Expansion joints are a critical component of any industrial application, including piping or ducting. With a wide range of designs and materials to choose from, the proper selection and optimal installation of expansion joints is critical to ensure reliable and safe operation.
Commercial and industrial installations with any type of pumping, piping or ducting also almost always include expansion joints or movement joints. Expansion joints are necessary safety components in order to mitigate the effects of thermal expansion, vibration-induced movement and even external factors such as seismic activity or ground settlement.
Made of a variety of materials such as stainless steel, rubber or polytetrafluoroethylene (PTFE), expansion joints help ensure structural integrity. For example, when industrial processes require large temperature changes, the thermal expansion of metal components can introduce stresses that can lead to fatigue. Expansion joints can eliminate this potential source of failure.
Single Flange Limit Expansion Joint
Due to their inherent flexibility, rubber expansion joints have many particularly beneficial properties, provided it meets the application temperature/pressure requirements. This makes them suitable for many applications, including sound absorption, heat and shock. Known for their durability and ability to withstand extreme environments, rubber expansion joints are commonly used in harsh applications such as pulp and paper, chemical processing, water and wastewater, mining and metals, and pumping applications. Rubber expansion joints are also often used to reduce fluid noise from the rotating equipment they are connected to.
Usually made of natural or synthetic oil-based elastomers, materials used for rubber flexible joints include EPDM, neoprene, neoprene and Hypalon, Nitrile and natural rubber, and other materials including metal or steel wire reinforcement, nylon, polyester, aramid fiber or PTFE.
In some extreme environments, such as high or low PH chemical systems, expansion joints are made of molded PTFE or PTFE-lined rubber. As a non-reactive material, PTFE has some advantages for chemical processing industries where highly corrosive materials may be present. Molded PTFE or PTFE-lined rubber expansion joints are specifically designed to protect piping in contact with strong industrial and reactive materials.
Systems with braided metal hoses are designed to control vibration, reduce noise, relieve pressure and compensate for potential misalignments while withstanding higher operating temperatures/pressures. Suitable for many different mechanical applications such as pumps, compressors and other heavy equipment, these connectors are made from a variety of different metals, including copper and stainless steel, to suit the most extreme applications.
Given that expansion joints often operate in potentially rigorous processes such as power, steel, pulp and paper, mining and chemicals, proper selection, installation and maintenance are key to ensuring reliability and maximizing performance for optimum service life. In situations where expansion joint failure can lead to system downtime, material selection and optimal installation are key. For example, rubber expansion joints that are used improperly or installed improperly at too high a temperature will lose the oil inside the rubber over time, resulting in a loss of elasticity. This will cause the expansion joint to become brittle and prone to accelerated failure.
Check the expansion joint manufacturer's performance characteristics and seek assistance with design considerations based on the manufacturer's application experience to reduce the likelihood of failure. Some initial considerations when selecting an expansion joint are selecting a size appropriate for the application and available footprint, and the rating of the expected temperature and pressure range the equipment will see during its service life. Other factors may include the viscosity of the fluid being pumped, if it contains solids, and whether there are any potential incompatibility issues between the process fluid and the expansion joint material. Total cost of ownership is also a key factor in selecting the best expansion joint for any given application.
Q: I have a wall system with multiple windows spaced closely together with arches. Obviously I need expansion joints in the 80-ft length of masonry above these arched windows.
Where should I install the expansion joints?
A: It is very difficult to install expansion joints when the arch openings are closely spaced. There are basically two approaches for providing expansion joints at walls containing multiple arched windows.
The most common is to place the expansion joint in the pier between the adjacent arches. However, since the pier is only 32-in. wide, there probably will not be enough masonry adjacent to the expansion joint to resist the lateral thrust of the arch.
The expansion joint cannot be placed within a true arch itself since the arch relies on compression to carry load to the masonry on each side. An expansion joint, by its very definition, disrupts this region of compression, which would cause the arch to fail.
One solution is to use curved steel angles to support the masonry at some of the arched openings to permit the installation of expansion joints. A joint can be installed at the apex of these false arches since they are no longer structural.
Expansion joints and pipe layout
Even the best and most expensive products are more likely to fail if they are not installed properly. Conversely, proper installation of the correct product will not only extend the life of the system, but will also increase the total life of the entire system.
Proper pipe alignment is high on the priority list. Offset installations automatically put expansion joints in a difficult situation and can cause very real hazards to the product and the operator. Expansion joints are not designed to compensate for inaccuracies in piping installations, nor should they be used to correct them. Likewise, vibration should be minimized and expansion joints should be located as close as possible to the fixed anchors or control rods that should be used for non-anchored piping systems. Adequate pipe support is also important, as expansion joints should not have to bear the weight of adjacent piping/equipment in order to function properly.
The location of the expansion joint (siting) is another key consideration. Ideally, expansion joints should not be installed in areas where they cannot be inspected. In addition, where expansion joints convey hazardous materials, an external metal shield should be considered to protect personnel in the event of a leak or failure, as the fluid will flow parallel to the piping system, rather than radially out.
It is also important to consider the type of expansion joint and its material. For example, while it is common practice to place pipe insulation over metal expansion joints, this practice should be avoided when using rubber expansion joints. Insulation can allow heat to build up and dry out the rubber, making it more brittle and thus enhancing the failure mode.
On a more general level, during expansion joint installation, operators should inspect expansion joints for any damage, install external hardware properly and ensure proper tightening to ensure leak-free operation.
Following a few simple guidelines and making every effort to ensure that expansion joints are installed correctly will inevitably pay operational dividends.
Although properly sized, specified and installed expansion joints do not require any maintenance, a regular inspection program is still highly recommended. Inspections can identify any problems such as leaks, corrosion or blistering and cracks in the rubber expansion joint. Checking for signs of wear does not guarantee that damage will not occur, but early detection of any potential problems does significantly reduce the total value of the risk. As with all equipment, following the manufacturer's recommended maintenance schedule will likely produce the best results in ensuring maximum service life. When properly installed and maintained, expansion joints can reasonably be expected to have a service life of 7 to 10 years, depending on the application. However, the
Proper use of expansion joints is an effective solution for managing the movement, vibration and cyclic motion associated with temperature changes. With a wide range of sizes, styles, materials and specifications available, the right expansion joint can be used for even the most demanding applications. But to make the most of any expansion joint, choose the right one and make sure it is installed correctly.