metaleng123
Petroleum
- Jan 18, 2021
- 17
Dear Gents and Ladies,
I'm currently doing a job that involves P91 welding and after RT testing we got incomplete penetration on a 20 mm length ( VT inspector missed it during welding).
Backgroung :
- Materials are A335 P91 ( 355,6 x 11,13 mm Pipe) + A234 WP91 ( 355,6 x 11,13 mm Cap). Pipe is 1260 mm (49,54") in length, beveled on both sides (single V groove), one side is within our scope and the other end will be a field weld.
- Filler is AWS A5.28 ER90S-B91. Ni+Mn < 1
- Fabrication standard is ASME B31.1 (PQR and WPQ acc. to ASME IX)
- The sequence so far is: Preheat @ min. 250C, Interpass @ max.350C, heating method: electrical resistances. After welding was completed the joint was not allowed to cool below the min preheat temp and an postheating / hydrogen bake out was performed @ 350C, soaking 2 hours; cooled down to room temperature and 24H rest in order to be RTed ( where the defect was spoted).
After reviewing some relevant docs. ( well engineered weld repair of Gr. 91 EPRI 3002003833 and EPRI 3002006390 Best practice for manufacturing of Gr.91 Steel components ) I think the correct repair procedure would be:
Since the weld cannot be accessed from the inside, the whole area where the defect is located should be grinded (the whole 11,13 mm thickness), surface NDT should be performed, re-welded using the existing PQR and WPQ (thermal variables shall be respected), the NDT re-done and if acceptable sent to PWHT.
Given that EPRI 3002003833 gives more guidance when HAZ cracking is involved, is my way acceptable? Also any advice or opinion would be highly apreciated.
I'm currently doing a job that involves P91 welding and after RT testing we got incomplete penetration on a 20 mm length ( VT inspector missed it during welding).
Backgroung :
- Materials are A335 P91 ( 355,6 x 11,13 mm Pipe) + A234 WP91 ( 355,6 x 11,13 mm Cap). Pipe is 1260 mm (49,54") in length, beveled on both sides (single V groove), one side is within our scope and the other end will be a field weld.
- Filler is AWS A5.28 ER90S-B91. Ni+Mn < 1
- Fabrication standard is ASME B31.1 (PQR and WPQ acc. to ASME IX)
- The sequence so far is: Preheat @ min. 250C, Interpass @ max.350C, heating method: electrical resistances. After welding was completed the joint was not allowed to cool below the min preheat temp and an postheating / hydrogen bake out was performed @ 350C, soaking 2 hours; cooled down to room temperature and 24H rest in order to be RTed ( where the defect was spoted).
After reviewing some relevant docs. ( well engineered weld repair of Gr. 91 EPRI 3002003833 and EPRI 3002006390 Best practice for manufacturing of Gr.91 Steel components ) I think the correct repair procedure would be:
Since the weld cannot be accessed from the inside, the whole area where the defect is located should be grinded (the whole 11,13 mm thickness), surface NDT should be performed, re-welded using the existing PQR and WPQ (thermal variables shall be respected), the NDT re-done and if acceptable sent to PWHT.
Given that EPRI 3002003833 gives more guidance when HAZ cracking is involved, is my way acceptable? Also any advice or opinion would be highly apreciated.
