Can butt weld flanges be welded directly to heads?
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I saw a drawing that did not follow the proper standards: in it, the DN1000 end cap was welded directly to the equipment flange, without the use of any transition pieces, and it was a butt-welded flange. Is it reasonable to do this? It is said that the equipment is already in use. There is an existing DN2400 butt-welding equipment flange; can it be used in this way and welded directly to the head? If a short section is added, what is the minimum length required? What are the consequences if no short section is added? My foundation in mechanics isn’t very strong; I would appreciate it if everyone could discuss this from the perspective of standards and stress conditions. Additionally: What are the similarities and differences between this situation and the floating head of a heat exchanger?
Personally, I don’t think there’s anything reasonable or unreasonable; as long as the calculations work, it’s feasible.
Are they connected with bolts? The connection is a problematic aspect; I think the design is unreasonable
Whether it is reasonable or not depends on the circumstances. In the case of fixed tube sheet equipment, a short section is added to ensure an adequate flow area for the medium inside the equipment’s tube box; as for the rest, it is sufficient as long as the requirements of the process calculations are met. When I used to work on filters, I often did this by welding the end cap directly to the flat weld flange.
I used to do the same thing when working on shell-and-tube heat exchangers.
I have worked on fixed-tube-sheet heat exchangers; I’ve done this as well! It seems possible, as long as the calculations are successful and the liquid volume in the tube box meets the requirements! !
Thank you all for participating! I also asked a few friends yesterday, and overall it seems to be as the person on floor 5 said – ordinary filtration equipment and heat exchangers that can be calculated for properly would all be handled in this way. Feel free to post about other types of devices as well. Thank you all again~~
Flat-face flanges are rarely used; I’m not sure if they’re feasible. Welded flanges, on the other hand, are acceptable. We specifically asked those responsible for formulating the standards about this issue
I’m not sure whether the butt-welded flanges mentioned by the original poster refer to the standard 4701 flanges; if so, there’s no problem with that, as long as the fillet weld height meets the standard requirements and does not extend beyond the straight edges. However, for 4703 flanges, the technical specifications include a requirement regarding the minimum length of the tube section. (I think it’s not necessarily necessary to shorten this section; if it is added, at least this length should be maintained, from the perspective of the force analysis model.)
If the poster is referring to the 4701 flange, a DN1000 diameter can only be directly welded using carbon steel equipment. If it is a lined flange, it is obvious that the weld should be located at the transition part of the head; this is not ideal, and a short section should be added.
If the flange of 4703 is welded directly to the head, then there should be no problems. For heat exchangers, the flange of 4701 is generally welded to a short stub.