PUMP SUCTION WITHOUT REDUCER
PUMP SUCTION WITHOUT REDUCER
(OP)
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.
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.





RE: PUMP SUCTION WITHOUT REDUCER
Please don't use CAPITALS - it's regarded as SHOUTING - and please don't double post
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: PUMP SUCTION WITHOUT REDUCER
You do not use a reducer in a pump suction (or any other line) because it is a mandatory requirement to have a reducer, you only use a reducer when there is a change in the line size.
Don't over think it!
prognosis: Lead or Lag
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
Why not? Almost every pump i've come across has suction reducers.
RE: PUMP SUCTION WITHOUT REDUCER
You wrote:
"Why not? Almost every pump i've come across has suction reducers."
Yes but ONLY because there was a change in pipe size.
prognosis: Lead or Lag
RE: PUMP SUCTION WITHOUT REDUCER
Vertical can pumps are not at all sensitive to suction line conditions, provided the pressure drop is not severe enough to reduce the NPSHA beyond what was specified to the pump manufacturer. Maybe if the barrel is extremely short it could be an issue, in that case there should be plenty of NPSHA and a vertical pump might not be the best choice.
The typical rules for straight pipe length of X diameters, no elbows directly before the flange, etc. have no effect (it is negligible) because the fluid falls down into the barrel and stabilizes before entering the impeller.
Much different for a horizontal pump, where the suction piping will affect the fluid conditions entering the impeller.
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
"The reducer on the inlet side of a pump ensures that the velocity of liquid in the suction line is slowed sufficiently to provide a smooth flow of liquid with minimized friction losses in the line to ensure as high as possible an NPSH available from the system.
The increaser on the discharge side of the pump is designed to increase the pipe diameter from the pump nozzle to reduce the velocity of the liquid in the discharge line in order to reduce the total head the pump is required to develop to operate the system."
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
The pipe sizes are different for a reason. Sometimes the reason is general best practice, and doesn't matter on a specific installation.
You can blindly follow best practices (nothing wrong with that) or you can ask why, but you can't always do both at the same time.
RE: PUMP SUCTION WITHOUT REDUCER
And also i discussed with my process and machinery department,
suction line size 6" according to process requirement. and Suction nozzle size 6" according to pump vendor requirement.
So, Reducer is not required. hence both size are same (i.e reducer is not mandatory at Suction side)
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
You wrote:"I am far from a pump expert, but I thought generally the discharged suction connection was one size larger than the line to reduce the velocity of the fluid through the pump. Is that not the case?"
You might want to do a little homework studying piping systems and process equipment.
a/ there is no such thing as "discharged suction connection" There is a pump suction nozzle which is sometimes referred to as the pump inlet. There is also a pump discharge nozzle sometimes referred to as the pump outlet nozzle.
b/ "connection was one size larger than the line to reduce the velocity of the fluid through the pump." I have lot worked on every pump system in the world but in my 45 years of actively working in the process plant engineering and design profession I have never come across a situation where the "connection was one size larger than the line to reduce the velocity of the fluid through the pump." I just did not happen.
What ever you read or heard someone say, it was wrong or you misunderstood it completely.
prognosis: Lead or Lag
RE: PUMP SUCTION WITHOUT REDUCER
All it need is common sense. The piping size are determine by the limit of flow velocity through it as the losses is proportional to the velocity ^2.
Therefore for a given flow rate, the larger pipe dia. = lower velocity = lower friction losses = lower required pump diff. head= lower running cost. For the suction pipe size, NPSHA will be a major factor. For the discharge piping sizing, a balance has to be made between capital cost and running cost.
When the piping engineer decided on the pipe sizes, he probably have no idea of the pump suction and discharge size.
And very often, the pump nozzle sizes varies with different pump makes even for the same flow and head.
Some pump configuration can allow the suction / discharge nozzles be custom made to suit the piping size to avoid the use of reducer /enlarger. Provided it does not affect the pump performance.
RE: PUMP SUCTION WITHOUT REDUCER
It's physically impossible for a change in line size to make any difference to the velocity of the fluid through the pump, if the pump and flow rate stay the same.
RE: PUMP SUCTION WITHOUT REDUCER
• misalignment between the suction nozzle and the suction pipe,
• a gasket located eccentrically in relation to the bore of the suction flange,
• or when the gasket projects into the suction line by being too small; to avoid such a situation the gasket bore should be at least 1/4 in. larger than the ID of the suction pipe.
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
"Rules of Thumb and Myths?
The suction line size should always be one size larger than the pump suction connection size.
While this certainly insures a lower mean fluid velocity, it is contrary to the rule which promotes that pipe
fittings should be eliminated (or at less minimized) in pump suction lines. A line size larger than the
provided pump connection size necessitates the incorporation of a reducer at some juncture. Maybe a
better rule of thumb would be that the suction line size should never be smaller that the pump suction
connection size."
Link
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
Maybe it is time to say enough is enough.
prognosis: Lead or Lag
RE: PUMP SUCTION WITHOUT REDUCER
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.
RE: PUMP SUCTION WITHOUT REDUCER
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
RE: PUMP SUCTION WITHOUT REDUCER
RE: PUMP SUCTION WITHOUT REDUCER
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.)
RE: PUMP SUCTION WITHOUT REDUCER
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.