Rubber Expansion Joints

Rubber Expansion Joints Manufacturer for Industrial Piping Systems

Industrial rubber expansion joints (flexible rubber connectors) are engineered flexible piping elements designed to absorb mechanical vibration, relieve thermal movement stress, offset axial and lateral pipe misalignments, and reduce fluid-borne noise in pressurized piping systems.

Available in nominal diameters from DN25 to DN3000 (1 inch to 120 inches), our rubber bellows handle operating pressures up to PN25 (362 PSI) and temperatures ranging from -30 deg C to +200 deg C depending on elastomer selection. All units are manufactured in accordance with ISO 9001 procedures and fully pressure-tested prior to shipment.

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Product Range

Single Arch / Sphere: Single-convolution body with floating metal flanges. Sizes: DN25 to DN3000 (1 inch to 120 inches). Primary function: Standard noise and vibration dampening at pump inlets and outlets.

Double Arch / Sphere: Twin-convolution elastomeric body. Sizes: DN40 to DN1000 (1.5 inches to 40 inches). Primary function: Extended axial, lateral, and angular movement capacities in compact spaces.

Threaded / Union Type: Threaded union ends (NPT / BSPT) with rubber body. Sizes: DN15 to DN80 (0.5 inches to 3 inches). Primary function: Small-bore HVAC lines, instrument piping, and booster pumps.

Wide Arch / Pipe Connector: Reinforced high-arch profile. Sizes: DN50 to DN2400 (2 inches to 96 inches). Primary function: Low stiffness requirement with higher non-directional movement.

Reducer Expansion Joint: Concentric or Eccentric rubber cone body. Sizes: DN50x40 to DN800x700. Primary function: Direct connection between unequal pipe sizes at pump nozzles.

Materials and Technical Specifications

Elastomer Selection Guide

EPDM: Working temperature -20 deg C to +120 deg C. Compatible media: Hot or cold water, steam under 120 deg C, weak acids, diluted alkaline solutions. Incompatible media: Mineral oils, petroleum derivatives, hydrocarbons.

NBR (Nitrile): Working temperature -15 deg C to +80 deg C. Compatible media: Crude oil, diesel, hydraulic oils, lubricants, compressed air with oil mist. Incompatible media: Strong acids, ozone, ketones, polar solvents.

Neoprene (CR): Working temperature -20 deg C to +90 deg C. Compatible media: Seawater, wastewater, mild chemicals, ozone, and weathering exposure. Incompatible media: Concentrated oxidizing acids, esters.

FKM (Viton): Working temperature -10 deg C to +200 deg C. Compatible media: Concentrated acids, solvents, high-temperature oils, aromatics. Incompatible media: Low-molecular-weight organic acids, ammonia.

Natural Rubber (NR): Working temperature -30 deg C to +70 deg C. Compatible media: Slurry, abrasive fluids, municipal raw water. Incompatible media: Ozone, oils, weathering exposure.

Physical Parameters and Tolerances

Parameter	Specification
Nominal Diameter	DN25–DN3000 (1–120 in)
Pressure Ratings	PN10 (10 bar / 145 PSI), PN16 (16 bar / 232 PSI), PN25 (25 bar / 362 PSI), Class 150, Class 300
Vacuum Resistance	Standard: -0.08 MPa; Vacuum Ring Reinforced: -0.1 MPa full vacuum
Burst Pressure	≥3 × working pressure rating
Reinforcement Layer	High-tenacity Polyester or Nylon Tire Cord Fabric, Multi-layer Matrix
Flange Materials	Carbon Steel (A105 / Q235B, Galvanized or Epoxy Coated); Stainless Steel (SS304, SS316, SS316L); Ductile Iron (QT450)
Drilling Standards	ANSI / ASME B16.5 Class 150/300; EN 1092-1 PN10/PN16/PN25; JIS 5K/10K/16K; BS 10 Table E

Applications

HVAC and Building Services

Chilled water circuits, cooling towers, and circulation pump headers.

Municipal Water and Wastewater

Raw water intake, sludge lines, isolation valves, and desalination plants.

Power Generation and Heavy Industry

Condenser cooling lines, turbine exhausts, and flue gas scrubber systems.

Chemical and Petrochemical Processing

Process fluid transfer, slurry handling, and crude oil transport lines.

Custom Manufacturing Capabilities

PTFE Liners: High-density PTFE or FEP internal liners cold-molded into the rubber carcass for zero-contamination chemical service and aggressive acid resistance.

