Rubber Expansion

Expansion Joints, also known as bellows expansion joints, are flexible elements that absorb movements in the pipe system. These absorb movements are defined by axial, lateral, angular, and universal movements. There are several different bellows expansion joints tied universal, expansion joint, single unrestrained bellows expansion joint, universal expansion joint, gimbal bellows expansion joint, in-line pressure balanced bellows expansion joint, gimbal bellows expansion joint, and single tied bellows expansion joint. A Bellow Expansion Joint can be used as an offset like a ball joint.

Bellows expansion joints are often included in industrial piping systems to accommodate movement due to thermal and mechanical changes. When the process requires significant temperature changes, metal components change size. Expansion joints with metallic bellows are designed to accommodate specific movements while minimizing the transfer of forces to sensitive components in the system. Metal bellows expansion joints are primarily used in applications where thermal expansion is an issue. When the temperature of the pipe increases, the metal expansion joint compresses to compensate for the movement, taking stress off the anchors and the pipe. Rubber bellows expansion joints are designed to reduce vibration and dampen sound transmission. They are also designed to take the following movements: Compression, Extension, Angular, Torsional, and Lateral. The rubber bellows expansion joints are made of natural rubber and synthetic materials. The rubber bellows expansion joint can be made of EPDM, Buna, nitrile, neoprene, and butyl.

Gimbal bellows expansion joints are the same as the hinge type, except that instead of being limited to deflection in only one plane, it can accept bending or angulation in any plane. It contains two sets of hinge pins or pivots, the axis of each set perpendicular to the other. Each set of pins is connected with a central gimbal ring, in much the same way that a universal joint on an automobile works. This unit provides the same type of restraint and resistance to axial forces, such as the pressure thrust and shear forces, as the hinge type. Hyspan Products is a source.

The universal bellow expansion joint consists of two bellows separated by a pipe section or spool. The primary purpose of this arrangement is to have a unit that will accept large amounts of lateral deflection. The amount of lateral deflection they can accept depends on the amount of angulation each pipe bellows can absorb and the distance between the bellows. For a given bellows element, the lateral deflection capability can be increased or decreased by simply changing the length of the center spool.

The single bellow expansion joint is simply a bellows element with end connections. Regardless of accessories, it will deflect in any direction or plane that the bellows will. It requires that the piping be controlled as to the direction of the movements required of the unit. The bellow expansion joint should not be expected to control the movement of the pipe and will not resist any deflections with any force other than the resistance of the bellows.

Hinged Pipe Expansion Joints contain hinges or pivots which allow the unit to bend in a single plane. These units are designed to restrict axial deflection, either an extension or compression. The hinge mechanism is typically designed to accept full pressure thrust. Also, because of the hinge mechanism’s design, shear loads, such as from the weight of adjacent piping, can be accepted by this pipe expansion joint, relieving the piping designer of having to provide additional supports and anchors required by the Single type. American Boa is a source for these types of Bellows Expansion Joints. To get help with an American Boa RFQ click here.

The bellows expansion joint continues to be an essential component of the piping system to assist with thermal growth.

Metal Expansion Joints

Metal Expansion is a phenonium caused by heat to make metal expand. The heat causes atoms to vibrate, which causes the surface area of metal to grow. This is called thermal expansion. In a metal bellows expansion joint, the bellows compress. Grains in the metal will grow as metal is heated, causing metal expansion. This is also called kinetic energy. The metal expansion causes kinetic energy. One object’s movement causes another object’s movement. A great example of this is wind causing a windmill to turn. Imagine molecules and atoms growing, causing metal expansion. This is what happens to a Pipeline Expansion Joint, or a metal expansion joint.

When designing a piping system, you must consider the metal expansion of the pipe. The different metal expands at different rates. The metal properties must be known as the temperature and mass of the pipe. Without knowing the dynamic thermal factors, the metal expansion can cause tremendous damage to buildings, supports, pumps, valves, and other ancillary parts of the process. This could lead to a catastrophic shutdown or worse. The complete pipe system must be analyzed, including pipe supports, clamps, variable, and constant springs. Not only can there be metal expansion, but other materials such as PFC, HDPE, Plastic, Teflon, PVC, and rubber also have their unique growth properties. A rule of thumb for steel and metal expansion. For each 100F rise in temperature, steel will grow up to .07 inches in length. That could mean an over 9-inch increase in a 100-foot pipe. That increase in length could damage structures and fracture the piping system. Read more on metal expansion joints.

The question that comes up the most, “is how do you determine metal expansion which causes piping expansion? To calculate how much the length of steel will increase, you need to know how much the temperature increases and the original length of the steel. Like most materials, steel expands when the surrounding temperature increases. Each material has a different response to the heat, characterized by its thermal expansion coefficient. The thermal expansion coefficient represents the amount that steel expands per degree increase.

