Posiflex Expansion Joints

Viking Johnson

Posiflex expansion joints provide relief for piping system stress caused by thermal and mechanical vibration and/or movement, and can also be utilised to overcome problems of noise. These flexible connectors are fabricated from a wide range of rubber compounds, open or filled, single or multiple arch and are designed to accommodate the needs of individual pipe systems conveying materials as diverse as fluids, foodstuffs, chemicals or crude oil.


Posiflex expansion joints offer a range of benefits in installation and use, particularly an ability to cope with multi-dimensional movement including rotational and lateral. A full bore design means no obstruction to the flow and reduced turbulence.


  • Compensate for Axial Movements
  • Compensate for Lateral, Torsion and Angular Movements
  • Vibration and Sound Absorption
  • Corrosion/Erosion Resistant
  • Minimal Dimensions
  • Ease of Installation
  • Shock Resistant
  • Greater Recovery from Movement
  • Freedom from Embrittlement
  • Eliminates Electrolysis
  • Economy
  • Maintenance Free


For the selection of the most suitable PosiFlex expansion joint,the following basic criteria must be determined:

Size – joint nominal bore size, required face-to-face length and mating flange size/specification.

Pressure – operating, design, surge and test pressure of the system

Movement – axial, lateral, angular, and torsional (if applicable)

Medium – type of fluid, air, gas or powder

Temperature – minimum and maximum range

1. Size
PosiFlex expansion joints are available in sizes from 25mm (1”) nominal bore up to of approximately 3600mm (144"). NB. Special, larger sizes available on application, with dimensions available on request.

2. Pressure
When making any design calculations on PosiFlex expansionjoints it is important to consider the maximum pressure of thesystem, not the operating pressure. This could be either surgeor test pressure. Remember that pressure may be positive ornegative (vacuum).

The pressure capabilities of a PosiFlex joint are limited by thereinforcement of the carcass at the arch area. Standardpressure ratings exist for each style of PosiFlex expansion joint.If requirements exceed these ratings, special constructions areavailable on request.Standard face-to-face dimensions of the joints are detailed onthe technical datasheets, other non standard dimensionsavailable on request.

3. Movement
PosiFlex expansion joints are designed to accommodate axial(compression and elongation), lateral, angular and torsionmovements.All movement capabilities are dependent upon the size andnumber of arches. For increased movement capability, morearches can be added (up to a maximum of four for most sizes).

4. Medium
The medium conveyed through the PosiFlex expansion joint canbe fluid, gaseous or powder. The tube material of the joint mustbe compatible with the medium it is carrying.Abrasive materials may require a thicker and/or softer tube toimprove service life.Note that in some cases the surrounding environment must beconsidered. The outer cover may be exposed to oils, chemicals,acid fumes or sunlight.Refer to chemical resistance tables to select thecorrect tube and cover elastomers. Remember that temperatureconsiderations must be taken into account when selectingelastomers.

5. Temperature
Temperature ratings of expansion joints are governed by the materials of construction.