Knowledge Series: Arch Type Rubber Expansion Joints
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Arch Type: Introduction
• What is an Arch Type rubber expansion joint?
• An Arch Type rubber expansion joint is a full faced integral flange designed expansion joint that incorporates an arch profile. These types are available in several construction design series based on the application pressure requirements.
• Benefits of an Arch Type Design:
• Arches are a source for movement in expansion joints
• Different arch shapes provide benefits for a variety of applications
• Larger arch shapes or multiple arches result in greater overall movement capabilities of the expansion joint
• Included in this section:
• Single Narrow Arch Type
• Multiple Arch Type
• Wide Arch Type
• Lightweight Type
• PTFE Lined Type
Arch Type: Single Narrow Arch
• Single Narrow Arch Type:
• Construction is of fabric and rubber, reinforced with metal rings or wire. The full-face flanges are integral with the body of the joint and drilled to conform to the bolt pattern of the companion metal flanges of the pipeline. This type of rubber face flange is of sufficient thickness to form a tight seal against the metal flanges without the use of gaskets.
• Design Notes:
• Narrow arch is preferable for suction lines, design has a natural resistance to vacuum
• Allows for shorter face-to-face dimensions compared to Wide Arch Type
Arch Type: Wide Arch
• Wide Arch Type:
• This type, similar to the Narrow Arch Type, is available in metallic reinforced and non-metallic reinforced design. The Wide Arch Type typically features greater movements than the standard Arch Type with a wider arch profile.
• Non-Metallic Reinforced Wide Arch Design: Constructed like the Arch Type except the carcass does not contain wire or metal ring reinforcement. Pressure resistance is accomplished with a special external flanged retaining rings furnished with the joint. Not recommended for vacuum applications.
• Metallic Reinforced Wide Arch Design: A molded version of the Arch Type utilizing solid steel rings in a carcass, at the base of the arch. The reduced body thickness can require special retaining rings.
• Design Notes:
• Larger movement capabilities than Narrow Arch Type
• Less turbulence is desired for media flow
Non-Metallic Reinforced Wide Arch Design
Metallic Reinforced Wide Arch Design
Arch Type: Multiple Arch Type
• Multiple Arch Type:
• Expansion joints with two or more arches may be manufactured to accommodate movements greater than those of which a Single Arch Type expansion joint is capable.
• Design Notes:
• Multiple Arch expansion joints of most manufacturers are composites of standard sized arches and are capable of movements of a single arch multiplied by the number of arches.
• Reduced spring rates with multiple arches compared to single arch design
• Requires longer face to face dimension compared to single arch design
Arch Type: Lightweight Type
• Lightweight Type:
• Both the Single Arch and Multiple Arch Types are available in a lightweight series from most manufacturers. Dimensionally the same as the standard product, except for reduced body thickness, this series is designed for lower pressure and vacuum applications.
• Design Notes:
• Lightweight expansion joints give less spring rate at the cost of lower pressure/vacuum ratings
• Commonly used in gravity feed lines, shaker tables & load cells
Arch Type: PTFE Lined Type
• PTFE Lined Type:
• Arch Type expansion joints are available in many standard pipe sizes with Fluoroplastic liners of TFE and/or FEP. These liners are fabricated as an integral part of the expansion joint during manufacturing and cover all wetted surfaces in the tube and flange areas.
• Design Notes:
• Fluoroplastic provides exceptional resistance to almost all chemicals within the temperature range of the expansion joint body construction.
• Suitable for high temperatures
• Availability limited to most standard sizes
• Some special configurations not available, consult manufacturer
• Mostly used in chemical processing and pulp & paper industries
For additional technical information regarding Arch Type rubber expansion joints as well as other rubber expansion joint designs consult the Fluid Sealing Associations Technical Handbook for Expansion Joints Piping (https://www.fluidsealing.com/)
