Glass lined fitting and process for glass lining of pipe fitting

In a method of glass-lining metallic pipe fittings a glass liner 13 is inserted into the bore 12 of the fitting 10 and at least the glass liner 13 is heated until it becomes viscid when it is radially expanded into engagement with the bore 12. As shown the fitting 10 which has flanges 14, 19 is closed at one end by a closure member 26 and has an extension member 20 provided with a liner of asbestos or other material to which glass will not adhere attached to the other end. The fitting is preferably coated with at least one ground glass coat 11 after which the glass liner 13 is inserted. The whole assembly is heated and when the glass liner has reached its softening point air pressure is applied through tube 31 so that the liner 13 engages with and fuses with the coating 11. The members 20, 26 are removed and the end surfaces of the glass liner and metal fitting are ground to provide smooth gasket facing surfaces. In another embodiment a tee-shaped fitting is lined with glass by a similar method. The lining is done in two stages, a first glass liner is inserted, heated and radially expanded, the air pressure being maintained in order to rupture the glass liner at the point of intersection of the bores of the fitting. A second glass liner is inserted into the other bore until the closed end is adjacent the point of intersection of the bores. The second glass liner is heated and radially expanded, the air pressure being maintained until the closed end ruptures. The ruptured portions of the two glass liners overlap to provide a substantially uniform glass lining.