What is the meaning of the technical term rated condition for centrifugal pumps?

　　What is the meaning of centrifugal pump rating terminology?

　　01

　　Every industry has its own terminology, and the centrifugal pump industry is no exception. There are many terms that every salesperson, design engineer, end-user, and maintenance person dealing with pumps needs to understand, and it is vital that you know them if you hope to become a competent pump industry professional.

　　02

　　The API 610 11th edition standard defines “rated service” as the point at which the seller certifies that the pump performs within the tolerances specified in this international standard, usually the rated service point is the point at which the specified flow rate is maximized.

　　Practical engineering applications, the rated condition is the pump is designed for operation of the operating point, as well as in the pump performance test needs to be assessed during the verification of the operating point.

　　If the pump system is designed around a flow rate of 300m ³ / h, head 50m of the pump, and the pump must be verified during the pump performance test in the condition of the (actual) performance, then the flow rate of 300m ³ / h, head 50m is the rated condition of the pump.

　　The rated condition point is also known as the performance guarantee point, the performance acceptance point or the main operating condition point.

　　Rated condition usually indicates that the pump will run continuously (for a long time) point, therefore, it is usually recommended that the rated condition is located in the pump's priority operating region (POR), and the rated condition should always be located in the pump's allowable operating region (AOR).

　　Practical engineering applications, many of our design institutes / engineering companies are accustomed to the rated condition point is defined as the pump design condition point (i.e., the performance guarantee point), and the continuous long-time operation point is defined as the normal operation point or economic operation point. For this case, the best selection or design is: the pump rated condition point in the best efficiency point (BEP) on the right, the pump's normal operation point in the left side of the BEP.

　　03

　　During the pump performance test, the pump test curve must be very close to the rated condition to meet the buyer's requirements. Different test standards and acceptance criteria, different buyer regulations, requirements and rated conditions of the “close” degree will be different, that is, the allowable test tolerance is different.

　　If the above system pump test standards and acceptance criteria for: GB / T 3216-2016 “rotary power pump hydraulic performance acceptance test 1, 2 and 3”, 1B level, from the standard table 8 1B level acceptance level can be found in the test tolerance: flow rate of ± 5 %, head of ± 3 %, then:

　　Head tolerance: when the pump is operated at a flow rate of 300 m³/h, the head must be between 48.5 m and 51.5 m.

　　Flow rate tolerance: When the pump is operated at 50 m head, the flow rate must be between 285 m³/h and 315 m³/h.