Process for constructing clamp-welded pipe joint

摘要

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 by a plurality of, for example, three tangentially disposed bolts. The abutted frustroconical skirts taper from a broad cross section adjacent the pipe wall radially outwardly to a narrower cross section. The sunken seal welded ridge is at the peripheral margin of the abutting surfaces and is set off by annular channels around the periphery of the abutted skirts. Collet segments define an inside annular concavity which fit over and receive the abutted frustroconical skirts. Complementary to the frustroconical skirts, the inside annular concavity of the collet tapers from a broad cross section at the margin nearest the pipe wall radially outwardly to a narrow cross section. When the collet is clamped over the abutted skirts with seal weld there between, the mating and finished surfaces are compressed 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.