Rectangular Metal Corrugated Expansion Joint

1. Definition and Structural Components

A Rectangular Metal Corrugated Expansion Joint is a highly engineered flexible connector designed for rectangular ductwork and low-pressure piping systems. It is primarily installed to accommodate thermal expansion, absorb mechanical vibration, and reduce structural stress on connected equipment.

Main Components

• Bellows (Corrugated Element): The core flexible component, engineered from premium metal sheets to allow multi-directional movement.

• Conexiones finales: Heavy-duty welded ends or flanges (matched to duct dimensions) for seamless system integration.

• Internal Liner (Flow Liner): An optional structural shield that reduces fluid turbulence, minimizes erosion, and prevents resonant vibration caused by high-velocity media.

• Cubierta exterior: A protective metal shield safeguarding the bellows against external mechanical damage and environmental corrosion.

• Tie Rods / Limit Rods: Hardware assemblies designed to control the movement range and absorb pressure thrust forces.

• Reinforcement Beams: External structural steel welded into the convolutions to prevent bellows deformation under high-pressure conditions, particularly critical for large span dimensions.

• Gusset Plates: Heavy-duty corner reinforcement plates designed to distribute stress uniformly at the rectangular corner joints.

2. Functions, Key Characteristics, and Applications

Primary Non-Metallic Expansion Joint Functions in Piping & Ducting Systems

• Thermal Displacement Compensation: Efficiently absorbs axial compression/extension, lateral offset, and angular rotation caused by temperature fluctuations.

• Misalignment Correction: Compensates for minor installation tolerances and structural settling.

• Vibration and Noise Isolation: Damps high-frequency mechanical vibrations from fans, blowers, and engines, significantly reducing acoustic transmission.

• Stress Relief: Protects costly downstream equipment (such as boilers, turbines, and dust collectors) from excessive nozzle loads.

Key Operational Features

• Multi-Directional Flexibility: Simultaneously handles multi-axis movements within a compact face-to-face length.

• High Temperature & Pressure Resistance: Engineered to withstand extreme operating conditions, typically ranging from -196°C to 1000°C (-320°F to 1832°F).

• Custom Geometric Configurations: Available in multiple corner configurations, including round corner, single-mitre corner, and double-mitre corner to fit specific flow profiles.

Typical Application Scenarios

• Generación de energía: Fossil fuel power plant duct systems, flue gas desulfurization (FGD) systems, and SCR systems.

• Sistemas HVAC: Large-scale commercial and industrial ventilation air ducts.

• Industrial Exhaust & Ventilation: Steel mills, cement kilns, and smelting plant exhaust ducting.

• Petrochemical & Chemical: Process gas ducting and low-pressure chemical vapors.

• Marine & Heavy Machinery: Large marine diesel engine exhaust systems and generator test facilities.

3. Design Standards, Material Selection, and Connections

Engineering & Compliance Standards

• EJMA (Expansion Joint Manufacturers Association): The globally recognized authoritative standard for bellows calculation and life-cycle design.

• ASME Section VIII, Division 1 & ASME B31.3: Governs pressure vessel calculations and process piping integration compliance.

• GB/T 12777 & JB/T 6171: National Chinese standards for metal bellows expansion joints.

Material Selection Matrix

Material Grade	Technical Characteristics	Typical Application Scenarios
SS304 / SS304L	General-purpose, excellent cost-efficiency, reliable oxidation resistance.	Standard HVAC, clean air ventilation, and low-temperature flue gas.
SS316 / SS316L	Superior pitting corrosion resistance due to Molybdenum content.	Chemical processing, marine exhausts, and mild chloride environments.
SS321	Titanium-stabilized alloy, excellent intergranular corrosion resistance.	High-temperature exhaust ducts, gas turbine piping (up to 600°C).
SS310S	Ultra-high temperature oxidation resistance.	Furnace ducts, cement kilns, and extreme thermal applications (up to 1000°C).
Inconel 625	Exceptional fatigue strength, resists chloride-ion stress corrosion cracking.	Petrochemical FCCU units, severe acid gas, and high-pressure/high-temp ducts.
Hastelloy C-276	Outstanding resistance to strong reducing and oxidizing corrosive media.	Severe chemical flue gas scrubbing, wet desulfurization systems.

