Can a displacement pump operate with the discharge valve mostly closed without damage?

A displacement pump relies on the differential pressure created by the pump action to move fluid. When the discharge valve is mostly closed, the pump continues to try to push fluid against the restriction created by the closed valve. This can lead to a buildup of pressure within the pump, which may exceed the design limits of the equipment.

The primary concern with operating a displacement pump under these conditions is the risk of damage from hydraulic overload. If the pressure rises too high, it can cause seals to fail, components to rupture, or the motor to overheat, potentially leading to a catastrophic failure of the pump. Furthermore, running the pump under such conditions for an extended period could lead to excessive wear and tear, decreasing the overall lifespan of the pump.

In essence, while a displacement pump can withstand some variations in system pressure and flow, consistent operation against a mostly closed discharge valve is not advisable due to the high risk of damage. Therefore, the assertion that a displacement pump cannot operate safely and without damage under these conditions is accurate.