why was this a cut out?
why was this a cut out?
(OP)
I have a 20"condensate line that terminates in the main condensor of a 500mw steam turbine. The pipe is A106 sch 40 20". The wps calls for a gtaw root pass with Er70s-2 wire and smaw 7018 root, fill and cap.
The service temp and pressure are 50 psig and 350 deg F.
A hydrostatic test was required but could not be done due to isolation points in the line. Instead an mpi was done on the root pass and Rt on the remainder of the joint,the weld failed due to "suck back" on the root pass.
My question is instead of using an Rt procedure could not an mpi of the entire weld have been done instead? The condensate line met none of the requirements for Rt testing in service pressure, temp or wall thickness.
What is the limit of "suck back" allowed?
sftyvlv
The service temp and pressure are 50 psig and 350 deg F.
A hydrostatic test was required but could not be done due to isolation points in the line. Instead an mpi was done on the root pass and Rt on the remainder of the joint,the weld failed due to "suck back" on the root pass.
My question is instead of using an Rt procedure could not an mpi of the entire weld have been done instead? The condensate line met none of the requirements for Rt testing in service pressure, temp or wall thickness.
What is the limit of "suck back" allowed?
sftyvlv





RE: why was this a cut out?
RT examines the whole weld a and looks for porosity, slag inclusions, lack of fusion and full penetration (suck back)
No suck back of lack of fusion is disireable
RE: why was this a cut out?
Great question. In my opinion, the code of construction would be ASME B31.1, and using the requirements for NDT in Table 136.4,you are correct, the only requirement for NDT would have been only a VT based on a temperature at 350 deg F but your pressure is below 1025 psig.
Since someone wanted an RT, and you have no linear, crack-like indications and only suckback, you could attempt to disposition "as-is" or fit for service. There is really no obligation for RT at this pressure unless the owner specified it and contractually it must be done.
RE: why was this a cut out?
RE: why was this a cut out?
Sftyvlv
RE: why was this a cut out?
Why was the RT selected for NDT? Was this the owners requirement or what?
RE: why was this a cut out?
Now, don't for one minute think I am minimizing the need for proper welds at the joints of terminations into the condenser. I've repaired too many and beefed too many up beyond their original specification to do that. The service conditions just raise a red flat with me.
rmw