Backwelding plug on U-stamped vessel
Backwelding plug on U-stamped vessel
(OP)
This is an ASME U installation where we have had our ASME rated welders weld barstock inserts into a reactor. The customer doesn’t want to use these any more and wants to weld a threaded plug into the barstock. Please refer to the attached file.
Does backwelding this plug put us out of compliance with Section VIII, Div.1?
Thanks & Regards,
Tim
Does backwelding this plug put us out of compliance with Section VIII, Div.1?
Thanks & Regards,
Tim





RE: Backwelding plug on U-stamped vessel
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Backwelding plug on U-stamped vessel
RE: Backwelding plug on U-stamped vessel
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Backwelding plug on U-stamped vessel
I don't know how applicable section 3.3.4.4 is to my situation, but it seems to be a close approximation of what we want to do. I mention this only because it stresses that the "requirements of the original code of construction are satisfied."
RE: Backwelding plug on U-stamped vessel
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Backwelding plug on U-stamped vessel
RE: Backwelding plug on U-stamped vessel
RE: Backwelding plug on U-stamped vessel
RE: Backwelding plug on U-stamped vessel
RE: Backwelding plug on U-stamped vessel
...the scope of this Division shall include...
(3) pressure retaining covers for vessel openings,
such as manhole or handhole covers, and bolted covers
with their attaching bolting and nuts;
My perspective is that a threaded plug is functionally the same as the specific items listed in (3) and therefore I'd interpret this as being in spec. I'd have to ask my heat exchanger focused colleagues as to whether or not the plugs on a plug sheet of an air cooled heat exchanger are typically considered in- or out- of scope. Seems to me they should be in scope.
RE: Backwelding plug on U-stamped vessel
General Blr. CA,USA
RE: Backwelding plug on U-stamped vessel
Nutsforbolts
"Give me pipelines, or give me death!"
RE: Backwelding plug on U-stamped vessel
But here goes...
The scope of the pressure vessel ends at the coupling, in the same way that if you build a pressure vessel which has a pipe nozzle intended to butt-weld into a piping system, without an attachment flange, the vessel scope ends at the end of that pipe nozzle. You can weld to that pipe nozzle without having to follow the requirements of the pressure vessel code in relation to hydrotesting etc.
However...
...that doesn't mean you can just weld and walk away!
The ongoing O&M codes DO set rules in relation to this kind of work. Minimum requirements will include compliance with ASME IX for welding, welder and procedure qualifications etc., as well as the NDE/testing requirements of the associated in-service code, or piping code in the case we're talking about my example of a weld to a pipe nozzle.
As has been mentioned, seal welding of existing threaded connections to prevent future leakage is something that is done all the time. It is also a questionable practice for new construction in my opinion, with the socket weld being preferable, but there are conditions under which it can be done without significant concern of future problems. The big issue is getting the threaded joint clean enough so that sound welding can be done- removing thread sealant completely from a threaded joint post assembly can be very difficult to accomplish, and it's an easy corner to cut when nobody is looking since the final joint can't be RT'd in any meaningful way. This is one place where careful supervision is required.
Hope that is accurate, and if it is accurate, I hope that helps!
RE: Backwelding plug on U-stamped vessel