STRETCHING THE BOUNDARIES FOR ELASTOMERIC EXPANSION JOINTS

New Technologies Enable Greater Reliability, Lower Life Cycle Costs

Today’s manufacturing environment is designed to operate more efficiently than ever before. New plants incorporate state-of-the-art technologies that increase productivity and profits while reducing operating costs. Even older plants can reap the benefits of modern technology through capital investments, or retrofits of existing resources.

Design improvements are possible in nearly every phase of a manufacturing environment, from the machines that generate finished products to the piping that conveys fluids or gases through various processes. In many cases, pipes are exposed to variations in ambient temperature and thus become subject to possible dimensional changes. This presents major problems when high stresses are introduced into the system; should failure occur at any point in a piping or ducting system, downtime and repair costs can mount exponentially by the minute.   Additionally, the failure could result in serious safety and environmental issues resulting in possible injury and fines.

Responding to this challenge, engineers have, over time, come to rely on one of two primary methods to regulate thermal expansion and contraction of a piping system. One is by leveraging the pipe’s natural flexibility through incorporation of pipe loops, offsets and Z bends. Often, the cost of additional pipe, fittings and labor needed to fabricate a pipe loop render this approach cost prohibitive. This also increases radiant heat loss or gain within a system, and it drives up the risk of a pressure drop, which can be more than 25 percent higher than that of a straight line run of pipe.

Alternatively, modern engineers more often than not call upon manufactured products; include rubber, or elastomeric expansion joints to thwart problems before they begin. Such joints serve as crucial points of flexibility in a piping or duct system and are designed to provide stress relief from mechanical and thermal movement. Elastomeric expansion joints were designed specifically to provide pipe motion compensation in as short a space as possible in a piping system. Consequently, they are extremely effective against forces of vibration, shock, electrolysis, noise and corrosion. Overall, a properly designed expansion joint system can protect pipes, ducts and their flanges from premature wear, cracking and breakage and greatly enhance system reliability.

Increasingly, pipe and building codes make engineers eminently accountable for shifting ground movements, while growing concern over the environmental impacts of buildings make specification requirements in general even more stringent. With composites, such as PVC, fiberglass and plastics that will “grow” more than steel, and thus have the ability to account for additional system movement, when it occurs, becomes more critical. Additionally, the strength and longevity of leading elastomeric joint products enables greater building efficiency and lower overall operating costs.

As reliability goes, so goes profitability. In today’s competitive environment, businesses simply cannot afford to let system downtime affect their ability to produce and ship product on schedule. Therefore, elastomeric joints have an indirect – but no less important – role in ensuring product quality, process reliability and profitability.

Not long ago, leading joint manufacturers took a critical look at the relationship between the pressure capability of an expansion joint and the media temperature. Engineers also studied concurrent movements and spring rates. Over time, they applied cutting-edge technology developed in the tire industry to manufacture hand-built pressurized piping expansion joints that incorporate woven polyester fabric and polyester tire cord in a fabric matrix bonded within an elastomeric tube and cover. The inherent strength of polyester tire cord allows the joint to provide greater strength and higher pressure capabilities.

These new advances in rubber expansion joint technology provide dramatically “lower forces to deflect” allowing users to save money through lighter anchoring systems and less reinforcement on the piping and flanges. New technology has also spawned expansion joints that are “plastic pipe friendly.” Because it takes less force to “flex” the expansion joint, there exists less of a possibility that the forces will break the pipe or flange.

So how can you leverage this latest technology within your own designs? Consider some key variables when specifying expansion joints for your next project:

