4 replies to this topic

[tham_selva]

Dear all,

We need to pump methanol solvent from a distillation tank under vacuum to a storage tank which cannot be vacuumised. Problem is that we cannot increase the suction head by lowering the pump of raising the tank. Is it possible by any other means ? If centrifugal pump is not possible what are the other options available. Kindly help me out.

Thanks in advance.

- Selvan

[JoeWong]

Sometime Barrel pump and Progressive cavity Pump are used when we have NPSH problem. For your case, may check but the success application would be low...

[Prajapati]

You can use low NPSH PUMP

[djack77494]

Selvan
There is a wide variety of centrifugal pumps. I'm sure several models could meet your needs. You must be mindful of the NPSH you have available, and ensure that it exceeds the NPSH required by the specific pump you select. Of course, both will vary as the flowrate through the pump varies, so use the maximum expected flowrate to be conservative.

The only thing you can do to control the NPSH required, is done during the pump selection phase. Once you have your pump, that part is done. You can increase the NPSH available by reducing hydraulic losses en route to the pump, by increasing the static head (say by raising the low liquid level in the tank), by increasing the pressure, or by reducing the fluid's temperature. Undoubtedly, some of these variables will be fixed, so your options will be more limited.

If you need additional assistance, you will need to supply more specifics for your situation.
Doug

[Zauberberg]

If pumped liquid is at its boiling (or bubble) point, one possible option for increasing NPSH available is to employ heat exchanger for liquid subcooling upstream of the pump. A careful analysis has to be carried out for comparing benefitial vapor pressure reduction VS fluid pressure drop across heat exchanger. For heavy fouling applications this is certainly not the right solution.

Regards,