Patent ID: 11965513
Assignee: SAUDI ARABIAN OIL COMPANY
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F | IPC F

Claim 16:
17. A method of operating centrifugal pumps related to net positive suction head (NPSH), the method comprising:
designating a group of centrifugal pumps in a system, each centrifugal pump in the group of a same construction and having same manufacturer NPSH required (NPSHr) as determined for the same construction, wherein the manufacturer NPSHr does not vary among the centrifugal pumps of the multiple centrifugal pumps at a given flowrate of pumped fluid,
wherein a manufacturer or vendor after completion of manufacture each centrifugal pump of the group, respectively, performs a factory acceptance test (FAT) of each individual centrifugal pump, respectively, giving FAT data unique to each individual centrifugal pump, the FAT comprising a functional test, wherein the FAT data comprises FAT NPSHr for each centrifugal pump as a function of the flowrate of pumped fluid determined via the functional test performed for each individual centrifugal pump, respectively, wherein the FAT NPSHr is capable of deviating from the manufacturer NPSHr;
wherein the FAT data gives FAT NPSHr for each centrifugal pump of the group as a function of the flowrate of pumped fluid based on the FAT performed on each individual centrifugal pump, respectively, of the group, and wherein the FAT NPSHr at a given flowrate of pumped fluid varies among the centrifugal pumps of the group;
generating a single equation for the group based on the FAT data of the centrifugal pumps collectively in the group, wherein generating the single equation for the group based on the FAT data comprises selecting FAT NPSHr values that are a maximum numerical value of the FAT data among the centrifugal pumps in the group at respective differing flowrates of pumped fluid and fitting the FAT NPSHr values as selected to an equation to give the single equation, the single equation correlating NPSHr with the flowrate of pumped fluid and giving the same NPSHr for each centrifugal pump in the group at a given flowrate of pumped fluid, wherein output of the single equation is only NPSHr;
specifying a NPSH margin for NPSH available (NPSHa) above the NPSHr;
calculating, via the single equation, the NPSHr for each centrifugal pump in operation of the group at a respective operating flowrate of the pumped fluid;
comparing the NPSHa for each respective centrifugal pump in operation of the group to a sum of the NPSH margin plus the NPSHr as calculated via the single equation for each respective centrifugal pump in operation of the group; and
shutting down a centrifugal pump in operation of the group in response to the NPSHa for that centrifugal pump being less than a sum of the NPSHr calculated via the single equation for that centrifugal pump plus the NPSH margin as specified.