46 CFR § 56.70-10 - Preparation (modifies 127.3).
(a) Butt welds (reproduces 127.3)—(1) End preparation.
(i) Oxygen or arc cutting is acceptable only if the cut is reasonably smooth and true, and all slag is cleaned from the flame cut surfaces. Discoloration which may remain on the flame cut surface is not considered to be detrimental oxidation.
(ii) Butt-welding end preparation dimensions contained in ASME B16.25 (incorporated by reference; see 46 CFR 56.01–2) or any other end preparation that meets the procedure qualification requirements are acceptable.
(iii) If piping component ends are bored, such boring shall not result in the finished wall thickness after welding being less than the minimum design thickness. Where necessary, weld metal of the appropriate analysis may be deposited on the inside or outside of the piping component to provide sufficient material for machining to insure satisfactory fitting of rings.
(iv) If the piping component ends are upset they may be bored to allow for a completely recessed backing ring, provided the remaining net thickness of the finished ends is not less than the minimum design thickness.
(2) Cleaning. Surfaces for welding shall be clean and shall be free from paint, oil, rust, scale, or other material which is detrimental to welding.
(3) Alignment. The inside diameters of piping components to be joined must be aligned as accurately as practicable within existing commercial tolerances on diameters, wall thicknesses, and out of roundness. Alignment must be preserved during welding. Where ends are to be joined and the internal misalignment exceeds 1/16-inch, it is preferred that the component with the wall extending internally be internally trimmed (see Fig. 127.3) so that adjoining internal surfaces are approximately flush. However, this trimming must not reduce a piping component wall thickness below the minimum design thickness and the change in the contour may not exceed 30°.
(4) Spacing. The root opening of the joint shall be as given in the procedure specification.
(b) Fillet welds (modifies 127.4.4). In making fillet welds, the weld metal must be deposited in such a way as to obtain adequate penetration into the base metal at the root of the weld. Piping components that are to be joined utilizing fillet welds must be prepared in accordance with applicable provisions and requirements of this section. For typical details, see Figures 127.4.4A and 127.4.4C of ASME B31.1 (incorporated by reference; see 46 CFR 56.01–2) and 46 CFR 56.30–10(b). See 46 CFR 56.30–5(d) for additional requirements.