An Overview of Single Sphere, Twin Sphere, and Union Double Sphere Flexible Joints

Aug 3, 2023 | Company News, News

Flexible connectors are used in piping systems to absorb vibration, compensate for misalignment, and accommodate movement. Rubber spherical joints allow angular flexibility and lateral deflection while preventing leakage and stress on pipes. Flexible Rubber Joint Single Sphere, twin sphere, and union double sphere joints each provide unique motion capabilities for different system requirements.

Flexible Rubber Joint Twin Sphere

What Are Flexible Rubber Joints?

Flexible connectors contain an elastomeric sealing element that allows controlled omnidirectional movement. This flex absorbs forces like vibration, thermal expansion, or ground settlement that could otherwise damage piping. Common flexible joint types include:

The flexible spheres are often made of natural rubber compounds with excellent fatigue resistance. A rugged outer sleeve restraint prevents overextension. End connections suit various pipe materials and sizes.

Key Benefits of Flexible Joints:

  • Absorb vibration from pumps and other equipment to reduce noise and pipe stress.
  • Compensate for pipe misalignment during installation or from ground settling.
  • Accommodate thermal expansion and contraction of long piping runs.
  • Provide leak-tight seals for gases, liquids, sewage, chemicals.
  • Permit some pipe movement after earthquakes to prevent breaks.
  • Offer corrosion resistance for a wide range of fluids.
  • Easy installation using standard tools. No special skills needed.
  • Long service life with elastomer compounds lasting decades.

With their ability to manage various pipe stresses, flexible connectors are essential components in many fluid handling systems.

Single Sphere Joints

As the name implies, single sphere joints have one spherical rubber element that flexes to allow angular movement in all directions. The single ball design provides:

  • Angular flexibility up to 4-5° off the joint centerline.
  • Tilting and rotation to compensate for pipe misalignment.
  • End connections in carbon steel, stainless steel or brass.
  • Sizes from 1/2″ to 12” diameter pipes.
  • Pressures up to 232 psi at 73°F depending on size.
  • Temperatures from -30°F to 180°F.

Single sphere flex joints handle vibrations and minor misalignments in shorter pipe runs. The limited angular deflection makes them suitable for small to moderate offsets. They are not designed for lateral pipe movement.

Twin Sphere Joints

Twin sphere flexible connectors contain two spherical rubber elements separated by a center metal sleeve. The dual balls provide:

  • Angular flexibility up to 3° off centerline.
  • Lateral deflection up to 3/8″ on larger sizes.
  • Flanged or threaded end connections in steel, brass, iron.
  • Sizes from 1/2″ to 24” pipes.
  • Pressures to 360 psi based on size and material.
  • Temperatures from -35°F to 250°F.

With their lateral flexibility, twin sphere joints accommodate offsets, expansion and contraction in longer pipe runs. The dual balls provide smoother flexing action and dampen vibration better than single spheres.

Double Sphere Union Joints

Union double sphere joints use interlocking spherical elements that increase both angular and lateral flexibility compared to single designs. Key features include:

  • Angular flex up to 5° from joint center.
  • Lateral offset capability over 1″ depending on size.
  • Integral union-end connections speed up installation.
  • Sizes from 1/2″ to 12″ diameter pipes.
  • Pressures from 145 psi to 360 psi based on size.
  • Temperatures from -30°F to 230°F.

The interlocked balls allow the joint to elongate and compress along with angular flexing. This makes union double sphere joints ideal for absorbing thermal expansion and contraction in piping systems. The dual sphere design also damps vibration extremely well.

Choosing The Right Flex Joint

With their range of motion capabilities, flexible connectors can solve many piping challenges. Follow these guidelines for selecting optimal joints:

  • Match joint pressure and temperature rating to system conditions.
  • Determine required angular and lateral flexibility. Double sphere allows most motion.
  • Get appropriate end connections to match pipe types in the system.
  • Size connector consistent with pipe diameters. Avoid using undersized joints.
  • Look for design compliance to standards like MSS SP-83 and MIL-DTL-27210.
  • Validate manufacturer testing and quality control of seals, materials, and production.
  • Install per manufacturer instructions, allowing room for joint movement.
  • Inspect regularly for wear, cracks, leaks, corrosion, over-extension.

Equipping piping systems with the right flexible couplings saves time and costs by preventing damage from vibration, expansion, and misalignment. Connect confidently using quality single sphere, twin sphere, and double sphere flex joints.