Custom Control Rod Assemblies: Designed with elastomeric grommets for noise dampening or gusseted limit plates calculated for maximum thermal growth limits.

Offset and Custom Face-to-Face Lengths: Custom molding available for plant retrofit projects requiring exact replacement lengths without piping modifications.

Multi-Arch Configurations: Triple or quadruple arch designs for extreme settlement compensation in underground or marine piping.

Quality Control and Testing Standards

Every rubber expansion joint is manufactured under ISO 9001 quality management procedures and tested prior to dispatch.
Raw Elastomer Verification > Rheometer Vulcanization Test > Tire Cord Tension Test > Internal Curing Inspection > Hydrostatic and Leakage Test > Final Assembly Clearance

Hydrostatic Pressure Testing

100% shell test executed at 1.5 times design pressure for 15 minutes without pressure drop or structural deformation.

Elastomer Tensile and Elongation Test

Tensile strength equal to or greater than 15 MPa, elongation at break equal to or greater than 350% verified per batch using ASTM D412 standards.

Ozone and Aging Resistance

Accelerated thermal-aging tests (ASTM D573) ensuring long-term flexibility without surface crazing.

Manufacturing Standards Compliance

Designed in accordance with FSCA / EJMA guidelines and EN 14917 / HG/T 2289 standards.

Packaging and Delivery

Flange and Sealing Face Protection

Plastic end caps and wrapped corrosion-inhibitor film applied over elastomeric sealing beads and machined flange faces.

Plywood Case Packaging

Export-grade ISPM-15 compliant heat-treated wooden cases; large diameter units (greater than DN1200) fixed to custom heavy-duty steel skid frames.

Documentation Included

Manufacturer Test Certificate (EN 10204 3.1), Hydrostatic Pressure Test Report, Material Traceability Sheet, and Installation Guidelines.

Our Factory

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FAQ

Q: When should I use control rods (limit tie rods) with a rubber expansion joint?

A: Control rods are required when the piping system is unanchored or when joint movement must stay within structural tolerances. Under internal fluid pressure, an unanchored joint expands along its axis, generating thrust forces that can damage connected pumps or pull the joint out of its flanges. Control rods absorb this pressure thrust and limit maximum movement.

Q:Can rubber expansion joints handle vacuum conditions?

A: Standard single-sphere rubber joints withstand moderate vacuum up to approximately -0.08 MPa (-600 mmHg). For full vacuum applications (-0.1 MPa) or pump suction sides, a metal support ring or internal wire reinforcement must be embedded inside the arch during vulcanization to prevent the rubber wall from collapsing inward.

Q: What causes early rubber degradation or swelling after installation?

A: Swelling, softening, or surface cracking typically indicates chemical incompatibility or temperature overexposure. For instance, using standard EPDM in lines containing petroleum oils causes rapid matrix swelling and structural breakdown. NBR must be specified for oil media, while Viton or PTFE-lined joints are required for harsh solvents and high-temperature acids.

Q: Is a flange gasket required when installing rubber expansion joints?

A: In most standard installations, additional gaskets are not required. The integral rubber flange face of the expansion joint acts as a full-face sealing gasket against flat-face mating flanges. However, if mating with raised-face (RF) metal flanges or uneven surfaces, installing compatible full-face gaskets prevents rubber shearing and ensures a uniform seal.

Q: What is the difference between molded and hand-built rubber expansion joints?

A: Molded joints are manufactured using fixed metallic compression molds, resulting in precise dimensions, smooth surface finishes, and lower unit costs for standard sizes (DN25 to DN600). Hand-built joints are wrapped layer-by-layer over custom mandrels, allowing unlimited size capabilities (DN600 to DN3000 and above), custom face-to-face dimensions, and specialized fabric reinforcement layers for high-pressure or non-standard offsets.

Q: How do you verify pressure performance before shipment?

A: Every batch undergoes hydrostatic pressure testing at 1.5 times working pressure, held for a minimum of 15 minutes to verify pressure containment, shell integrity, and zero leakage. We provide EN 10204 3.1 Material Test Certificates and pressure test inspection reports with every shipment.

We're well-known as one of the most experienced rubber expansion joints suppliers in China. With abundant experience, we warmly welcome you to buy high quality rubber expansion joints in stock here and get quotation from our factory. For price consultation, contact us.

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