46 CFR 59.15-5: -5 Stayed furnaces and combustion chambers.

(a) Where the plate forming the walls of stayed furnaces or combustion chambers become bulged between staybolts, repairs may be made by inserting an additional staybolt in the center of such space supported by the four staybolts.

(b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the defective portion of the plate must be cut away until solid material is reached, the patch must be riveted on the waterside, and the staybolts renewed, and extended through the new plate.