welding an olet for thermowell on longitudinal seam?

[Baedor]

Hi.
there's this problem found at welding shop, as mentioned in title, we have overlapping seam problem.

For further info. the material is SS316Ti, Wall thickness is 22.23mm the design condition of pipe is 3.5 BarG and 515'C

The longitudinal seam is heat treated by manufacturer.

Is it okay to drill out the hole across weld seam and attach a new olet for thermowell and apply 100% RT?

thank you

 

[metengr]

Before you drill a hole and install the weldolet on the shell, you need to make sure no additional reinforcement is necessary. What code of construction are you working under to perform this activity? API or ASME?

 

[Baedor]

It's ASME 31.3

 

[metengr]

Ok, follow the necessary requirements to check for reinforcement. If none is needed, follow the requirements for welding and post weld NDT. Don't forget to radius the edge of the hole in the shell to reduce local stress concentration.

 

[moltenmetal]

If you're going to do RT, the only sensible time to do so is before you cut the hole, to ensure that the affected section of weld seam is free of porosity or other flaws which might have been missed during manufacture of the pipe. Is spot RT of that section of the long seam prudent? If it were my pipe, I'd consider doing it.

You're installing an o-let which is a self-reinforcing fitting, so reinforcement calcs aren't required, especially for a non-moment connection like a thermowell. You must weld out the full bevel of the fitting per the manufacturer's instructions to achieve its full design pressure/temperature rating. RT after that welding process would be impossible to interpret. Any other code-required NDT must be done- not sure what, if anything, that would entail aside from the hydrotest of the completed assembly.

If you're installing a thermowell into the o-let, I presume this is a soc-o-let. The weld between the o-let and the thermowell will be a fillet.

Is this good practice? No, but it's also not likely to be a serious problem in this case.