Do you know what kind of expansion joint you need?
Ensuring you have the correct expansion joint for your specific applications is essential for reliable operations. They come in a variety of materials, including metal, fabric, rubber, and PTFE-lined. To help you make an informed decision about the type of joint you need, we have curated a list of each joint and crucial details you should know.
Metal Expansion Joint
Metal expansion joints, also known as metal bellows, are elastic-like vessels that can be easily compressed when pressure is applied or extended under a vacuum. They are ideal for absorbing the thermal movement and vibration in piping systems transported at high temperatures, such as vibration caused by exhaust gases or steam.
There are several different types of metal bellows, including:
- Duct Type
- Dual
- Single
- Universal
- Externally Pressurized
- Hinged and Gimbal
- Ring Controlled
- Pump Connectors
- Expansion Compensators
Metal expansion joints are great for applications with pressure or temperatures over 250°F. They consist of annealed type 321 stainless steel sheet rock that is rolled into a tube and seam-welded.
Fabric Expansion Joint
If you’re dealing with high temperatures and low pressure, fabric expansion joints are the ideal choice. Also commonly used in industrial plants, fabric joints are installed in ducts and piping systems as flexible connections that accommodate or compensate for thermal expansion, vibration, or misalignment.
They are composed of two major components. The first includes the joint attached to the pipe or duct line with a metal frame. The second component is the two ends of the metal frame, which are connected by a fabric belt. Expansion joints are also available in a variety of product types, including the FC Series Fluoroplastic, FL Series Fluoroplastic, and M Series.
The metal frames of the expansion joints can vary between two basic shapes: the “A” frame and the “J” frame. The first frame consists of two angle irons with a belt attached to the horizontal plane, while the vertical plane connects to the ductwork.
In contrast, the “J” frame features a standoff that holds the belt above the flowline, allowing for added insulation. If you are dealing with an application that potentially involves sediment in the gas, flow liners may be a good option. Flow liners can prevent ash build-up within the expansion joint.
Rubber Expansion Joint
Rubber expansion joints safely absorb vibrations, especially those caused by the temperature-induced expansion and contraction of pipes. This type of joint is able to handle hot air or gases in industrial ductwork, power plants, and pollution control equipment. The average lifespan of rubber joints is typically between seven and 10 years. They are available in single- and multiple-arch designs and can be custom-built to fit your application requirements.
If you’re looking for rubber expansion joints, understanding the various types is essential. There are several types of rubber joints, including spherical, spool-type, wide arch, low spring rate, reducing concentric and eccentric, and PTFE-lined. What’s the difference between these types of rubber joints?
Spherical
Spherical rubber expansion joints are most often used in water, oil and gas, mining, automotive, and HVAC applications. These joints cannot have filled arches and are molded. They also have floating flanges for easy installation. Unlike spool-type expansion joints, spherical joints can handle higher pressure ratings.
Spool Type
These types of expansion joints are either hand-built or hand-wrapped. They can have filled arches that are great for heavy-duty applications like wastewater plants or pulp mills. However, the filled arch should only be used when 20% or more solids are present in the media. With a wider arch, spool-type expansion joints can provide more movement than spherical joints.
Wide Arch
Wide-arch expansion joints have a larger arch than traditional spool-type rubber expansion joints, allowing lower spring rates and greater movement.
Low Spring Rate
These types of joints are available for PVC, CPVC, FRP, and HPDE piping. To avoid catastrophic failure, low spring rate expansion joints are required for plastic piping because it cannot handle the same force as standard carbon steel piping.
Reducing Concentric and Eccentric
When the pipe’s size does not match the mating equipment, concentric and eccentric expansion joints are ideal for the application.
PTFE Expansion Joint
Also known as Polytetrafluoroethylene (PTFE) expansion joints or couplings, these joints are ideal for industrial piping applications that may be exposed to erosive or corrosive environments. PTFE expansion joints are primarily used for chemical service but have short face-to-face lengths that make them universal for applications. Additionally, they can be used for aggressive media.
PTFE joints excel in chemically reactive piping environments and are available in a wide range of designs, sizes, and customized configurations. This makes it easy to find the ideal fit for your application.