Opinions on "Heat to Fit" Piping Practices
Opinions on "Heat to Fit" Piping Practices
(OP)
The engineering group I’m in recently became aware of a fairly common practice performed by our production/manufacturing group that spurred an ongoing debate. When needed to make (B31.1/B31.3) piping runs fit, they use a torch to heat the pipe, usually at an elbow, and apply enough force to deflect/deform it to achieve the desired alignment. There has been no follow up testing or inspections.
When they weren’t able to produce any type of procedure for this practice the we were tasked to create an engineering specification/procedure which basically took the form of, “don’t do it.” Recognizing the potential for it to happen any way, we included a list of follow up tests and inspections that included dye penetrate testing, mag partical testing, and 30-minute 1.5xMAWP hydro-testing. Their counter to those requirements was to perform just a low pressure leak test which we find unacceptable.
I’m curious as to other perspectives on this matter.
When they weren’t able to produce any type of procedure for this practice the we were tasked to create an engineering specification/procedure which basically took the form of, “don’t do it.” Recognizing the potential for it to happen any way, we included a list of follow up tests and inspections that included dye penetrate testing, mag partical testing, and 30-minute 1.5xMAWP hydro-testing. Their counter to those requirements was to perform just a low pressure leak test which we find unacceptable.
I’m curious as to other perspectives on this matter.





RE: Opinions on "Heat to Fit" Piping Practices
I think that the lack of answers to your post, is an answer on it's own. I hate to think of the consequences of such practice. I would first carefully (and without many waves) investigate the chances I've got to keep the guarantees for the piping material. The supplier will void the guarantees immediately.
It is very likely the bends are ruined by local overheating and uncontrolled deformation of the most sensitive areas of piping bends. You could definitelly expect some crack initiation on inside or outsiede of those bends, depending on the degree of bends deformation, the depth of those cracks is your job to determine, at worst you'll have to determine the remaining life of those bends... If you're lucky, perhaps no aparent damage of the bends has been sustained, hence a thorough NDE of those areas would support the continuing use of the bends.
Good luck,
gr2vessels
RE: Opinions on "Heat to Fit" Piping Practices
My perspective is that this practice can be performed if one has a technical understanding of the pipe material properties, behavior of these properties and requires nondestructive testing (NDT). For carbon steel and low alloy steel (less than 3% Cr), one can get by using heat and force provided it is under controlled conditions AND there is NDT (surface and/or volumetric) performed to assure no defects were introduced as a result of this process.
Some materials are forgiving as indicated above while other materials are not. You certainly need some type of guideline for others to follow with regards to heating, cooling and forces applied that is only used for certain materials.
RE: Opinions on "Heat to Fit" Piping Practices
I'm intentionally not mentioning what service the piping is in since I don’t believe that matters. I will say this; it’s more than just cooling water service.
RE: Opinions on "Heat to Fit" Piping Practices
Conducting such activities for "proper alignment/fit" to rotating equipment connections can be detrimental to the rotating equipment. Certainly, the nozzles for rotating equipment are designed to withstand some stress/loads, but placing excessive/additional stress/loads on these connections (i.e. force fit piping) is generally not practiced (my observations). The additional stress placed on rotating equipment housing/casing can cause operational problems (i.e. premature bearing failure, etc.).
For fixed/static equipment, this is a different matter, but there are limitations as well at the connections.
Good Luck!
-pmover
RE: Opinions on "Heat to Fit" Piping Practices
If these practices are there, then it must be working too(if done by experienced crew!). I believe there were, are and will always be cost effective practices as such contradicting the code effective practices, as long as its not going to hurt anyone.
regards,
Siddharth
Siddharth
These are my personal views/opinions and not of my employer's.
RE: Opinions on "Heat to Fit" Piping Practices
RE: Opinions on "Heat to Fit" Piping Practices
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Opinions on "Heat to Fit" Piping Practices
If you are tasked with writing a procedure for an unacceptable pratice because the practice will go on, then whoever ordered you to write the test procedure ought to insist or, if high enough on the staff, order that the procedure you wrote be followed. Failure to follow the test procedure should have loss of employment consequences.
