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Calculating the Required Power for a Pump

05/20/2009 9:06 AM

Sir,

1. I would like to know , how can we calculate the require power(hp/kw) for the pump which is lifting the liquid(whatever it may be the head,discharge qty. etc.)

2. If a reciever tank of having 1cubic meter capacity is fitted in vertical direction can we connect the incomming air line at the top side of the tank and the outgoing line at the bottom side of the tank ? what does it effect, is there any improvement in pressure ?

Please give me in details.

S. gururaja

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Guru
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#1

Re: Calculating require power for a Pump

05/20/2009 9:39 AM

<...calculate the require power(hp/kw) for the pump which is lifting the liquid(whatever it may be the head,discharge qty. etc.)...>

The minimum power input to any fluid mover is the pressure rise multiplied by the volumetric flowrate, expressed in compatible units. To this needs to be added bearing losses, motor losses, etc.

<...connect the incomming air line at the top side of the tank and the outgoing line at the bottom side of the tank ? what does it effect, is there any improvement in pressure ?...>

There will be practically no measurable difference in pressure between top and bottom.

Putting the outlet at the bottom has the advantage that any entrained particles or liquids in the incoming air will be flushed out of the receiver at the earliest opportunity. This is an advantage in the case of steel receivers in contact with entrained water, resulting from inadequate drying before compression, as there is less opportunity for corrosion products to form inside the vessel. It will therefore have a longer insurance life as a result.

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#2

Re: Calculating the Required Power for a Pump

05/20/2009 5:30 PM

1 ) pump horse power calculation

I will repeat the same answer for the same question asked around one month before

HP = ω × Q × H / 75 ×ξ

Where; ω is water density = 1000 Kg / CU meter

Q is pump discharge in Cubic meter /second

H is total head In meter

ξ is pump efficiency

example: for water pump with discharge of 60 CU. meter per hour at a total head 40 meter

HP = ω × Q × H / 75 ×ξ

ω = 1000 Kg / Cu meter

Q = 60 / 3600 =0.01667 Cu meter / second

H = 40 m

Consider pump efficiency 60 %

HP = 1000 ×0.01667 × 40 × 100 / 75 × 60 = 14.8 HP

2) For air receiver may I differ with bottom connection for outgoing air line?

This because compressed air contain water vapor which tends to condensate in air receiver due to expansion and big tank surface. Also some oil vapor escape from compressor to air receiver.

Condensate water with oil drops rejected out from the lowest point for tank bottom either manually or through automatic drain.

In case of connecting out going pipe to this bottom point, all condensate water, oil with any other deposits will discharged to air service line. In such case water separator, oil separator filter and air filter will be all under worse working condition, more frequently change for filters and overloading for air cooler.

Almost air receiver has incoming air line at the down third of the tank not at bottom also out going line at the upper third.

In all condition I think it will not affect air pressure but quality of product outgoing air will affected.

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#5
In reply to #2

Re: Calculating the Required Power for a Pump

05/24/2009 9:15 AM

Thank you sir, for sending details

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Guru
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#3

Re: Calculating the Required Power for a Pump

05/21/2009 12:53 AM

Best way is to refer Pump Performance curves from pump manufacturer, as the efficiency is not a constant figure. Assuming efficiency in good calculations given in other posts may mislead you.

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#4
In reply to #3

Re: Calculating the Required Power for a Pump

05/21/2009 9:58 AM

dear gusha.

consider mean assume, only assumption not constant.

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