Help and support F.A.Q.

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Which technical details are required to enable a quick and accurate quotation to be submitted?

The following information is required at a minimum:

  • Nominal width
  • Connection type (welded ends/flange data)
  • Pressure
  • Temperature
  • Medium
  • Movement absorption
  • Type of tension

What is the service life of rubber/steel expansion joints from STENFLEX®?

Service life of STENFLEX® rubber expansion joints

The service life of rubber expansion joints depends on the following
influencing factors:

    • Operating temperature
    • Operating pressure
    • External environmental influences
    • Exposure to media
    • Flow speed
    • Mechanical load
    • Pressure surges and any instances of extreme values
    • Movements
    • Vibrations
    • Installation

     

    It is not possible to give a general answer regarding the period of use/service life of rubber expansion joints for these reasons as it depends on the respective case of application.
    We recommend regularly checking the installed rubber expansion joints using the following non-destructive test methods:

      • Visual check for external damage or leaks
      • Measurement of Shore hardness (max. 83 Shore A). Rubber expansion joints with Shore hardness greater than 83 Shore A must be exchanged (replaced). 

       

      Service life of STENFLEX® steel expansion joints
       
      Many of our steel expansion joints have been used for decades in an incredibly wide range of application areas and guarantee problem-free operation on site.
      As a general rule, steel bellows are designed for a temperature of +20°C and a nominal pressure and load of 1000 load changes.
      A load change entails the following: turning out from the zero position, the expansion joint moves into the maximum positive position (elongation), back over the zero position into the maximum negative position (compression) and then back to the zero position.

      Excluding the permitted operating conditions

        • Pressure
        • Temperature
        • Movement
        • Number of load changes

         

        the following influencing variables can also impact the service life of expansion joints:

          • Corrosion
          • High-frequency vibrations
          • Resonance vibrations
          • Pressure surges
          • Temperature shocks
          • Improper installation

          In which nominal widths is it possible to purchase expansion joints from STENFLEX®?

          Rubber/PTFE expansion joints; DN 15 to DN 3600
          Steel expansion joints; DN 15 to DN 2800

          Are seals required when installing rubber expansion joints?

          No special seals are required as the expansion joints are self-sealing. The sealing surfaces of the flanges must be even and clean. Additional seals are not required; a seal only needs to be fitted when installing guide sleeves.

          Up to what temperatures and operating pressures can rubber expansion joints be used?

          To ensure reliable operation, expansion joints and pipe connectors may only be operated within the admissible pressure, temperature and movement limits. When using them, the operating data specified on the dimensional drawings, construction drawings and the type plate must be taken as limit values.
          The operating pressures specified on these documents relate to a temperature of 20°C (unless stated otherwise).
          As the strength of the bellows materials decreases as the temperature increases, the pressure must be decreased in the case of an increased temperature.

          Up to what temperatures and operating pressures can steel expansion joints be used?

          As a general rule, steel bellows are designed for a temperature of +20°C and a nominal pressure and load of 1000 load changes.

          The maximum permitted temperature of a steel expansion joint can be up to a maximum of 550°C for material 1.4541, for example (within the permitted movement limits), provided the pressure was reduced due to the increased temperature.

          To ensure reliable operation, expansion joints and pipe connectors may only be operated within the admissible pressure, temperature and movement limits. When using them, the operating data specified on the dimensional drawings, construction drawings and the type plate must be taken as limit values.

          With expansion joints, is it necessary to observe service or maintenance intervals?

          Operators must make sure the expansion joints and pipe connectors are easily accessible and that visual inspections can be carried out on a regular basis.
           
          Check the expansion joints and pipe connectors in accordance with the applicable regulations to make sure they are in a sound condition. In case of defects (e.g. blistering, surface cracks or irregular deformations), contact our Technical Advisory Service. Repairs are not permitted.

          The Shore strength of the flexible rubber elements of expansion joints and pipe connectors must be checked at regular intervals. If the hardness exceeds 83 Shore A, the element must be replaced for safety reasons.

          Where is it possible to download the CE compliance letter on the website?

          Where can I find data sheets on your website?

          How is an expansion joint installed?

          Can a rubber expansion joint be subjected to torsional stress?

          Expansion joints and pipe connectors must not be subjected to torsional stress (twisting) during installation/removal or during operation. This particularly applies to types with a threaded connection (hold hexagon tight with wrench).

          How important is it to adhere to the tightening torque?

          If the respective screw tightening torques specified in the installation instructions are not observed, leaks may occur in the flange connection.

          Which movement absorption value is specified in the data sheets for steel expansion joints – the +/- value or the total value?

          If a movement absorption value is accompanied with the subscript "tot", this value represents the total possible movement.

          Example: D axtot= 28mm

          This means that the expansion joint has a total movement value of 28 mm (= +/- 14 mm)

          Where are fixed points required in pipelines?

          An expansion joint or pipe connector as a flexible pipeline element separates the rigid system and makes the pipeline unstable if there are no fixed points. The internal overpressure induces forces in the pipeline. The direction and level of force depend on the nominal width, the internal pressure of the pipeline, the movement to be absorbed and the pipeline. No fixed points result in the pipeline being shifted. The flexible element would be stretched to its load limit, which would eventually cause the elastic connection to break.

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