Maximum closing pressure difference before the control valve
Thread Content
The outlet pipeline of the centrifugal pump is equipped with a return line that leads back to the storage tank. The pressure in the storage tank is 1.6 MPag, while the pressure at the pump outlet is 2.2 MPag; the maximum shut-off pressure is 2.4 MPag. The maximum allowable pressure drop across the control valve is 50 kPa. When the demand from downstream users decreases, the pressure at the pump outlet rises. When this pressure exceeds 2.2 MPag, the control valve opens more, increasing the amount of flow that returns. What are then the pressures before the control valve, after the control valve, and the maximum shut-off pressure difference across the valve?
The control valve is installed on the return pipeline; the pressure before the valve corresponds to the pump’s head, while the pressure after the valve is equal to the equipment pressure plus the pressure drop and the resistance that needs to be overcome. The shutdown pressure is the pump’s maximum head; the flow rate of the control valve should be an appropriate multiple of the pump’s minimum operating flow rate
2.2 before the valve and 1.6 after the valve (the pipeline should be relatively short, so pipeline resistance is not taken into account; however, if a pressure-reducing orifice is installed on the return pipeline, the pressure before that orifice is used). Closing pressure difference: 2.4. Generally, this closing pressure difference represents the maximum pressure before the valve, as the worst-case scenario is that the pressure after the valve is 0