Pipe Joints 131
dharm
d:\N-Design\Des8-1.pm5 Seventh Print
8.3.1 Socket and Spigot Joint
This type of joint is used for underground pipelines of large diameters. In this, one end of a
pipe is made into a socket and the other end into a spigot. After placing the spigot end into the
socket, the space between them is filled-in, partly by rope (jute or coir) and the remaining by
molten lead (Fig. 8.6).
Because of the flexible nature of the joint, it adapts itself to small changes in level due to
settlement of earth.
Socket end
Spigot end
Lead
Rope
f
280
(^3585)
100
12
f
240
f
185
f
180
f
150
Fig. 8.6 Socket and spigot joint
8.3.2 Flanged Joint
This type of hydraulic joint is used extensively, where fluids under high pressures are to be
conveyed. In this, oval shaped flanges are cast integral with the pipe ends. The flanges are
joined with bolts and nuts.
For proper alignment of the pipes, a spigot or projection is formed in the centre of one
flange and is made to fit in a corresponding socket or recess provided in the other flange. A
gasket, made of rubber or canvas is compressed between the spigot and socket ends (Fig. 8.7).
8.4 Special Pipe Joints
In addition to the various types of joints discussed above, there are certain pipe joints which
are used only in special cases. Two such joints, viz, union joint and expansion joint, are discussed
below.
8.4.1 Union Joint
This is a special joint used on small pipes, which cannot be connected using a coupler (refer
article 8.5.1 for particulars), when they are fixed in position or when they are too long to
rotate.
In the union joint shown in Fig. 8.8, the nut A, with both external and internal threads,
is screwed on to the end of one pipe. Another nut B, with a step on its external diameter, is
screwed on to the end of the other pipe. The two nuts and pipes are drawn together by the
coupler nut C. A packing ring inserted between ends of the two pipes, makes the joint air tight.
