江苏LNG高压泵饱和蒸汽压差联锁的优化

Optimization of saturated vapor pressure difference interlocks of Jiangsu LNG HP pumps

汽蚀会导致高压泵性能下降，缩短使用寿命，因此必须设置饱和蒸汽压差联锁以保护高压泵。根据离心泵的汽蚀原理和汽蚀判别式，对江苏LNG现有高压泵饱和蒸汽压差联锁进行分析，发现现有公式计算的准确性和精确性不够。据此提出了选取运行高压泵中泵罐叶轮处最高温度为取温点的改进方法，并重新分段拟合LNG温度一饱和压力公式，以确保高压泵饱和蒸汽压差联锁能够及时、准确地触发，保证其不发生汽蚀。同时，结合工艺操作提出高压泵防汽蚀的操作建议，包括启泵前增加低压输出汇管压力，保证高压泵泵罐保冷量，启泵后尽快调节出口调节阀等。（图7，表1，参6）

HP pump cavitation can result in bad performance and affects pump service life, so saturated vapor pressure difference interlocks have to be installed to protect HP pumps. According to the cavitation principle and cavitation discriminant of centrifugal pump, the present saturated vapor pressure difference interlocks of HP pumps at Jiangsu LNG terminal are analyzed and points out the accuracy of current formula is insufficient. Base on that, puts forward the improving method of selecting the highest pump impeller temperature as the temperature measurement point and the LNG temperature- saturated vapor pressure formula is fitted again to make sure the process interlock can be triggered in time and correctly with no cavitation. At the meantime, brings up some proof-cavitation proposals based on the process operation, such as increasing the output pressure of low-pressure pipe before startup, ensuring cold conservation for the HP pump tanks and adjusting the outlet valve immediately after starting pump, and so on.（7 Figures, 1 Table, 6 References）.