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For any industrial application that includes piping or ducting, expansion joints are a critical component. With a vast range of materials and designs to choose from, correct selection and optimal installation of expansion joints is vital to ensure safe operation.
In installations where pumping, piping, or ducting is present, you will invariably find an expansion joint. Expansion joints are a necessary safety component because they help mitigate the effects of thermal expansion, movement induced by vibration or even external factors such as seismic activity or ground settlement, expansion joints are a necessary safety component.
A wide variety of materials are available in the manufacture of these components such as stainless steel, rubber, or Polytetrafluoroethylene (PTFE). Expansion joints help ensure structural integrity in a piping system. For instance, where industrial processes require large changes in temperature, thermal expansion of metal components can introduce stresses which may cause fatigue. Expansion joints can eliminate this potential source of failure.
Selecting the Right Expansion Joint
Expansion joints are frequently found operating in potentially rigorous processes such as the power, steel, pulp & paper, mining, and chemical industries, so correct selection, installation, and maintenance is key to ensuring reliability and maximizing performance, getting the best service life. Where failure of an expansion joint could lead to downtime of a system, materials selection and optimal installation are key. Rubber expansion joints, for example, if incorrectly used at excessively high temperature or are improperly installed will lose flexibility over time as oils within the rubber are lost. This will lead to the expansion joint becoming brittle and prone to accelerated failure.
Some initial considerations when selecting an expansion joint are to choose one which is suitably sized for the application and the available footprint, as well as rated for the anticipated range of temperatures and pressures that the equipment will see during its operational life. Other factors may include the viscosity of the pumped fluid, if it includes solids, and if there are any potential incompatibility issues between the process fluids and the expansion joint materials. Total cost of ownership is also a critical element in choosing the best expansion joint for any given application.
Correct Expansion Joint Installation
Even the best and most expensive product will become more prone to failure if it is badly installed. Therefore, installing the right product correctly can not only extend the life of a system, but can also enhance its total lifespan.
Correct piping alignment is high on the list of priorities. An offset installation automatically puts the expansion joint in a difficult situation and may create very real hazards for both product and operators. Expansion joints are not designed to compensate for inaccuracies in piping installation and should not be used to correct them. Similarly, vibration should be minimized, and expansion joints should be located as close as possible to fixed anchors or control rods which should be used in un-anchored piping systems. Sufficient pipe support is also critical as the expansion joint should not carry the weight of adjacent piping/equipment to operate correctly.
It is also important to consider the type of expansion joint and its materials. For example, while it is common practice to place piping insulation over metallic expansion joints, when using rubber expansion joints this practice should be avoided. Thermal insulation can allow heat to build up and dry out the rubber making it become more brittle, enhancing the failure mode.
Maintaining Expansion Joints
While an expansion joint that is correctly sized, specified and installed should not require any maintenance, a regular inspection program is nonetheless highly recommended. Inspections can identify any issues such as leaks, corrosion or blisters and cracks in rubber expansion joints. Checking for signs of wear does not guarantee that damage will not occur but identifying any potential problems early does significantly reduce the total value at risk. As with all equipment, following the manufacturer’s recommended maintenance schedule is likely to yield the optimal result in terms of securing a maximized service life. When installed and maintained correctly, expansion joints may reasonably expect a 7 to 10-year service life, though specifics are dependent on the application. However, this does require sticking to a policy of strictly following manufacturer’s recommendations.
Used correctly, expansion joints are an effective solution to manage movement, vibration and the cyclic motion associated with temperature changes. Available in a broad range of sizes, styles, materials and specifications, suitable expansion joints are available to service even the most demanding applications. But to get the most out of any expansion joint choose the right one and ensure it is installed correctly.
Proco Products, Inc. is the leading expansion joint manufacturer in the supply of expansion joints for piping and ducting systems. Find out more about expansion joint offerings from Proco by visiting their website.
