Pipe Joints 133
dharm
d:\N-Design\Des8-1.pm5 Seventh Print
119 82
5
35 80 35
10
C
A B
f
70
f
50
f
(^90) M
100
M 100
f
130 M
70
M70
f
90
f
90
f
96
f
96
f
92
f
92
65
138
f
50
f
70 f
80 f
85
Fig. 8.8 Union joint
8.4.2 Expansion Joint
Long pipes, carrying steam and other hot fluids may undergo axial expansion and contraction
due to variations of the fluid temperature. Expansion joints are used to accommodate such
expansions or contractions.
Corrugated copper fitting (Fig. 8.9a) or a loop made of copper pipe (Fig. 8.9b) may be
placed between two pipes at suitable intervals, to act as an expansion joint.
(a)
D
R
R
45°
45°
D
R
(b)
Fig. 8.9 (a)–Corrugated fitting, (b)–Loop
For better results, an expansion joint, a gland with stuffing box is used. In this, the
sleeve B can have free axial motion in the stuffing box A. The pipes to be joined are connected
to the sleeve B and stuffing box A, at their ends, through flanged joints.
Leakage through the joint is prevented by the asbestos packing D, stuffed in the box
and compressed by the gland C, as the nuts E are tightened. The flanges of the sleeve and the
stuffing box are connected by bolts F. When the pipes experience expansion or contraction,
either the sleeve or the stuffing box or both move axially. The nuts used with the bolts F, may
be adjusted to permit the axial movement (Fig. 8.10).
When an expansion joint is used in a pipe line, it is advisable that the pipes are not
rigidly clamped but are suspended on hangers or supported on rollers (Fig. 8.11).
