Calculate how much a pipe, bar or vessel grows or shrinks with temperature, for expansion loops, thermowell and sensor mounting checks.
ΔL = α L ΔTSteel and stainlessPlasticsExpansion loops
× 10⁻⁶ /K
°C
°C
Length change96 mm
New length50.096 m
Strain0.192 %
How this result was calculated
ΔL = α × L × ΔT = 12 × 10⁻⁶ × 50 × 160 = 96 mm
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Linear Expansion Formula
ΔL = α × L × (T2 − T1)
α is the mean coefficient of linear expansion over the temperature range. Values shown are typical for about 20 to 100 °C; they rise slightly at higher temperatures.
Worked example
A 50 m carbon steel steam line heated from 20 to 180 °C grows 12 × 10⁻⁶ × 50 × 160 = 96 mm.
Key insight: restrained thermal expansion creates huge forces: fully restrained steel builds up about 2.5 MPa of stress per °C. That is why long hot lines need loops, bellows or guided supports.
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Frequently Asked Questions
How much does steel expand per degree?
About 0.012 mm per metre per °C, so 1.2 mm per 100 m per °C.
Why do plastic pipes need more expansion allowance?
PVC expands about four times and HDPE more than ten times as much as steel for the same temperature change.
Does thermal expansion affect instruments?
Yes: it moves tank nozzles, changes the length of displacers and capillaries, and loads small bore impulse lines.
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