Copper Tubes Expansion Loops

Overview

Engineering reference data for Copper Tubes Expansion Loops in piping systems.

Key Formulas

Continuity

$A_1 v_1 = A_2 v_2$

Mass conservation in pipe flow.

Pressure Drop

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Darcy-Weisbach equation.

Pipe Area

$A = \frac{\pi D^2}{4}$

Cross-sectional area of a pipe.

Variables

Expansion Loop Design

Expansion loops are used to absorb thermal expansion in copper piping systems. When copper tubes are heated, they expand linearly, and without proper accommodation, this expansion can cause stress, buckling, or joint failure in the piping system.

Loop Capacity Considerations

The capacity of an expansion loop depends on several factors:

• Tube diameter and wall thickness (type K has the thickest wall)
• Temperature differential (ΔT)
• Loop leg length
• Anchor spacing

Thermal Expansion Formulas

The linear expansion of copper tubing can be calculated as:

$\Delta L = L \cdot \alpha \cdot \Delta T$

Where:

• $\Delta L$ = change in length (in or mm)
• $L$ = original pipe length (in or mm)
• $\alpha$ = coefficient of thermal expansion for copper ($9.3 \times 10^{-6}$ in/in·°F or $16.7 \times 10^{-6}$ mm/mm·°C)
• $\Delta T$ = temperature change (°F or °C)

Anchor Spacing Guidelines

Piping should be pre-stressed when anchored to minimize the stress in the system under normal operating conditions. This reduces the range of stress cycling and extends system life.

Pre-Stressing Recommendations

When installing expansion loops in copper tube systems:

1. Install piping at the mean temperature of the expected operating range
2. Secure anchors firmly to structural members
3. Support pipe weight with guides that allow axial movement
4. Size loops for the maximum anticipated temperature differential

Design Notes

• Type K copper tube has the thickest walls among copper tube types (K, L, M) and is commonly used for underground and high-pressure applications
• Loop configurations can be U-bends, Z-bends, or coil arrangements
• Multiple smaller loops may be preferable to a single large loop in space-constrained installations
• Always verify expansion loop capacity against the specific tube size and operating conditions of your application

References

• Original Source