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Piping loops might seem unimportant, but they are a critical part of a piping system for many reasons. Mitigating thermal expansion effects on piping is the key to its ability to function, and piping loops are critical for this. Your project can reap the benefits of expansion loops, and ensure that your piping system’s service life is extended. This is why knowing what they are is important.  So, if you are looking for additional information on piping loops, examples of piping loops, sliding elements, facts on thermal expansion, and pipe stress, you’ve reached the right place. Find out all about expansion loops in this article by Pro Support Solutions.

What are expansion loops?

A piping expansion loop refers to a loop that is added to a particular “u”-shaped structure of a pipe run. They can be made from a standard pipe and are placed between the top and bottom elbows in the middle of the two anchors of the pipe. 

What do expansion loops do?

Expansion loops are used in piping systems to help with thermal displacement and thermal movement. If thermal movement reaches a value that is higher than expected, expansion loops can keep thermal displacement to a minimum and deflect stress from the piping system. A piping engineer or stress engineer can use piping expansion loops to achieve sufficient flexibility in a pipe run, and ensure that the pipe length can handle the potential expansion stress that thermal expansion or contraction causes.

How do expansion loops work?

Expansion loops work in a few key ways. First, they offer a particular piping leg in a direction that is perpendicular to make thermal expansion absorption easier. Then, when bending stresses occur, the stress builds at the loop’s elbows and the bend passes through the horizontal pipe. When it gets to the bottom pipe, and the loop rises, the stress and bend finally reduces.

Which other factors contribute to pipe stress?

One of the main other factors that contributes to pipe stress is the pipe’s outer diameter. The outer diameter of the pipe can impact how successfully the pipe copes with pipe stress and whether it can deflect the maximum amount of stress and function efficiently.  To provide an example, CPVC pipes can expand approximately 1.6 inches, regardless of the outer diameter, if they undergo a temperature of 120 degrees Fahrenheit or a minimum temperature of 80 Fahrenheit. 

What does thermal pipe expansion and contraction mean?

Thermal expansion and contraction of pipes refers to the way that piping materials or hot fluids expand and contract due to temperature changes in the different materials flowing through the pipes. A higher temperature, or temperatures higher than the maximum temperature, will lead to pipe expansion. If there is a temperature change, the minimum temperature can lead to pipe contraction.  The pipe expands in cases where there is a constrained pipe run at both sides. Recognizing how temperature change and the temperature range causes a piping system design to fail is important. Piping engineers must therefore know the minimum and maximum temperature of the pipe’s materials.

How does thermal movement affect pipes and how do pipe loops help?

Thermal movement and thermal expansion can lead to system failure in piping if it remains unchecked. This may result in an unreliable system and eventual repairs to save it. However, pipe loops can help engineers to avoid issues with thermal movement.  Thermal movement and internal pressures can lead to pipe buckling, as well as damage to pipe valves and clamps. It might even cause pipe fractures in the pipe material and also cause carbon steel damage to the pipe material. Using a pipe loop can help engineers to ensure the pipes accommodate the thermal movement, reduce it, and save the system.

What types of expansion loops are available?

There are a few different types of expansion loops available for your project. Some of the main styles include symmetric and non-symmetric loops, or 2 dimensional and 3 dimensional loops.

Symmetric and asymmetric loops

The symmetry of expansion loops can be classed as symmetric or asymmetric. Symmetric expansion loops are equidistant from the fix supports and anchors, whereas asymmetric expansion loops are not.

2 dimensional and 3 dimensional loops

If you have sloped lines in which two-phase flow is a potential, 2 dimensional loops are the ideal choice. In other scenarios, a 3 dimensional expansion loop is a good option.

What is the perpendicular length and how is it affected by thermal expansion?

The perpendicular length is the expansion loop’s length. It’s best to have a greater expansion loop length as this is ideal for a piping system. However, because it can be difficult to support a long perpendicular leg length, an expansion loop is required.

What should you use if an expansion loop doesn’t fit?

