Piping Forces on Centrifugal Pump Connections
Piping Forces on Centrifugal Pump Connections
(OP)
What are allowable (or reasonable) axial, transverse horizontal and vertical loads imposed by the connected piping on a horizontal centriifugal overhung back pull-out process pump? The pump in question is a Goulds 3196 XLT-X 4x6-17(15.5). It meets ANSI B73.1M and RESP 73H.
I know that API-610 specifies allowable loads for pumps that meet that Spec. and I believe they are a function of the nozzle size and the pump weight (among possibly other things). My pump is ANSI and I haven't been able to find similar information for it. Thanks for any help.
I know that API-610 specifies allowable loads for pumps that meet that Spec. and I believe they are a function of the nozzle size and the pump weight (among possibly other things). My pump is ANSI and I haven't been able to find similar information for it. Thanks for any help.





RE: Piping Forces on Centrifugal Pump Connections
RE: Piping Forces on Centrifugal Pump Connections
RE: Piping Forces on Centrifugal Pump Connections
Now assume an engineer is too lazy, cheep, or lacks the skill to do a flexibility analysis on the pipe system and just specifies an expansion joint. This might be fine if it is an atmospheric pressure system; however, lets say this is a booster pump and the system has an inlet pressure of 100 psig. Now there is a load on the pump housing (not the nozzle, but the back of the pump housing) that equals the effective area of the expansion joint time the pressure. This will be in the 4000 lbf range. Assume a 12” high pedestal supporting the pumps. Now you have 4000 ft*lbf on a pedestal supported pump that was designed for 870 ft*lbf moment + 700 ft*lbf from the axial load. Congratulations you have just created a problem by installing an expansion joint. No problem with thermal expansion though, now it is loading from pressure that is the problem.
In addition, now you need to install a rigid anchor that can handle the 4000 lbf load for the pipe side of the expansion joint. Also, you get to ensure the pump base mount is good for 4000 lbf in the axial direction plus the induced moment.
The point here is to show that to recommend an expansion joint, without sound engineering analysis, is a poor practice. In fact, you can create an additional expense for anchors, increase the loading on the pump, and shorten the life of the pump just because the engineering work was not done. Expansion joints on pumps should not be a first choice.
RE: Piping Forces on Centrifugal Pump Connections
Naresuan University
Phitsanulok
Thailand
RE: Piping Forces on Centrifugal Pump Connections
... but this is not a reasonable answer. You need to get the allowable nozzle loads from Goulds. They have the data available. Then you use their formulas to calculate the resultant moments and forces and see if you are within their allowables. Use your pipe stress program to calculate the component applied forces and moments and plug those components into the Goulds formula.
There is a new proposed HI standard for allowable nozzle loads on ANSI B73 pumps but I think it is still a 'suggestion', at this point. You could get a copy from HI. You would have to ask Goulds if that XLT complies with the HI standard but I bet it doesn't because the standard is pretty new.
Expansion joint is the last resort. Pete
Thanks!
Pete
RE: Piping Forces on Centrifugal Pump Connections
Regards checman
RE: Piping Forces on Centrifugal Pump Connections
The joint manufacturer can not help you with application; they can only build a joint to your specs. They can't help you properly deal with and design around things like pressure thrust, pipe support issues, etc. As I said, an exp joint is always the LAST resort. There is usually a way to design it out of the system unless you are dealing with very high temperatures or equipment like steam turbines. Skilled piping designers and pipe stress engineers are the way around exp joints.
Thanks!
Pete
RE: Piping Forces on Centrifugal Pump Connections
Do you believe that the salesman at Hyspan is capable of pipe stress (flexure) analysis, and performs this service for their customers when they request it?
Do you think that the salesman at Hyspan is willing to accept the liability for designing pipe systems?
Do you think that the salesman at Hyspan is a licensed professional engineer willing to stamp the design he has made for you?
Do you think it is in the salesman’s financial interest to tell you that for most nozzle connections you do not need to use an expansion joint?
The answer to all of the above is NO!
Please tell me just what you think the salesman’s job is at Hyspan, to tell you that you are wasting money installing expansion joints on your pipe design. Or, that you have improperly designed the piping systems and to go back and do your engineering work? Or better yet, if the design is flawed, and if he knows how, he could redesign your piping system for you so you don’t need expansion joints. Now there is a salesman that will be on the bread line soon.
checkman, you must be involved in vibration/sound isolated systems or you are not engineering your pipe systems. This is common place with the HVAC folks because they don’t engineer their pipe systems. HVAC folks typically leave that to the plumbers and only specify the diameter of the line. Perhaps the only way to stay profitable in residential and commercial building design is to push off some of the design work on the installer/contractor.
Specifying expansions joints is no substitute for detailed engineering. Hyspan makes a high quality expansion joint and when I used to be involved in industrial piping, I would specify them where they were needed. This would be less than 5% of the time.
RE: Piping Forces on Centrifugal Pump Connections
RE: Piping Forces on Centrifugal Pump Connections
1/ Start the piping AT the pumps, and work away from them. Most intallations work TOWARD the pumps, and any misalignment of the piping occurs right at the pump connections - the absolute worst place.
2/ Properly trained steamfitters/pipefitters should be able to have the piping arrive pretty much dead-on. A huge number of plant management people think "Well, it's just pipe...ANYBODY can do it." If the guys are using prybars and come-alongs to make the last joint, then something is VERY wrong.
At the end of the day, this type of problem is a management issue. Who is allowing this situation to occur in the first place, and then to continue to exist?
RE: Piping Forces on Centrifugal Pump Connections
Hot systems usually use an API pump and require careful modeling and analysis. These systems usually contain spring cans and/or spring hangers, which must be properly set and checked after system startup.
No way would I use expansion joints or flex hoses on anything other than water pumps unless the piping system just could not be designed otherwise. In my opinion, using these things will lead to an increased maintenance effort as well as increasing the chance for loss of containment. I have seen too many failed expansion joints in the past 30 years.