| abstract |
Each workpiece, esp. two pipes (1,2) being butt welded, is sealed in its bore with an inflatable bag or balloon (3,4). The two bags are joined to each other via two hose couplings and a gas outlet nozzle (5). Both bags (3,4) are inflated by an inert or protective gas, so nozzle (5) occupies a posn. in the middle of the welding zone inside the two pipes (1,2). Only one gas supply pipe is used to supply one of the bags (3,4), because the gas flows via nozzle (5) into the other bag while also flowing into the ends of both pipes (1,2). The advantage is that one pair of bags (3,4) can be used for pipes of different dia. |