; ①There is one booster for each tank; since no standby booster is available, continuous propylene transportation can not be guaranteed; ②The three boosters for three tanks require excessive heating steam to prevent frosting in winter; ③The fact that both liquid and gas pipes for booster have only one valve makes it difficult to repare any fault booster.The modified boosting system now consists of two boosters, with only one running for the three tanks for normal operation, thus steam consumption is reduced.Attention shall be paid to the following points in order to realize better economic benefit: ①Modification should be carried out during the performance of tank overhaul, ②Valves should pass strict pressure test, ③Qualified welding shall be achieved for the pipeing in boosting system.