Tetra Engineering will be presenting our technical paper on "Impact of Startup Purge Credit on Combined Cycle Plant Operation" at the ASME Power and Energy Conversion 2015 Conference in San Diego, California, USA on June 30, 2015. It describes the technical basis for purge credit operation and provides an example of the impact on fatigue lifetime in key Heat Recovery Steam Generator components. See the full program at the ASME website here.
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Normal boiler and Heat Recovery Steam Generator Operation have required a complete purge of the boiler by fresh air before startup firing to remove potentially explosive fuels and other substances from the boiler/HRSG. For power plants in daily two-shift cycling (or more frequent starts) this not only adds time to the startup sequence but can impose significant thermal stresses on hot components exposed to cooler purge air.
Peter Jackson, President of Tetra Engineering Group was invited to present Tetra's experience on Purge Credit implementations at the 501F User Conference this February (2019).Combined cycle power plants use fuels and other materials that can cause fires or explosions in the combustion turbine, ducting, or heat recovery steam generator. Purging that equipment with ambient air to displace residual combustible gases before starting is a normal safety practice. But when plants are cycled, the disadvantages of purging often outweigh the advantages.
