Internal Sleeve for Metal Expansion Joints

An internal sleeve, also known as a flow liner, is a cylindrical insert fitted inside a metal expansion joint. Typically, one end of the sleeve is welded or fixed, while the other remains free to accommodate bellows movement without restriction. This design ensures both functionality and protection during thermal expansion and system operation.

Purpose and Function Internal sleeves play a critical role

• Protecting bellows from direct exposure to high-velocity, abrasive, or corrosive flow media.
• Reducing flow turbulence and vibration, which helps improve system efficiency and extend the lifespan of the expansion joint.
• Preventing the buildup of solids or particulates in the bellows convolutions, which could lead to mechanical fatigue or failure.

Design Criteria

The selection and design of an internal sleeve depend on several key factors, including:

• Flow direction, velocity, and medium properties (such as chemical composition or presence of particulates).
• The orientation of installation horizontal, vertical, or inclined.
• The geometry of the bellows and pipe bore.
• Application-specific requirements such as single-ply, removable, or telescopic sleeve configurations.
• Each sleeve type is engineered to minimize flow disturbance while allowing full movement of the expansion joint.

Compliance with EJMA Standards & customer expectations EJMA provides specifications for calculating the appropriate sleeve thickness, overlap length, and radial clearance to ensure safe and efficient operation.