Inspections of more than 500 units over the past 10 years reveals common challenges faced by mid-life HRSGs, particularly those used in combined cycle plants to offset renewable generation and other aggressive operating strategies.
A heat-recovery steam generator (HRSG) is much like other power generation equipment—run it at design conditions and chances are it will run with high availability and require only routine maintenance for many years. Mechanical problems within the HRSG are usually site- and vendor-specific, but experience has identified many common failure modes. The most common cause of HRSG failures (after malfunctioning equipment such as sprays or duct burner controls) is a change in operating profile, typically from base load to daily cycling, especially in markets with must-run wind generation. Although a change in operating routine doesn’t automatically translate into gross degradation in HRSG reliability, pressure parts are often susceptible to having less design margin and more vulnerability to consequential damage caused by other equipment.
This article identifies common unit failure mechanisms you should consider when developing your HRSG inspection strategy for low-load operations and two-shift cycling.
Tetra Engineering Group Inc., has inspected more than 500 HRSGs over the past 10 years (many of which are F-class or G-class triple-pressure duct-fired units in two-shift cycling operation with reheat steam turbines), representing a cross-section of all the major HRSG manufacturers (see sidebar). About 70% of inspections were of large reheat HRSGs. The inspected units represent all North American Reliability Corp. regions as well as many units in emerging markets (Mexico), and the mature 50-Hz markets in Europe and the Middle East. Uniquely, many of the Middle East units are non-reheat units commonly integrated with a large desalination facility for integrated power and water operations.
The full article was published in POWER MAGAZINE and can be found here.