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centrifugal pump selection

07/23/2008 1:35 PM

how can i select centrifugal pump and calculate capacity and head requirement of pump or any other parameters.

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#1

Re: centrifugal pump selection

07/23/2008 1:41 PM

Contact the pump manufacturers, they would have pump curves. (just a chart)

The pump curves are based on using water @ 70%. And other type of media, may have to contact the manufacturer.

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#2
In reply to #1

Re: centrifugal pump selection

07/23/2008 2:10 PM

like to add the other information these pump curves tells you, is horsepower, RPM, NSPH, volume, and pressure.

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#3
In reply to #2

Re: centrifugal pump selection

07/23/2008 2:25 PM

But main parameters like capacity and head and flow how can i decide

r u there on net can we chat my id is sandeepplokhande@yahoo.com

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#9
In reply to #3

Re: centrifugal pump selection

07/24/2008 8:59 AM
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#4

Re: centrifugal pump selection

07/23/2008 3:20 PM

Calculation of flow

The flow is mostly a matter of choice.

For example Discharge per emitter x number of emitters.

The water supply to a household will change with number of people and with standard of living.

Total head.

Discharge pressure + static head + Friction losses.

With Q and H known one can proceed with choosing pump, driver etc.

You need to supply more detail for CR4 to be of any assistance.

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#5
In reply to #4

Re: centrifugal pump selection

07/23/2008 3:57 PM

still i m not convince let me give u one example

total pipe length 60 mtrs

no of bends 6

no of valves 2

height 15 mtrs

how can i calculate head requirement

how can i calculate friction losses

discharge pressure it the pressure requrement for system and static head is highest point of system

please let me know

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#6
In reply to #5

Re: centrifugal pump selection

07/23/2008 4:26 PM

hers a link for calc. hear - pressure.

as far as pd due to pipe length with type of pipe or tube or what.

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#8
In reply to #5

Re: centrifugal pump selection

07/24/2008 8:03 AM

Hi Sanddeep,

Total head of a Pump =( Zd-Zs)+(Pd-Ps)/ρg+(V²d-V²s)/2g

Where:

1st term=differance between delivery and suction branches.

2nd term=difference in pressure heads between delivery and suction branches.

3rd term=difference of velosity heads between delivery and suction branches.

ρ=fluid density,

g=gravitational acceleration.

Take care of the units system that you will follow.

To calculate the friction losses,you refer to tables in any pump hand book.For each type of valve you are using there is a loss in meters(meters of pressure head not unit of length).You have to know the pipe inner diameter and material to be able to know the losses from the table.

Regards

Sayed Sarhan

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#7

Re: centrifugal pump selection

07/24/2008 12:45 AM

I was gone for my beauty sleep and my time is limited today.

A quick fix would be to go to your pipe supplier and get

friction curves or tables and equivalent length of fittings,

They may also be able to help you with the required flow and discharge pressure.

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#10

Re: centrifugal pump selection

07/24/2008 8:59 AM

To calculate the flow and head requirements of a centrifugal pump, you must first develop a system head curve. To do this, you need to use a table of friction losses in the type of pipe you are using. These tables are created from a formula called the Hazen & Williams formula. They have a table showing the values for each type of pipe. The tables show the head loss per 100' of pipe and they are available in many pump manufacturers' catalogs. Probably also can get them on line somewhere.

Having gotten a copy of the appropriate tables, you will see that they are shown for various flows. Take a sheet of paper and write down the flows in a column on the left side of the paper. Take the total length of the pipe in hundreds and multiply that by the value given for each of the flows you have listed. Put those numbers in the next column. Then you must know the static head (eleveation difference between the start and the end of the pipe). Add that number to the friction loss calculated for each flow listed. The result is the total dynamic head (TDH) of the system at the given flows.

Now you must determine the flow you need. This you will determine for your application. Let's say you need a flow of 150 GPM. You will look at the chart you have developed and pick a flow near to or at 150 GPM and see what TDH you have listed for that flow. For example, let's take 45' of TDH. Your conditions, then, would be 150 GPM @ 45' TDH. That is what you will look for when selecting your pump.

Now, you choose a pump that has that condition point in a good location on its curves. You will take the pump curve and plot the numbers in your chart for the various flows on that pump curve. Then you will connect these points to reveal a curve. Where your system head curve crosses the pump characteristic curve is the delivery point. The pump curve will show various impeller diameters or it may show various speeds or both. The system head curve will cross each of these curves and each crossing is a delivery point for that curve.

Now, there are various other considerations that you may want to discuss. Some of those are the bends and fittings in the line, as those will exert some friction losses on the system; the type of pump you need, such as solids handing pumps, grinder pumps, high head pumps, and any number of other specialties. These are all concerns that you may wish to address.

And, of course, since you have asked your question in this forum, I will tell you how I would advise anyone who would asked me the same question, "Get an engineer."

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