Socket Fillet Weld

[Cor123]

Just a quick question regarding fillet welds. We are observing low fillet weld throat (2.0 mm) on a 0.75" offtake pipe with 5.56 mm nominal wall thickness. Design Pressure is 28 barg and 3 mm CA.
I calculated the theoretical weld throat using B31.3 The calculated theoretical weld throat is 4.29 mm. We also calculated the shear stress which is 453.09 psi.
This shear stress is below the 0.8 X allowable stress = 16000 psi which means that the fillet weld should be ok for pressure containment.
My question is there any critical threshold (from standard or good practice ) below which in service fillet weld would need to be reinforced /repaired although it passes the shear stress calculation. I believe that although the the calculations for shear stress says ok, the weld throat thickness is too low. Also risk of loosing more material when doing surface prepation.
Api 570 also mentions that the B31.3 acceptance criteria might not be appropriate for in service weld inspection. Hence my confusion, as what's the appropriate acceptance criteria for in service welds that have corroded. Please not that there are no crack like flaws. The issue is purely preferential weld corrosion.

 

[racookpe1978]

If you have a throat thickness of 2 mm, and a calculated required minimum throat thickness of 4.9, why do you assume it can hold the pressure? I'm either not reading your statement properly, or you have calculated the required throat thickness improperly.

 

[Cor123]

Many thanks for the response. I calculated the theoretical weld throat using paragraph 328.5 in B31.3 using 1.09×Tnom×0.707.
I assumed that it will be seeing shear stress and used the design pressure to calculate it. I then compared this to B31.3 0.8×allowable stress.
My question is, are there any other ways to accept or reject the weld throat thickness for in service corroded fillet welds?
When do you decide time to reinforce or repair the weld? Any document /standard to back this up?
Any help would be appreciated.