How to Guide

57
ABS, PVC and CPVC pipe, like other piping materials, undergo
length changes as a result of temperature variations above and
below the installation temperature. They expand and contract
4.5 to 5 times more than steel or iron pipe. The extent of the
expansion or contraction is dependent upon the piping material’s
coefficient of linear expansion, the length of pipe between
directional changes, and the temperature differential.
The coefficients of linear expansion (Y) for ABS, PVC, and
CPVC (expressed in inches of expansion per 10°F temperature
change per 100 feet of pipe) are as follows:
Material Y (in./10°F/100 ft)
ABS 0.66
ABS Plus 0.500
PVC 0.36
CPVC 0.408
The amount of expansion or contraction can be calculated
using the following formula:
∆L = Y (T1-T2) x L h
10 100
∆L = Dimensional change due to thermal expansion
or contraction (in.)
Y = Expansion coefficient (See table above.)
(in./10°F/100 ft)
(T1-T2) = Temperature differential between the
installation temperature and the maximum
or minimum system temperature, whichever
provides the greatest differential (°F).
L = Length of pipe run between changes in
direction (ft)
Example: How much expansion (e) can be expected in a
60 foot straight run of 2” diameter PVC pipe installed at
70°F and operating at 120°F?
Solution:
∆L = .360 (120 - 70) x 60 =.360 x 5 x .6 = 1.08 inches
10 100
There are several ways to compensate for expansion and
contraction. The most common methods are:
1. Expansion Loops (Fig. 1)
2. Offsets (Fig. 2)
3. Change in direction (Fig. 3)
Modulus of Elasticity & Working Stress
ABS PVC CPVC
Modulus of Working Modulus of Working Modulus of Working
Elasticity Stress Elasticity Stress Elasticity Stress
(psi) (psi) (psi) (psi) (psi) (psi)
73° F 250,000 N/A 400,000 2,000 423,000 2,000
90° F 240,000 N/A 372,000 1,500 398,000 1,820
100° F 230,000 N/A 352,000 1,240 385,000 1,640
120° F 215,000 N/A 316,000 800 355,000 1,300
140° F 195,000 N/A 280,000 440 330,000 1,000
160° F N/A N/A N/A N/A 300,000 800
180° F N/A N/A N/A N/A 271,000 500
200° F N/A N/A N/A N/A 241,000 400
Per ASTM F 645
Table 1
DESIGN & ENGINEERING DATA
Expansion and Contraction of
PVC Schedule 40, PVC Schedule
80, PVC PR 200 and PVC PR 160
Expansion Loop Formula
L = 3 ED (∆L)
2S
Where:
L = Loop length (in.)
E = Modulus of elasticity at maximum
temerature (psi) (Table 1)
S = Working Stress at maximum
temperature (psi) (Table 1)
D = Outside diameter of pipe (in.) (pages 22-34)
∆L = Change in length due to change in
temperature (in.)
Example:
CPVC 3/4” pipe operating at a maximum temperature of 180°
F (T1) and at a minimum temperature of 70° F (T2) with a
length of run of 10’.
The Modulus of Elasticity equals 290,000 and the Working
Stress equals 500. The system will expand and contract
18.484 inches.
Support Guide
Restraint
L/4
(4.621”)
L/5
(3.697”)
L
L
L
2L/5
L/2
(9.242”)
(18.484”)
L
(7.394”)
(6”
minimum
)
(6”
minimum
)
(4.621”)
LOOP
OFFSET
CHANGE IN
DIRECTION