• Reaction forces: The forces that are exerted on the matting flanges have a profound impact on long-term operation. The “old school” rule of thumb is: P/4 x D² X Pressure = Reaction Force(Thrust). However, newer technology expansion joints use actual testing at different pressures. This “build to suite” approach reduces the tendency to overbuild systems. This translates into a lighter anchoring system, and it lessens the need to specify additional reinforcement on the piping and flanges. Simply stated, lower forces mean less stress on piping system components. These newer joints also allow for lighter mounts on pumps, resulting in lower life cycle costs.
• Spring rates: Spring rates determine how easily the expansion joint can move from a neutral position. Newer composition and engineering allows the joint to be moved during installation to compensate for minor misalignments, thus reducing labor costs.
• Shape of convolution: Newer arch designs can replace the need for most filled arch designs, flowing arch designs, standard arch designs and wide arch designs. This greatly simplifies the number of replacement stocking items needed for a basic system.
• Pressure capabilities: The increased pressure capabilities of today’s advanced elastomeric technologies eliminate the need for low-pressure, standard pressure and most high-pressure designs.
• Movement capabilities: New single-arch designs provide greater axial extension and compression, torsional and angular movement, lateral movement and vibration flexibility without increasing the face-to-face requirements. Utilizing materials such as EPDM, Neoprene and Nitrile, cover the needs for the majority of elastomeric design requirements. Additionally, expansion joints constructed from standard materials, such as, Nitrile are resistant to many hydrocarbons, fats, oils, greases, hydraulic fluids and chemicals, while EPDM joints are resistant to animal and vegetable oil, ozone, and strong and oxidizing chemicals.

Applications

Elastomeric expansion joints are widely used in a number of critical applications. These include:

• Oil & Gas/Chemical Processing/Pulp and Paper: Today’s advanced elastomeric expansion joints effectively reduce noise and vibration by acting as a shock absorber in systems that handle reactive liquids or gases, corrosive chemicals or abrasive slurries.

• Power Generation: Plants that generate fossil fuel or nuclear energy have come to rely on elastomeric expansion joints to help ensure system life and maximum size capability. Elastomeric joints prove especially accommodating to a wide variety of movements and variations, with designs to compensate for thermal expansion and contraction on cooling water lines, steam turbine exhaust lines, condenser lines, condensate lines, feed suction lines and aeration systems.

• Pollution Control/Wastewater Treatment: Elastomeric expansion joints have proven extremely resistant to corrosion and abrasion. Combined with their overall flexibility, they are well suited to use in raw and secondary sewage lines, centrifugal air blowers and scrub stacks within sewage and/or water treatment plants and air scrubber systems. Other typical installations include sludge pumps, aeration blowers and lines, and grit pump systems.

• HVAC: New designs now incorporate elastomeric joints within HVAC systems for a wide spectrum of commercial, industrial, residential and mixed-use buildings to relieve equipment flange stress, regulate seismic movement, compensate for any possible misalignment and mitigate vibration and noise from normal building operation.

• Marine: Perhaps nowhere is motion and flexibility within a piping system more important than on a ship. Compact and durable, elastomeric joints ideally suited to meet these challenges. They also effectively dampen noise, and they eliminate the damaging effects of electrolysis. Elastomeric joints from today’s leading manufacturers are highly resistant to the corrosive effects of salt water, brackish water and brine.

Additional applications that use elastomeric expansion joints include aerospace/defense, mining, agricultural, material handling and food processing.

Quality Control

Companies assume significant and unnecessary risk by selecting expansion joints from sources that do not possess a depth of experience and leadership in technology development over many decades. Given the significance of expansion joints in ensuring reliability throughout a manufacturing process, it is wise to consider manufacturers that maintain a level of control in all aspects of the expansion joint production process. Additionally, make sure the joints you specify for a particular application meet all established standards for that application (e.g., U.S. Navy and U.S. Coast Guard requirements for Marine applications).

In Summary

Backed by decades of research, development and field successes, elastomeric expansion joints have clearly emerged as viable products that offer high levels of efficiency, innovation and overall performance. As external costs and pressures continue to squeeze profitability, plant owners throughout the world can realize significant savings and achieve peace of mind by leveraging the latest expansion joint technology as a means to lowering costs and increasing process reliability. Knowing your system requirements and how expansion joint functionality can meet those requirements will help ensure that your piping system is designed and maintained to the optimum degree.

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Located in Lodi, California on a seven-acre plant site with 160,000 square feet of manufacturing space "under roof.” Holz serves customers in a wide variety of industries including Mining, Agriculture, Oil & Gas, Aerospace/Defense, Material Handling, Food Processing, Power Generation, Pollution Control, Wastewater Treatment and the HVAC Market.

For additional information about Holz 320EZ Rubber Expansion Joint, or other Holz Rubber Products, contact Holz Rubber Company at 800-285-1600, or sales@holzrubber.com.