Pump selection

[tribleprince]

i have a tank of 550m3 volume and i want to fill this with water. how can i select a suitable pump.

i did some working on it. i determined its flowrate. i supposed that time required to fill this tank is 10hours, so i got pump flowrate. how can i determine its inlet and outlet dia (flange inner dia). is there any need to consult any pump catalogue and select my suitable pump (as per my requirements). then according to this pump i select my piping.

Please guide me.
thanks

 

[macmet]

You should contact a couple pump suppliers in your area and ask for quotes. Provide fluid media and temp, flow rate, head and anything else you think they may need for the pump (voltage?).

Then compare the quotes you get for performance, delivery and price.

 

[dabluffrat]

no need to consult pump catalogue or pump suppliers without knowing the required pressure. Size your pipe dia based on desired flow rate, smaller dia pipe is cheaper. Then calculate the pressure drop for that given pipe dia (system pressure) from your tank inlet to the source accounting for losses through the pipe and changes in elevation. If this pressure is too high, size a larger pipe dia.



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[tribleprince]

thanks dabluffrat
how can i calculate pipe size, i have only one input and that is volume flowrate, but i dont have the velocity. please guide me if u have any solution or formula.

actually tank is 25m high and having a dia of 5.5m. i want to fill the tank from the bottom. so its mean it has a head of 25m and the pump should have to supply water at that pressure head.
the tank is open to atmosphere. i want to calculate the NPSHa too. how can i determine the tank pressure or i should take the absolute pressure same as atmosphere during calculating NPSHa.

thanks

 

[TenPenny]

Where is the water coming from, that you are going to fill the tank with?

Where will the pump be located? What material will the pipe be made from?

 

[tribleprince]

water will come from an other tank and pump will be located at the same level of the bottom of the tank(to be filled).
pie material will be of CS or may be MS.

 

[JoeySoap]

If you want to use a centrifugal pump and have a constant rate of tank fill from empty to full, then you need to fill from the top. This is because the flow rate delivered from a centrifugal pump will vary depending on whether the tank is empty, half full, nearly full or somewhere in between when filled from the bottom. Aim for a velocity of 2.5 to 3 metres per second in the filling pipe. HTH.

 

[Artisi]

Re JoeySoap's comment - likewise if the level in the source tank is not constant then the flowrate from the pump will vary.

 

[TenPenny]

For that flow rate, probably a 100mm pipe makes sense.

 

[dabluffrat]

You want to maintain a fluid velocity in the pipe around 3-5 m/s. Use your Flowrate, Q, and select various pipe diameters. Calculate area, A, and solve for velocity, V.

Q = VA

If the tank is open to atmosphere then you have approx 14.7 psia. This equates to roughly 34 ft (14.7 x 2.31) available being open to atm.

NPSHa = Ha - Hvpa + Hst - Hfs

Ha = Head being open to atm (34 ft)
Hvpa = Head in ft corresponding to the vapor pressure of the fluid
Hst = Static height in ft that the liquid supply level is above or below relative to the pump CL or impeller CL (depends on type of pump)
Hfs = All line losses (friction loss and velocity head loss) up to the suction flange of the pump.

Good link

http://www.eng-tips.com/viewthread.cfm?qid=30500

Did you know that 76.4% of all statistics are made up...

 

[dabluffrat]

Forgot to ask, why do you want to fill the tank from the bottom?? fill it from the top, much easier and will require less power ($$$)... also, have you considered what's going to happen when the tank is full? do you have level switches in the tank to kill the pump?

Did you know that 76.4% of all statistics are made up...

 

[tribleprince]

thnks dabluffrat

i want to fill the tank from bottom because, i want to empty the tank to the same tank from i will pump the water, you can say both tanks will interchange the water.
for this purpose can i use one pump?. by using piping arrangements but the pump suction and discharge will remain same only bypass piping will be made


thnks

 

[Artisi]

There is no reason why the pump cannot be connected to both tanks via a pipe and valve system on both the inlet and discharge side.

 

[wimple]

The diameter of pumps In/Out flanges, should also be different from that of the pipe, because you need normally put a convergent/divergent respectively in/out of pump

 

[JohnGP]

tribleprince,

With discharge into the bottom of the tanks you may need to include a flow control valve in the system to take account of the change in pumping conditions as the levels change in the two tanks. You start with a high suction head/ low delivery head, and progress to a low suction head/high delivery head situation. (Gravity flow should even work for a while.) With a flow control valve, the pump won't have to be capable of such a wide flow capability.

But here's me thinking centrifugal pump - maybe a positive displacement pump would be a better choice, with motor selection based on the maximum differential head?