Thermal Expansion Explained

What is thermal expansion?

Thermal expansion occurs when materials are heated and particles vibrate more leading to an increase in the length, volume and area of materials. In hot water systems pipework is heated and this can lead to movement in the pipework. This is due to the metal pipework expanding so that it moves away from its rest position as the length, area and volume of the pipework increases. Your systems are then put at risk as added stress on your pipework can result in costly damages and misalignment to your systems. In severe cases this can lead to failures in the pipework system due to the stress placed on the pipework as the metal undergoes linear expansion in a fixed position causing the pipe to bend.

Pipework can also be subject to thermal contraction when the temperature of water passed through the system is lowered. The reduction in length, area and volume of pipework can cause breakages between the pipe supports and pipework and even to the structure of the building itself. The contraction of pipework again can cause misalignment in water systems without appropriate corrective measures.

How can I reduce stress caused by thermal expansion?

Fixing damages to pipes as a result of thermal expansion is costly and can cause you to fall behind in deadlines. Luckily, there are precautions you can take to ensure that your hot water and heating systems are protected for a long service life. This includes the utilisation of thermal movement products such as expansion bellows, anchor brackets and slide guides.

Slide Guides, such as our EMFLEX Slide Guide & Rubber Lined Clip Set, avoid bowing and bending in the pipework by allowing the pipes to move in an axial direction when they undergo heat expansion or contraction and move from their original position. By supporting the expansion of pipework in the water system, this reduces stress on the system as a whole by realigning any lateral movement that has been caused through forces acting on the pipework.

Anchors are used to secure the pipework in place and control movement to prevent any damage. Cleated anchor brackets can be manufactured to any centreline which you require with the use of extended legs, or they can be ‘packed out’ with a Unistrut frame. Our EMFLEX Type CAB/N Anchor Brackets are one of our best selling products, and work in conjunction with our expansion bellows and twin clip slide guide sets to solve your thermal movement problems. More detailed information on these anchors can be found on our data sheet.

Expansion bellows, such as our Screwed Expansion Joints, work to absorb pipework expansion and therefore protect the pipework from excessive stress. For this specific expansion joint we recommend the installation of an anchor point toward the end of the pipe run either side of the bellows to help withstand the forces in the pipeline due to the internal pressure in the bellows. These joints are particularly effective as pressure placed on the pipework is transferred to the expansion bellow which is better designed to withstand the forces as a result of thermal expansion.

How can Minikins help?

Calculating the impact of thermal movements is difficult. Not only do you need to take into account the thermal properties of your pipework material, but also the routing of your system should be accounted for with changes in direction also having an effect on how your material changes can be dealt with.

Not all pipework expands at the same rate, as for different materials the coefficient of expansion changes. For example the linear expansion of copper is 16.7 micrometres per degree whereas the linear thermal movement of steel is 11.6 micrometres per degree. Hence, the varying rates of heat expansion on pipe materials leads to different levels of movement and misalignment in different water systems. Therefore, it is always recommended to use expert advice when finding solutions to thermal expansion problems.

At Minikins we specialise specifically in calculating thermal movement in water systems and finding expansion solutions. This typically involves calculating the increase in volume of carbon-steel, copper and other types of pipework when the water passing through the system heats or cools the pipework. We can then advise you on suitable adjustments to your water systems to eliminate the effects of expansion and reduce stress throughout the pipework.

For a free instant analysis, drop your drawings files here. Or alternatively, ring one of our experts on 01423 326 789.

Useful links

Examples of pipework bending due to thermal expansion:

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