Section 59.10-10 - Corroded surfaces(a) Corroded surfaces in the calking edges of circumferential seams may be built up by welding to the original thickness under the following conditions: (1) The thickness of the original metal to be built up between the rivet holes and the calking edge must not be less than one-fourth of the diameter of the rivet hole, and the portion of the calking edge to be thus reinforced must not exceed 30 inches in length in a circumferential direction.(2) In all repairs to circumferential seams by welding, the rivets must be removed over the portions to be welded for a distance of at least 6 inches beyond the repaired portion.(3) After repairs are made the rivet holes must be reamed before the rivets are redriven.(b) It is not permissible to build up or reinforce a grooved or corroded area of unstayed internal surfaces by means of welding, except that widely scattered pit holes may be built up by welding.(c) Where external corrosion has reduced the thickness of flat plates around hand holes to an extent of not more than 40 percent of the original thickness and for a distance not exceeding 2 inches from the edge of the hole, the plate may be built up by welding.(d) Where stayed sheets have corroded to a depth not exceeding 40 percent of their original thickness, they may be reinforced or built up by welding. Where the staybolts are fitted with riveted heads, the staybolts in the reinforced area must be renewed, but where the staybolts are fitted with nuts, the nuts may be removed and after reinforcing has been applied; collars may be welded around the staybolts in lieu of the nuts. Such reinforced areas must not exceed 400 square inches nor more than 30 inches in one direction. Two such areas in any one plate may be reinforced provided that the distance between the reinforced surfaces is not less than 30 inches.(e) When the corroded portion of a staybolted surface exceeds 400 square inches, it is permissible to make repairs by cutting out the defective portion and replacing it with a new plate, the edges of the new plate to be welded in position. In such cases, new staybolts must be fitted, and where welding is performed through a line of staybolts, welded collars must be used to attach the staybolts.(f) Eroded seams of welded pressure vessels may be repaired by rewelding the wasted portion. The wasted section of the seam must be excavated sufficiently by grinding, flame or arc gouging or chipping to ensure proper weld penetration. Rewelded seams must be nondestructively tested in accordance with Section VIII of the ASME BPVC (incorporated by reference, see § 59.01-2 ).CGFR 68-82, 33 FR 18887, Dec. 18, 1968, as amended by USCG-2003-16630, 73 FR 65189 , Oct. 31, 2008