Rubber expansion joints are likely the least understood and most abused component in a piping system. They are flexible, stretchy and easily forced into lots of places despite what the installation instructions say. Most of the time, rubber joints are merely an afterthought in multi-million dollar piping systems – until things go awry.
The rubber joint is unmatched for vibration isolation. If properly installed, a rubber joint can greatly reduce equipment nozzle loads. Its resilience allows it to be installed in many different systems under a range of temperatures, pressure, and media. What could possibly go wrong?
Keeping aging facilities and equipment maintained is an everchanging task that can jeopardize the goal of maximizing uptime. Years of thermal cycling, vibration or foundation settling can disorient piping or pumps. Piping engineers will use rubber expansion joints to account for these types of challenges in a rigid piping system. Permanent misalignment can set
in after years of operation. The original size expansion joint could no longer be the best fit when it comes time to replace.
Replacing a permanently misaligned expansion joint connection with the original part could lead to reduced service life and/or missed expectations of the new expansion joint. Determining the best way to accommodate this when it comes time to replace the existing expansion joint can have long-term effects on reliability.
It has long been recognized that rubber expansion joints (REJs) provide critical design functions that impact the reliability of the entire piping system. This has led some industry professionals to an overly conservative calendar-based replacement program and others to a somewhat reckless approach based on running equipment to failure.
Maximizing an expansion joint’s functional benefits while minimizing its inherent risk has always been a goal for the industry.
Until recently, end users have addressed this concern by using performance replacement REJs along with best practices for maintenance, reliability and operations (MRO).
The practice of insulating over metallic expansion joints to minimize heat loss in a piping system may be common, but it is not a good idea to follow this same practice with rubber expansion joints.
Rubber expansion joints typically consist of synthetic (oil-based) elastomers (ethylene propylene diene monomer [EPDM], neoprene, chlorobutyl, nitrile or clorosulphonated polyethylene-CSM) combined with polyester or nylon and wire reinforcing that provide pressure-restaining capability.
If an end user were to install a typical rubber expansion joint in a system needing insulation to cover the joint in a “hot” application, that individual must consider the probability of failure resulting from heat exposure.
This component can compensate for misalignments up to 1/8 of an inch.
Rubber expansion joints are used in piping installations to compensate for thermal growth, relieve piping stress during operation, and reduce vibration and noise caused by rotating equipment. While a rubber expansion joint can compensate for pipeline misalignment, this compliant product has installation and operations limitations. the best method for installing most piping products, including rubber expansion joints, is to follow standardized piping practices and use an installation tolerance of less than 1/8 of an inch.
The criteria for expansion joint selection for fluid piping applications focuses on the expansion joint’s quality, durability and capabilities. To ensure that the rubber expansion joint’s installation provides optimal service life, operators and maintenance personnel must consider specific conditions and take a systematic approach. Piping systems require some degree of flexibility. Inadequate flexibility can lead to a catastrophic, potentially life-threatening system failure, making flexibility an important consideration when selecting an expansion joint.
When discussing expansion joint selection, the conversation typically focuses on the quality, durability and capabilities of the expansion joint. However, the expansion joint’s role in the overall energy efficiency and optimization of the piping system is often overlooked.
All piping systems require some degree of flexibility. Inadequate flexibility can lead to a catastrophic system failure that could even be life-threatening, making flexibility an important consideration in expansion joint selection.
Elastomeric expansion joints have long been recognized for their ability to reduce noise and vibration and accept fluctuating thermal movements in piping systems. Recent advancements in engineered elastomers and textiles led to the development of expansion joints with improved performance and operating life. Equally valuable is their unique ability to be installed in offset and misaligned applications. These cost saving features have made the expansion joint a pivotal component in replacement and retrofit projects, as well as in new construction.