System condition detection using inlet pressure
A controller for a municipal water system having a pump connected to a suction line, featuring a signal processor and a memory module configured to: receive suction line pressure sensor signaling sensed by a suction line pressure sensor arranged on the suction line and containing information about a suction line pressure of water flowing in the suction line; receive low suction pressure limit signaling programmed in the memory module and containing information about a low suction pressure limit of the water flowing in the suction line; and provide control signaling containing information to control the operation of the pump depending on a relationship between the suction line pressure and the low suction pressure limit, based upon the suction line pressure sensor signaling and the low suction pressure limit signaling received. The control signaling may contain information to reduce or stop the water flowing in suction line if the suction line pressure falls below the low suction pressure limit.
1 . A water system comprising:
a suction line configured to provide fluid to be pumped;
a pump having a pump housing with a pump inlet and a pump discharge, and configured to receive controller signaling and pump the fluid through the pump housing from the pump inlet to the pump discharge;
a suction line non-return check or foot valve coupled to the pump inlet, having a suction line valve inlet and a suction line valve outlet, and configured to allow the fluid in the suction line to flow in a suction line direction from the suction line valve inlet to the suction line valve outlet and prevent the fluid from flowing in an opposite suction line direction;
an inlet pressure transducer arranged on the suction line, and configured to sense pump inlet pressure between the suction line non-return check or foot valve and the pump inlet and provide inlet pressure transducer signaling containing information about the pump inlet pressure sensed between the suction line non-return check or foot valve and the pump inlet;
a discharge line non-return check valve coupled to the pump discharge, having a discharge line valve inlet and a discharge line valve outlet, and configured to allow the fluid in the discharge line to flow in a discharge line pumping direction from the discharge line valve inlet to the discharge line valve outlet and prevent the fluid from flowing in an opposite discharge line direction;
a discharge pressure transducer arranged on the pump discharge and coupled to the valve outlet of the non-return check er fool valve, and configured to sense pump discharge pressure and provide discharge pressure transducer signaling containing information about the pump discharge pressure sensed;
a controller having a signal processor configured to:
receive the inlet pressure transducer signaling and the discharge pressure transducer signaling, and
provide the controller signaling containing information to control and protect the pump based upon system flow by directly measuring a pressure difference between the inlet pressure transducer signaling and the discharge pressure transducer signaling across the pump housing in order to derive system conditions, including periodically turning the pump ON to prevent loss of prime.
2 . A water system according to claim 1 , wherein
the system conditions include a net positive suction head (NPSH) condition; and
the controller is configured to receive signaling containing information about a required net positive suction head (NPSHr) in order to meet a given flow and pressure design point and an available net positive suction head (NPSHa) and provide the controller signaling to reduce pump flow from the pump outlet when the NPSHa falls below the NPSHr to protect the pump.
3 . A water system according to claim 1 , wherein
the system conditions include a low suction pressure limit condition; and
the controller is configured to receive a low suction pressure limit and provide the controller signaling to reduce or stop pump flow from the pump outlet when the pump inlet pressure falls below the low suction pressure limit to protect the pump.
4 . A water system according to claim 1 , wherein
the system conditions include a loss of prime condition when the non-return check or foot valve leaks; and
the controller is configured to receive the inlet pressure transducer signaling that contains information about a negative inlet pressure sensed, and provide corresponding signaling containing information about the negative inlet pressure sensed.