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

Claim 10:
11. A method of operating centrifugal pumps related to net positive suction head (NPSH), the method comprising:
grouping multiple centrifugal pumps in a system for application of a single equation to the multiple centrifugal pumps, the single equation giving NPSH required (NPSHr) as a function of flowrate of pumped fluid, wherein the single equation is utilized for all of the multiple centrifugal pumps, outputs only NPSHr, and gives the same NPSHr for each centrifugal pump of the multiple centrifugal pumps at a given flowrate of pumped fluid,
each centrifugal pump of a same construction and having same manufacturer NPSHr as determined by 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 multiple centrifugal pumps, 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 as determined via the functional test performed for each individual centrifugal pump, respectively, wherein the FAT NPSHr is capable of deviating from the manufacturer NPSHr;
developing the single equation based collectively on the FAT data of each centrifugal pump of the multiple centrifugal pumps, wherein the FAT data is determined via the respective functional test performed for each individual centrifugal pump of the multiple centrifugal pumps, wherein the FAT data is capable of varying respectively among the multiple centrifugal pumps at a given flowrate of pumped fluid, wherein the single equation is developed based on select values of the FAT NPSHr, and wherein the select values are only maximum numerical value of FAT NPSHr among the centrifugal pumps at each given flowrate of pumped fluid;
specifying as a protection 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 multiple centrifugal pumps;
determining the NPSHa for each centrifugal pump in operation of the multiple centrifugal pumps;
comparing the NPSHa for each respective centrifugal pump in operation of the multiple centrifugal pumps to the NPSHr as calculated via the single equation for each respective centrifugal pump in operation of the multiple centrifugal pumps; and
shutting down a centrifugal pump of the multiple centrifugal pumps 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.