4 replies to this topic

[ayan_dg]

Why pump discharge line size is kept one standard size smaller than pump suction line ? If it is equal what's the problem ?

[Art Montemayor]

Ayan:

You are looking at the pump dimensions backwards. Try looking at them with the argument: "The pump SUCTION line size is kept one standard size larger than the pump DISHARGE line in order to avoid suction NPSH and suction problems. There is no problem."

This response is analagous to the ancient saying, "The glass is not half-empty; it is half-full". Besides, there is nothing that anyone outside the pump manufacturers can do about it. Until we all start to fabricate our own pumps, there is nothing that will be done about this pump feature.

[djack77494]

You are looking at the pump dimensions backwards. Try looking at them with the argument: "The pump SUCTION line size is kept one standard size larger than the pump DISHARGE line in order to avoid suction NPSH and suction problems.

Expanding on Art's input slightly, the criteria for sizing pump suction lines is always more conservative, in terms of lesser acceptable velocities and pressure drops, than those of pump discharge lines. Pump suctions can be particular, wanting well developed flow and pressures well in excess of the liquid's vapor pressure. The discharges seem to be more forgiving.

May your glass be more than half full,
Doug

[Zauberberg]

Look at NORSOK standard, page 17-19 (it is also availiable online, but I can't remember where) and things will be more clear. In the case that excellent replies from Doug and Mr Montemayor didn't make you feel confident enough.

[attachment=834:NORSOK_P...s_Design.pdf]

Best regards,

[ayan_dg]

Thanks all for your valuable inputs.