  1. Use a thermometer to measure the change in temperature in degrees Fahrenheit. For example, if the actual temperature was 70 degrees Fahrenheit and the final temperature was 75 degrees Fahrenheit, you would have a temperature increase of five degrees.

Multiply the temperature change by 7.2 x 10-6, which is the expansion coefficient for steel. Continuing the example, you would multiply 0.0000072 by 5 to get 0.000036. Multiply the product of the expansion coefficient and the temperature increase by the original length of the steel. Finishing this example, if the steel rod were originally 100 inches long, you would multiply 100 by 0.000036 to find that the steel would be 0.0036 inches longer when subjected to heat.

The easy way is to google pipe expansion rates; there are several sites to refer to get metal expansion rates.

1 Kennan, Mark. “How to Calculate Thermal Expansion of Steel”, 14 July 2021.

Rubber Expansion Joints

Also, we are discussing rubber expansion concerning rubber expansion joints. We will first define expansion. It is the ability to stretch or elongate an item. Rubber has those very properties. In a piping system, it is necessary to have flexibility in the pipe to handle thermal growth, vibration, and other movements. These movements can be obtained with rubber expansion. The correct terminology is through rubber expansion joints.

There are several different materials for handling pipe expansion due to thermal growth; they include metal, fabric, and rubber. We will focus on rubber expansion. Some of the materials used for rubber expansion are buna, EPDM, butyl, nitrile, and neoprene. These materials can handle rubber extension. They are synthetic materials. Organic rubber comes from a tree called “Hevea brasilienis” a great majority of natural rubber comes from this tree. The tree is tapped to bleed the polymer from inside the rubber tree itself. The demand for these final products is immense. It is believed that Christopher Columbus learned from the Indians in central America the concept of cultivating rubber trees, which were known in the now Amazon region 1600 years BC. Another tree, called the Castilla Rubber tree, has to be harvested to obtain its latex rubber. Charles Goodyear invented vulcanization by heating rubber and adding chemicals; it made the rubber more robust and allowed rubber expansion. In the late 1800s, Brazil held a monopoly on rubber until trees and seeds were smuggled out to Asia and other parts of the world. They are changing the cost and making the product cheaper. Through the years, different inventors came up with the need for rubber expansion. Thousands of items to rubber expansion. Tires, shower curtains, paint, telephones, car parts, etc.

The worldwide demand for items that needed rubber expansion continued to grow. Droughts, wars, land expansion made it more challenging to get rubber expansion items. Scientists from the United States and Germany developed synthetic materials such as neoprene, nitrile, and latex. These new materials could replace rubber trees and have better corrosive agents. Rubber expansion could be used to handle pipe movement due to the thermal growth of the pipe.  Rubber expansion joints date back to the old Uniroyal Company, which invented the rubber expansion joint in 1930.

Rubber expansion joints offer inherent flexibility and strength to meet the most challenging temperature/pressure requirements. Known for their capability to withstand extreme environments, our rubber expansion joints are commonly found in harsh applications such as water and wastewater, pulp and paper, chemical processing, mining, metals, and pumping applications. For rubber expansion joints, the most common elastomers are ethylene propylene diene monomer (EPDM) rubber, polytetrafluoroethylene (PTFE), polychloroprene (Neoprene), nitrile rubber, butyl rubber, natural rubber, & synthetic elastomers. Rubber expansion joints are generally more versatile than other joints, although chemical compatibility issues, pressure, and temperature may preclude them from being used under some process conditions. Rubber expansion joints effectively handle compression (movement inward), extension (movement outward), lateral offset motion, vibration, and sound dampening in a short overall length.

When selecting expansion joints for process pipes and equipment, engineers should begin by following a set of criteria that the industry has generally agreed upon as a method of taking a comprehensive look at the requirements of the joint. The set of criteria is known by the acronym “STAMPED.” Gathering information according to this set of factors and questions will provide an excellent basis for which expansion joints should be used. The components of the acronym are defined here:

  • S size (what are the diameter and pipe thickness of the pipes under consideration?)
  • T temperature (what is the process temperature?  Is the temperature variable?  What is the rate of temperature change?  Under all process situations, will the process temperatures stay below the temperature rating for the joint expansion material?)
  • An application (what are the details of the application? What type of equipment is being connected? What are the characteristics of the process media? Is it acidic, basic, or neutral? Is the joint located outside or indoors?)
  • M movement (what type of movement will the collective experience?  Compression and expansion, vibration, lateral movement, complex motion, and the magnitude of that movement?  What forces will the movement exert on the adjacent equipment, and what is the magnitude of those forces. Also, is the pipe anchored, and will there be a need for control rods?
  • P pressure (what is the pressure inside the pipeline?  Does it vary?)
  • E end fittings (how are the pipes capped?)
  • D delivery (how are the joints to be installed?)

