Basic pump operation 1

[jhend8rix]

Excuse my ignorance but this is driving me crazy - If the discharge pressure of a pump is greater than the suction pressure then why doesnt the flow go backwards through he pump?

 

[Artisi]

Very basic physics dictates that the flow is from low pressure to high pressure ie, from inlet to discharge.

Have a look at the following link:-

http://www.ask.com/web?o=0&qsrc=6&l=dir&q=Centrifugal+Pump+Principles

 

[BigInch]

High P to low P. Artisi you're having a bad day, no?

The pump captures a bit of fluid, adds energy and pushes or slings it out the discharge end. There is some recirculation from the high pressure to the low pressure areas that goes through the mechanical clearances, but usually not all that much.

If you connect the discharge to the suction with a clear plastic pipe segment going around the exterior of the pump, you'll see the high to low pressure flow.

http://virtualpipeline.spaces.msn.com

 

[Cheddarcaveman]

Further to these "slightly technical replies", inside the pump there are "seals" which are called wear-rings, that effectively seal between the inlet (suction) and outlet (discharge).
These wear-rings are fixed into the pump casing, and the impeller (the pumping mechanism), rotates inside them. There is a very small clearance between the impeller and the wear-ring and this acts like a labyrinth seal.
As long as the discharge is open, there will be very little recirculation within the pump.
If you start to close the discharge, then more and more pumped product will circulate inside the casing. You will also notice that, as there is reduced "flow" through the pump, it will heat up. You will also notice that the motor amps are greatly reduced in this condition as the pump is not doing much work. This is why it is common practise to start a pump with a shut, or almost shut discharge valve.

 

[BigInch]

Uh... even "slightly technical" seemed to be too much in light of the manner of the question.

http://virtualpipeline.spaces.msn.com

 

[TenPenny]

What type of pump are you talking about?

For example, in an air operated diaphragm pump, there are inlet and outlet check valves.

In a centrifugal pump, the answer is that it DOES go back from the discharge to the suction. But only a small amount does this.

 

[BenThayer]

 

[BigInch]

"There is some recirculation from the high pressure to the low pressure areas that goes through the mechanical clearances, but usually not all that much.
"

http://virtualpipeline.spaces.msn.com

 

[Artisi]

Let's not get too technical for this posting, learning to crawl would be a good start before we enter the olympic marathon.

 

[BigInch]

I was definately on a crawl.

http://virtualpipeline.spaces.msn.com

 

[hydromech]

Hey...I design water pumps, oil pumps and fuel pumps.

Centrifugal pumps...gerotor pumps...gear pumps...piston pumps.

Trying to anything other than crawl is too hazzardous.

Basic mechanics seperates negative and positive pressure.

Regards

Adrian