6.4.3 Joints

- Several types of joints such as rubber gasket joint konwn as Tyton Joint
- machanical joint konwn as Screw Gland Joint
- Conventional joint known as Lead Joint are used.

6.4.3.1 CATEGORIES OF JOINTS

Joints are classified into the following three categories depending upon their capacity for movement.

(a) Rigid Joints-

Rigid joints are those which admit no movement at all and comprise flanged, welded and turned and bored joints. Flanged joints require perfect alignment and close fittings are frequently used where a longitudinal thrust must be taken such as at the valves and meters. The gasket used between flanges of pipes shall be compressed fiber board or natural or synthetics rubber. Welded joints produce a continuous line of pipes with the advantage that interior and exterior coatings can be made properly and are not subsequently disrupted by the movement of joints.

(b) Semi Rigid Joints

Semi rigid joints is represented by the spigot and socket with caulked lead joint. A semi rigid joint allows partial movement due to vibration etc. The socketed end of the pipe should be kept against the flow of water and the spigot end of the other pipe is inserted into this socket. A twisted spun yarn is filled into this gap and it is adjusted by the yarning tool and is then caulked well. A rope is then placed at the outer end of the socket and is made tight fit by applying wet clay, leaving two holes for the escape of the entrapped air inside. The rope is taken out and molten lead is poured into the annular space by means of a funnel. The clay is then removed and the lead is caulked with a caulking tool. Lead wool may be used in wet conditions Lead covered yarn is of great use in repair work, since the leaded yarn caulked into palce will keep back water under very low pressure while the joint is being made.

(c) Flexible Joints

Flexible joints are used where rigidity is undesirable such as with filling of granular medium and when two sections cannot be welded. They comprise mainly mechanical and rubber ring joints or tyton joints which permit some degree of deflection at each joint and are therefore able to stand vibration and movement. In rubber jointing special type of rubber gasket are used to connect cat iron pipe which are cast with a special type of spigot and being socket in the groove, the spigot end being lubricated with grease and slipped into the socket by means of a jack used on the other end. The working conditions of absence of light, presence of water and relatively cool uniform temperature are all conducive to the prservation of rubber and consequetly this type of joint is expected to last as long as the pipes. Hence, rubber jointing is to be preferred to lead jointing.