It is no secret that one of the greatest demands for an expansion joint is the expectation to serve a long, leak-free life with little to no maintenance. Once installed, these flexible rubber connectors should require little attention. The preservation of this investment (and one’s sanity) can be maximized with an in-depth overview of how control units can prevent a new expansion joint from being overstressed.
The purpose of a control unit is to act as a safety device against excessive movement resulting from pressure thrust. A typical control unit assembly is comprised of threaded rods, steel gusset plates, nuts and washers.
The requirements of heating, ventilation and air conditioning (HVAC) and plumbing piping systems can be very different from the process industry. HVAC systems use piping to convey fluids for the transfer of energy between different areas of a building. Plumbing piping brings in fresh water while removing the waste from a building. This energy transfer and water movement must all happen efficiently and quietly without disturbing the people living and working in a building. It can be a challenge for the system designers.
The heat transfer fluid (usually water) and fresh water are pumped throughout the building. Pumps vibrate and create noise as they move water. Pumps are also located in a central mechanical room. Architects are notorious for locating these rooms in the worst possible place in a building.
The Piping Expansion Joint Division of the FSA recently completed revisions for the 8th edition of the Piping Handbook, now called the Piping Expansion Joints Technical Handbook. The revised handbook includes a contemporary format with new three-dimensional graphics. The technical content has been expanded and revised to reflect a wider variety of expansion joints and to make the handbook more relevant to the user.
The handbook provides up-to-date compilations of construction standards and guides for specifying and purchasing non-metallic expansion joints and flexible pipe connectors. It is based on the latest information concerning research, design and application of rubber (elastomer) expansion joints by engineers associated with the FSA’s Non-Metallic Expansion Joint Division member companies.
Many members of the Fluid Sealing Association (FSA) Non-Metallic Expansion Joint Division and of the Expansion Joint Manufacturers Association (EJMA) feel that expansion joints are the forgotten components of many piping systems. Other piping systems components – flanges, gaskets, strainers, valves, pumps and the pipe itself – seem to get most of the design time.
In many ways, expansion joints are the most important components of a well-designed piping system. They are the “living and breathing” dynamic part of the whole system.
Without well-designed and well-placed expansion joints, parts such as pump nozzles, valve bodies and pipe anchors could face excessive loading and vibrational fatigue. Without proper compensation, thermal growth at elevated temperatures can damage some pipes, reducing their operation life.
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.