CENTRIFUGAL PUMPS - HOW TO PRIMING THE PUMP STEPS AND PROCEDURE

 CENTRIFUGAL PUMPS - HOW TO PRIMING THE PUMP STEPS AND PROCEDURE

WHAT IS PUMP PRIMING AND WHY ITS REQUIRED?

• Priming simply means preparing or getting something ready for operation. for a centrifugal pump to work properly, you need to fill it up with water.

• When everything is right, a standard (non-self-priming) centrifugal pump looks like this. The pump will resume operation once the air is removed.

• Most centrifugal pumps are not self-priming. In other words, the pump casing must be filled with liquid before the pump is started, or the pump will not be able to function. If the pump casing becomes filled with vapors or gases, the pump impeller becomes gas-bound and incapable of pumping.

• So energy impart on air is much lesser. So impeller CANNOT impart enough energy to air to go out of casing and suck water so priming is compulsory for in case of centrifugal pump. In case of reciprocating pump, it can push out all air by itself as it has suction and delivery valves to displace “fluid” positively

PROCEDURE AND STEPS FOR PRIMING:

• The air escapes through the pump discharge nozzle whilst the fluid drops back down and is once more entrained by the impeller. The suction line is thus continuously evacuated. 

• The design required for such a self-priming feature has an adverse effect on pump efficiency. Also, the dimensions of the separating chamber are relatively large. For these reasons this solution is only adopted for small pumps, e.g. garden pumps. 

• More frequently used types of self-priming pumps are side channel and water ring pumps. Another type of self-priming pump is a centrifugal pump with two casing chambers and an open impeller. This design is not only used for its self-priming capabilities but also for its degassing effects when pumping two phase mixtures (air/gas and liquid) for a short time in process engineering or when handling polluted fluids, for example when draining water from construction pits.

• This pump type operates without a foot valve and without an evacuation device on the suction side. The pump has to be primed with the fluid to be handled prior to commissioning.

• Two-phase mixture is pumped until the suction line has been evacuated and the fluid level has been pushed into the front suction intake chamber by atmospheric pressure. During normal pumping operation this pump works like an ordinary centrifugal pump.

• Centrifugal pump with two casing chambers suction process

• Centrifugal pump with two casing chambers pumping duty