PUMP SUCTION WITHOUT REDUCER 3

[jsn1980]

VERTICAL LPG PUMP IS DESIGNED ACCORDING TO API 610 10TH EDITION

AS PER PUMP VENDOR DRAWING,
PUMP SUCTION NOZZLE SIZE 6", PUMP DISCHARGE NOZZLE SIZE 4"

AS PER P&ID
PUMP SUCTION LINE SIZE 6", PUMP DISCHARGE LINE SIZE 6"

IS POSSIBLE PIPING WORK CAN BE DONE WITHOUT REDUCER AT SUCTION NOZZLE ? (SINCE SUCTION NOZZLE SIZE AND SUCTION LINE SIZE ARE SAME)

IN MY EXPERIENCE PIPING LINE SIZE ALWAYS ONE SIZE GREATER THAN NOZZLE SIZE.

 

[pennpiper]

Well we certain have gotten a long distance away from jsn1980's original question.
Maybe it is time to say enough is enough.

prognosis: Lead or Lag

 

[macmet]

Pennpiper,

I feel you were unnecessary harsh about what should have been seen as a typo. Clearly any engineer would know that one connection cannot be a discharge and a suction at the same time and that there was a mistake there.

Like I said, I am not a pipe expert, I don't work with pumps, buy pumps, spec pumps... I was doing some additional reading on a topic I found interesting. I was trying to get clarification on what I was told once upon a time.

The senior engineers are often too quick to jump on the younger engineers on this site who are on this website trying to learn more about the profession.

 

[LittleInch]

macmet, What you may have understood was that - in general - the inlet nozzle of a pump is one size larger than the discharge nozzle, in part to reduce inlet losses into the pump and prevent cavitation. Some pumps are the same, but many follow this convention.

Although having a reducer into a pump is common, this does not turn it into a RULE. You design to your own specific requirements and if you don't need a reducer, use the smaller pipe - it and any flanges, valves etc will cost less than a bigger pipe if you don't need it.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[macmet]

Thanks LittleInch. That makes sense. I thought it might be related to cavitation.

 

[Artisi]

If everyone takes time to actually look at the majority of process pumps, you will notice that the inlet flange is (nearly always) of a larger diameter that the outlet flange. Ever wondered why, could it possibly be that the pump designer actually knows what he is doing and to reduce inlet losses, designs the pump with an optimised inlet flange size selected to match an inlet pipe which would results in acceptable velocity / head loss.
It also wouldn't hurt to also look at the impeller eye diameters on many of the process pumps where you find that the eye diameter is in many cases of a lesser diameter than the inlet flange / pipe diameter, again ever considered why the particular flange size was selected.

The only time that the inlet pipe needs increasing in diameter is a case of a long inlet line increasing the head loss to a point where NPSHa becomes a problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[DubMac]

I am sick and tired of these nasty disagreements among all of you who I deem "Forum Friends. Especially since you are all wrong.....

At least maybe thinking wrongly about the OP's service. Its a vertical pump, most likely a vertical "canned" pump with a fab steel discharge head. The suction inlet to the pump is not at the suction flange, it is well below that. One of the beauties of a vertical with a fabbed discharge head is the option for identical suction and discharge flanges; piper's dream. You don't have to upsize suction line to save NPSHA....just dig a deeper hole and lower the suction impeller.