The expansion joint is a type of engineered rubber product designed to minimize the transmission of vibration and abrasion. It is used in a variety of systems, including mechanical, chemical, water, and oil and gas. These joints have multiple advantages. They are resilient, abrasion resistant, and can withstand a wide range of temperatures. They can be installed in both horizontal and vertical surfaces, and they are a cost effective way to protect equipment. They are manufactured in a variety of materials, including EPDM, IIR, and PTFE.
The design of an expansion joint depends on many factors, including the material, the pressure, and the angular movement. It is essential to select an expansion joint that is designed to accommodate a wide range of local actions and weather conditions. Also, it is important to choose an expansion joint that is watertight and able to expelling debris.
The expansion joint consists of a body, fabric or steel wire reinforcement, and a flexible rubber bellow. The bellow is vulcanized after molding. It is typically made from either natural or synthetic elastomers, such as Nitrile, PTFE, and Hypalon. In applications where the joint is exposed to chemicals or raw sewage, a different elastomer should be selected.
Unlike metal or fiberglass expansion joints, the bellow of a rubber joint is not subject to embrittlement. In addition, it is able to flex freely to recover from imposed movements. This expansion joint rubber is an advantage, as it allows the expansion joint to absorb greater lateral motions. It is best suited for applications where vibration is needed to be absorbed.
An automated manufacturing process for rubber expansion joints introduces increased quality and efficiency. Using a computer, the process can be optimized for accuracy and speed. This results in significant production time reduction. It is also possible to produce a variety of expansion joints from the same elastomer, resulting in a consistent product. It is also possible to customize designs to fit customer requirements.
In the past, a lot of manual labor was involved in the production of mandrel-built rubber expansion joints. The resulting joints have a long, flowing arch that is less efficient than the narrow arch of a hand-built joint. In addition, the inner ply of the rubber pulls away from the body of the expansion joint in systems with too much vacuum. This can lead to an electrolytic action.
For higher temperature applications, a metal joint is better suited. It can handle temperature ranges of 120 deg Celsius. A rubber expansion joint can also be used, but will fail when exposed to temperatures that exceed its rating.
In order to maintain its abrasion resistance, the bellow of a rubber joint can be made from synthetic elastomers. These elastomers are also heat resisting. Depending on the application, the bellow may be reinforced with solid metal rings or wires. Generally, the cords are applied in pairs.
Spherical and spool arch type expansion joints are similar. Both have extended flange rings, which enclose part of the joint’s body. This creates a seal between the flanges, reducing the pressure drop. However, the spherical joint has the advantage of eliminating the need for gaskets between the flanges.