Aligning two pipes for butt welding, using expanding mandrel - to obtain smooth bore for pneumatic conveying of fragile goods

TLDR: In this paper, two pies are centred and aligned by an expanding mandrel prior to being joined by butt welding process, which comprises: (a) expansion of the mandrel until it meets the pipe with the smaller diameter and provides pipe with a circular cross-section; (b) conversion of a second pipe to circular crosssection, and/or expansion of pipe, depending on the ovality of pipe and the diametrical tolerances of pipe; (c) combined expansion of two pipes is finally efected.

Abstract: Two pies are centred and aligned by an expanding mandrel prior to being joined by butt welding Process comprises: (a) expansion of the mandrel until it meets the pipe with the smaller dia and provides pipe with a circular cross-section; (b) conversion of a second pipe to a circular cross-section, and/or expansion of pipe, depending on the ovality of pipe and the diametrical tolerances of pipe; (c) combined expansion of the two pipes is finally efected The expansion may be carried out via a work cylinder, the expansion being limited by a safety valve on a pump feeding the work cylinder Alternatively, expansion may be continued until >=1 pipe is forced against an outer reinforcing ring The pref mandrel uses expanding segments fitted with Cu pads pressed against the pipes Method may be used eg for welding pipes used as pneumatic conveyors in hospitals etc for bottles of blood or medicines; or for conveying powders No surface roughness or weld metal is present in the bore of the pipes at the welded joint, ie there is no interference with the travel of conveyed objects