The welded butt joint can be furnished in any diameter or wall thickness and is suggested for exposed joints that will be subject to excessive bending, in-service thermal cycling, or vibration. Most steel pipe installed using horizontal directional drilling (HDD) methods are furnished with butt joints. The joint can be welded from either the inside or outside, or from both sides. Single welded butt joints can be furnished with or without backing. Backing assists in placement of a sound root pass. Backing also aids in aligning pipe ends during assembly and welding, although it limits joint deflection. Design joint deflections are accomplished by miter cutting one or both ends of the mating pipes. Miter cutting only one pipe end is acceptable as long as the assembled joint between the resulting ellipse of the cut end and the mating pipe square end does not yield an edge offset that violates the guidelines of the governing welding standard, code, or specification.
