EPDM or NBR Rubber Expansion Joint – Which Bellows Material is Right?
The bellows material determines media compatibility. EPDM is suitable for water, hot water, steam and weak acids or alkalis. NBR is designed for oil-bearing media, fuels and hydrocarbons — but is not suitable for hot water or steam service.
The correct material should be verified against the actual process medium, as the chemical resistance of bellows elastomers varies significantly by type. Use the Fergo Chemical Resistance Tool to identify the compatible material for your medium quickly.
- EPDM: Water, cooling water, hot water, steam, weak acids/alkalis
- NBR: Oils, greases, fuels, natural gas, hydrocarbons
Technical Specifications: DN, PN, Flange and Face-to-Face Length
Fergo rubber expansion joints are structured by nominal size, pressure rating, material and connection type to enable fast, accurate product selection.
Specification Overview
- Nominal size: DN15 to DN500
- Pressure rating: PN10 / PN16, max. operating pressure 16 bar
- Bellows: EPDM or NBR, nylon-reinforced
- Flanges: Galvanised steel, stainless steel or galvanised spheroidal graphite iron
- Connection: Flanged to EN 1092 or internally threaded (sleeve) to BSPP
- Face-to-face length: 130 mm, 150 mm, 200 mm (sleeve version 203 mm)
- Temperature range: −30 °C to +110 °C (depending on bellows material)
- Option: Vacuum support ring for negative-pressure applications
Flanged or Threaded Rubber Expansion Joint?
The choice depends on the existing pipe connection. Flanged expansion joints are bolted between two pipe flanges and are suited to larger nominal sizes and higher mechanical loads. Threaded sleeve versions with BSPP internal threads install without special fittings and fit into confined spaces.
The double-arch sleeve version provides high movement absorption in a compact face-to-face length. For flanged connections, Fergo offers versions in galvanised steel, stainless steel and spheroidal graphite iron.
Installation and Movement Absorption
Rubber expansion joints with a solid rubber flange face are self-sealing and require no additional gaskets. During installation, counter-flanges must be flat across the full sealing face; flanges with tongue-and-groove profiles must not be used, as they damage the sealing surface. Detailed installation guidelines for rubber expansion joints cover fixed-point positioning, guide supports and permissible movement ranges.
Design is typically carried out in accordance with EJMA with flanges to DIN EN 1092-1. A vacuum support ring protects the bellows under negative pressure but reduces the available movement range by approximately 50 %.
Applications for Rubber Expansion Joints
Rubber expansion joints are used wherever pipelines are exposed to movement, vibration or thermal expansion. Typical sectors include drinking water and water treatment systems, HVAC, chemical and petrochemical processes, power generation and biogas plants.
In water and HVAC applications they relieve pumps and protect downstream components such as butterfly valves from vibration loads. In chemical and energy plants they maintain pipeline integrity under changing temperatures and pressures.
Buy Rubber Expansion Joints from Fergo
Fergo supplies rubber expansion joints from DN15 to DN500 with EPDM or NBR bellows, flanged or threaded connections and PN10/16 — available from stock with fast delivery. Filter the right rubber expansion joint for your pipeline by nominal size, material and connection type. For uncertain media compatibility, verify the bellows material in advance with the Chemical Resistance Tool.
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