Welding Flanges to stub connections on Brazed Plate Heat Exchangers

[ET50]

I hope this is the right place to ask this question. If you have Brazed Plate Heat Exchangers that are CE approved (meet ASME requirements), and they are supplied with stub connections, can flanges be welded on these stub connections legally per code(s) or do they require additional testing and inspection and need to have the equivelent of an "R" stamp on them? Sorry to be so vague, but this is something we are concidering and we're not sure if after welding these heat exchangers to put flanges on if they will still be acceptable per ASME and CE (PED) requirements. These heat exchangers would be part of the system that I asked about the "R" stamp on the pressure vessel. The entire system must meet CE (PED) requirements which means it must meet ASME requirements.

 

[gr2vessels]

ET50,
After the hydrotest and final inspection, the exchanger cannot be welded on under any condition, unless it is an approved alteration and it follows the national board ruling, including the R-stamp requirement. Hence, you need an R-stamp holder to provide the alteration, inspection and testing, and put his R-stamp on the nameplate.
cheers,
gr2vessels

 

[ET50]

gr2vessels,

I need to check these heat exchangers again because although they are CE certified I don't believe they had any ASME name plate or marking on them. I'm not sure if this matters or not because ultimately the entire system with the Brazed Plate Heat Exchanger in it, must meet PED requirements. This involves Pressure vessels and pressure piping per ASME code, so I do believe they require documentation per ASME and if we weld flanges on them I believe they require an "R" stamp as well. This entire CE requirement per PED is new to me as is full understanding of the codes involved. I'm just making sure we do everything by the book so we don't have issues in the future with inspectors, customers or other agenceies. I've heard the phrase "best Engineering practices" thrown out there to cover things like this, but I don't buy into that.

 

[metengr]

What does the local regulatory body or Jurisdiction require? If they require nothing administratively, you can weld the flanges on the stub ends assuming the organization has an R-Certificate. One has to review Code boundaries, which is usually the weld prep end of a welded or brazed nozzle (Section VIII, Div 1).

 

[rakuday]

ET50,

Firstly, if a flange is welded onto the stub end of BHE, it is very difficult to maintain parallelism (even if you employ a certified welder). If parallelism is not maintained, then the pipes will induce stress on the stub ends and this leads to failures in the BHE’s.

Secondly, the simplest way to get around this problem is to ask the BHE supplier to weld the flanges to the coolers and then certify the coolers. In this approach, it is very easy for the supplier to maintain all the critical tolerances. Also, all types of flanges can be supplied with the cooler along with varied length (extension) of the pipe to accommodate the piping arrangement. Ofcourse, this comes at a slightly higher cost, but its worth it.

Thirdly, the length of stub end on BHE are relatively less and this leads to weld difficulty (though not very critical, but better to consider).

Thanks

 

[gr2vessels]

I'm pretty sure that after the final certification, you may not make alterations without re-certification, at least equivalent of R-stamp and appropriately inspected, tested and documented. Who's going to believe you that after welding flanges, pressure retaining components, your exchanger remains safe? From safety point of view, there is no difference between ASME and PED, hence the you'll need EC re-certification.
Cheers,
gr2vessels

 

[ET50]

gr2vessels,

I agree 100% with your assessment.

rakuday,

I agree with you as well when it comes to the weld issues, and I also agree that the easy way is to have the BPHE's purchased with the flanges attached, however we have a situation where our supplier won't do that, and because our design is based on that particular manufacturers heat exchanger it will take us some time to change our design to use another manufacturer. We are pushing for them to comply, but we can't force them to do it. They claim they they don't have the capability to supply them to us with flanged connections yet other manufactures do it all the time.

Thanks for everyones opinion.

 

[ET50]

A co-worker (Engineer) is now attending an ASME class, and he was told by the instructor that the boundry of the heat exchanger ends at the stub ends, and it's then fine to weld flanges onto the heat exchanger without any rework paperwork. This doesn't seem correct but it came from an ASME instructor so are we to agree with him or not?

If this wasn't a heat exchanger and was a pressure vessel with a 2 inch pipe stub would it be legal to weld a flange on it? My gut feeling is there is no difference here because they are both pressure vessels and they both should require re-certification of some sort. Life would be easy if this is acually the case and we are free to weld flanges on all the stub ends.

Thanks in advance, to all the experts out there.

 

[gr2vessels]

ET50,
The welded flange will be part of a pressurised system;- it will not be a piping item, hence it will be ignored by the piping safety requirements (and the piping code requirements). It will not be part of the heat exchanger, because your instructor stated that the boundry of the heat exchanger ends at the stub ends. Who will then bear the responsibility of the welded addition to the exchanger? Is it you, the welder, the manufacturing company or the instructor on the ASME class? Have a wild guess!
Cheers,
gr2vessels