Screwed / Threaded Rubber Expansion Joint
- 1.Union threaded ends (BSP/BSPT/NPT) for easy installation in tight spaces without flange bolts.
- 2.Multi-sphere rubber bellows with NR/NBR/EPDM liners for water, oil, acid and alkali media.
- 3.Working pressure 1.0 MPa, burst pressure 3.0 MPa (3x safety factor); vacuum resistance 53.3 kPa (400 mmHg).
- 4.Multi-directional movement: axial stretch 5–10 mm, axial compression 22–24 mm, lateral shift 22–24 mm, angular deflection ±45°.
- 5.Standard temp: -15°C ~ +115°C; special grade: -30°C ~ +250°C for extreme conditions.
- 6.Nylon fabric & steel wire reinforcement for stable performance under frequent vibration.
- 7.Sizes DN20–DN80 (¾”–3″), suitable for most small-bore HVAC, plumbing and process pipes.
- 8.Fits water, seawater, compressed air, oil, dilute acid & alkali; used in chemical, marine and power industries.
Screwed / Threaded Rubber Expansion Joint
DEVEL Screwed Rubber Expansion Joints are compact, threaded-end flexible connectors engineered for small-bore piping systems where conventional flanged joints cannot be practically installed. Featuring a multi-sphere elastomeric bellows body with forged cast iron or stainless steel union-type threaded end fittings, these joints provide simultaneous axial, lateral, and angular movement absorption while isolating pump and equipment vibrations from the surrounding pipeline network — making them a cost-effective, tool-light alternative for plumbing, HVAC, shipboard, and chemical process piping in restricted access environments.
Key Features at a Glance
- Quick Threaded Union Connection. Forged cast iron union-type end fittings with BSP/NPT/BSPT male threads allow tool-free hand-tight installation and rapid removal for maintenance. Eliminates the need for flange bolting, torque wrenching, and gasket management — reducing total installation time to under 5 minutes per joint even in confined pipe chases, mechanical rooms, and below-slab drain pits where flange bolt access is physically obstructed.
- Multi-Directional Movement Absorption. The multi-sphere rubber bellows simultaneously accommodates axial extension (5–10 mm), axial compression (22–24 mm), lateral offset (22–24 mm), and angular deflection up to ±45° — all in a single compact unit. This multi-plane flexibility is critical for absorbing thermally induced pipe growth, seismic pipe drift, and pump foot vibration in building utility shafts without stressing pipe joints or cracking fittings.
- High-Performance Elastomeric Construction. Inner and outer rubber layers in NR (Natural Rubber), NBR (Nitrile), or EPDM are reinforced by a multi-ply nylon cord fabric pressure body and embedded steel wire pressurizing rings. This composite laminate delivers burst pressure resistance of 3.0 MPa (30 kgf/cm²) against a working pressure of 1.0 MPa (10 kgf/cm²), providing a 3× safety factor compliant with industrial pipeline design codes for critical building services.
- Wide Media Compatibility. The selection of NR, NBR, or EPDM elastomers and optional PTFE inner liners enables deployment across diverse process fluids including water, seawater, hot water, compressed air, hydraulic oil, dilute acids, alkali solutions, and chemical reagents — making a single product family capable of serving mixed-media utility networks without requiring separate product SKUs for each fluid type.
- Extended Temperature Service Range. Standard service temperature spans −15°C to +115°C with special compound upgrades available for extreme cold service to −30°C and high-temperature process applications up to +250°C, covering standard HVAC chilled water through industrial steam condensate and hot-oil jacketed lines — a temperature envelope comparable to metal expansion joints at a fraction of the installed cost and weight.
Key Structural & Operational Features
- Composite Laminate Bellows: Inner/outer rubber layers (NR / NBR / EPDM) + multi-ply nylon cord fabric reinforcement + embedded steel wire pressurizing rings deliver 3.0 MPa burst resistance at 1.0 MPa working pressure — a robust 3× safety factor for reliable long-term service.
- Forged Cast Iron Union Ends: Thread woggle joint (union) end fittings in forged cast iron provide corrosion resistance, high clamp load capacity, and positive sealing engagement across BSP, NPT, and BSPT thread standards without requiring specialized assembly tooling.
- Angular Deflection ±45° Total: Combined angular deflection of (a₁ + a₂) = 45° allows the joint to accept out-of-alignment pipe installations without imposing bending stress on the rubber bellows — a critical feature for as-built piping tolerance compensation during plant commissioning.
- Full Vacuum Rating: 53.3 kPa (400 mmHg) vacuum rating supports suction-side pump installations, vacuum process piping, and condensate return systems without risk of bellows collapse or seal failure under negative pressure operating cycles.
