Pipes and Tubes - Temperature Expansion

Pipes expands when heated and contracts when cooled. The expansion of the pipes can be expressed with the expansion formula

The temperature expansion of pipes depends on the start and final temperature of the pipe and the expansion coefficient of the piping material at the actual temperature. The general expansion formula can be expressed as:

dl = α Lo dt             (1)

where

dl = expansion (m, inches)

Lo = length of pipe (m, inches)

dt = temperature difference (oC, oF)

α = linear expansion coefficient (m/moK, in/inoF)

Mean expansion coefficient may vary with temperature as:

Mean Expansion Coefficient - α - (10-6 in/in oF)
Material Temperature Range (oF)
- 32 32 - 212 32 - 400 32 - 600 32 - 750 32 - 900 32 - 1100 32 - 1300
Alloy Steel
(1% Cr. 1/2% Mo)
7.7 8.0 8.4 8.8 9.2 9.6 9.8
Mild Steel
(0.1 - 0.2% C)
7.1 7.8 8.3 8.7 9.0 9.5 9.7
Stainless Steel
(18% Cr. 8% Ni)
10.8 11.1 11.5 11.8 12.1 12.4 12.6 12.8

Formula (1) can also be used with SI units. The expansion coefficient must be adjusted to oC.

Example - Thermal Expansion of Heated Alloy Steel

100 feet of alloy steel pipe is heated from 32 to 212oF. The expansion coefficient is 8 10-6 (in/inoF).

The expansion can be expressed as:

dl = (8 10-6 in/inoF)(100 feet) (12 in/ft) ((212 oF) - (32 oF))

    = 1.728 inches

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