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What is a rubber expansion joint? How do I go about choosing one?

May 26,2023

rubber expansion joint is a flexible connector used to absorb noise, shock, vibration, physical and thermal energy. It is made of natural or synthetic elastomers and can be reinforced internally with fabric and metal for strength and compression resistance, while metal reinforcement can be used externally for motion control.

Why use rubber expansion joints?

Rubber expansion joints are flexible and allow for simultaneous movement within fluid systems, vibration isolation, noise reduction, and resistance to wear and chemical attack.

The following are the main advantages of rubber expansion joints:

Motion absorption

Compared to metal expansion joints of similar length, rubber joints can absorb greater motion. Equipment such as pumps, compressors and pipelines may deflect due to wear and settlement of the supporting structure.

Rubber expansion joints can routinely manage the resulting lateral, torsional and angular movements, while strategically positioned rubber expansion joints can mitigate thermal expansion and contraction movements.

While metal joints typically have a low lateral movement capacity, the movement allowance provided by rubber expansion joints has positive benefits in terms of extended system life and maintenance intervals.

Vibration Reduction

Reducing vibration is important to prevent unbalanced forces from accumulating to levels that could damage the fluid system. Rubber hoses and expansion joints suppress these disturbances and resist shock stresses from hydraulic shocks and water hammer.

Noise reduction

As systems age and wear, imbalances can occur, resulting in unwanted noise. Rubber expansion joints suppress sound transmission through their rubber-to-steel interface. Compared to all-metal joints, thick-walled rubber expansion joints provide higher sound transmission reduction.

Corrosion, wear and erosion resistant

Metal joints are usually thin-walled elements with wall thicknesses between 0.15 mm and 2 mm. Rubber joints are thicker, ranging from 12 mm to 25 mm or more. While metal expansion joints are susceptible to chemical attack and wear, rubber joints are resistant to wear and erosion.

A wide range of natural, synthetic and special-purpose elastomers and fabrics can be used to create high-performance rubber expansion joints for challenging operating conditions. Specialty polymers resist chemicals, oil, sunlight, acid mist, ozone, and external coatings can be added to provide further protection.

Expansion joints can be lined with PTFE (polytetrafluoroethylene) and FEP (fluoroethylene propylene) within the joint body. When fluoroplastics are used in rubber expansion joints, this results in better thermal stability, low friction and resistance to aggressive fluids, chemicals, wear and erosion.

Fatigue Resistance

The ability to bend and absorb gives rubber expansion joints a distinct advantage over metal joints because natural and synthetic elastomers do not suffer fatigue damage, loss of ductility or electrolytic reactions. This results in a long-lasting expansion joint.

Easy to install

Compared to metal expansion joints, rubber expansion joints are lighter in weight and easier to handle and install. The elastomeric expansion joint's vulcanized rubber and fabric flange are integral, so no additional gaskets are required, which also eliminates the need for gasket maintenance checks. In addition, the elastomeric expansion joint balances the uneven surface of the pipe flange to provide an airtight seal.

Industry Applications

Rubber expansion joints are found in all fluid systems. Rubber expansion joints relieve movement stress, isolate vibration, reduce noise and compensate for misalignment in piping systems. Rubber expansion joints do not replace metal expansion joints in all applications, but are recognized as the best choice for many applications involving high vibration and noise reduction.

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