In response to changes in fuel costs, environmental issues, alternative energy supplies and other drivers, many plant owners often consider cycling their boilers to operate on/offline or at reduced loads during low demand. Most units currently in service and supplied pre-1980 were designed to operate at base load, so cycling operation and faster ramp rates could adversely impact critical boiler components. 

Since the 1970s, B&W has analyzed, tested, engineered solutions and developed best practices for cycling units originally designed for base load service. Whether then, during the rising interest in nuclear power and the high cost of natural gas and oil, or now, with low natural gas prices and supplemental solar and wind power, a thorough condition assessment is essential to determining potential equipment modifications that can make the unit more flexible and achieve cycle goals.

There are four types of operation related to boiler cycling which are of interest:

Each method for cycling presents a different set of challenges. In reviewing options for addressing them, B&W considers overall equipment operation including:

1. Combustion system flame stability
2. Fuel delivery system 
3. Air quality control / emissions
4. Circulation 
5. Pressure part life assessment