Why is a safety valve needed at the outlet of a positive displacement pump?

Theoretically, the pressure of a positive displacement pump can be infinitely high, and its hazards are much greater than those of a centrifugal pump!

The outlet pressure of a centrifugal pump is limited by its head; when the outlet valve is completely closed, the pressure remains within a certain limit and stays within the design pressure range of the equipment and pipes, so no significant risk is incurred； However, if the outlet valve of the centrifugal pump remains closed for an extended period, with no fluid flow within the pump, it may cause the medium inside the pump to vaporize at high temperatures, lead to cavitation, and damage the mechanical seal ； However, the safety relief device cannot solve this problem; it can be addressed through pump flow monitoring. However, when a positive-displacement pump is in operation and the valve at its outlet is closed or blocked, the pressure at the pump outlet can rise rapidly and to extremely high levels. In the absence of a safety relief device, this can easily lead to damage to the equipment and pipelines.

1 The first one protects the pump body. 2 Each centrifugal pump has a maximum pressure that it will not exceed; no setting is required for this

When a centrifugal pump starts operating, there is a minimum return line that also serves to prevent overpressure.

The principles behind the two types of pumps are different; once a centrifugal pump is designed, the maximum pressure at its outlet is essentially fixed； For positive displacement pumps, as long as the material is of excellent quality, the pressure can be extremely high.

When the maximum discharge pressure of the centrifugal pump reaches the maximum allowable operating pressure of the pipeline, a safety valve is also required