The high costs associated with forced outages required that plants engage in any effort to anticipate problems in steam and power generation components that are susceptible to service-related damage. Inspection is therefore an essential O&M activity to determine the present condition of any power plant equipment. Offline inspections during outages are mandated at regular intervals in accordance with the requirements of local regulatory bodies and insurers. The required scope of these inspections is often limited. Damage mechanisms vary in severity depending on the design layout and materials selected by the boiler/HRSG OEM, the plant operating regime and the units age and operating history.
Tetra Engineering has performed thousands of field inspections on an extremely broad range of thermal steam generation plants, from small fire tube boilers to the latest large triple-pressure with reheat HRSG units. The fundamental basis for any effective offline inspection is the visual inspection, which means that the inspector(s) must be highly experienced. Nearly anyone can point out an obviously broken fixture, what’s important is to look for the more subtle damage and to link the damage with suspected mechanisms and root causes. Therefore, it’s essential that to ensure inspection quality for any boiler or HRSG is that the inspector understands the process and the potential associated damage phenomena in detail. This is where Tetra Engineering’s extensive Root Cause Analysis (RCA) work experience is critical, our inspectors don’t just do field inspections, they are also regular and essential contributors and participants in our desktop RCA and Remaining Life Analysis (RLA) studies.
In addition to the impact of their fundamental design differences, today’s boilers and HRSGs are subject to a wider range of duty in power applications. Whereas baseload operation was once normal for utility-scale steam generators and in particular HRSGs, today’s electric power market dictates that units operate in cycling duty. This has resulted in many units experiencing damage much earlier in life, particularly older HRSG units that were designed with baseload operation in mind. Newer boilers and particularly HRSG designs require components to operate at higher pressures and higher temperatures while still achieving the requisite flexibility to meet today’s market demands. The result is greater risk of certain types of damage such as creep as well as fatigue and corrosion fatigue from increased thermal stresses due rapid starts.