46 CFR §59.10-35

1. (a)Wrapper plates or back heads must be cut between two rows of staybolts or on a line of staybolts where the thickness is approximately the same as the original construction. If welding is employed on a line of staybolts, the staybolts must be fitted with a welded collar.
2. (b)The edges of wrapper plates riveted to tube sheets and back heads must be removed by cutting out the rivets.
3. (c)The edges of existing plates and new plates must be beveled by chipping, flame cutting or grinding so as to form a suitable groove whereby complete penetration of the weld metal will be obtained. The edge preparation and preheat must comply with the requirements of § 59.10-5(h).
4. (d)The edges of the new plate must be butt-welded, and the plate must be riveted to the flanges of the tube sheet and back heads and the staybolts renewed.
5. (e)Sections of wrapper plates of combustion chambers outside of stayed areas may be repaired by welding provided the welded joints are stress-relieved by means of controlled heat and the joints are nondestructively tested.