Booster Station Design

[formoreinfo]

I am a new graduated mechanical Engineer , I have been assigned to do a design for a well facility with a booster station. The well capacity is 250m3/hr , a submersible pump will be used to pump water from the well to 2000m3 balancing tank.after the balancing tank need to supply three areas , the first area need 150m3/hr at 22 bar , the second area need 50 m3/hr at 16 bar , and the third area need 50m3/hr at 10 bar. My question is related to the design of the booster pumps that need to be installed to take water from the tank to the three areas. the first two areas are connected to the same transmission pipeline , the third area is isolated with different pipeline from the first two areas , My question : can I pump water for the first two araes with the same pump , or it is recommended to use two different pumps after isolating both lines ?

 

[Artisi]

The head pressures of 22, 16 and 10, are these the head pressures at the pump station or at the distribution points?

 

[formoreinfo]

22,16, and 10 are the head pressure at the pump station . this difference between them is due to the static head (elevation) of the reservoirs for each area that we will pump for.

 

[itsmoked]

It is sounding to me like you should have separate pumps so one pump failure doesn't take down two thirds of your reservoirs.

Furthermore with reservoirs you will have the problem of one of the reservoirs becoming full and the other still needing supply and a pump sized for both.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Artisi]

You need to explain the pipeline configuration for the first 2 units and include the friction heads so that the interaction of the higher head requirement can be looked at in relation to the lower head requirement.

However, itsmoked has given good advice - seperate pumps on seperate pipelines - simple and a lot less trouble

 

[BRIS]

You need to provide more detail - you say you are supplying 3 areas and imply that the supply to each area is directly into the distribution system not into tanks.

If you supply from a single pump station then the pump duty point will need to be 250 m3/hr at 22 bar and you will have excess pressure in your two lower systems. If this is a problem you need to add pressure regulators.

 

[formoreinfo]

BRIS ,

MY concern about the firet two reas : 150m3/hr at 22 bar AND 50 m3/hr at 16 bar . THE WATER WILL BE PUMPED THROUGH ATRANSMISSION PIPELINE FOR BOTH AREAS RESERVOIR.I KNOW IT IS BETTER TO HAVE TWO DIFFERENT TYPE OF PUMPS WITH TWO LINES , BUT IN CASE I WILL RUN THE SYSTEM WITH THE MAXIMUM CAPACITY PUMP (150m3/hr at 22 bar) , ALL WHAT I NEED TO DO IS TO INSTALL PRESSURE REGULATOR ?

 

[BRIS]

You are pumping to reservoirs not directly into distribution?

It is a fact of life that when you have two or more reservoirs on a system one will stay full and the others empty.

The total flow you have is 250 m3/hour and the maximum dynamic head is 22 bar. That will be your pump duty point. The problem is that if you run at that because you have excess head in the lower reservoirs you will get more flow into these and less in to the top reservoir. Your pump will operate to the right of the duty point (producing more flow at less head). This will happen until the two lower reservoirs are full and close off their inlet control valves. Thereafter all the flow goes to the top reservoir and your pump will operate to the left of the duty point producing higher head and les flow (e.g you could be pumping say 200 m3/hour to the top reservoir at 25 bar - the higher head being lost in friction at the higher flow) and nothing to the other two which are full). On average over a 24 hour period you may get distribution you intended. You would need to draw system curves for each possible operating scenario (flow to all three, flow to 1 and 2 flow to 2 and 3 flow to 1 and 3)

Alternatively you can try and control the flow distribution

1) The simplest solution would be to put orifice plates into the pipelines into the lower reservoirs. Your duty point is 22 bar so you would need orifice plates to lose 22 - 16 = 4 bar to area 2 and 22-10 =12 bar to area 3.
2) Same thing but more accurate and expensive would to provide pressure control or flow control valves to areas 2 and 3.

My solution would be to provide no control and ensure that the pump remains within its duty range when operating under any of the scenarios described above. If need be I would make final adjustments once in operation by adding orifice plates.

The decision between using one pump or separate pumps should be based on costs. Capital costs of 3 pumps are higher but operating costs are less. (With 3 pumps you are pumping only the head that you want for each area whereas with one pump you are having to lose the excess pumping head to the two lower areas)

 

[itsmoked]

Nice synopsis BRIS.

I would add that redundancy may actually be more important than just costs.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Artisi]

From Bris - "The decision between using one pump or separate pumps should be based on costs. Capital costs of 3 pumps are higher but operating costs are less. (With 3 pumps you are pumping only the head that you want for each area whereas with one pump you are having to lose the excess pumping head to the two lower areas)"

A capital / running cost analysis should be one of the first things to do when looking at a pumping project like this, the power costs for running inefficient units resulting from throttling, oriface plates, control valves plus the costs of the control devices etc etc are huge and can far exceed the capital costs of carefully selected single units in very short order.

 

[BigInch]

If you are interested in the case of one pump at maximum pressure you could conceivably regulate flows to all locations off of a single discharge. That method might be attractive, if the highest, or higher pressure subsystems had proportionally the largest flowrates and required the longest relative operation times.

Perhaps reliability and ease of operation or increased functionality could be gained or improved with multiple units too, but 3X the space, 3X the maintenance costs, etc. can offset energy consumption for a considerable length of time, especially if the energy losses can be minimized in any alternative requiring fewer pumps.

http://virtualpipeline.spaces.msn.com

 

[formoreinfo]

Thanks alot for all your inputs

 

[Artisi]

At the moment I think we are all talking in general terms as there appears to be data to which we are not aware. Lengths of pipe run to each of the "areas", pipe diameters, duty cycle for each area etc etc. So I guess we all have a different focus in trying to make some sense from it while not being fully informed.
But this seems fairly normal for a lot of questions raised in this forum and the discussions certainly raise many and various approaches of which many are very informative and interesting.

 

[BRIS]

I agree with the points made by Artisi - running costs and the environmental impacts of inefficient operation need to be assessed, but just to digress a little. Working in oil rich countries of the Middle East and North Africa, where energy costs are negligible, we cannot get our client's interested in operation, maintenance, running costs or global warming. As a result we have a lot of systems where pumping head is destroyed at reservoir inlets (good business for the control valve manufacturers). To improve efficiency we have proposed using pumps in reverse flow as turbines to recover some of the energy due to excess head at the reservoir inlets. We have one scheme that is going ahead.

 

[itsmoked]

Recover it how? For?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Artisi]

Running pumps in reverse as turbines to generate power is not new, especially in situations where there is the potential to recover energy as pointed out by BRIS - but as BRIS has raised the subject I leave it to BRIS to expand on this point.

 

[BigInch]

Bris, I've worked over 10 years in the Mideast where as you mention, economics is usually flipped upside down from the rest of the world. When diesel is cheaper than water, it has a lot of sometimes unexpected ripple down effects. Now imagine working for the state oil company. Besides the big pumps, high pressures, relatively tiny diameters for the flow and the fast velocities that always made for a nice surge system in a pipeline design, the guys would use diesel for washing our trucks! Diesel was 15 cents and water was around 60 a liter. Allowing water to run from a hose was almost a stoning offense, so you could only buy the carwash water supply by the 1 liter bottle. I still associate the smell of kerosene with going shopping on Thursday morning and coming back to a clean truck for the rest of the weekend.

I will make one comment in regard to running the pump's backwards, with the lack of maintenance that is endemic in the region, I would think you would only get 1/3 of the typically very short lifetime out of those pumps. And they probably won't wait for them to stop before flipping the switch to "forward".

http://virtualpipeline.spaces.msn.com