Patent ID: 11920603
Assignee: nan
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F | IPC F

Claim 6:
7. A system for pumping a fluid, comprising:
a pump comprising a suction side and a discharge side;
a motor for driving the pump, the motor being drivingly connected to the pump via a shaft;
a return line providing a feed-back conduit for the fluid from the discharge side to the suction side;
a control valve for controlling the flow of the fluid through the return line;
a first sensor device for monitoring a first system parameter (P1) which is a function of the differential pressure across the pump;
a second sensor device for monitoring a second system parameter (P2) which is a function of a torque of the pump; and
a control unit which is arranged to:
receive monitored first system parameter values (P1m) from the first sensor device and, for each monitored first system parameter value (P1m), identify a minimum allowable second system parameter value (P20);
receive monitored second system parameter values (P2m) from the second sensor device and, for each monitored second system parameter value (P2m), compare the monitored second system parameter value (P2m) with the identified minimum allowable second system parameter value (P20); and
regulate the control valve based on a relationship between the monitored second system parameter value (P2m) and the minimum allowable second system parameter value (P20) such that the monitored second system parameter value (P2m) does not fall below the minimum allowable second system parameter value (P20);

wherein the system comprises a variable speed drive for operating the motor, and wherein the control unit is arranged to monitor the second system parameter (P2) by sampling the second system parameter (P2) from the variable speed drive;
wherein the control unit is arranged to compensate the minimum allowable second system parameter value (P20) for at least one of mechanical losses in at least one of the motor and the pump and electrical losses between the variable speed drive and the motor; and
wherein said mechanical losses are determined based on a rotational speed of the pump and said electrical losses are determined based on a power of the pump and the rotational speed of the pump.