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Ageing Assessment of Elastomers for Offshore Applications: A Comprehensive Guide to API TR 17TR2-2003
Understanding the Technical Report on Elastomer Ageing for Subsea Production Systems
API Technical Report 17TR2-2003, titled Ageing of Elastomers for Use in Offshore Applications, provides essential guidance for engineers and material specialists working with elastomeric components in subsea production systems. Although classified as a technical report rather than a normative standard, API TR 17TR2 offers a structured approach to evaluating the long-term performance of elastomers exposed to the demanding conditions of offshore environments. This article examines the scope, technical requirements, implementation considerations, and compliance notes related to this important document.
Scope and Purpose of API TR 17TR2-2003
The principal objective of API TR 17TR2 is to present a methodology for assessing the ageing behavior of elastomers that are used in equipment for offshore drilling, production, and subsea systems. The report focuses on the physical and chemical changes that occur over time in elastomeric materials when subjected to the combined effects of temperature, pressure, aggressive well fluids, and rapid gas decompression.
Specifically, the report covers:
- Identification of the primary ageing mechanisms relevant to offshore applications.
- Guidance on selecting appropriate test methods for ageing evaluation.
- Considerations for accelerated ageing studies and extrapolation to service life.
- Factors affecting elastomer compatibility with produced fluids, injection chemicals, and environmental conditions.
Note: API TR 17TR2 is not a mandatory specification but a recommended practice to assist operators, manufacturers, and engineers in making informed decisions about elastomer material selection and qualification.
The report is closely tied to other API 17 series standards such as API 17A (Design and Operation of Subsea Production Systems) and API 6A (Wellhead and Tree Equipment), and it is often referenced when elastomer ageing data is needed for design validation.
Key Technical Requirements and Ageing Mechanisms
API TR 17TR2 identifies several ageing mechanisms that must be considered when evaluating elastomers for offshore service:
Thermal Ageing
Elevated temperatures accelerate the oxidation and crosslinking changes in elastomers. The report provides guidance on using Arrhenius-based methods to predict thermal ageing rates, including recommended activation energies for common elastomer types.
Decompression (Rapid Gas Decompression – RGD)
Elastomers exposed to high-pressure gas may absorb significant amounts of gas. When the pressure is rapidly reduced, the gas expands and can cause internal fracture (blistering). The report addresses factors such as gas type, pressure, temperature, and elastomer hardness that influence RGD resistance.
Chemical Exposure
Contact with production fluids (crude oil, gas, water) and injected chemicals (corrosion inhibitors, scale inhibitors, etc.) can cause swelling, hardening, or softening. The report describes methods for evaluating chemical compatibility through immersion tests and changes in physical properties.
Hydrolysis and Fluid Absorption
Many elastomers absorb water or hydrocarbon fluids, leading to a loss of mechanical properties. The report highlights the importance of testing in the intended fluid environment at representative conditions.
| Ageing Factor | Potential Effects | Critical Property Changes |
|---|---|---|
| Elevated temperature | Oxidation, loss of elasticity, embrittlement | Hardness increase, elongation decrease, compression set |
| Rapid gas decompression | Internal cracking, blistering, loss of sealing capability | Visual damage, tensile strength reduction |
| Chemical exposure (H₂S, CO₂) | Swelling, hardening, chemical attack | Volume change, hardness change, weight gain |
| Hydrolysis (hot water/steam) | Scission of polymer chains, softening | Modulus and tensile strength reduction |
Implementation and Application in Subsea Design
Engineers can use the principles in API TR 17TR2 to develop a custom ageing evaluation plan for a specific subsea component. The typical workflow begins with a detailed definition of the service conditions (operating temperature range, maximum pressure, fluid composition, and expected duty cycles). Next, representative elastomer samples are selected, and accelerated ageing tests are performed in accordance with the guidance provided.
Tip: When planning accelerated ageing tests, always include duplicate samples and ensure that the ageing environment closely mimics the actual service fluids and pressure conditions. The report recommends testing at multiple temperatures to enable robust Arrhenius analysis.
API TR 17TR2 also emphasizes the interdependence of ageing mechanisms. For example, a material that performs well under thermal ageing may still fail rapidly when exposed to both temperature and sour gas. Therefore, the report encourages multi-factor ageing scenarios where practical.
Example: For a subsea connector seal operating at 120°C and 150 bar with a gas cap, the evaluation could include thermal ageing (aged 30 days at 150°C), followed by RGD testing, and then a chemical immersion test in simulated formation water. The property retention criteria are typically defined by the equipment standard (e.g., API 17A or API 6A).
