Twin Sphere Joint (FTC)

A Twin Sphere Joint, sometimes referred to as a Twin Sphere Rubber Expansion Joint, is a flexible connector designed with two spherical bellows to absorb movement, vibration, and noise in piping systems.
The FTC type generally indicates a Flanged Type Connector, where the rubber body is fitted with integral or floating flanges for secure installation.

Construction

1. Body

   • Material: Reinforced synthetic rubber such as EPDM, NBR, or Neoprene (depending on media).

   • Design: Two spherical bellows increase flexibility and movement absorption.

2. Reinforcement

   • Multiple plies of high-strength synthetic fabric, sometimes combined with steel wire reinforcement for higher pressure.

3. End Fittings

   • FTC Type: Flanged connections, either fixed or floating, in carbon steel, stainless steel, or ductile iron.

   • Flanges drilled to standards such as ANSI, JIS, DIN, or BS.

4. Inner Liner

   • Rubber grade selected to resist specific media (water, oil, chemicals, etc.).

Typical Specifications

• Size Range: DN25 (1") to DN1200 (48") or larger.

• Working Pressure: 10 bar (PN10) standard, higher ratings available on request.

• Vacuum Resistance: Up to –650 mmHg with internal vacuum support.

• Temperature Range: –20 °C to +100 °C (depending on rubber compound).

• Movement Capability:

  • Axial Compression: ~20–30 mm

  • Axial Elongation: ~10–15 mm

  • Lateral Deflection: ~15–20 mm

  • Angular Deflection: up to 15°

Applications

• HVAC Systems – vibration isolation for pumps, chillers, and cooling towers.

• Water & Wastewater – flexible connections for pipelines in treatment plants.

• Industrial Piping – chemical plants, oil refineries, and power stations.

• Marine & Offshore – seawater and ballast water systems.

• Pumps & Compressors – absorb pulsations and reduce stress on equipment.

Advantages

• Twin sphere design provides greater movement absorption than single sphere joints.

• Noise & vibration reduction improves system performance.

• Corrosion-resistant construction with suitable flange and rubber material selection.

• Long service life under dynamic conditions.

• Easy installation with standard flanged ends.