# Npsh problem

1. Sep 6, 2009

### pray4mojo

At an oil refinery, a mobile centrifugal pump is used to pump warm crude oil from a storage tank. Liquid level in tank at elevation of 3 metres above pump. Suction side of pump is fed with a flexible hose that is 10 metres long.
Crude oil density: 846 kg/m3
Crude flow 4000 kg/h
Internal diameter of flexible hose: 50mm
Vapor Pressure of crude oil: 0.0654 bar (a)
Friction head in suction line: 1.2 m

NPSA Available = [P(atm) - Pv] / [density * grav] + hs - hf

[where u = Q/pi*r^2]

I have plugged in my values into the two above equations to find out NPSHa and Velocity head.
However, the 10m value that is mentioned for the flexible hose i did not plug in.Does this 10m value need to be used in the solution or is it just for the purpose of a sketch?
My solution is attached, any help will be kindly appreciated.
Thanks,
Mojo

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2. Sep 7, 2009

### FredGarvin

Re: Npsh

Think about a term for the friction in the inlet piping...You already show the term for it.

3. Sep 7, 2009

### pray4mojo

Re: Npsh

So the Head loss in the suction line will be the frictional head loss which is the 1.2m value given in the question..

Also The formula is H(v) = u^2/2g
[where u = Q/pi*r^2]

Therefore when calculating Q, i must divide by 3600 and also multiply by radius squared and Pi and After converting Q to m3/s,

4. Sep 8, 2009

### FredGarvin

Re: Npsh

Your NPSHa looks good. I get .022 for the velocity head though.

5. Sep 8, 2009

### pray4mojo

Re: Npsh

Thanks Fred,

I reworked my solution to the velocity head and got an answer of 0.02281m also..

Converting my u value to m3/hr involved 4000/846 then multiplying by 3600 and the area