Why Are Expansion Joints Necessary in Piping Systems?
Within the manufacturing industry, piping is essentially as described; a system of pipes used to carry fluids, such as liquids and gases, from one location to another. Piping systems can be designed for extreme high temperatures or low temperature cryogenic service but what these two applications have in common is that both will expand and contract with the increase or decrease in temperature.
What Are Expansion Joints?
Metal Expansion Joints are constructed with a metal bellows, end fittings and accessories such as flow liners, tie rods, covers etc… They can be found within most piping systems. The metal bellows operates much like a spring but they are sealed to contain the fluid pressure that flows through the expansion joint, responding to the movement of the connected piping. Without expansion joints in the piping system thermal expansion would create such high stresses that welds would crack, pipes would bend and anchors would fail.
How Do They Work?
An expansion joint element located in a piping system is made up of generally more than one coil (otherwise known as a convolution or corrugation). The corrugations are designed to withstand the internal pressure of the system. In addition, the typical bellows assembly is positioned to flex under the thermal movement of the connected piping.
As a result of the extreme flexibility, the expansion joint is incapable of absorbing any longitudinal loads by its own. Therefore, it requires piping anchors and guides in order to transfer the longitudinal loads to the expansion joint while maintaining the overall stability of the entire piping system.
Types of Expansion Joints
- The Expansion Joint
The single expansion joint is designed to undergo a small amount of lateral and angular movements while within the piping system. A double expansion joint consists of two or more bellows which are joined by common connectors.
- The Universal Expansion Joint
The Universal Expansion joint contains two bellows connected by a center pipe and is fitted with tie rods. These types of joints are mainly used to absorb any combination of the three basic movements in the piping system which are axial, lateral and angular. The true benefit of the universal expansion joint is the ability to absorb large amounts of lateral offset.
- The Hinged Expansion Joint
The hinged expansion joint is designed to absorb angular rotation in the plane perpendicular to the hinge pins. The hardware consists of two hinged plates at 180 ° apart which are joined to the end connection. The hinged hardware is designed to absorb the pressure of the expansion joint assembly and absorb lateral deflection.
- The Gimbal Expansion Joint
The gimbal Expansion joint is designed to absorb angular movement in any plane. It consists of two sets of hinges, connected to a floating gimbal ring, designed to absorb the pressure of the expansion joint assembly.
- The Externally Pressurized Expansion Joint
The Externally pressurized expansion joint by design is capable of large amounts of axial compression or extension. This type of expansion joint is not suitable for lateral offset or angular movement. Another benefit of the externally pressurized design is that the bellows is fully protected by the outer pipe casing. This case also protects personnel in the event of a bellows failure.
The Thermal Expansion of Piping Materials
It’s common knowledge that materials expand when heated and contract when cooled. With this in mind, pipes are not immune to these laws of nature; therefore, they will also expand and contract in varying temperatures. The piping engineer must consider the materials that are used to construct the piping system in order to determine how much expansion will take place. Once the rate of expansion is known for a particular pipe alloy the engineer can specify where the expansion joint should be located as well as the anchor and guide placement.
Want to Find Out More?
If you want to learn more about the role of expansion joints in your piping systems, get in touch with us. Triad Bellows offers a range of products and services to meet the exact requirement of your individual piping arrangement. Custom metal expansion joint products are what they specialize in.