The STAMPED criteria can go a long way toward narrowing down the choices in expansion joints to steel or rubber. However, there are still many choices within each category, and different designs are available for conditions and applications. For example, if an application requires a great deal of movement, there are joints with more convolutions or arches built into the bellows of the joint. Again, expansion joint vendors can be a resource here. Read more on metal expansion joints.

Beyond the so-called Rule of 250, the selection of joint expansion material should get more specific. EPDM and butyl rubber expansion joints are suitable up to 250°F, but Neoprene is only reasonable to 220°F and nitrile rubber up to 212°F.

We know a little about how rubber expansion became a worldwide multi-billion-dollar market. A natural rubber tree started companies such as Dupont, Uniroyal, and Goodyear. Without rubber expansion, we would not have cars, boats, airplanes, computers, or most household items. Rubber compensators are also known as rubber expansion joints. Rubber compensator joints are used.

Fabric Expansion Joints

Fabric Expansion Joints are part of a family of expansion joints. There are more than three types of expansion joints—metal, Rubber, Fabric, and growth type for foundations or concrete. Expansion Joints are a bellows-type device. Expansion joints are used to absorb thermal expansion. They can also be used to absorb contraction in cryogenic lines and to reduce vibration in piping systems. Construction materials for the bellows can be stainless steel or rubber, or even a composite material.

 In building construction, an expansion joint is a mid-structure separation designed to relieve stress on building materials caused by building movement induced by thermal expansion and, contraction caused by temperature changes, sway caused by wind. Seismic events. These are not fabric expansion joints.

Another non-fabric expansion joint is Expansion joints are put in place before the concrete is poured. Expansion joints allow the slab to move and not put stress on whatever it abuts. These joints are placed where a slab meets a building, a slab meets another slab, and a pool deck meets the coping.

Minimize Concrete Cracking and Damage with Expansion Joints. ASPHALT EXPANSION JOINT comprises asphalts, vegetable fibers, and mineral fillers formed under heat and pressure between two asphalt-saturated liners. It is waterproof, permanent, flexible, and self-sealing. These are not fabric expansion joints.

Yet another non-fabric expansion joint, an expansion joint or movement joint, is an assembly designed to hold parts together while safely absorbing temperature-induced expansion and contraction of building materials and vibration or allowing movement due to ground settlement or seismic activity. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.

Building faces, concrete slabs, and pipelines expand and contract due to warming and cooling from seasonal variation or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under stress-induced—compensators. Expansion joints are also called compensator joints.

Other types of non-fabric expansion joints: Control joints, or contraction joints, are sometimes confused with expansion joints but have different purposes and functions. Concrete and asphalt have relatively weak tensile strength and typically form random cracks as they age, shrink, and are exposed to environmental stresses (including thermal expansion and contraction). Control joints attempt to attenuate cracking by designating lines for stress relief. They are cut into the pavement at regular intervals. Cracks tend to form along with the cuts rather than randomly elsewhere. To read more on fabric expansion joints. This is primarily an aesthetic issue; the appearance of even, regular cracking, which may be hidden in the joint’s crevice, is often preferred over random cracking.

Thus, expansion joints reduce cracks, including the overall structure, while control joints manage cracks, primarily along the optical surface.

Roadway control joints may be sealed with hot tar, cold sealant (such as silicone), or compression sealant (such as rubber or polymers-based crossed linked foams). Mortar with a breakaway bond may be used to fill some control joints.

Now we can discuss fabric expansion joints and metal and rubber. Pipe expansion joints are necessary for systems that convey high-temperature substances such as steam or exhaust gases or absorb movement and vibration. A typical joint is a bellows of metal (most commonly stainless steel), plastic (such as PTFE), fabric (such as glass fiber), or an elastomer such as rubber. A bellows is made up of a series of convolutions, with the shape of the convolution designed to withstand the internal pressures of the pipe but flexible enough to accept axial, lateral, and angular deflections. Expansion joints are also designed for other criteria, such as noise absorption, anti-vibration, earthquake movement, and building settlement. Metal expansion joints must be designed according to rules laid out by EJMA; for fabric expansion joints, there are guidelines and a state-of-the-art description by the Quality Association. Pipe expansion joints are also known as “compensators,” Compensator joints compensate for the thermal movement.

Some types of rubber expansion joints are made with a molding process. Typically molded joints are medium-sized expansion joints with bead rings produced in large quantities. These rubber expansion joints are manufactured on a cylindrical mandrel wrapped with bias cut fabric ply. The bead rings are positioned, and the end sections are folded inwards over the bead rings. This part is finally placed in a mold, molded into shape, and vulcanized. This is a highly automated solution for large quantities of the same type of joint.

Other types of expansion joints can include fabric expansion joint, metal expansion joint (Pressure balanced expansion joints are a type of Metal expansion joints), toroidal expansion joint, gimbal expansion joint, universal expansion joint, in-line expansion joint, refractory lined expansion joint, hinged expansion joint, reinforced expansion joint and more. Some would use a Ball Joint.