Single-axis high-pressure expansion joint

Single-Axis High-Pressure Expansion Joint Overview

A single-axis high-pressure expansion joint is an axial metal bellows assembly designed to accommodate thermal compression and extension in higher-pressure industrial piping systems.

The metal bellows deforms along the pipeline axis as the connected pipe expands or contracts with temperature changes. This helps reduce thermal movement loads transferred to piping connections and adjacent equipment.

The bellows geometry, number of plies, wall thickness, reinforcement, connection ends and installed length should be engineered according to design pressure, operating temperature, process medium, required movement and design cycle life.

Key Features

• Accommodates axial compression and axial extension
• Engineered for higher-pressure and elevated-temperature piping conditions
• Available with single-ply, multi-ply or reinforced bellows construction
• Available with welded, flanged or project-specific connection ends
• Optional flow liners, external covers and protective components
• Compact construction for straight-pipe axial movement compensation
• Custom manufacturing based on operating data and project drawings

Construction

A single-axis high-pressure expansion joint generally consists of a metal bellows, pipe ends or connection flanges, an optional internal flow liner, an external protective cover and any required reinforcing, guiding or shipping-restraint components.

The metal bellows is the primary flexible element and accommodates axial movement. Pipe ends or flanges connect the assembly to the adjoining piping. A flow liner may be used to improve the internal flow path and protect the bellows from high velocity, turbulence or abrasive particles.

High-Pressure Bellows Design

Higher internal pressure increases the pressure stresses and stability requirements of the bellows. Depending on pressure class, diameter and movement requirements, the bellows may use multiple plies, root reinforcement, equalizing rings or another engineered reinforcement arrangement.

The number of plies, material thickness, convolution geometry and reinforcement should be selected through engineering calculations considering design pressure, temperature, movement, fatigue life and the applicable manufacturing requirements.

Material Options

Bellows can be manufactured from stainless steel grades such as 304, 316L and 321, or from other project-specified stainless steels and corrosion-resistant alloys.

Pipe ends, flanges, flow liners and protective covers can be manufactured from carbon steel, stainless steel or other specified materials. Final material selection should be based on medium compatibility, corrosion conditions, operating temperature, design pressure and required service life.

Movement Capability

A single-axis high-pressure expansion joint is primarily designed for axial compression and extension along the pipeline centerline. It should not be used to accommodate significant lateral movement, angular movement or torsion unless specifically engineered for those conditions.

Actual movement capacity depends on bellows material, convolution geometry, number of convolutions, number of plies, installed length, design pressure and required cycle life.

Pressure Thrust and Piping Supports

A conventional unrestrained axial expansion joint does not eliminate the pressure thrust generated by internal pressure acting on the effective area of the bellows.

The piping system therefore requires main anchors capable of resisting pressure thrust, bellows spring force and other system loads. Suitable pipe guides are also required to direct movement along the axis and reduce the risk of misalignment, instability, torsion or over-travel.

Typical Applications

• Industrial steam and high-temperature hot-water pipelines
• Power-generation, energy and thermal transmission systems
• Petrochemical and chemical process piping
• Metallurgical, mining and higher-pressure industrial pipelines
• Straight pipe runs exposed to significant temperature variation
• Projects requiring custom pressure ratings and axial movement capacity

Installation Guidelines

• Verify flow direction, installed length and preset movement
• Maintain proper alignment of the connected piping
• Do not force the joint into position to correct piping errors
• Do not subject the bellows to torsion or unsupported pipe weight
• Install main anchors and pipe guides according to the piping design
• Protect the bellows from welding arcs, spatter and mechanical damage
• Remove or adjust shipping restraints according to the manufacturer's instructions

Information Required for Selection

Please provide the following information so that the high-pressure bellows construction and movement arrangement can be properly evaluated:

• Nominal diameter or pipe outside diameter and wall thickness
• Design pressure, operating pressure and testing requirements
• Design, operating and installation temperatures
• Process medium and corrosion requirements
• Required axial compression and axial extension
• Required number of operating cycles or design fatigue life
• Face-to-face length and available installation space
• Weld-end dimensions, flange standard or other connection requirements
• Flow velocity and internal flow-liner requirements
• Pipeline anchor and guide arrangement
• Material, inspection, packaging and quantity requirements

We can design and manufacture single-axis high-pressure expansion joints according to pressure, temperature, medium, movement, connection dimensions and project drawings. Final bellows construction, materials, pressure rating, movement capacity, installed length and inspection requirements are subject to the approved technical specification and manufacturing drawing.