Expansion Loop Length Calculator

Calculator Inputs

Unit system

Switching will keep your last posted values.

Material preset

Loads defaults for α, E, and allowable stress.

Sizing method

Use empirical only for rough early checks.

Straight run length, L₀ (m)

Length between anchors or change points.

Pipe outside diameter, D (mm)

Use actual OD, not nominal size.

Temperature change, ΔT (°C)

Operating minus installation temperature.

Thermal expansion coefficient, α (per °C)

Typical steel ~ 12×10⁻⁶ /°C.

Elastic modulus, E (GPa)

Typical steel ~ 200 GPa.

Allowable stress, S (MPa)

Use project allowable at operating temperature.

Results appear above this form after submit.

Formula Used

1) Thermal expansion of the straight run: ΔL = α · L₀ · ΔT

2) Elastic stress sizing for a simple U-shaped expansion loop (preliminary sizing): L_l = √( (3 · E · D · ΔL) / (2 · S) ) where E is modulus of elasticity, D is pipe OD, and S is allowable stress.

The calculator also shows an optional quick empirical estimate used in some field checks: L ≈ 6 · √(D · ΔL) (with inches for D and ΔL).

How to Use

Choose your unit system and a material preset.
Enter the straight run length between anchors or fixed points.
Enter the pipe outside diameter and expected temperature change.
Review α, E, and allowable stress; adjust for your specification if needed.
Click Calculate to view thermal growth and recommended loop leg length.
Download CSV or PDF to keep a project record.

Example Data Table

Scenario	Run length	Pipe OD	ΔT	Method	Recommended leg
Hot water line	30 m	60.3 mm	60 °C	Elastic	≈ 800 mm
Steam header	50 m	114.3 mm	150 °C	Elastic	≈ 2,100 mm
Chilled water	40 m	88.9 mm	35 °C	Elastic	≈ 1,000 mm

Example values are illustrative; use project-specific properties and stresses.

Calculator Inputs

Formula Used

How to Use

Example Data Table

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