There are a few examples of equipment that can be used instead of an expansion loop if one will not fit. You might choose expansion joints that permit axial movement, such as an expansion bellows, but always remember that it’s important to consider the pipe’s pressure if you choose this type of expansion joint. 

What is an expansion joint and why are they a good choice?

Although expansion loops are very useful, they do need a significant space. You have the option of using an expansion joint to cope with large diameter lines or low pressure.  What’s also important is that no adequate support structure is needed to support an expansion loop’s weight, and that expansion loops might be safe but require more space.  An expansion joint is specially assembled to absorb significant shock and permit the piping to move. They are normally used in areas that are smaller and enclosed.

Expansion loops: Which design factors can affect them?

There are a few main design factors that can affect expansion loop installation. Not only should you consider the linear expansion amount, and the factors that impact the linear expansion amount, but you should also think about the length of the pipe, the working stress and the stiffness of the pipe – also known as modulus of elasticity.

Linear expansion

Linear expansion refers to how much a pipe will expand or contract. The levels of thermal expansion on different materials are affected by different coefficient factors. Piping systems are tested to determine the linear expansion amounts. Linear expansion is also affected by the length of the pipe run and, as mentioned, the temperature range and can impact the expansion loops that you select.

Working stress and structural integrity

The structural integrity of piping material can be affected by the working stress. This is best described as how much stress a material can handle while it is being used. Movement can impact the structural integrity and is one example of working stress in piping. Since expansion loops must restrict movement, it’s important to consider how working stress affects the structural integrity and which expansion loops best contain the movement of your piping expansion loop.

Modulus of elasticity or stiffness of the pipe

The stiffness of the pipe, also referred to as the modulus of elasticity, can determine whether it can withstand thermal expansion due to the pipe’s ability to extend or contract. So when it undergoes a force or experiences thermal expansion forces, a pipe’s modulus elasticity should be considered when choosing expansion loops.

Expansion loops: With which types of equipment and how are they installed?

Expansion loops are normally installed in pipe runs and run over pipe racks. They tend to be installed at every 500-meter pipe length.  The integration of piping loops for piping expansion and contraction should take place during a project’s design phase. This will ensure that any pipe joints stress, and the leaks that may occur as a result, are kept to a minimum. 

How do expansion loops compare to expansion offsets?

There is a difference between expansion loops and expansion offsets. Though both help with expansion and contraction, they are used in different ways.

Expansion loops vs. expansion offsets

Expansion loops can be used in “u” shaped pipe configurations that are supported with pipe support brackets. The hanger enables the movement of the pipe, so it can move forwards and backwards, although it is slightly rigid. During expansion, the “u” shape gets narrower and during contraction the pipe opening widens when materials expand because of increased kinetic energy and the change in the molecular structure of the material flowing through the piping. Expansion loops also contribute to pressure loss. With an expansion offset, they are used as a deflection mechanism that other piping engineers use if they need to ensure that a pipe will avoid fixed structures. You might need to use an offset for straight runs that are long, and for this setup an adjoining pipe may permit some movement.  In an expansion offset, you may need to place a hanger at a defined distance from the corner elbow of the piping system.

Pipe supports for vertical pipes and movement limitation

Using pipe supports to support piping systems and a vertical pipe is important for movement limitation that can occur due to temperature changes. The vertical length can be supported by hangers. 

Which elements should I choose to accompany an expansion loop?

The best elements and components that you should choose to accompany an expansion loop are sliding elements. Some of the sliding elements include sliding plates, sliding sledges, and sliding bases (by MEFA). You might also choose suspensions and sliding supports which are ideal for axial expansion requirements.

Choose from MEFA’s piping expansion loop components for the best quality

Choosing expansion loop components can be a challenge since all manufacturers claim to be the superior option, however MEFA is backed by 70 years of industrial excellence and is one of the leaders and best manufacturers of fastening technology. MEFA is second to none in terms of exceptional quality. When you choose your expansion loops, check out MEFA’s selection of components and get more advice on thermal expansion by visiting Pro Support Solutions.