Redesign of Cryogenic Pump in Liquefied Natural Gas Storage Tank Considering Thermal Effect

Abstract

Liquefied natural gas (LNG) takes up six hundreds of the volume of natural gas to be reached below the boiling temperature (-162 degrees C), which makes storage and transportation much easier. Imported Liquefied natural gas is transported to ground storage tanks via pipeline using cargo pump on the LNG carrier vessel. In LNG receiving terminal, primary LNG pumps are installed in the storage tanks and supply the LNG to secondary pumps with 8 bar. So the primary LNG pumps should be maintaining stable conditions to manage the LNG in stock. In this paper, to find out the cause of abnormal vibration at LNG primary pump, vibration analysis has been performed. Therefore, it was estimated and confirmed that random low frequencies were originated from fluid instabilities due to the inducer bolt being loosed because of the thermal expansion difference between bolt and other part in the cryogenic fluid. So, to prevent the looseness of inducer bolt, the dimensions of inducer bolts are modified. After modification, low frequency bands could be disappeared and pumps could recover its original performance characters.