Carlon Expansion Joints for PVC Rigid Nonmetallic Conduit - Manual (Page 4)

Setting Expansion Joint for Temperature
When a more precise calculation for expansion is needed,
it can be calculated as follows:
1. You must determine the maximum temperature range. This is done by subtracting the lowest
temperature you anticipate from the highest temperature you anticipate.
Example: Let’s say in winter, we expect the temperature to get down to -10°F and in the summer, we
expect the temperature to get as high as 110°F. The maximum temperature range is 110 -(-10) = 120°F.
2. The length of run between fixed points must be determined. Let’s assume 90 feet for this example.
3. The total expansion change can be calculated as follows:
Total expansion change in inches = (coefficient of thermal expansion) x (maximum temperature range)
x (length of run in inches).
Example: Total expansion change = (3.38 x 10 -5 in./in./°F) x (120˚F) x (90ft x 12in./ft) = 4.38 in.
Thus, travel can be covered with one 6 inch expansion joint.
4. The “set position” can be determined from the following example.
Example: If the temperature at installation was 65°F, the difference from maximum is 110°F- 65°F = 45°F.
Use ratio: (difference from maximum) / (Total expected range) = 45/120 = .375 in.
(0.375) x 6 inch travel = 2.25 in.
The piston at 65°F would retract 2.25 inches.
A.
For medium temperature
(65˚ - 75˚ F) set piston
1 / 2 way in barrel.
B.
For cold temperature
(20˚ - 30˚ F) set piston
1 / 4 way in barrel.
C.
For hot temperature
(95˚ - 105˚ F) set piston
3 / 4 way in barrel.
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