Advanced Methodologies for Remaining Life Assessment
High and normal operating temperatures can degrade metallurgical properties and produce damage not seen at lower temperatures. The design codes for components in this temperature range only provide basic design requirements, but actual component behavior is strongly dependent on the existing operating conditions and service environment. To prevent both under-utilization and failure of equipment, the challenge for owner-users is to accurately predict remaining life, prevent unnecessary repairs or replacements, and extend equipment life and availability.
Equity has in-depth experience in evaluating the suitability for service of components operating in the high temperature range and subject to a variety of damage mechanisms. Our membership and support of joint industry programs sponsored by the Materials Properties Council (MPC) Project Omega for creep damage evaluation and MolyHy for assessment of High Temperature Hydrogen Attack (HTHA) gives us special expertise in state-of-the-art technologies for equipment assessment.
Equity’s David Osage is a recognized high temperature expert:
- Drafted creep life assessment rules for Part 10 in API 579-1/ASME FFS-1
- Authored Appendix F of API 579-1/ASME FFS-1
- Active members of MPC Project Omega since its inception in 1984
- Created VCESage remaining life assessment module
- Active members of MPC MolyHy program
We can help you understand – and deal with – the various ways high temperatures can impact your equipment and the interactions between mechanical, metallurgical, and environmental causes of high temperature damage mechanisms.
Practical Advice for a Complicated Problem
Equity's close working relationship with MPC provides us access to extensive materials property information, and insight into innovative analytic methodologies. MPC's Project Omega methodology can be used to accurately determine the remaining life of aging equipment not only by providing materials properties that are the best in the industry, but also through a procedure for conducting creep strain rate tests from the assessment day forward, thereby avoiding the need for a precise past pressure and temperature operating history. The methodology has been validated through experience and is published in API 579. Most of the major integrated oil companies are using this technology with great success.
Equity uses a phased approach to help you mitigate and manage the damage mechanisms that most often cause costly failure: creep, High Temperature Hydrogen Attack, metallurgical embrittlement, and thermal stresses/fatigue. This approach saves time and money by giving you the ability to stop applying technology as soon as the essential need is satisfied.
- Phase 1 – Preliminary calculations based on previous industry inspections and nominal operating conditions
- Phase 2 – More sophisticated stress analysis and better understanding of the materials involved; possibly some chemical analysis
- Phase 3 – Creep testing through one of the most respected labs in the country
- Phase 4 – Remaining life calculations
- Phase 5 – Probabilistic assessments
This working process assures that you won't get caught in a consulting quagmire of doing unnecessary work that yields marginal value. Our goal is to give you practical advice.
Equity uses the MPC Project Omega approach to identify vulnerable equipment long before inspectors can find advanced damage. We have applied this method to many fired heater tube assessments and have found that, in most cases, the predicted life is much longer than using standard industry guidelines such as API 530. The Omega method enables us to optimize heater throughput and tube life based on the accuracy of our assessments.
We use our proprietary VCESage software program to perform remaining life calculations. The heater tube creep module in our VCESage program contains both the API 530 and the API 579 Omega equations, materials data, and also considers tube wall thinning.
We have also applied the Omega approach and properties to other equipment operating in the creep regime with similar results (hot wall reactors, piping, valves, etc. See section “Beyond Heater Tubes”)
High Temperature Hydrogen Attack (HTHA)
HTHA, particularly of C-0.5Mo steels, is a continuing industry challenge in high temperature / hydrogen environments. This issue is relevant now that many refineries are converting existing equipment as part of low sulfur fuels projects.
Equity engineers have been involved with API 941 for over 35 years, and we are members of the MPC JIP Moly-Hy, which has developed innovative technology to better characterize incipient damage and assistance with remaining life/FFS issues. We can help your facility identify potential HTHA issues with Risk-Based Inspection (RBI) methods, and then with inspection and assessment planning. We can also help you manage replacement versus maintenance decisions.
Our Buckeye II Sampler cuts small samples without the need for weld repair. Samples are analyzed for methane content and voids.
We are the only engineering consulting company in the MPC Moly-Hy Joint Industry Program.
There are number of changes that occur with certain alloys due to high temperature exposure:
- Sigma Phase Embrittlement of austenitic stainless steel
- Carbide Precipitation in many alloys
- 885F(430C) Embrittlement in ferritic stainless steel
- Temper Embrittlement of 2.25Cr alloys
- Reheat Cracking of 1.25Cr steel
These changes can be subtle, but can lead to big failures. Our materials experience can guide you as to when, where and how to look for these changes.
Beyond Heater Tubes: Help with Other At-Risk Components
Equity has performed hundreds of heater tube assessments, using VCESage software plus the API 530 design code for heaters and the API 579-1/ASME FFS-1 FFS Standard. However, many components require more sophisticated analysis, including vessels, piping, and other heater components.
Equity performs finite element stress analysis to simulate temperature and structural response of complex components and loading conditions. We are one of the few firms to commonly employ advanced stress analysis techniques in conjunction with the MPC material models (that is, advanced non-linear inelastic stress analysis combined with an understanding of metallurgical properties) to simulate high temperature response and characterize creep damage.
This multifaceted approach can be beneficial in assessing high temperature damage in the following:
- Process heaters (coke heaters, cat reformers, steam/ammonia reformer heaters
- Heater components (tube sheets, hangers, ducts, headers)
- Hot piping and valves
- FCCU reactor and regenerator components
- Reactor health/remaining life
- Thermal diffusion calculations for start-up and shutdown; safe envelopes
- PWHT simulations to advise on difficult applications
- Hot-tap analysis
Equity performs these state-of-the-art assessments quickly, to help you make informed decisions in a timely manner.