Length of straight pipe before the suction of pump
Length of straight pipe before the suction of pump
(OP)
Hi all-
Can anyone advise on what the required length of straight pipe before inlet of centrifugal pump is.
Any link where I can look into for quidelines?
Thanks All
Can anyone advise on what the required length of straight pipe before inlet of centrifugal pump is.
Any link where I can look into for quidelines?
Thanks All





RE: Length of straight pipe before the suction of pump
You really need to qualify your question a little more.
Is this a Centrifugal Pump or a Positive Displacement (PD) Pump?
If Centrifugal pump/base plate mounted/horizontal shaft what is the Suction/Discharge nozzle configuration (Top/Top, End/Top, Side/Side)?
If Centrifugal pump is it a Vertical "Inline" pump?
If PD pump what type (Piston, Gear, Diaphram, other)?
What is the suction nozzle size?
What is the suction line size?
RE: Length of straight pipe before the suction of pump
Johnny Pellin
RE: Length of straight pipe before the suction of pump
RE: Length of straight pipe before the suction of pump
Let your acquaintances be many, but your advisors one in a thousand' ... Book of Ecclesiasticus
RE: Length of straight pipe before the suction of pump
RE: Length of straight pipe before the suction of pump
A minimum of 5 pipe diameters is normally sufficient unless the flow is extremely disturbed prior to this point.
johhny's advice re double suction pumps is extremely important "it is especially important for pumps with double suction impellers that to avoid elbows that turn the pipe parallel to the pump shaft. This can result in uneven flow to the two impeller eyes."
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: Length of straight pipe before the suction of pump
Since my application didn't have the luxury of the required or actually ANY upstream straight length, I piped the inlet from above with a vertical reducing elbow into the suction of the pump perpendicular to the pump shaft centerline.
rmw
RE: Length of straight pipe before the suction of pump
The "Pump Handbook" discusses recommended suction piping schemes.
Suction pipe diameter should be one nominal pipe size greater than the suction nozzle size. An eccentric reducer can be mounted on the pump suction
RE: Length of straight pipe before the suction of pump
htt
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Length of straight pipe before the suction of pump
RE: Length of straight pipe before the suction of pump
http:/
RE: Length of straight pipe before the suction of pump
Regarding Johnny's comment re HSC pumps and bends etc, I was just re-confirming an important point.
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: Length of straight pipe before the suction of pump
I have over 40 years in lots of Industries that use lots of pumps and even some time within the pump industry. Likewise, I have never been involved with a pump that had a suction diffuser on it although I have seen a few in very light what I would call commercial applications - building water systems, hospital boiler rooms, etc.
It is not something that comes to my mind when faced with a pump suction problem.
rmw
RE: Length of straight pipe before the suction of pump
RE: Length of straight pipe before the suction of pump
How is this such a rare sight?? Do you all deal with END SUCTION pumps often?
RE: Length of straight pipe before the suction of pump
What is your definition of "industrial"?
rmw
RE: Length of straight pipe before the suction of pump
End suction pumps are very common in all industries.
Municipal tends to use horizontal split case running at 4 pole motor speed because of a historical view tha slow running pumps cost less to maintain because they last longer.
If a full cost benefit analysis is performed it may work out that a 2 pole speed pump, with its smaller frame (& components) works out to have a lower total life cycle cost. Also need to take into account the real estate used for the larger frame size pumps, buildings, aircon, VSDs, cable and pipe lengths etc not just the prime cost of the pumps.
Spares for a smaller frame pump are cheaper than a larger frame pump.
Before posters jump on what I have said I repeat "may be". The calculations need to be done.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Length of straight pipe before the suction of pump
MechEngNCPE, still haven't convinced me or others by the look of it on the use of suction diffusers. Bear in mind there are probably millions of HSC pumps throughtout the world of which I have seem a very small proportion, none of which were fitted with suction diffusers and in some case with pretty poor inlet conditions and operating fairly well.
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: Length of straight pipe before the suction of pump
Lord Kelvin
Do or measure the numbers whether it be life cycle costing or the design of suction conditions!
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Length of straight pipe before the suction of pump
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: Length of straight pipe before the suction of pump
To me Industrial is Pulp & Paper, Chemical, Metallurgical, Refining and Petrochemical, etc.
Commercial is more like buildings and light manufacturing, laundrys and the like.
Municipal is kind of in a world all of its own with other governmental entities.
When I worked for a British company, their use of the word "industrial" meant what "electric utility" does in the states.
In what I define as Industrial, I have never seen the use of suction difussers. And I would add to that that I have never seen them in Electric Utility applications as well. I have, however seen them in building systems and municipal applications and maybe the occasional steam laundry.
rmw
RE: Length of straight pipe before the suction of pump
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: Length of straight pipe before the suction of pump
Suction diffusers are handy when one can not meet the recommended pipe diameter and straight run before suction end mating. However as another poster stated Diameter is as important if not more important then straight pipe length. Industry norm depends completely on the industry. Having seen many things some of them very unusual yet they worked. In Power Generation we like 5 times the diameter for straight run and one and half times suction for diameter with an eccentric reduction.
All of this can be found in the various handbooks and lets not forget that all of this is a moot point if NPSH is not met.
RE: Length of straight pipe before the suction of pump
Worth your first star.
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: Length of straight pipe before the suction of pump
rmw
RE: Length of straight pipe before the suction of pump
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: Length of straight pipe before the suction of pump
Sometimes one really wonders what someone was or was not thinking.
Spud says; Meticulous effort and willingness to learn are honorable traits.
RE: Length of straight pipe before the suction of pump
In respect of suction design instead of just using Sank's Pumping Station Design, ANSI/HI 9.8 or the US Army references on the subject engineers try and think of ways of designing pump suctions. If only they stopped "thinking" and tried ways that have worked for decades the problems would not arise.
I have seen many a pump design modelled using FEA only to see the same solution that would have taken 5 minutes of reading.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Length of straight pipe before the suction of pump
I would suggest that pumps that have been oversized by "others" normally run to the left of BEP as a result of being throttle back to reduce flow to the real system neeeds. Further, being oversized also impacts on pipeline sizes, motor sizes etc.
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: Length of straight pipe before the suction of pump
Spud says; Meticulous effort and willingness to learn are honorable traits.
RE: Length of straight pipe before the suction of pump
And I have been a victim of it, and have been guilty of deliberately undersizing equipment, pumps included, because I knew that some anal superior was going to brainlessly add his/her "fat" no matter what was done in the initial sizing.
The bad scenario is when there are several steps up the approval ladder and everyone up the ladder adds some "fat" because they don't have the ability to think through what the engineer has (or has not) done with respect to doing their job and sizing the pump correctly in the first place. Because of this fubar, as an example, while not a pump per se but closely related, I have seen actuators with 3" output shafts coupled to driven devices with 1" input shafts. There is a mismatch. Someone added too much fat somewhere and I hold that that is brainless.
rmw
RE: Length of straight pipe before the suction of pump