Connection Specifications

• Flanged Connection: Built to standard industrial specifications (ANSI/ASME B16.5, B16.47, EN 1092) or entirely customized to match existing rectangular duct flanges.

• Welded End Connection: Beveled ends designed for direct welding into the ductwork, ensuring zero-leakage performance.

4. Technical Specifications & Performance Ranges

Technical Parameter	Typical Range / Capabilities
Nominal Size (W × H)	$300\times 300\text{ mm}$ up to 5000×5000 mm (custom oversized dimensions available)
Axial Compensation	$+25\text{ mm}$ a +200 mm
Lateral Compensation	$\pm 15\text{ mm}$ a ±100 mm
Angular Rotation	±1∘ a ±8∘
Working Pressure Range	$\text{PN }0.025\text{ MPa}$ a PN 0.4 MPa (reinforced configurations handle higher pressures)
Working Temperature	−196∘C a 650∘C(up to 1000∘C with internal refractory lining and SS310S/Inconel)
Applicable Medium	Flue gas, hot air, steam, dusty gases, exhaust fumes, and corrosive vapors

5. Technical Selection Guide for Procurement

To receive an accurate engineering proposal and quotation, please clarify the following parameters during inquiry:

1. Operating Parameters

• Temperature Profile: Design temperature, maximum operating temperature, and minimum ambient installation temperature.

• Pressure Profile: Maximum system design pressure and potential vacuum/negative pressure values.

• Flow Media: Type of gas/fluid, particulate concentration (for abrasive dust), and chemical composition (to prevent chemical attack).

2.Válvula de suministro de agua Displacement Demands

• Calculated thermal expansion in Axial (compression/extension), Lateral (parallel offset)y Angular planes.

• Anticipated cyclic frequency (fatigue design life requirement, e.g., 1000, 5000, or 10000 cycles).

3. Dimensional & Layout Constraints

• Exact internal or external duct dimensions (W × H).

• Face-to-face (FTO) installation length limits.

• Duct wall thickness and material grade of the mating ductwork.

4. Optional Accessories

• Is an internal flow liner required? (Highly recommended if velocity exceeds 6 m/s for gas).

• Are external protective covers o shipping bars required?

6. Pre-Shipment Inspection (PSI) & Export Packing Standards

To guarantee that components arrive on-site in pristine mechanical condition, our strict quality control framework involves the following steps:

Technical Inspection Criteria

• Dimensional Tolerances: Absolute verification of face-to-face length, flange flatness, and bolt-hole alignment (standard tolerance maintained within±3 mm o ±1/8′′).

• Welding Quality Assurance: Non-Destructive Examination (NDE) including Liquid Penetrant Testing (PT) and Radiographic Testing (RT) on critical corner welds to ensure zero porosity and undercut defects.

• Leakage and Pressure Testing: Soap bubble testing or hydrostatic pressure testing conducted at1.5× design pressure when structural design permits.

• Traceability Documentation: Comprehensive QA dossier compiled for the client, including Material Test Reports (MTRs), EJMA calculation data sheets, NDE reports, and pressure test certificates.

Heavy-Duty Export Packaging Requirements

CRITICAL HANDLING PRECAUTION: Metal bellows are precision flexible elements highly vulnerable to torsion and impact. Shipping bars/spacers must remain securely painted and locked during transit and installation. They should only be removed after the expansion joint is completely welded or bolted into the rigid piping system.

• Protección del medio ambiente: The entire assembly is wrapped in heavy-duty weatherproof plastic or vacuum-sealed VCI anti-rust film.

• Mechanical Structural Bracing: Rigid internal timber or steel bracing is inserted inside the duct to prevent any lateral shifting or collapsing of the bellows during transit.

• Protección de brida: Mating faces are covered with thick plywood or heavy rubber gaskets to prevent scratches or deformation on sealing surfaces.

• Crating Specification: Packed into ISPM-15 compliant, IPPC-certified fumigated wooden cases or reinforced steel frames, featuring clearly marked center-of-gravity, lifting points, and standard international shipping symbols ("Fragile", "This Side Up").