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What Are Expansion Joints Used For?

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Expansion joints are designed to safely absorb the movement in pipework systems due to heat-induced expansion and contraction of pipework. When a pipeline is subject to a change in temperature it will expand or contract in direct proportion to that change. Expansion joints are primarily designed to compensate for thermal expansion but it is not the only movement being imposed on the pipeline system. Other types of movements can occur that need to be taken into account when providing a pipework flexibility solution such as building settlement, wind loading, vibration from rotating and reciprocating machinery.

Metallic expansion joints are designed to safely absorb the dimensional changes of pipework systems and ducts caused by heat induced expansion and contraction. They are essential in pipework systems that are used to convey substances of a high temperature, such as steam, heated water or exhaust gases. Expansion joints can also be designed for other applications, such as noise and vibration caused by reciprocating machinery, building settlement and in some extreme environments earthquake movement. Expansion joints are very important components with in a pipework system as they not only solve the problems associated with pipework movement but offer such advantages as reducing stresses and loads to connecting equipment such as pumps and steam turbines. Without them, pipes would not be able to withstand the forces exerted upon them and entire pipework systems would fail. When correctly selected and installed expansion joints act to prolong the service life of the pipework system and reduce the risk of downtime and for additional maintenance and repair.

How do they work?
Expansion joints – sometimes called expansion bellows, flexible joints or compensators – are devices that comprise of a flexible element known as the bellows membrane that is fitted to end connections that are best suited to the pipework they are to be installed in. Most bellows membranes are manufactured from stainless steel and are made up of a series of convolutions manufactured to withstand the pressure of the system but also must be suitable to accept the movements for which they are designed. The bellows membrane comprises of a series of convolutions designed to withstand the internal pressures of the system, but at the same time flexible enough to accept axial, lateral and angular deflections.

When faced with a pipework expansion problem there will be a wide choice of solutions dependant on the on the specific configuration of the piping network and also suitability of nearby structures to accept the forces that will be imposed on them when installing expansion joints.

The accepted methodology for providing a justifiable pipework work flexibility solution is as follows:

1)    Consider if the problems of pipe expansion can be solved by natural flexibility.

Most pipelines usually have an inherent flexibility and therefore if routed in in a particular manor such as introducing changes in direction certain pipework systems can be designed to eliminate or reduce the need for expansion joints. However very often due to the constraints imposed by site conditions it is not always possible to reroute the system such that natural flexibility provides an acceptable solution. Also the pipe anchors must be strong enough to hold the forces needed to flex the pipe which can be as high as several tons.

2)    Consider if the problems of pipe expansion can be solved by installing pipe loops

If the pipework system does not have sufficient natural flexibility to accommodate the movement then the option of installing pipe loops could be considered. Pipe loops can be manufactured using elbows and straight pipe and when sized correctly can provide induced flexibility to a pipework system. Again as with natural flexibility pipe loops are not always a suitable option because of constraints imposed by site conditions and the size of the pipe loop needed to accommodate the thermal expansion

3)    Consider if the problems of pipe expansion can be solved by installing expansion joints.

If natural flexibility or pipe loops cannot deal with expansion in a pipework system we must consider an expansion joint solution. There are two distinct types of expansion bellows.

These being:
1)    Axial Expansion Joints – This type of expansion joints accommodates pipe movement by the dimensional shortening or lengthening along its longitudinal axis.
2)    Lateral / Articulated / Angular / Gimbal Expansion Joints – This family of expansion joints accommodates pipe movement by controlled flexing of the bellows membrane. This range of expansion joints provide a different type of movement to axial expansions such as lateral, angular and universal movements. Lateral movement is movement perpendicular to the bellows longitudinal axis whilst angular movement is the rotation of the bellows longitudinal axis at one end relative to the other. Universal movement enable the expansion joint to absorb applied axial, lateral and angular movements.

The choice between the solutions is critical. The wrong choice will impose unacceptable forces on the building or steelwork with catastrophic consequences.

What industries use expansion joints?
Expansion joints are used in all kinds of different sectors and in a huge range of different industrial contexts. Essentially, wherever there is a need to control pipework movement expansion joints are required. They are used in factories and power plants wherever thermal expansion needs to be controlled, such as pipelines that connect with condensers or power turbines. They are used in oil and fuel gas applications.

Specific industries that use expansion joints include the Energy sector such as nuclear power plants and district heating schemes. The Petrochemical industry on oil refineries, pumping stations and oil rigs. Civil engineering, waste management, sewage treatment, recycling, water treatment, aerospace, aviation, defence, the automotive industry, agriculture, mining, metals manufacturing, food and dairy manufacturing and packaging, and so on. Please ask to see Stourflex case studies detailing specific applications within these industries.

What different varieties of expansion joints are there?
Stourflex expansion joints come in a wide variety of designs. We offer a standard range of products that are available off the shelf for immediate delivery and also customised expansion joints that are designed to meet specific client requirements. Our range of expansion joint products includes axial, lateral, angular and gimbal.

Expansion joints are available with a range of end connections to suit client requirements such as flanged, screwed, mapress system fittings, weld ends and grooved ends. However should site conditions demand a unique solution then end connections can be adapted to most applications. All of our designs are based on the very latest specifications laid out by the Expansion Joint Manufacturers Association (EJMA).

Contact us at Stourflex immediately and ask us more about our extensive range of expansion joints