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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
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.
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.
With regard to the disposal of expansion joints, what do you have to consider?
Disposal of rubber expansion joints
When disposing of rubber expansion joints, it is important firstly to identify the area of use and secondly the medium with the expansion joint has come into contact with. Rubber expansion joints on their own do not contain any substances that are a hazard to health and are therefore harmless. If the expansion joint has not come into contact with substances that are harmful to the environment/health, you can dispose of it yourself.
To do this, remove the steel flanges and recycle them after thorough cleaning. The rubber bellows used can be disposed of with the residual waste after cleaning. Additionally used materials, components and lubricants must be removed from the expansion joint and should be disposed of separately. For larger disposal quantities, please contact your disposal service provider or a local recycling center.
In case of contact with critical media which may have left residues on the expansion joint, please contact your local disposal service provider to work out a plan for safe and environmentally friendly disposal. Under no circumstances should you dispose of it in the residual waste.
Disposal of steel expansion joints
Steel must be disposed of by type and separately from other types of waste. Large quantities can be collected in special containers and handed over to your disposal service provider.
Note
Information for proper waste treatment refers to the German ordinance. If necessary, please check the country-specific differences directly with your disposal service provider.