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g_nraja
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Join Date: Oct 2008
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Centrifugal Pumps

10/21/2009 11:11 AM

If I want to run the cooling tower pump we arrived head,flow rate.based on the information we can derive the hp of motor.I would have selected low rpmmotor ( 1440rpm ) instead of 2880 rpm what will be the consequences.And I want to throttle the centrifugal compressor shall i throttle at suction side or delivery side.
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Tornado
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#1

Re: centrifugal pump operation and principle

10/21/2009 11:23 AM

For two centrifugal liquid pumps producing the same head, the lower rpm one will have a larger diameter. It may cost more but will typically give longer service, especially with seals. If there is a need to throttle the flow, it should be done in the pump discharge; otherwise cavitation is likely. (Extreme throttling in the discharge can also lead to cavitation.)

Centrifugal gas compressors would be throttled in the suction.

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lyn
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#2

Re: centrifugal pump operation and principle

10/21/2009 11:39 AM

I don't understand. Do you have the pump/motor? Do you have just the pump?

Running a pump designed for 1440RPM at 2880RPM will require more power.

Throttle the output of a pump, but not too much or it will overheat.

And finally, which is it? A pump or a comperssor?
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Parithimaal
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Join Date: Oct 2009
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#3

Re: Centrifugal Pumps

10/22/2009 12:34 AM

Dear,

If you reduce the RPM the head developed will go down and power consumption also reduced its good. Please do check with the manufacturer about NPSH requirement.

Please check with the performance curves or the affinity laws to calculate your head requirement and the process requirement.

Regarding the centrifugal compressors, it is better to use the inlet guide vanes than the outlet throttle than the delivery side. If you throttle at delivery you will be wasting the power.

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Mag
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#4
In reply to #3

Re: Centrifugal Pumps

10/22/2009 8:56 AM

Throttle the discharge, or you will starve the pump, creating a host of problems. for the process and the pump itself.

It's energy-inefficient to throttle. Put on your accountant/environmentalist hat and see if there is another way.

Be sure to account for the most likely modes of operation you will encounter for this process. Is it going to be versatile, or is it going to be run at one settling for the life of the process, or run infrequently, or must it be pieced together with junk you have laying around for a temporary fix. All may lead you to different cost-effective solutions. Obvious stuff, but all worth considering.
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PWSlack
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#5
In reply to #4

Re: Centrifugal Pumps

10/26/2009 8:47 AM

<...It's energy-inefficient to throttle....accountant/environmentalist hat and see if there is another way....>

A good suggestion. The original poster might want to invest in variable speed drives rather than throttling valves, perhaps?

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