Technical Properties & Operating Limits
| Technical Parameter | Engineering Specification |
|---|---|
| Product Type | Screwed / Threaded Rubber Expansion Joint (Union End) |
| Working Pressure | 1.0 MPa (10 kgf/cm²) |
| Burst / Explosion Pressure | 3.0 MPa (30 kgf/cm²) — 3× safety factor |
| Vacuum Rating | 53.3 kPa (400 mmHg) |
| Angular Deflection | (a₁ + a₂) = 45° |
| Applicable Temperature | Standard: −15°C to +115°C | Special: −30°C to +250°C |
| Applicable Media | Water, seawater, hot water, air, compressed air, oil, dilute acid & alkali, and other compatible chemical media |
| Elastomeric Compound | NR (Natural Rubber), NBR (Nitrile), EPDM — selection based on media compatibility |
| Reinforcement Layer | Multi-ply Nylon Cord Fabric (Key Frame) + Steel Wire Pressurizing Rings |
| End Fitting Material | Forged Cast Iron (Union Type Thread Woggle Joint) — Carbon Steel or Stainless Steel optional |
Bill of Materials — Component Breakdown
| No. | Component Name | Material |
|---|---|---|
| 1 | Inner & Outer Rubber Layer (Bellows Body) | NR (Natural Rubber), NBR (Nitrile), EPDM |
| 2 | Main Pressure Body (Key Frame) | Nylon Cord Fabric (Multi-ply Reinforcement) |
| 3 | Pressurizing Ring (Embedded Reinforcement) | Steel Wire |
| 4 | Threaded Union End Fitting | Forged Cast Iron (standard) / Stainless Steel (optional) |
Dimensional Matrix & Movement Capabilities
| Nominal Diameter DN | Face-to-Face Length L (mm) | Axial Displacement (mm) | Lateral Displacement (mm) | Angular Deflection | ||
|---|---|---|---|---|---|---|
| mm | inch | Extension | Compression | |||
| 20 | ¾ | 200 | 5–6 | 22 | 22 | 45° |
| 25 | 1 | 200 | 5–6 | 22 | 22 | 45° |
| 32 | 1¼ | 200 | 5–6 | 22 | 22 | 45° |
| 40 | 1½ | 200 | 5–6 | 22 | 22 | 45° |
| 50 | 2 | 200 | 5–6 | 22 | 22 | 45° |
| 65 | 2½ | 265 | 8–10 | 24 | 24 | 45° |
| 80 | 3 | 285 | 8–10 | 24 | 24 | 45° |
* Non-standard sizes, custom face-to-face lengths, and special thread standards (BSPT, NPT, G thread) available on request. Contact DEVEL engineering team for customized specifications.
Field Installation Directives
- Thread Compatibility Verification: Before installation, confirm that pipe thread standard (BSP, BSPT, NPT, or G) and size matches the union end fitting specification. Mismatched thread engagement may cause joint rotation or seal leakage under operating pressure. Apply PTFE thread tape to all male threads before assembly.
- Natural State Installation: Install the joint in its natural, unstretched state — do not pre-compress or pre-extend the bellows to compensate for pipe misalignment. The joint is designed to operate within its rated movement range during service, not to correct installation errors. Centering the bellows at zero displacement maximizes available movement capacity in both extension and compression directions.
- Union Nut Torque: Tighten union nuts by hand first to achieve thread engagement, then apply 15–30 Nm wrench torque using a smooth, alternating sequence to achieve even seating of the union face seal. Avoid over-tightening which may crack the cast iron union body or cold-flow the rubber sealing face beyond its elastic limit.
- Storage & Handling Precautions: Store away from high-temperature heat sources, ozone-generating equipment (motors, arc welders), UV radiation, and solvent vapors. Do not paint joint surfaces or wrap with thermal insulation that bonds to the rubber — restricted radial expansion will accelerate fatigue cracking of the bellows body.
- Periodic Inspection: Inspect the rubber bellows surface every 12 months for surface cracking, ozone crazing, or permanent set deformation. Rubber components are subject to natural aging — joints operating in high-temperature, high-cycle, or chemically aggressive service environments should be inspected every 6 months and replaced proactively before failure occurs.
Typical Applications
Building HVAC & Plumbing
Chilled water distribution, heating loop supply/return, domestic hot water recirculation, and fan coil unit connections in commercial and residential buildings where access restrictions prevent flanged joint use.
Water Supply & Pump Stations
Municipal water supply mains, irrigation pump suction/discharge connections, booster pump installations, and fire fighting pump assemblies requiring vibration isolation and thermal expansion accommodation.
Marine & Shipboard Piping
Engine room cooling water, bilge pump discharge, seawater service lines, and deck equipment connections aboard commercial vessels and offshore platforms where weight and space constraints are critical design factors.
Chemical & Industrial Process
Chemical plant utility lines, cooling water systems, compressed air distribution, oil and petroleum product transfer, and dilute acid/alkali process lines where NBR or EPDM compound selection provides appropriate chemical resistance.
Power Generation & Utilities
Thermal power plant circulating cooling water, condensate recovery systems, auxiliary cooling loops for generators and transformers, and water-cooled rectifier systems requiring compact, tool-free maintenance connections.
Refrigeration & HVAC Equipment
Refrigerant-compatible secondary coolant circuits, glycol chiller loop connections, cooling tower make-up water piping, and compressor inlet/outlet isolation where screwed joints provide rapid service access without complete system drain-down.
Product Tags
Screwed Rubber Joint
Threaded Rubber Joint
Union End Connector
NR / NBR / EPDM
Vibration Isolator
DN20–DN80
Small Bore Joint
HVAC Piping
Water Supply
Marine Piping
Chemical Resistant
Nylon Cord
1.0 MPa Rating
Threaded Rubber Joint
Union End Connector
NR / NBR / EPDM
Vibration Isolator
DN20–DN80
Small Bore Joint
HVAC Piping
Water Supply
Marine Piping
Chemical Resistant
Nylon Cord
1.0 MPa Rating
Request a Custom Quote for Your Project
Factory-direct pricing available. DEVEL engineering team ready to assist with rubber compound selection, thread standard matching, and custom sizing for your specific pipeline application.
