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Length of straight pipe before the suction of pump 2
- Thread starter ciise
- Start date
ciise,
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?
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?
Our specifications require a straight run of at least 5 pipe diameters before the first elbow. We prefer to have 10 diameters of straight pipe when it is practical to do so. This is applied to all centrifugal pumps regardless of configuration. But, 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.
Johnny Pellin
Johnny Pellin
MechEngNCPE
Mechanical
Have at least 5 pipe diameters of strait pipe before the suction inlet. If it is an end suction centrifugal pump, then provide a suction diffuser. I assume you are talking about a horizontal split case?
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- #7
Suction diffuser - Why?
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.)
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.)
I had a recent design where a colleague suggested the use of a suction difusser for a horiz split case double suction pump. I checked it out out of respect for his position but couldn't find any benefit from it or any reason to use it. They seem to be very popular in commercial building pumping systems.
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
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
No one in this thread has yet mentioned recommended suction pipe diameter. Suction pipe size is also a factor affecting reliability.
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
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
The reference standard you could use is ANSI/HI 9.8.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
MechEngNCPE
Mechanical
Artisi, it is common practice in industrial pumping as well when you have END SUCTION centrifugal pumps - he did not specify what type of pump.
Some useful tips in the link below
MechEngNCPE, I would comment that in over 30 years in the pump industry I very once came across nor used a suction diffuser, not saying that there isn't a role for them in certain cases.
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.)
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.)
Artisi,
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
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
QualityTime
Civil/Environmental
I have seen many large municpal double suction pumps which have eccentric reducer followed by a downward elbow (or a reducing elbow) on the suction side of the pump and there are no problems. Very often the 5 or 10 pipe diameters cannot be met in the real world. The incoming piping, as stated above, should be perpendicular to the pump shaft.
MechEngNCPE
Mechanical
I have seen about 30 end suction pumps ranging from 5 to 100hp in industrial settings. I'm thinking condenser/chilled water, as well as heating hot water pumps. I prefer end suction over horizontal split case for the reasons given above. I do like Vertical split case pumps however, no need for suction diffuser there.
How is this such a rare sight?? Do you all deal with END SUCTION pumps often?
How is this such a rare sight?? Do you all deal with END SUCTION pumps often?
"Industrial" covers building services and manufacturing as opposed to mining, mineral processing, municipal, pharma, petrochem and nuclear.
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.
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.
stainer, I would tend to agree with you for building services and some areas of manufacture, however depends on what area of manufacture and on the application. I also think our 50 Hz environment influences the 2 pole argument to a great extent.
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.)
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.)
"In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be."
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.
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.
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