There are two main factors that affect the parameters of the pump inside the tank:
1.1 Influence of impeller diameter
Generally speaking, the smaller the impeller diameter, the finer the overall structure of the pump. The reduction of pump well diameter will directly lead to a decrease in project cost. Due to the fact that there are usually more than one pump well inside an LNG storage tank, and some even install backup pump wells, reducing the diameter of the pump well to increase the effective volume of the LNG storage tank, that is, to improve its utilization rate, has certain significance.
1.2 The impact of NPSHr on the required cavitation allowance
Similar to other centrifugal pumps, LNG tank pumps also have their required NPSHr cavitation allowance. During operation, to avoid cavitation, there should be sufficient pressure head at the inlet of the pump, which means that the liquid in the LNG tank cannot be completely emptied and a sufficiently high liquid level must be maintained. In the case of a certain safety margin, the smaller the cavitation allowance, the lower the allowable minimum liquid level height in the tank, the larger the effective volume of the tank, and the higher the utilization rate.