Compliance Considerations and Testing Notes
Compliance with API TR 17TR2 is not mandatory unless explicitly referenced in a purchase specification or a design code. However, many operators and manufacturers adopt the report’s methodology as part of a best-practice qualification program. Key compliance aspects include:
- Documentation: The ageing test plan, conditions, results, and extrapolation methodology must be fully documented and traceable.
- Material variability: Because elastomer formulations can vary between batches, it is prudent to test compounds from at least two production batches.
- Failure criteria: Clearly defined acceptance limits for property changes (e.g., maximum hardness change of ±10 Shore A, minimum elongation retention of 50 %) should be established before testing.
Warning: Do not rely solely on Arrhenius extrapolation without verifying the acceleration factor with intermediate measurements. The report cautions that the standard Arrhenius model may not be valid for all elastomers, particularly when secondary reactions such as plasticizer loss or anti-degradant depletion occur.
Best Practice: Combine API TR 17TR2 guidance with finite element analysis (FEA) of the seal geometry to better understand the effects of ageing on sealing contact stress over time. This integrated approach can significantly improve the reliability of life predictions.
The table below summarizes the most frequently referenced test standards and parameters suggested in API TR 17TR2:
| Test Type | Reference Standard | Common Conditions (example) |
|---|---|---|
| Thermal ageing (air oven) | ASTM D573 / ISO 188 | 70–200°C, 7–90 days, periodically test properties |
| Fluid immersion | ASTM D471 / ISO 1817 | Test fluid (simulated well fluid), temperature representative of service, 7–28 days |
| Rapid gas decompression | Norsok M-710 / API 17K | Gas: CO₂ or CH₄, pressure 100–200 bar, temperature 20–80°C, depressurisation rate 20–70 bar/min |
| Compression set | ASTM D395 / ISO 815 | Method B, 25% deflection, tested after combined ageing |
© 2026 — This article is provided for informational purposes. Always refer to the latest version of the original API document (API TR 17TR2) for authoritative guidance.
Frequently Asked Questions
Q: Is API TR 17TR2-2003 a mandatory standard?
A: No, it is a technical report and not a normative standard. Its use becomes mandatory only if specifically invoked by contract or project specification. Nevertheless, its methodology is widely considered industry best practice for elastomer ageing evaluation in offshore applications.
A: No, it is a technical report and not a normative standard. Its use becomes mandatory only if specifically invoked by contract or project specification. Nevertheless, its methodology is widely considered industry best practice for elastomer ageing evaluation in offshore applications.
Q: What is the difference between API TR 17TR2 and ISO 23936-2?
A: ISO 23936-2 (Petroleum, petrochemical and natural gas industries — Non-metallic materials — Part 2: Elastomers) is a later international standard that covers similar ground but includes more detailed qualification requirements. API TR 17TR2 is older and more focused on ageing mechanisms and test methodologies rather than full material qualification. Many users now reference both documents for a comprehensive approach.
A: ISO 23936-2 (Petroleum, petrochemical and natural gas industries — Non-metallic materials — Part 2: Elastomers) is a later international standard that covers similar ground but includes more detailed qualification requirements. API TR 17TR2 is older and more focused on ageing mechanisms and test methodologies rather than full material qualification. Many users now reference both documents for a comprehensive approach.
Q: Can API TR 17TR2 be applied to elastomers used in topside or onshore facilities?
A: Although the report was developed for offshore/subsea environments, many of the ageing mechanisms are equally relevant to other hydrocarbon service conditions. It can be adapted for topside and onshore applications, but care should be taken to adjust test conditions to the specific environmental extremes.
A: Although the report was developed for offshore/subsea environments, many of the ageing mechanisms are equally relevant to other hydrocarbon service conditions. It can be adapted for topside and onshore applications, but care should be taken to adjust test conditions to the specific environmental extremes.
Q: How often should elastomer ageing tests be repeated based on this report?
A: The report does not prescribe a fixed re-validation interval. However, it recommends that ageing data be re-evaluated whenever there is a change in the elastomer formulation, manufacturing process, service conditions, or if field failures are observed. Periodic testing (e.g., every 3–5 years) for critical components is common practice.
A: The report does not prescribe a fixed re-validation interval. However, it recommends that ageing data be re-evaluated whenever there is a change in the elastomer formulation, manufacturing process, service conditions, or if field failures are observed. Periodic testing (e.g., every 3–5 years) for critical components is common practice.