What could happen if a positive displacement pump is started against a closed discharge valve?

What could happen if a positive displacement pump is started against a closed discharge valve?

A positive displacement pump operating against a closed discharge valve will continue to produce flow until the pressure in the discharge line has increased until the line bursts or the pump is severely damaged – or both. The relief valve can be internal or external.

What should be the status of the suction and discharge valves when starting a centrifugal pump?

Every centrifugal pump must be primed, vented and full of liquid before it is started. The pump you are about to start must be properly vented and primed. The suction valve must be fully open.

What happens if you dead head a positive displacement pump?

Positive displacement pumps, which are what gear pumps are, should not be deadheaded, as they will break immediately. The exception to this for gear pumps is when the viscosity is so low that the fluid slipping backwards through the pump is actually relieving it (giving the fluid somewhere to go).

What happened to the reciprocating pump when left untouched?

2. What happens to the reciprocating pump when left untouched? Explanation: When left untouched over a period of time, the reciprocating pump undergoes wear and tear. Reciprocating pumps have a good life provided that they are not left untouched.

Why start a centrifugal pump with discharge valve closed?

When the pump is started with no discharge pressure, the flow will go to maximum and power required will go to maximum and the motor will trip on over load. Starting with a closed discharge valve and slowly opening will fill the system so that hydraulic friction will reduce the flow to match the available power.

Why do centrifugal pumps need to start with the discharge closed?

It’s lower, which is why you should always start a centrifugal pump with the discharge either closed or just cracked open. The electrical load depends on the work done on the pumped fluid, so if it’s not pumping anything, the load is reduced.

How do you start a centrifugal pump?

Centrifugal pump start up procedure. 1. Open the suction valve. 2. Open any recirculation or cooling lines. 3. Fully close or partially open the discharge valve, depending on system conditions. 4. Start the driver.

Why is my centrifugal pump motor not working?

If a centrifugal pump motor cannot run with the discharge throttled without tripping and the overload protection is set correctly, the odds are very high that the motor is under-sized for the application or there is a mechanical overload being caused by a pump component or motor component failure.

What is a dead-headed centrifugal pump?

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. 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.