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#1

# suction pump up on land

If I have my inlet at - 200 meters depth where the pressure is 20 bars does the added pressure at the inlet require less power than if I put a suction pump up on land? Is there any difference?
02-25-2014 09:08 AM
Top #2
The 20 bar pressure will be reduced to 0 bar at the top 200 meters above. If you use a suction pump (I don't think a Suction Pump can suck water from 200 meters depth) then what is important is what will be the pressure at the outlet of suction pump.
02-25-2014 11:46 AM
Top #3
A suction pump can "lift" from 25ft or 7.62m at sea level.
Is the 20bar at the inlet of the pipe or the inlet of the suction?
02-25-2014 02:36 PM
Top #4
Dear Krut, power consumptin will be nearly same for the pump as teh differential head across the pump remauns same. But structurally the pump should be much more rugged if suction pressure is 20 bar. Mechanical design of the pump should be compatiable enough to take up teh 20 bar suction pressure plus the head developed by the pump itself.
02-25-2014 05:31 PM
Top #5
As Anis and Prakriti said the 20 bar at 200 m depth will transform to 0 bar at sea level. So, there is not any advantage, except the sumergence that the suction pipe need to avoid vortex (only a few meters).
The energy required depends on the differential heights (water level surface in the discharge tank - water level surface in the suction side).
02-25-2014 07:38 PM
Top #6
what is the water depth above the suction depth?
02-25-2014 10:15 PM
Top #7
The pump is inside of a hull at a depth of 200 meters. The piping up to the top is inside at 15 psi. So the water pressure going into the Inlet is at 20 bars.
02-26-2014 01:07 AM
Top #8
In this case you will have to take care of following things:

1. What is the allowable maximum pressure for the pump? Since at inlet it is 20 bar, add to it the differential pressure of the pump. You will get the working pressure of the pump. This working pressure should be less than the allowable maximum pressure of the pump.

2. If you are getting the required pressure at the top then there is no need to add suction pump at the top. However, if you add a Suction Pump at the top then the main pump (inside of a hull) will require slightly less power but the added power of the Suction Pump will increase the Total power consumed (i.e. Power of Suction Pump + Power of Main Pump inside the Hull).
02-26-2014 03:32 AM
Top #9
the answer to your question is yes, the pump will require more power to overcome the losses in the discharge pipe and less power if moved to the surface, but considering the following points:
1- the water level is relatively constant with reference to the new installation point (Maximum level difference between water surface and the pump impeller eye level should be 6 to 7 m approx. )and, 2- the inlet opening is moved upwards within the water bulk to a level below the surface of water (reduce the suction pipe length)

I believe that the initial installation depth of the pump (200 m) has a reason, and most probably it is the variation of the water level upstream the pump or any other operational reason; In such a case, the inlet pressure is not as mentioned (20 bars) and you can not install the pump above the ground.
If you can provide more data on the application we can provide a more precise answer.
02-26-2014 06:25 AM
Top #10
Under big inlet pressure one can apply a higher speed pump, and higher specific speed will add to the efficiency under the same flow rate and head. Thus the break power will reduce.
02-26-2014 08:50 AM
Top #11
I think this is a simple question. Without going into complexities, I will say that you won't be able to pump water assuming LWL post drawdown from 200 mtrs with a centrifugal pump and I doubt that other pumps will suit your purpose. But lets assume that you have a pump at the surface which pumps up water from 200 mtrs suction lift and then pumps up the water to elevation x mtrs . as the diffeentialhead is the same, power required will be more or less equal (Piping friction losses will be present in both cases). This system will not be a very reliable one as vaccum does not get along well with nature. Something or the other will always spell trouble.
Have you considered two stage pumping i.e. a submersible pump at the bottom and a horizontal pump at the top. The horizontal pumps c/l should be well below the submersible pump discharge point thereby making priming of the horizontal pump redundant. You will require an ESR (elevated service reservoir) so capital costs may be a little high but the system will save a lot more in maintenence alone.