Pump head discharge H
The pump head refers to the energy obtained by a unit weight of liquid after passing through the pump. It is expressed as H, and the unit is m, that is, the height of the liquid column discharged.
The effective energy obtained by a unit pressure of liquid after passing through the pump is also called the total head or full head. It can also be said that the energy difference between the liquid at the outlet and the inlet of the water pump. But it must be explained that it is only related to the performance of the pump itself, and has nothing to do with the inlet and outlet pipelines. The unit of head is N·m or m liquid column height.
For high-pressure pumps, the pressure difference between the pump outlet and the pump inlet (p2-P1) is sometimes used to approximate the size of the head. At this time, the head H can be expressed as:
Where P1 is the pump outlet pressure, Pa;
P2 is the pump inlet pressure, Pa;
p is the liquid density, kg/m3;
g is the acceleration of gravity, m/S2.
Head is the key performance parameter of the water pump, according to the needs of petroleum and chemical processes and the requirements of the pump manufacturer.
① Normal operating head The pump head determined by the discharge pressure and suction pressure of the pump under normal production conditions of the enterprise.
② Maximum required head The pump head at the maximum discharge pressure (suction pressure remains unchanged) that may be required when the production conditions of the enterprise change.
③ Rated head The rated head is the head of the water pump under the rated impeller diameter, rated speed, rated suction and discharge pressure. It is determined and guaranteed by the pump manufacturer, and this head value should be equal to or greater than the normal operating head. Generally, its value is taken as equal to the maximum required head.
④ Closing head The closing head is the head when the pump flow is zero. It is the maximum limit head of the pump. Generally, the discharge pressure under this head is used to determine the maximum allowable working pressure of the pump body and other pressure-bearing components.
