Relationship between pump head and outlet pressure

Thread Content

One of the important parameter indicators of a water pump is head, which is defined as the height to which the water pump can lift water. It is usually denoted by the symbol H, and its unit is meters. The head of a water pump, measured with reference to the centerline of the impeller, consists of two parts. The vertical distance from the centerline of the water pump impeller to the water surface of the water source, that is, the height to which the water pump can draw water up, is called the suction lift, or simply the suction head ； The vertical height from the center line of the water pump impeller to the water surface of the outlet tank, that is, the height to which the water pump can lift water, is called the water lifting head, or simply the head. The head of a water pump is the sum of the suction head and the discharge head. It should be noted that the head indicated on the nameplate refers to the head that the water pump itself is capable of generating; it does not include the head loss caused by frictional resistance in the pipeline flow. This is something that cannot be ignored when selecting a water pump. Otherwise, water will not be able to be pumped in. There is the following relationship between the pump pressure and head: P=pgH ； In the formula, P represents the pressure difference (in Pa), and p represents the density of the medium (in kg/m3) ； g: Gravitational acceleration, which can generally be taken as 9.8 m/s2. H: Head (in meters) ； Based on the relationship above, the outlet pressure of a multi-stage pump can be calculated as long as the density of the medium and the head are known; conversely, the height that the medium can reach can be determined if the inlet and outlet pressures of the multi-stage pump along with the density of the medium are known. For a medium with a density equal to that of water, it can be roughly assumed that a pressure difference of 1 MPa is equivalent to a head of 100 m. Therefore, it can be said that the head and pressure of a multi-stage water pump are in a constant relationship, being equivalent to each other.