Who will hang if there is ever a failure due to 'them' preforming the heat-to-fit process?
Responsibility and accountability..
Ted
RE: Opinions on "Heat to Fit" Piping Practices
RE: Opinions on "Heat to Fit" Piping Practices
Also, it would probably be good idea to define the differences between "heat to fit" and heat treatment for stress relief.
RE: Opinions on "Heat to Fit" Piping Practices
As a young engineer while working at a manufacturing company I designed a process that consisted of several skids that had to be butted up together in the field and the piping connections made up. I was pretty amazed when we went to the field and the piping connections fit without any modification AT ALL. We just put the bolts and gaskets in the flanges and tightened. It can be done. Why aren't these people doing it.
One reason it might have worked so well in that case which was steel pipe was that the production bay that made these skids normally worked with sil-brazed CU/NI pipe that wasn't forgiving so they were accoustomed to getting it right in the first place. I think that what is going on in your place is that since they are allowed to "heat to fit" or "beat to fit" as the case might be they don't need to do it right the first time.
I've used the rose bud to get out of a bind on several occasions throughout my career, but it was as a last resort and not as normal course of action.
Something doesn't sound right here.
rmw
RE: Opinions on "Heat to Fit" Piping Practices
I agree completely.
It can be done right the first time. I'm currently building skidded packages myself, and when there are competent installers in the field, everything will bolt up without rosebuds or hammers. When something doesn't align properly, our normal course of action is to re-fabricate on site. No "heat to fit"!
RE: Opinions on "Heat to Fit" Piping Practices
Earlier, Hydtools posed the question, “Who’s in charge?” Our Engineering and Manufacturing groups have a common manager who wants everyone to get along which is something I can appreciate, to a point. Some topics just aren’t (or shouldn’t be) open to negation and common grounds can’t always be reached.
Again, the engineering group’s position is against the practice but for convenience the manufacturing group embraces it with minimal follow up inspection and testing. One aspect to the procedure we (engineering) were told to write (for the manufacturing group) imposes enough (appropriate) inspection and testing that “heating to fit” was no longer the path of least resistance.
Okay, so what cleared the log jam? The companies QC group from an entirely different department weighted in fully supporting the testing and inspection we prescribed. I wasn’t there but I’m told the manufacturing lead and some foremen were, “We gotta do all that…well that sucks.”
I don’t want to offer the impression that a lot of this goes on. We’re a good company and produce good products. Like everyone else, we have our internal battles.
RE: Opinions on "Heat to Fit" Piping Practices
Ted
RE: Opinions on "Heat to Fit" Piping Practices
I've never seen pipe heated and then mechanically distorted to make it fit, but then again I'm pretty glad I've never seen it. Sounds like a process that would be tough to control. Mind you, it's better than just straining the pipe to make it fit cold...seen that plenty of times...Bubba's got a great big "paip wrainch" and teeny little brain...
RMW: yes, you can fit pipe precisely if you know what you're doing. What you can't do is shop fabricate pipe in one shop to an iso, and mount vessels in another shop to a matching layout drawing, and expect everything to fit when they finally meet one another- without providing field welds or doing templating or dummying of the equipment. The combination of angular and positional tolerances while fabricating the piping make such "blind fitting" to drawings alone impractical- the positional and angular control, measurement and QC you'd need to make that work precisely enough are actually more expensive than the field welds in the end, unless the field welds are impossible.
The best you can do without field welds and/or templating is to get it reasonably close- and angular tolerances bedevil that approach. 1/2 degree over ten feet is a pretty big distance, and I've yet to see a pipefitter ACTUALLY work to +/- 1/2 degree regardless what they say on the iso. It's often when we engineers think that the field welds are unnecessary and the drawings are king that the "beat it to fit" or "heat it to fit" approaches get applied in the field. They're done in an attempt to avoid chopping up "finished" pipe to make it truly fit, rather than doing it right in the first place.
BTW: thanks for stealing the "beat it to fit" line- but you forgot to add, "...and paint it to match!"