Sage-Tips

What happens when the discharge end of the pump is closed when the pump is working?

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. This will increase the temperature of the liquid (due to friction) in the pump casing to the point that it will flash to vapor.

What will happen while starting if discharge valve of reciprocating pump is closed?

By closing the discharge valve, the starting current can be reduced. As we know, at the start of any motor, the current will be high. If we start the pump with discharge valve closed, it means there no discharge head and minimum resistance to the pump and so current drawn is minimum.

What happens when the discharge valve of a running positive displacement pump is closed?

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 are the reasons behind low discharge No discharge of liquid through pump?

Worn impeller, wear ring, wear plate If the vanes on the impeller are worn, the hydraulic capacity of the pump is reduced. Same with the wear ring and wear plate. When clearances open up due to wear, more recirculation occurs inside the pump, reducing the pump’s flow.

What happens to the pressure at the discharge of the pump when the flow increases or when the discharge valve goes from a fully closed position to fully open?

When the flow increases, the discharge pressure of the pump decreases, and when the flow decreases the discharge pressure increases (ref. tutorial2. htm). Do not let a centrifugal pump operate for long periods of time at zero flow.

Why discharge valve is closed in centrifugal pump?

>The discharge valve of the pump has to be closed during startup. This is maintained so, inorder to prevent sudden load on the power system, if the valve is open. If you look at the characteristics of the pump, the power required ,increases with flow rate.

Can a positive displacement pump run backwards?

The liquid is carried between the gear teeth and the casing to the opposite side of the pump. The meshing of the gears forces the liquid into the outlet line. By reversing rotation, the function of the nozzles will be reversed and the pump will be able to pump ‘backwards’.

What causes low discharge pressure in pump?

The slowed flow may be caused by a collapsed suction hose lining, a leaking gasket, a plugged suction line or a damaged or worn impeller or wear plate. To determine the cause of any decrease in flow, the discharge pressure and the suction vacuum should be measured while the pump is operating.

What happens if a centrifugal pump runs dry?

Centrifugal pumps are build to run with the working medium as water. Whenever pump is run dry i.e. without water, air is the working fluid which does not act as a coolant. So the pump will be overheated and damage the bearings, shaft and impeller. Basically it will seize the pump.

Why does the pump discharge pressure drop when the impeller fails?

The pump was not experiencing cavitation and the process fluid is a clear liquid with no grit, ruling out erosion to the pump impeller. Internal leakage within a pump can cause a reduction in the pump’s discharge pressure. The impeller’s rotation imparts kinetic energy to the fluid within the pump.

What happens when you choke the flow of a pump?

Choking the Flow from a Pump Makes it Work Easier. Centrifugal pumps are counter-intuitive. As pressure on a pump increases, the power required decreases. In other words, if you put a valve on the discharge of a pump and begin to restrict the output flow, the power required by the motor will decrease.

What happens if you put a valve on a pump?

In other words, if you put a valve on the discharge of a pump and begin to restrict the output flow, the power required by the motor will decrease. Most people already have it in their head that choking a pump back will make the pump work harder and use more power.

What are the causes of Excessive slip in a hydraulic pump?

If clearances are too wide for the type of fluid pumped, excessive slip will occur. Fluid will continue to recirculate inside the pump, yielding lower flow out of the pump. 5. Debris in the impeller If the eye of the impeller is plugged with debris, it removes the hydraulic capacity of the impeller to create an area of low pressure. 6.