What do you mean by priming in centrifugal pumps?

Question

process priming

Answer 1

Normally, centrifugal pumps are filled with water from the pump casing down to the suvction line. This way air is evacuated. Without priming, the pump won't be able to suck water or other liquids efficiently.

Answer 2

I'm not sure about centrifugal pumps, but priming a pump is just adding a little water to the pump in order to start the suction process (so it doesn't run dry - gotta have water in pump in order to pull water out of hole.)

Answer 3

priming is a process of filling water to the pipe in order to prevent air flow

Answer 4

*All centrifugal pumps must be primed by filling them with water before they can operate. The objective of priming is to remove a sufficient amount of air from the pump and suction line to permit atmospheric pressure and submergence pressure to cause water to flow into the pump when pressure at the eye of the impeller is reduced below atmospheric as the impeller rotates.

When axial-flow and mixed-flow pumps are mounted with the propellers submerged, there is normally no problem with re priming of these pumps because the submergence pressure causes water to refill the pumps as long as air can readily be displaced. On the other hand, radial-flow pumps are often located above the water source, and they can lose prime. Often, loss of prime occurs due to an air leak on the suction side of the pump. Volute or diffuser pumps may lose prime when water contains even small amounts of air or vapor. Prime will not be lost in a radial-flow pump if the water source is above the eye of the impeller and flow of water into the pump is unrestricted.

In some cases pumps are primed by manually displacing the air in them with water every time the pump is restarted. Often, by using a foot valve or a check valve at the entrance to the suction pipe, pumps can be kept full of water and primed when not operating. If prime is lost, the water must be replaced manually, or a vacuum pump can be used to remove air and draw water into the pump.

A self-priming pump is one that will clear its passages of air and resume delivery of liquid without outside attention. Centrifugal pumps are not truly self-priming. So called self-priming centrifugal pumps are provided with an air separator in the form of a large chamber or reservoir on the discharge side of the pump. This separator allows the air to escape from the pump discharge and entraps the residual liquid necessary during re priming. Automatic priming of a pump is achieved by the use of a recirculation chamber which recycles water through the impeller until the pump is primed, or by the use of a small positive displacement pump which supplies water to the impeller.

*Impeller top must be submerged with the process fluid or water without any air.

*If you want to pump the air in case of a centrifugal pump , pumping water , operating at the speed of 2900 RPM , then you have to run the pump at a speed of [2900 x 800] as the ratio of specific gravity of air to water is 1/800.And it is practically impossible.

*If you don't prime the pump and start the pump ,then you will not get the flow,pump will run dry and ultimately damage the mechanical seal or gland packing .

Answer 5

Primed - mean filled with water, before they can operate

Two basic types of priming systems are common—the vacuum

method and the pump-fill method. The pump fill method only

can be used where there is a foot valve on the suction line; the

vacuum method can be used with or without a foot valve.

Types:

Automatic priming

PUMP-FILL PRIMING

VACUUM PRIMING