TECHNICAL TOOL
Thermal expansion of stainless: calculating the growth of a run
A run of piping grows as it heats, and the family of the grade changes the result by more than a third. Enough to move the sizing of expansion loops and supports.
Result
- Growth
- 64,3 mm
Band used: single value, no documented temperature range
Indicative value — coefficient from the reference set’s inherited generation, with no associated temperature range.
How it works
Enter the length of the run, the installation temperature, the service temperature and the grade. The tool returns the growth in millimetres, calculated from the grade's expansion coefficient.
The interesting result is not the absolute value but the gap between families. An austenitic expands around 35% more than a duplex and 40% more than carbon steel. On a 30 m run between 20 and 150 °C, the gap between a 316L and a 2205 exceeds 12 mm — enough to change the number of loops, the travel of expansion joints and the position of anchor points.
It is also why changing grade mid-project is never neutral: replacing an austenitic with a duplex without revisiting the expansion drawing means changing a design parameter without saying so.
Limits of this calculation
Frequently asked questions
- Why does a duplex expand less than an austenitic?
- Because half its structure is ferritic, and ferrite expands less than austenite. It is a family property, not a grade property: all duplex grades behave comparably, and so do all austenitics.
- Is a 12 mm gap really significant?
- On a network, yes. It translates into expansion joint travel, load on anchor points, and residual stress if the expansion drawing has not been revisited. It is an order of magnitude that changes a design, not a decimal place.
- Does the calculation apply to buried or insulated pipe?
- The free-growth calculation is the same; what changes is the restraint, and therefore the stress generated if growth is prevented. That is precisely what this calculator does not address.