What are the dangers of closing the water valves when the pump is on?

As the valve closes or the pump trips, the pressure downstream can fall to a level that the fluid boils, creating a vapour cavity. This suction can cause the liquid to flow backwards and the cavity collapses as it approaches the closed valve or stopped pump.

What would happen if you block the outlet of a gear pump?

If the output port of a non-positive-displacement pump were blocked off, the pressure would rise, and output would decrease to zero. Although the pumping element would continue moving, flow would stop because of slippage inside the pump.

What will happen if discharge valve of centrifugal pump is closed?

If the discharge valve is closed and there is no other flow path available to the pump, the impeller will churn the same volume of water as it rotates in the pump casing. The vapor can interrupt the cooling flow to the pump’s packing and bearings, causing excessive wear and heat.

What happens if the pump is working with no fluid?

When driving the pump at fixed speed, if the equilibrium is achieved at a flow very lower than the design flow, the pump will experience flow distortions causing high vibrations and lower efficiency. At low flows the pump NPSHr may increase and overcome the NPSHa, taking the pump in dangerous cavitation condition.

What causes suction of fluid into the gear pump?

Gear pumps use the actions of rotating cogs or gears to transfer fluids. The rotating element develops a liquid seal with the pump casing and creates suction at the pump inlet.

Can you run a centrifugal pump against a closed valve?

A centrifugal pump is dead-headed when it is operated with no flow through it, for example, with a closed discharge valve or against a seated check valve. The vapor can interrupt the cooling flow to the pump’s packing and bearings, causing excessive wear and heat.

What happens when we close the valve in delivery line of a centrifugal and reciprocating pump during its operation?

The delivery valve connects the pump outlet and the delivery pipe. It remains closed before the pump is switched on. The delivery valve is closed again before the pump is switched off so that the delivery pressure is not transmitted to the suction pipe (otherwise there may be some backflow from the reservoir).