Pipe expansion joints (compensators) are key components used to absorb displacement and deformation in pipeline systems caused by thermal expansion and contraction, vibration, or foundation settlement, ensuring the safe operation of pipelines. The following is its detailed description:

1. Main functions

Compensation for displacement: Absorb displacement in axial, lateral, angular or multiple directions.

Vibration and noise reduction: Alleviate the shock transmitted by the vibration of equipment such as pumps and compressors.

Sealing and leak-proof: Prevent leakage at pipe connections caused by displacement.

Protection system: To prevent stress concentration from causing damage to pipelines or equipment.

2. Common types

Metal expansion joint

Bellows type: Displacement is compensated through the elastic deformation of the bellows, and it can withstand high pressure and high temperature (such as steam pipes).

Hinge type: Suitable for angular displacement, often used in L-shaped pipes.

Universal type: Multi-directional compensation, used for complex pipelines.

Pressure balance type: Eliminate internal pressure thrust and protect the fixed bracket.

(2) Non-metallic expansion joints

Fiber fabric type: Corrosion-resistant, suitable for large displacements (such as flue gas ducts).

Rubber type: Good vibration damping effect, suitable for low-temperature media such as water and air.

(3) Other types

Sleeve type: It compensates for axial displacement through sliding sleeves, but has high sealing requirements.

Spherical compensator: It achieves multi-directional compensation by the rotation of a sphere.

3. Core Structure

Bellows: Made of metal (stainless steel, alloy) or non-metal (rubber, polytetrafluoroethylene), with a core expansion element.

Flange/end pipe: Connects the pipeline system.

Pull rod/hinge: Restricts the direction of displacement or withholds pressure thrust.

Guide tube: Protects the bellows from being eroded by the medium (high-temperature and high-speed fluids).

4. Key parameters for selection

Medium characteristics: temperature, pressure, corrosiveness (for example, chemical pipelines need acid-resistant materials).

Displacement: The calculated values of axial, lateral and angular displacements.

Installation conditions: Space limitations, pipe direction (horizontal/vertical).

Standard specifications: Comply with international or industry standards such as ASME, EJMA, and GB/T.

5. Typical Application scenarios

Thermal expansion compensation for steam and hot water pipelines in thermal power networks.

Petrochemical/Chemical industry: Reactor, heat exchanger connection pipes.

Power industry: boiler flue gas ducts, steam turbine pipelines.

Municipal engineering: Long-distance laying of water supply and heating pipelines.

6. Key points for installation and maintenance

Pre-deformation: Pre-stretch/compress according to the cold position (such as stretching 50% compensation during installation).

Guide support: To prevent lateral displacement of the pipeline from damaging the expansion joint.

Regular inspection: Monitor bellows corrosion, leakage or fatigue cracks.

Replacement cycle: Non-metallic expansion joints are usually 5 to 10 years, while metallic ones can last for more than 15 years.

7. Faults and Solutions

Leakage: If the seal fails, replace the bellows or tighten the bolts.

Instability: Overload causes the bellows to twist, and the load needs to be recalculated.

Corrosion perforation: Improper material selection or the medium containing chloride ions (such as high-nickel alloys required in seawater conditions).

8. Industry standard reference

International: ASME B31.3 (Process Piping), EJMA (Expansion Joint Manufacturers Association).

Domestic: GB/T 12777 (Metal Bellows Expansion Joints), HG/T 20677 (Chemical Pipelines).