Pipe joining apparatus

A purge bladder apparatus comprises an inflatable bladder 44a,b formed from an elastomer with an elongation of at least 500%. A housing 43a,b has the inflatable bladder mounted on it, and comprises an inlet 45a,b for receiving a purge gas to inflate the bladder, and a retainer 42a,b to secure the bladder to the housing. The housing can comprise a through flow pipe 46b such that a portion of the purge gas can be flowed through the housing. The elastomer can be a polysiloxane nanocomposite elastomer. A pipe joining system 40 for welding abutting pipes 49a,b comprises a first apparatus with a first bladder, and a second apparatus with a bladder with the through-flow pipe, and a supply of purge gas. The first apparatus is inserted in the first pipe and the second in the second pipe, each either side of a weld line. The purge gas flows through the through-flow pipe to inflate the first bladder and to create a gas tight seal. The gas then flows into the second bladder to inflate it and create a further gas tight seal. The weld is then performed under a positive pressure of the purge gas.