In the most of piping handbooks mention 5*OD at the suction of pumps. But I've never seen this for vertical in-line, BB4 and BB5 in several projects. I need a good reference for this issue.
"3.1.2.6 The pump suction line shall have a straight run (typically five diameters) between the suction flange and first elbow, tee, valve, reducer, permanent strainer, or other obstruction sufficient to ensure stable uniform flow at the pump suction nozzle.
Note: A piping straight run length of five pipe diameters, based on the pump suction nozzle size, is usually sufficient to ensure stable and uniform the pump suction nozzle. In some situations, the type and orientation valves and elbows in the pump suction line may affect the flow distribution to the impeller and necessitate a longer piping straight run length. Flow straighteners may also be utilized to reduce the piping straight run length."
The straight run length of five pipe diameters is usually sufficient to ensure stable and uniform flow at the pump suction. This piping arrangement results in fewer failures over the life of the pump due to vibrations caused by flow induced turbulence. The manufacturer of the pump should also be consulted for additional specific requirements for the particular pump.
Brad - you need to get a vendor installation guide to see what it says. Attached is a typical from flowserve - see section 4.5.2 Some pump types and inlet nozzle orientation means they are less sensitive to swirl and eddies than other pumps. I don't believe there is a general rule for some types of pumps and different ones for others.
If for some reason you don't have 5D, then flow straightness or smoothers can be used such as plates (look up "flow conditioning plates)
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Yes 5 -10 diameters for end suction pumps, horizontal split case are a different story and can have a bend mounted directly onto the inlet provided it is orientated correctly.
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, Do you have any reference for your statement about horizontal split case pumps?
The document Littleinch has attached was about horizontal split case pumps. It mentioned that this type of pumps need 5*OD straight run at suction. But it doesn't consider other type of pumps.
off hand no - or I should say can't put my hand to it. Will look for it and let you know unless someone else comes up with it in the meantime.
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.)
Offhand it often seems to be the pumps where the inlet nozzle is vertical which are not too bothered. It is as though the vendor accepts that no one wants a pipe stuck up in the air.
My view is that this requirement, apart form being a recognised good practice, is very vendor dependant. whilst the split casing pumps are less of an issue as the flow needs to turn a sharp 90 degrees inside the pump before entering the first impellor, I would always work on installing the straight length if you can or a flow conditioner if you can't.
If you don't do these relatively easy things and the pump doesn't work properly, the vendor just points to your piping and walks away chuckling to himself whilst the end client glares at you. 5D on most inlet piping really isn't that long in most cases.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
If I interpret the OP's post correctly, this is a vertical inline pump. I don't a picture of one handy but these pumps turn the flow 90 degrees IMMEDIATELY from suction flange to impeller suction. They are typically installed in the middle of straight runs of piping to conserve space (no foundation, motor sits on top of case) and many times have no support other than the piping flanges.
I don't have any supporting info handy, but would guess you'd never want to add to the extreme turbulence that the inherent design has to deal with as it is.
When referring to pipe diameter, the common nomenclature for pipe size is the pipe ID. My opinion is that the API recommendation is 5 (ID) pipe diameters of straight pipe as quoted above. Of course, this is the minimum.
The brochure from Flowserve for the BB5 has a few pictures showing the piping.
bimr (Civil/Environmental)
You wrote: "When referring to pipe diameter, the common nomenclature for pipe size is the pipe ID. My opinion is that the API recommendation is 5 (ID) pipe diameters of straight pipe as quoted above."
This statement is grossly incorrect. The proper Pipe size used when talking about piping is the 'Nominal Pipe Size" (NPS). The NPS for a given size is constant. The "ID" for a given NPS can be anywhere from 4 to 10 (or more) different sizes.
Sorry for the poor choice of words. Was just trying to note that the distance is 5 times the nominal pipe diameter instead of OD or ID for that matter.
.
BradSmith OP
This is from Aurora Pumps dated 7 March 2001.
"APPLICATION ENGINEERING NEWSLETTER
Long Radius Elbows on Split Case Pumps
Frequently we are fielding questions about pumping problems related to the installation of elbows on the suction of split case pumps. One consulting engineer inquired about the use of a long radius 90 degree elbows attached directly to the suction flange of a 411 horizontal split case pump. There is no objection to this, providing it is in a vertical position. "
Vertical can either be from above pump centreline or below - makes no difference.
The reason the bend / elbow can't be orientated parallel with the shaft is it could / will cause unbalanced flow into the double suction impeller.
If you are interested in more detail, suggest you do an internet search as there will be a lot more to see.
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.)
End suction centrifugal pumps with small diameter suctions (2" and smaller) can ignore that advice, reducing the required straight length. I can count the number of 2" pump suctions which had 10" or more of straight length upstream on perhaps one hand, and I've never seen one fail for reasons that could reasonably be attributed to that fact.
