The role of an expansion joint can be pretty critical in varied applications. The primary function of this unit is to relieve stress from the system where it is installed and prevent flange gaskets from being crushed.

When it comes to the choice of expansion joints, rubber and metal are two top materials taken into consideration. Experts search for plumbing flexible joints or expansion joints that are suitable to their specific application and needs.

Keep reading till the end to find out which one is the better choice between rubber expansion joints and metal expansion joints.

Difference Between Metal and Rubber Expansion Joints

Metal - A metal expansion joint has a flexible element (bellows) made of thinly gauge material, typically of stainless steel, engineered to absorb thermal and mechanical movements that are expected while in service.

Rubber - A rubber expansion joint has a flexible connector fabricated of synthetic and/or natural elastomers and fabric and, if required, internal metallic reinforcements designed to deliver stress relief performance in piping systems because of mechanical vibration and thermal movements.

Metal Expansion Joints vs Rubber Expansion Joints

In order to find out which expansion joints are a better choice, let us take into account different factors and how they perform for each of them.

Movements 

Both metal and rubber expansion joints have similar capabilities when it comes to movements in the axial plane (extension and compression). However, in case of lateral movements, the rubber expansion joints are better accustomed to absorb them than metal expansion joints having the same face to face dimensions.

For metal joints, there are constructions (dual and universal) available, where there is need for large movement in the lateral, but they are considered to be costly and having specialized design.

Temperature

Metal expansion joints have a greater temperature range, from -420°F to +1800°F. On the contrary, rubber expansion joints with standard materials and constructions have a fair range up to 230°F.

However, a majority of manufacturers provide specialized constructions up to 400°F. But one thing that makes rubber expansion joints superior to metal is that, for metal expansion joints, the working pressures are dropped down at elevated temperatures.

Erosion/Abrasion Resistance

Typically, the metal expansion joints have wall thickness ranging between .012” to .080”. But rubber expansion joints have a thicker wall from 0.5” to over 1”. Also, the thin gauge construction in the metal joints makes them susceptible to abrasive liquids and slurries to erosive chemicals.

Rubber joints on the contrary are highly resistant to erosion and abrasion of all kinds and tend to outperform the metal joints in terms of applications where such conditions prevail. To improve the life of metal joints, the use of fixed liners or drop-in are provided mainly to prolong the time to ultimate failure.

But that’s not all, there are many other factors where rubber expansion joints outperform metal expansion joints such as acoustical impedance, pressure, etc. Additionally, they are used for a wide variety of applications, making them plumbing flexible joints.