5 replies to this topic

[process101]

Hello
Hope everyone is doing good.I read on this forum about the pump inlet size, that it is most of the time design one size bigger then outlet line. The reasons are to maintain well flow and to avoid suction pressure problems. But in some situation like reflux pump, inlet line is smaller then outlet line or some time both inlet and outlet lines are of same size.Can some explain this?

Thank you very much for your help in advance.

[Art Montemayor]

With few exceptions, every centrifugal pump has a suction nozzle size that is one size bigger than the discharge. This is then followed by the general habit of making the suction LINE (leading to the suction nozzle) one size bigger than the nozzle.

I have seen suction and discharge nozzles of the same size on a few pumps, but these are, I presume, special pumps and special cases. I have never seen a discharge nozzle bigger than a suction nozzle.

You talk about "lines", and you should be careful in understanding what you are writing or saying. The pump and its nozzles have nothing to do with or about the lines that are connected to it.

[djack77494]

But in some situation like reflux pump, inlet line is smaller then outlet line or some time both inlet and outlet lines are of same size.Can some explain this?

I can explain this-it is not true. Art has fully described the situation. I must say that in seeing hundreds of actual pumps and thousands of pump designs, I have NEVER seen a pump suction nozzle smaller than the pump discharge nozzle. I have also never seen a pump's suction line smaller than the pump's discharge line. I don't believe a pump exists with the former situation. If you ever find the latter situation you may be assured that the engineer/designer who came up with the design is not an experienced (or competent) engineer/designer. It's just that simple.

[process101]

Thank you very much for your help.
But One Question what do think when inlet line is of same as
Discharge line? Is that Possible? The one I have in P & ID is the reflux pump.The Inlet is of 1" but
then it is reduced to 3/4". The outlet 3/4" too and then expansion is used to increase the line up to 1".
Thank you very much for your help in advance

[Qalander (Chem)]

Dear,
May I humbally add that We find in smaller diameter pipelines occasionally similar conditions, which are throttled with downstream side globe and Control Valves. This definitely can not make a rule of thumb you should appreciate.

Best Regards
Qalander

[JoeWong]

Thank you very much for your help.
But One Question what do think when inlet line is of same as
Discharge line? Is that Possible? The one I have in P & ID is the reflux pump.The Inlet is of 1" but
then it is reduced to 3/4". The outlet 3/4" too and then expansion is used to increase the line up to 1".
Thank you very much for your help in advance

process101,

To answer your question, yes. the inlet nozzle can be same as outlet nozzle.