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Fatigue Testing
We conduct fatigue or life-cycle testing on bellows to assess durability under cyclic load conditions. By simulating pressure fluctuations, movement and thermal cycling, we verify design life and failure thresholds. Fatigue testing has been conducted under cryogenic conditions down to -168ᵒC and high-temperature conditions up to +1400ᵒC. Fatigue testing ensures long-term reliability, safety and performance in applications where repetitive stress may lead to material fatigue or failure.
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What Is Fatigue Testing?
Fatigue testing or life-cycle testing, in regards to bellows and expansion joints and other flexible connectors, is to repeatedly test how many repetitions of the intended movement a specially-designed joint can undergo - in the same or harsher conditions which it is expected to endure during its duty - until its destruction.
For example, when manufacturing a joint designed to compensate for axial movement in a pipeline under a certain pressure or temperature, we test how many times that joint can repeatedly extend and contract (under the same pressure and temperature) until it is no longer usable.
That way, we can give you an accurate estimation on how long our product could be expected to last in your pipeline before it would require repair or replacement.
What Fatigue Testing Is Used For
Fatigue testing is used to answer the questions that matter in movement components:
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Will the bellows meet the required design life under the actual duty cycle?
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What combination of pressure, movement and temperature produces the governing stress range?
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Where is the likely failure threshold, and how much margin exists?
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How does the component behave when duty conditions include thermal cycling or pulsation?
This testing is particularly valuable when the consequence of failure is high: downtime, safety exposure, access constraints or severe operating environments.
What We Simulate During Life-Cycle Testing
A fatigue test programme is typically structured around the stress drivers that matter most in service:
Cyclic pressure
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pressure fluctuations and cycling that contribute to stress range;
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realistic duty profiles aligned to how the system operates.
Cyclic movement
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axial, lateral and angular movement cycling (as required);
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combined movement cases when the installed system does not move in a single plane.
Thermal cycling
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repeated heating and cooling that drives thermal stress and material response;
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temperature transients that can accelerate fatigue damage.
The goal is to reproduce the key conditions that drive fatigue initiation and propagation.
Extreme Duty Capability
Some projects require validation outside typical industrial ranges. Fatigue testing has been conducted:
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Down to minus 168°C for cryogenic duty validation;
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Up to plus 1400°C for high-temperature duty validation.
These extreme ranges are relevant for applications where material behaviour, thermal gradients and stress ranges can differ significantly from normal ambient systems.
When Fatigue Testing Is Most Valuable
Fatigue or life-cycle testing is typically recommended when you have one or more of the following:
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high cycle duty or tight fatigue-life requirements;
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severe pressure cycling or pulsation;
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thermal cycling that is frequent or aggressive;
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safety-critical or access-constrained installations (offshore, subsea, enclosed machinery spaces);
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a failure history where the root cause needs to be confirmed and eliminated;
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a new design, material selection, or configuration that requires empirical validation.
If your duty is standard and low risk, a catalogue-led approach may be sufficient. For unusual or severe duty, fatigue testing provides higher confidence.
What You Recieve
Deliverables depend on programme scope and specification, but typically include:
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confirmation of the test intent, load cases and cycle profile;
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test conditions: pressure, movement and temperature ranges used;
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pass/fail outcome against agreed criteria, and observed failure threshold if applicable;
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test records and documentation aligned to project requirements;
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practical engineering recommendations where design changes are indicated.
Where testing is part of a wider engineering programme, outcomes can be used to refine design, verification assumptions and inspection planning.
How To Request Fatigue Testing
To define an effective fatigue test scope and quote accurately, please provide:
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bellows or assembly drawings and identification details;
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operating and design pressure, plus pressure cycling or pulsation profile;
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required movement types and magnitudes, plus cycling rate if defined;
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operating temperature profile, including transients and thermal cycling expectations;
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target design life and cycle requirements;
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definition of acceptance criteria or failure threshold intent;
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any documentation, witnessing, or reporting requirements;
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programme constraints and required dates.
If you are investigating a failure, include photos, service history and the duty conditions at the time the issue occurred. That helps align the test profile to the real driver.
FAQs About Fatigue Testing & Life-Cycle Testing
What is fatigue, or life-cycle testing, used for on bellows? It is used to assess durability under cyclic pressure, movement and thermal loads, validating design life and identifying failure thresholds under realistic duty conditions.
Can you simulate combined pressure, movement and thermal cycling in one test programme? Yes. Test programmes can be structured to reflect how these loads interact in service, subject to the defined duty profile and test scope.
What temperature extremes can be included in fatigue testing? Fatigue testing has been conducted down to minus 168C for cryogenic duty and up to plus 1400C for high-temperature conditions, depending on project requirements.
When should we choose fatigue testing instead of relying on calculation or analysis alone? Fatigue testing is most valuable for severe duty, high cycle requirements, unusual configurations, or where the consequence of failure is high and empirical validation is required.
What do you need from us to quote a fatigue testing programme quickly? Drawings plus pressure, movement and temperature cycle profiles, target life requirements, acceptance criteria, and documentation expectations are typically sufficient.
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