Gas heater

A heat treating apparatus comprising an enclosed envelope for locating a turbine article to be treated in a protective atmosphere, the apparatus having means for supplying a protective atmosphere to the enclosed envelope, the enclosed envelope containing:

• a pumping chamber having a fan which simultaneously delivers fluid to multiple fluid conduits connected to the pumping chamber, each conduit having a separate outlet;
• wherein at least one of the fluid conduits has a heater which heats fluid in the conduit before delivery of the fluid to an outlet which supplies a plenum chamber having a plurality of apertures for directing the heated fluid towards a treatment region of the article as impingement jets;
• and
• wherein at least another of the fluid conduits is arranged to deliver a cooling flow of the protective atmosphere from the pumping chamber to an outlet outside the plenum chamber and directed at a further region of the article outside the plenum chamber, at the same time as the one of the fluid conduits delivers the heated fluid to the plenum chamber,
• wherein the turbine article is a bladed gas turbine component, the treatment region includes an aerofoil thereof and the further region includes a disc or hub on which the aerofoil is mounted.