High suction pressure application and low NPSHA

[trustmeok]

Hi, would appreciate any thoughts for a pump to handle the following duty - initial thoughts are a VS6 can pump due to the low NPSHA however the very high suction pressure is a concern from some pump suppliers that I have discussed application:-

Duty:-
Liquid: NGL (1 duty 1 on standby)
Design code: API 610 10th Edition
Flow rate: 40m3/hr
Suction pressure: 56.87 barg
Discharge pressure: 60.17 barg
Differential head: 65.2m
SG: 0.513
Vapour pressure: 57.87 bara
Pumping temp: 27 Deg C

316L SS construction (A-8)
Dual pressurised seals C2A3A0253B
Power supply 415/3/50

Thanks,

 

[BigInch]

Do you mean some mfgrs or all have expressed concern? It does seem to be a high pressure for a can. Those are usually for relatively light pressure loadings. Nowhere near 50B.

What about a rotary vane pump?

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[trustmeok]

BigInch,

The concern on high pressure came from one major supplier - Flowserve pumps, their product range is fairly extensive so I guess other manufacturers may have the same issue.

With an NPSHA of 0.34m is the rotary vane pump suitable? the reason for the VS6 selection was to increase the NPSHA with the can length.

The pump duty is liquid dehydration feed pump.

 

[BigInch]

I don't know how low they can go, but they are used a lot for pumping from LPG tanks at high vapor pressures. I think that's your main problem, correct?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[trustmeok]

Yes the NGL has a high VP hence hence the NPSHA being so low. Elevation of separator for the liquid source to the pumps is at 2.07 m above grade. My thoughts were to specifiy a canned pump to provide the required NPSHA for the pump.

Rotary pumps being positive displacement would assume design code to API 676, if you have any recommended manufacturers I would be interested to contact and review NPSHR for this design of pump - my gut feel is that NPHSR will be the issue in specifying this design.

 

[BigInch]

I've only speced vane pumps with much smaller capacity, so I don't personally know mfgr's with models in that size range.

NPSHR is always a bite on the * when there's high VP.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[trustmeok]

OK thanks for your input - I have subsequently found the original data from Flowserve at the FEED stage where they provided preliminary pump curve and data sheet detailing a suction pressure inline with the duty based on a WUC VS6 pump - So I am now asking them to look again at their design possibly bigger bearings and shaft etc, if they now believe this is to a problem as we move into more detail design work.