All piping systems expand and contract with changes in temperature. This issue must be addressed with appropriate system design to prevent damage to the system. Expansion during heating and contraction during cooling are typically accommodated at changes in direction within the piping system. Long, straight runs are more susceptible to measurable movement, so expansion loops or offsets are required to absorb these forces without damaging the system.

The rate of linear expansion does not vary with pipe size; the primary factor is the type of piping material. The effects of expansion/contraction are most pronounced on hot water or steam lines in which the temperature changes (∆T) are greater.

To calculate the amount of expansion or contraction, the coefficient of expansion (COE) must be known for the material. These coefficients are standardized and are based on temperature change. Separate coefficients are provided for °F and °C for each material. Because the COE is a ratio, it can be applied to any unit of length (inches, feet, millimetres, metres, etc.).

Table 1 shows the coefficients of linear expansion for commonly used piping materials including ferrous metals (alloys that contain iron), non-ferrous metals (alloys without iron), and thermoplastic pipe (sometimes called thermosoftening plastic). These are used in calculating the amount of expansion or contraction that may occur in piping systems.

Linear expansion can be expressed through the following equation:

[latex]\quad\text{Ch} = \text{COE} \times \text{L} \times \Delta\text{T}[/latex]

Where:

[latex]\quad\text{Ch} = \text{Change in length due to expansion or contraction}\\ \quad\text{COE} = \text{Coefficient of linear expansion}\\ \quad\text{L} = \text{Original length}\\ \quad\text{∆T} = \text{Temperature change of the piping material}[/latex]

Example:

Calculate the change in length of 55 feet of copper tube for a temperature change from 43°F to 185°F.

Solution:

[latex]\quad\text{Ch} = \text{COE} \times \text{L} \times \Delta\text{T}\\ \quad\text{Ch} = 0.0000093 \times 55\text{ ft} \times (185°\text{F} - 43°\text{F})\\ \quad\text{Ch} = 0.0000093 \times 55\text{ ft} \times 142°\text{F}\\ \quad\text{Ch} =0.072633 \text{ ft}[/latex]

Convert the answer to the nearest [latex]\frac{1}{16}\text{in.}[/latex]:

[latex]\quad0.072633 \text{ ft} \times 12 = 0.8716 \text{ in.} \times 16 = \frac{13.95}{16} \text{ in.} = \frac{14}{16} \text{ in.} = \frac{7}{8} \text{ in.}[/latex]

Example:

Calculate the change in length of 22 m of cast iron for a temperature change from 8°C to 22°C.

Solution:

[latex]\quad\text{Ch} = \text{COE} \times \text{L} \times \Delta\text{T}\\ \quad\text{Ch} = 0.0000106 \times 22\text{ m} \times (22°\text{C} - 8°\text{C})\\ \quad\text{Ch} = 0.0000106 \times 22\text{ m} \times 14°\text{C}\\ \quad\text{Ch} =0.0032648 \text{ m}[/latex]

Convert the answer to mm:

[latex]\quad0.0032648 \text{ m} \times 1,000 = 3.26 \text{ mm}[/latex]

Piping System Flexibility

The piping system must be sufficiently flexible to accommodate the movements of the components as they expand. In many cases the flexibility of the piping system, due to the length of the pipe and the number of bends and supports, means that no undue stress is imposed. In other installations, however, it will be necessary to incorporate some specific means of achieving this required flexibility. These include expansion fittings and expansion loops.

Expansion Fittings

An expansion fitting is one method of accommodating expected expansion. These fittings are placed within a pipeline and are designed to accommodate expansion and contraction without the total length of the pipeline changing. These are often referred to as an expansion bellows due to the bellows-type construction of the expansion sleeve (Figure 1).

Other expansion fittings can be made from the same piping in the form of a fabricated expansion loop. This can be a less-expensive option to satisfy the requirement for expansion control, but more space is typically needed to accommodate the piping arrangement.

Expansion Loops

Expansion loops can be fabricated from straight pipe and elbows welded together. If job-site specifications do not allow fabricated loops, manufacturers provide a variety of pre-made loop designs that may be used (Figure 2).

Self-Test C-1.17: Calculate the Expansion and Contraction of Various Piping Materials Due to Heating and Cooling

Complete Self-Test C-1.17 and check your answers.

References

BCcampus. (n.d.). Playlist: Tools and equipment videos. BCcampus MediaSpace. https://media.bccampus.ca/playlist/details/0_3g8xp22x/categoryId/175673 Playlist Details – Trades Access Common Core Line C: Tools and Equipment Videos – BCcampus

BC Industry Training Authority. (2019). Piping trades apprenticeship program: Use Tools and Equipment—Level 1 harmonized [Binder]. Crown Publications, Queen’s Printer for British Columbia. https://www.crownpub.bc.ca/Product/Details/7960000261_S

• Plumber: Competency C-1 Use Mathematics and Science
• Steamfitter: Competency C-1 Use Mathematics and Science
• Sprinkler Fitter: Competency C-1 Use Mathematics and Science

Camosun College. (2019). Line C: Tools and Equipment—Competency D-2 Apply Science Concepts to Trades Applications (Rev. ed.) [Learning guide]. BCcampus.  https://collection.bccampus.ca/textbook/fkXxtNTn/

Camosun College. (2015). Trades Access Common Core Competency D-2 Apply Science Concepts to Trades Applications. Victoria, B.C.: Crown Publications. Download for free from the B.C. Open Textbook Collection (https://open.bccampus.ca/browse-ourcollection/find-open-textbooks/).

Camosun Innovates. (2022). Tools and Equipment Videos [Video playlist]. Camosun College/BCcampus. https://camosuninnovates.opened.ca/

Flinn, C. (n.d.). OER for Trades: Math for Trades [Video collection]. BCcampus MediaSpace. https://media.bccampus.ca/channel/OER%2Bfor%2BTrades%3A%2BMath%2Bfor%2BTrades/175670
Note: these videos align with the open textbooks Math for Trades: Volume 1 and Math for Trades: Volume 2. All videos are by Chad Flinn and available under a Creative Commons Attribution 4.0 Licence.:

Media Attributions

All figures are sourced from Industry Training Authority (2019) and/or Camosun College (2019) and are used under the Creative Commons Attribution 4.0 (CC BY 4.0) licence unless otherwise noted. Images copyrighted by the BC Industry Training Authority are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 (CC BY-NC-SA 4.0) licence.