Generally, for most materials, a bend diameter 3 X tube o.d. is acceptable. As stated above, you will need to compute minimum tube thickness per ASME and apply TEMA rules to calculate thinning at u-bends. Beyond TEMA and ASME, you should contact tube supplier. Some materials present different...
I agree. Unless the customer specifies otherwise, our standarad practice is to perform RT prior to PWHT. Of course, many require us to RT after, in which case, we perform RT before and after.
You will likely want to weld the tubes to the tubesheet. It is difficult to get a tight seal with this combination of metallurgies when roller expanding only. It takes a lot of force to expand stainless steel tubes, and this often moves (yields) the carbon steel ligament between the tube...
PE's are nice, but irrelevant to the issue at hand. Hire competent personnel and you will do great. The Botanist example is an unfair argument. (You went from one extreme to the other.) I know many shops that have non-degreed personnel and they do okay, but I require engineers with degrees...
"Wow, no PE sign off for Div1 in the USA?? Is this regardless of pressure and contents? So you don't have to get designs verified at all? Sounds dangerous to me."
What's dangerous about that? I don't remember there being anything pertinent to Div. 1 on PE exam.
I don't believe that UT is feasible, since the tubesheet is perforated. Regarding a repair, you will likely be chasing cracks all day. About the time you think you have found the bottom of the crack, it spider webs to a larger mess of cracks. Hopefully, your schedule will allow replacement.
Vesselfab, I usually agree with your posts. In this case, let me explain our position. A few years back, our WPS was rejected by our client on the basis that the wire/flux combination wasn't certified by the mfg in the PWHT condition. This came as a shock to us since we had easily qualified...
As long as you successfully qualify the wire/flux combination per ASME section IX, it is legal per ASME. The problem is, the welding consumable mfg's do not "certify" the wire/flux combination in the PWHT'd condition. This shouldn't matter, since ASME doesn't require this certification, but...
What's the error? The exchanger could have been built exactly to spec and an error was made on the U1. Typically, the U1 should be sent back to the original fabricator for correction. A corrected copy is generated with the change signed by the A.I.
