Quest Integrity Group's Australia Office
Fitness-for-service (FFS) assessment is a multi-disciplinary approach to determine whether equipment is fit for continued operation. The equipment or system in question may contains flaws or other damage, or may be subjected to more severe operating conditions than anticipated by the original design. The outcome of a fitness-for-service assessment is a decision to run as is, repair, re-rate, alter or retire the equipment. A remaining life analysis may also be performed as part of the assessment, which is used to set future inspection intervals and to budget for capital expenditures when retiring existing equipment.
The three most common damage mechanism/flaw types are as follows:
The advanced level of assessment is conducted in accordance with best industry practice for fitness-for-service, and as experts in the field, Quest Integrity was involved in developing these guidelines. The codes that often used include: API 579/ASME FFS-1, BS7910, the British Energy codes for high temperature assessments R5 and R6 and AS3788.
Quest Integrity’s analysis capabilities include:
The figure below shows an assessment of a storage tank that suffered significant dents during operation; a Level 3 fitness for service assessment was conducted to determine if a repair was required. In this case, the tank passed the fitness-for-service assessment, which saved the clients millions of dollars by avoiding unnecessary repair and downtime.
In addition to the advanced assessment services, Quest Integrity’s Australia office also offers a wide variety of ultrasonic techniques including fully automated and distance encoded:
The inspection operators have experience with engineering and inspection in a wide range of applications and industries requiring condition assessment. Quest Integrity Australia’s inspection group is capable of conducting inspection, analysis, and reporting on:
The inspection team also has significant experience in detecting damage
such as high temperature hydrogen attach (HTHA).
Recently Completed Projects in the Refining and Syngas Industries
Remnant Life Assessment of Three Furnaces
Quest Integrity undertook Level 1 and Level 2 remnant life assessments in accordance with API 530 and API 579 of three furnaces: a vacuum charge heater, a delayed coker heater, and a hydrocracker heater. The assets had been in service for approximately ten years and were approaching the intended design life of 100,000 hours. They had also been subjected to temperatures higher than the initial design temperature for four years.
First, a Level 1 assessment was performed based on design data. The radiant section tubes from the furnaces did not pass the assessment due to excessive creep damage. A Level 2 assessment was performed based on actual and operational data. It was concluded that there was no immediate high risk of tube failure before the next year plant turnaround, but that wall thinning due to corrosion would have a large influence on remnant life of the tubes; therefore, it should be inspected regularly. Each furnace was given new operating limits to complete another 20,000 hours of service.
Engineering Critical Assessment of an Ammonia Storage Tank
Quest Integrity conducted an assessment to determine the safe use of a 1,400 ton capacity ammonia storage tank. As part of the assessment, Quest Integrity recommended a future inspection strategy and frequency. The assessment involved a review of the product characteristics, tank design, construction inspection and quality control, operational history and hazard factors or hazard levels. Finite-element (FE) stress analysis and a leak-before-break assessment (LBB) were also implemented.
Engineering Critical Assessment of a Turbo Gas Expander
Quest Integrity performed an engineering critical assessment of a gas expander rotor. The gas expander operated for 15 months with the cooling air supply blocked causing creep damage to the rotor’s blade location T-hooks. The main purpose of the assessment was to determine whether the shaft would be fit-for-service under continuous operation until the next scheduled outage. Finite element analysis (FEA) was used to assess the stresses and determine the remnant life, taking into account mechanical loading, thermal stresses and creep crack growth. Creep crack growth calculations were performed using Signal™ Fitness-For-Service software from Quest Integrity Group. The extent of accumulated creep damage was calculated and found that the creep life fraction consumed totalled only 27%. It was concluded that the gas expander was fit-for-service until shaft replacement in 2010.
Recently Completed Projects for the Hydro Power Industry
Fitness-for-Service Assessment of a Turbine Headcover with Internal Erosion Damage
A turbine headcover suffered from internal erosion-corrosion. Quest Integrity performed a Level 3 fitness-for-service assessment in accordance with API 579/ASME FFS-1 to determine whether the wall loss was acceptable according to code requirements. This involved Finite Element Stress Analysis. It was concluded that the headcover was acceptable for continued service.
Fatigue Assessment of a Pelton Wheel Shaft
Stress analysis, critical flaw and fatigue assessments were performed on a pelton wheel turbine shaft. Circumferential cracks which developed in the shaft near the runners had been ground out during several shut downs. It was a concern that the shafts were approaching the end of their serviceable life, but the assessment provided the client with an inspection period for future safe operation of their turbine.
Assessment of Spiral Casing
assessment of a spiral casing was performed to evaluate if it was designed as
intended and determine if it was susceptible to failure caused by cracking in
the welds. A review of the material in
combination with the stress analysis showed that the spiral casing was fit-for-service.
For more information, please contact Quest Integrity in Queensland, Australia:
Phone: +61 (0)7 5593 4220 or email A.Karstensen@QuestIntegrity.com