Ronald Koenis, principal metallurgical engineer for MegChem, talks about fitness-for-service (FFS) and remaining life assessments (RLAs) of welded components that operate within the creep range and those with crack-like flaws.
MegChem’s Materials and Forensic department offers expert services and failure investigations to insurance companies, law firms, manufacturers and industrial operations. “We conduct meticulous investigations of accidents and failures to establish root causes and the sequences of events leading to accidents or failures,” begins Koenis. “Typically, failures can involve boiler tubes, processing and engineering components, valves and flanges, bolts, bridges, polymers, ropes, non-ferrous components and even bicycle frames,” he says.
With regard to fitness-for-service (FFS) and remaining life assessments (RLAs), he says that theoretical and practical knowledge of degradation processes are combined with knowledge of materials and structural behaviour to establish if continued operation is feasible and safe.
“MegChem is well positioned and experienced with regards to FFS and RLAs. We make use of leading standards and documents such as BS 7910 and API 579-1/ASME FFS-1,” he says.
FFS assessments assure continued safe and reliable operation with reduced downtime and the elimination of unnecessary repairs. They offer additional time to plan shutdown activities and can significantly reduce costs.
An RLA, on the other hand, can be performed to establish a retirement or replacement plan for equipment nearing the end of its lifecycle or for equipment that has been in operation for longer than its original design life.
“This also applies to components with crack-like defects,” Koenis says. “The safe remaining life can be estimated based on the critical crack dimensions and the rate of propagation – and the assessments will typically be sup- ported with on-line monitoring.”
Other services offered by MegChem include: metallographic assessments; material phase and tempering condition assessments; creep degradation classifications; determination of material failure modes; degree of sensitisation in stainless steel components; wall and coating thickness measurements; portable, in-situ hardness testing; and failure reconstructions.
“Our material-related services include corrosion engineering, risk-based integrity (RBI) support and auditing, personnel training on metallurgical issues, independent review of testing facilities, heat treatment facilities and optimisations and welding engineering services,” he says, adding that the company also operates its own comprehensively equipped laboratory.
Introducing the concept of creep, Koenis says creep can be defined as the slow and continuous deformation of metals at high temperatures below the yield stress. “It is a time-dependent deformation of stressed components and all metals and alloys are susceptible,” he notes.
The rate of creep damage accumulation ...