Specifications Part 1 - Water Supply, Sewerage and Tube Well Works

frequently used and in normal or slightly corrosive environments, brass fittingsare commonly employed. In certain cases, threaded malleable cast iron fittingsare used.8.21.3 Insert Type Joints (see Fig.1)8.21.3.1 These are commonly used for MDPE pipes where in a serrated PE or metallicfitting is inserted into the pipe and tightened by a clip.8.21.3.2 The outer serrations of HDPE/metal insert type fittings lock into the PE pipes toprevent their coming out under sudden pressure surge. If the pipe bore isslightly undersized, a little heating by immersion in boiling water in case ofMDPE and oil bath (130 0 C) in case of HDPE would soften the pipe to enableinsertion of fittings. If the bore of the pipe is loose, the bore clip of worm drivetype will secure the fitting and ensure a leak proof joint. The insertion of thesefittings into the bore of the pipe is done with hand pressure only. As a measureof safety, worm drive type clip should be used in all cases. This type of jointingis used normally in small diameter pipes up to 110mm.8.21.4 Compression Fittings8.21.4.1 They are used for MDPE and HDPE joints. They are detachable joints and aremade of metals or plastics.8.21.4.2 In the majority of cases the metal fittings are based on the type of compressionfittings commonly used with copper tubes. In this type of joint the dimensions ofthe pipe are generally not altered. The joint is effected by an internal liner and acompression ring or sleeve which shrinks and therefore compresses the pipewall on to the liner, thus gripping to the wall of the pipes. The liner andcompression sleeve may also be a integral unit (see Fig. 2).8.21.4.3 In other case the flared pipe wall is compressed on a conica insert either bytwo male and female threaded metallic nuts (see Fig.3A) or by backing looseflanges (see Fig. 3B). The water seal is made by compression of ends of PEflared pipe between sloping surface of metallic nuts/flanges and conical inserts.8.21.4.4 Compression Joints with Collar/Pipe Ends and Flat Gaskets Aluminum alloyor brass fittings with male and female coupling parts are available for jointingwith metallic fittings. The male and female ends of the coupling are insertedface to face on two ends of the pipes to be jointed. Collars are made on thepipe ends by heating the ends with hot plate or electric coil. The two collars arebrought together and the female end of the coupling is tightened on the maleend. A water tight seal is made between the flanges. This is a detachable typeof jointing and is practicable up to 50mm dia pipes (see Fig.4)8.21.5 Fusion Welding8.21.5.1 Fusion welding is commonly used in HDPE and is permanent type of joint.8.21.5.2 Procedure of Butt Welding of HDPE pipes.8.21.5.3 The pipe should be cut square and the face of the pipe should be slightlyscraped prior to welding to remove oxidized layer. At the time of welding,leveling of the pipes is essential particularly in case of larger diameter pipes.Welding temperature should be 200 0 C and surfaces of heating mirror should be210 0 ± 5 0 C [heating mirror is a metallic plate heated up to the requiredtemperature either by electrical coil embedded inside or by blow torch. Theword mirror has come because this heating plate radiates heat (see Fig.5).]Urban Administration & Development Department Page 96