Law Supply, Inc.
Web Page - Lineal
Thermal Expansion Curve For PVC Pipe
The values for this
curve are based on a ten (10) foot section of pipe, Values for larger
spans can be obtained by multiplying the values form this curve by the
span length (in feet) and divided by ten.
This curve is based
on the equation
Expansion and Contraction During Installation
Pipe coupled-up ditch side in hot sun
expands appreciably, and pipe surface temperatures may be 120°F.
When the pie is filled with water for testing or service, the temperature
may drop to 70°F. This 50°F temperature change would cause
a contraction of 1.8 inches per 100 feet of PVC-1 (form chart), and would
cause coupling leads or failures if not controlled.
This contraction is normally handled by
snaking the pipe from side to side in the ditch during installation, and
covering with 2 or 3 inches of loose fill as the installation progresses
to prevent excessive surface temperature buildup on the pipe. The
joints are left exposed for subsequent testing for leads. When the
line is slowly filled with water for testing and air expulsion, the temperature
change, and resultant contraction, is easily handled by the additional
length in the snaked section.
Expansion and Contraction in Service
After the earth in a trench is well settled
or heavily compacted, the buried line is relatively immobilized and the
snaked line offers very little expansion and contraction control.
Where ambient ground and fluid temperatures
are nearly equal and relatively constant, the expansion and contraction
changes are absorbed in the pipe walls and slight linear movements in the
line.
However, in exposed lines or in buried
lines where ambient or ground temperatures differ appreciably, expansion
and contraction joints must be installed in the line at properly spaced
intervals to provide control.
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Last updated 03/31/2003
Information taken from CANTEX
Manual