Product Overview

Bellows Expansion Joint: A compensation element. Utilizes the effective of its working body (bellows) to absorb dimensional changes in pipelines, ducts, or vessels caused by thermal expansion/contraction, or to compensate for axial, lateral, and angular displacements. Also used for noise and vibration reduction. Widely applied in modern industries.

Category: Compensation element
Working Principle: Utilize the expansion and contraction deformation of the corrugated pipe in the working body
Application: Noise/vibration reduction

Product Introduction

Bellows Expansion Joints, commonly called expansion joints or伸缩节, consist of bellows (elastic element), end pipes, brackets, flanges, and ducts. Primarily used in pipelines to compensate for thermal displacement, mechanical deformation, and absorb vibrations – reducing pipeline stress and extending service life. Connection methods: Flanged or welded. Direct-buried joint typically uses welding (except trench installation).

Working Principle

A compensation device that uses the elastic伸缩变形 of bellows to absorb dimensional changes in pipelines/ducts/vessels due to thermal expansion/contraction. Capable of absorbing axial, lateral, and angular displacements.

Testing

Different joint types compensate differently (axial/lateral/angular/combined modes). For multi-displacement joints, displacements are synthesized into total equivalent axial displacement – the benchmark for testing.

The nominal displacement of standard bellows reflects their deformation capacity. In expansion joints, this "compensation amount" indicates maximum displacement absorption capability under specified conditions. During operation, bellows undergo displacement deformation while maintaining rated cycle life. Designers determine the number of convolutions based on per-convolution displacement capacity. Uniform load distribution ensures operational integrity and design lifespan.

Standards

Standard No.:GB/T 12777-2019

Standard Name: General Technical Specifications for Metallic Bellows Expansion Joints (Equivalent to EJMA/ASME)

Installation & Usage

1、Verify model, specifications, and piping configuration comply with design before installation.

2、For joints with inner sleeves: Align sleeve direction with media flow. For hinged joints: Align hinge plane with displacement plane.

3、Remove pre-deformation ("cold springing") fixtures only after pipeline installation.

4、Never use joint deformation to correct piping misalignment – compromises functionality, reduces lifespan, and overloads supports.

5、Protect bellows from weld spatter and mechanical damage during installation.

6、After installation:

• Remove yellow shipping restraints promptly.
• Set limit devices to designated positions per design.
• Ensure full compensation capability under environmental conditions.

7、Keep all moving parts unobstructed; ensure free movement.

8、Hydrostatic testing:

• Reinforce secondary fixed supports near joints.
• Add temporary supports for gas-system joints during water filling.
• Chloride ion content in test water ≤ 25 ppm.

9、Post-test: Drain water immediately and dry bellows interior.

10、Insulation contacting bellows must be chloride-free.

Bellows Expansion Joint: A compensation element. Utilizes the effective of its working body (bellows) to absorb dimensional changes in pipelines, ducts, or vessels caused by thermal expansion/contraction, or to compensate for axial, lateral, and angular displacements. Also used for noise and vibration reduction.