Lifting a pipe for quick repair of support
Lifting a pipe for quick repair of support
(OP)
Hi all,
I currently have a steam piping in-service which appears to have a pipe support resting on top of a guide support and has bent one of the guides.
Now the pipe carries steam at around 750 psi at 700 degF.
Likely what happened is that during start up and shutdown there was undesirable thermal growth perpendicular to the guide. So as the pipe moved downwards, the pipe support came into contact with the guide plate. I uploaded a simple sketch below. The small rectangle at the bottom of the trunnion is the guide plate which is bent.

Regardless of the system being in service or not, is there any way to judge if lifting the pipe about 8-12 inches (so the guide plate can be removed and replaced) will adversely affect the remainder of piping or even cause excessive localized stresses near to the lifting point ? Or will modeling of the piping be required with an imposed displacement be required to see how other pipe supports will behave ?
I currently have a steam piping in-service which appears to have a pipe support resting on top of a guide support and has bent one of the guides.
Now the pipe carries steam at around 750 psi at 700 degF.
Likely what happened is that during start up and shutdown there was undesirable thermal growth perpendicular to the guide. So as the pipe moved downwards, the pipe support came into contact with the guide plate. I uploaded a simple sketch below. The small rectangle at the bottom of the trunnion is the guide plate which is bent.

Regardless of the system being in service or not, is there any way to judge if lifting the pipe about 8-12 inches (so the guide plate can be removed and replaced) will adversely affect the remainder of piping or even cause excessive localized stresses near to the lifting point ? Or will modeling of the piping be required with an imposed displacement be required to see how other pipe supports will behave ?





RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support
For a quick check look for any pipe hanger in the vertical run above the kinked support plate restraints. That maximum movement of those supports would tell the max movement in the cold-to-hot change.
RE: Lifting a pipe for quick repair of support
Well 8 to 12 might be a stretch to give a welder some comfort however most likely they'd try to lift it like you said a few mm and cut out the plate and weld back using SMAW.
That's why I believe that during some transient condition, some excess (temporary) high temperature was experienced.
I will look into this and see.
But in general, if the pipe is to be lifted I would say at most 3-5 mm above the guide support would be sufficient correct ?
RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support
Don't lift the pipe at all if it is going to be a major drama.
Put a temporary support next to the trunnion, arc gouge the weld off (without damaging the trunnion) and replace with same size plate
or
Put a temporary support next to the trunnion, cut through the weld (horizontally) and replace with slightly thicker guide plate.
Cheers,
Shane
RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support
You haven’t been at all clear about how that support has failed, how it works and is detailed, or what movement caused the failure, magnitude, direction, etc. I would suspect that the movement was horiz. along the length of the lower horiz. pipe leg, it was not in/out of the page in your sketch. It would appear that the pipe system can tolerate that movement, it did not fail. You also need to delineate the details of the pipe system, lengths, sizes, support types and locations on both legs, etc. etc. You must make some judgement about the strength, flexibility, stiffness, stresses in the pipes under that movement, etc. The idea that you might lift that pipe elbow 8 to 12" to make a repair seems way beyond any reasonable exaggeration to make a point, it suggests you better really study the situation at hand before you act.
In its crudest form, to suggest detail intent, I would replace that vert. leg and base plate support at the elbow, with a WF shape 3' +/- long under the horiz. pipe centerline, and parallel to it. It would have a pipe saddle on top to support the pipe, and it would have a guided sliding mechanism down at the floor/footing to allow the pipe longitudinal expansion, without particularly imparting significant secondary forces/stresses into the pipe system. Undoubtedly, there are off-the-shelf items in the piping field for this purpose.
RE: Lifting a pipe for quick repair of support
I have uploaded some photos of the pipe support for a better visual guide. From the photos it looks to be that the pipe grew vertically and then out of the page then back down. Which I suspect only occured during a combination of transient conditions. I could be wrong in my preliminary thoughts here. But yes the pipe did not fail which I am guessing is because there was enough flexibility in the system. There is another trunnion support (just a rest support) about 8 feet downstream of the elbow and two control valves as well. At other plants of the same design, this support rests fine in the guide.
All other supports nearby appear to be ok (no near spring supports it seems)
Link for photos (upload to engineering.com wasn't seeming to work)
I believe there may be sufficient flexibility in the system to just reset the support in a manner that DekDee suggested but only when the system is shut down.
I agree but that is a suggestion that I was told by a higher up who does not really understand the mechanics of a piping system with respect to stiffness or how it affects other supports, etc. Which is why I wanted to know if it is a common practice to just lift the pipe, cut out the plate and then weld a new one i.e. basically reset the piping or if the common practice would be to model the entire piping and see if the supports are inadequate and so on (this means that I need to convince management that it is going to be reoccurring problem.) If I am going down that route, I will in fact check temperatures and pressures that the line is seeing or if condensate is in the line and so on.
[and yes I have higher ups who will question why I would want to spend time looking at these things rather not immediately knowing the answer, lifting the pipe and so on]
RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support
This situation seems to be anomaly when compared to other plants with the exact same piping arrangement. So a redesign may not be absolutely necessary.
RE: Lifting a pipe for quick repair of support
RE: Lifting a pipe for quick repair of support