Expansion Joints vs. Couplings: Comparative Perspective

When dealing with piping systems, there are various concepts and things to remember. But, two of the most important materials that you should know more about are expansion joints and couplings. 

Expansion joints take charge of absorbing vibrations and movement in pipelines, while couplings administer pipe routine and design. Learn more about the key differences between these two in this comparative guide that will tackle:

– What expansion joints and couplings are

– Major differences

What Are Expansion Joints?

Also referred to as movement joints, expansion joints are installed with concrete to prevent expansive cracks that might form due to temperature changes, hence their name. 

They work by securely holding parts together whilst absorbing safely the temperature-induced expansion and contracting of building materials. In other words, expansion joints provide room for movement in case there are seismic activities. 

What Are Couplings?

On the other hand, couplings are devices joining two or more pipes, but not really to facilitate movement, like what expansion joints do, but to maintain continuity. The materials used to create couplings are similar to those used to build the pipe infrastructure the coupling connects to, for the purpose of uniformity. Pipe couplings may either be rigid or flexible. 

Major Differences

Components and Types

For expansion joints, these are their components:

• Metal bellows: These bellows absorb movements caused by thermal expansion or contraction. They are situated within the mechanical device or flexible elements consisting of convolutions.  
• Tie rod: These rods attach to the assembly of the device. They can absorb pressure loads and other forces, such as dead weight. Interestingly, they protect bellows from movements that can cause anchor malfunction or failure. 
• End connections: Categorized with several variations, these facilitate the installation of pipe infrastructure.
• Protective covers and liners: Expansion joints sit inside a metallic cover that offers protection to them from harmful external factors.

Meanwhile, couplings can be identified with categories, instead of the components that expansion joints have. These are:

• Removable couplings: Those with a threaded style that facilitate the process of installation onto the infrastructure. These parts feature a wide base pipe segment and are sliced using a thread, making the ends of couplings always threaded. 
• Permanent couplings: These, instead, use soldering or brazing. During mounting and installation, they provide stability and seal properties in the event of missing support. 

When and How to Use Them?

Expansion joints are used mostly in refineries, cryogenic plants, chemical and petrochemical facilities, aerospace, and nuclear power plants. They are in-charge of securing the pipe structure from stress and strain, as well as vibration and mechanical noise. They also help compensate for system misalignment. 

On the other hand, couplings facilitate changes in pipe routing, obstacle crossing, and wall penetration. They are usually U- or elbow-shaped. They are beneficial in infrastructure that transport solids, liquids, air, and steam.

Different From Each Other, Yet Used Together

Comparing expansion joints with couplings is actually like comparing apples with oranges. They are entirely two different things. Expansion joints are responsible for absorbing vibrations and movement in the pipeline, while couplings facilitate piping routing and design. 

However, the most important thing to note here is that they are usually used together to improve the design and function of the pipeline. 

How YOUFUMI Can Help

Founded in 1989, YOUFUMI specializes in the research and development, design, and manufacturing of a wide range of lined valves, pipelines, and containers. And speaking for pipelines, our company has lined expansion joints that stand out for their high density, high permeation resistance, and compensating displacement, among other qualities. 

We strive for perfection for we believe customers deserve the best. We have valve torque testing equipment, valve leakage testing equipment, valve opening testing equipment, and more. We constantly aim for excellence in our products. For more information, connect with our team today!

Reference

Expansion Joints vs. Couplings: What’s the Difference? (1)

Expansion Joint in Concrete – Types and Characteristics – theconstructor.org (2)