Single-bellows Expansion Joint

The Single-bellows Expansion Joint (also known as a single-type axial expansion joint) is the most fundamental and widely used form of bellows compensator in piping systems. It utilizes the inherent elastic deformation of a metal bellows to absorb axial thermal expansion and contraction within a pipeline. Featuring a simple structure and facilitating easy installation, it is extensively employed in various straight-run piping systems—such as those found in chemical processing, power generation, HVAC, and water supply and drainage—to compensate for thermal expansion and contraction caused by temperature fluctuations. By doing so, it protects pipelines, valves, and equipment while reducing overall pipeline stress.

Product Structure

Composed of a stainless steel bellows and end connections (pipe stubs or flanges); contains no auxiliary components such as tie rods or hinges.

Bellows: Made of stainless steel (e.g., AISI 304, 316L, or 321); material can be customized based on the specific medium and operating conditions.

Connection Types: Available with welded pipe stubs or flanges.

Performance Characteristics

1. Simple, compact structure; cost-effective; requires minimal installation space.

2. Primarily designed to absorb axial displacement, with a limited capacity to compensate for radial and angular offsets.

3. Stable pressure-bearing performance, high fatigue life, and excellent corrosion resistance; suitable for a wide range of fluid media.

4. Available in sizes ranging from DN25 to DN6000, with pressure ratings from PN0.25 to PN16; non-standard dimensions can be customized.

Important Note: Single-bellows Expansion Joint cannot withstand the pressure thrust generated by internal pipeline pressure. The piping system must be equipped with fixed supports and guide supports to balance this thrust and prevent the bellows from being damaged by excessive stretching.

Application Scenarios

Thermal piping in power plants, HVAC piping networks, chemical process pipelines, sewage treatment piping, and standard straight-run pipe sections in the petroleum industry.

Technical Specifications

Selection Guidelines

1. Please provide the following information: pipe nominal diameter, design pressure, medium temperature, medium composition, and the required axial displacement compensation.
2. Straight pipe sections must be equipped with both fixed supports and guide supports; this is a fundamental requirement for safe operation.

3. For applications involving significant lateral or angular displacement, it is recommended to use multi-ply tie-rod type or universal hinge-type expansion joints instead.

FAQ:

Q1: Can project-specific fabrication drawings and calculation reports be provided during the tender/inquiry stage? 

A1: During the tender/budgeting stage, we can provide standard data sheets and general reference diagrams. Project-specific fabrication drawings and formal calculation reports will be issued after the order is confirmed. If the client requires a pre-award review of supplier drawings, this documentation service can be offered as an optional, value-added item with separate pricing.

Q2: Which international standards are followed for expansion joints and pipe supports/hangers? 

A2: Metal bellows expansion joints are designed in accordance with standards including EJMA, EN 14917, ASME B31.1/B31.3, ASME VIII Div. 1 Appendix 26, GOST 32935, GOST 27036, GB/T 12777, and GB/T 16749. Pipe supports and hangers comply with MSS SP-58, MSS SP-127, ASME B31.1/B31.3, EN 13480-3, GOST 22130-2018, and GB/T 17116.

Q3: What high-alloy materials are available for high-temperature corrosive environments, such as those found in FCC units? 

A3: We offer special alloys—including SS321, 316H, Inconel 625, and Hastelloy—suitable for catalyst piping and high-temperature erosion-corrosion conditions. A full Material Test Certificate (MTC) is provided for every heat/batch of material.

Q4: What export packaging options are available? How are oversized products packaged? 

A4: We provide standard export-grade plywood crates, as well as heavy-duty, moisture-proof, and anti-corrosion packaging designed for long-haul ocean freight. For oversized or overweight products that cannot fit into enclosed crates, we utilize heavy-duty steel cradles or frames, with special protective measures applied to the bellows and flange sealing surfaces; these are suitable for transport via break-bulk or flat-rack containers.

Q5: What technical documentation can be provided? 

A5: We have successfully secured formal projects and are capable of preparing a complete set of WPS (Welding Procedure Specification), PQR (Procedure Qualification Record), and ITP (Inspection and Test Plan) documentation. We also provide the full range of technical supporting data required for EAC/COC certification.

Q6: What is the product warranty period? 

A6: The warranty period is 24 months from the date the goods arrive at the port of destination, covering defects in manufacturing. This warranty does not cover damage resulting from improper transportation, incorrect installation, or operation under abnormal conditions.