Clamping and welding a pipe joint

Abstract

A seal-welded pipe joint mechanically braced by a clamp for preferred use in handling toxic and radioactive materials is disclosed together with a process for joining the same. The joint comprises a pair of abutted male frustroconical skirts, each attached integrally to the pipe segments to be joined and confronting each other at opposed mating and finished surfaces which define a sunken ridge at their periphery. A uniform continuous seal weld of relatively slight penetration seals the opposed mating and finished surfaces at the ridge. The pipe joint is physically secured by a plurality of, for example, three female frustroconical segments forming a circumscribing collet which is circumferentially clamped to the skirt. When the collet is clampd over the abutted skirts with seal weld there between, the mating and finished surfaces are compressd together, relieving the seal weld of shearing and normal stresses. The joining process includes the critical step of uniformly compressing the mating and finished surfaces together before seal welding at the ridge. A preferred embodiment of this compressing step includes drawing a vacuum within or evacuating the mated pipe segments to maintain intimate and uniform contact between the pipe segments at the finished and mated surfaces during seal welding and the following installation of the collet. The compression is released only after the weld has been checked for leaks and the collet tightened. Servicing of the joint by automatic cutting and welding equipment is set forth.