API 6A RTJ 6B Groove with CRA overlay - Spectacle blind

[svi]

thread794-422928
API 6A gives in Table 52 the rough machining detail. The depth to which material may be removed is 8 mm for a R39 4 1/16" class 5000 groove. This is the same as the raised face available on the flange.

I have a CS spectacle blind that needs to be overlayed with Inconel 625 weld overlay. The prescribed overlay thickness is 5 mm including the dilution thickness. The spectacle blind already has the min thickness at the groove bottom. If I am to machine this deeper to the 5 mm overlay depth needed. I suppose it would violate the above. Is there a consideration that the overlay thickness can be treated to contribute to the strength thickness.

 

[gr2vessels]

Hi svi,
Please review the ASME SA-265, Clause 7.0 and all the sub-clauses. The overlay may be included in the composite materials tensile strength.
Cheers,
gr2vessels

 

[svi]

Thanks gr2.

I note from ASME SA 265 which is a material standard, It says about overlay specimens are to be tested and what is an acceptable test result.

"(4) The tensile properties thus determined shall not be less
than the minimum and not more than 5000 psi (35 MPa) over
the maximum prescribed in the specification for the base steel
used. All other tensile test requirements of the specification for
the base steel shall be met."

Is that to say that once the min thk is reduced by machining for the rebuilding by overlay? The test specimen should have a strength through a test, at least the base material strength. A ceiling of 5 K psi is also said.

 

[gearteeth]

It is common to machine, WOL, re-machine. You need to have the proper hold points and NDE, approved weld procedures, etc.

10.1.2.3.5 "Corrosion-resistant ring grooves" of API 6A references your rough machining detail but adds that "Other weld preparations may be employed if the strength of the overlay alloy equals or exceeds the strength of the base material."