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Heat-Recovery Steam Generators: Issue #2

How to eliminate standby corrosion in HRSGs (and steam turbines)

nullYou can just hear someone on the plant staff saying to an HRSG inspector regarding unexpected waterside corrosion damage, "But we didn't do anything to cause this condition." Precisely the point: It was important to do something. That thought prompted Thermal Chemistry Ltd's David Addison to give the editors a short course on shutdown and layup practices designed to assure a flexible return to service for combined-cycle plants. more

Next-generation HRSGs designed to start faster, cycle


The shuttering of nuclear and coal-fired generation in the name of the environment has encouraged manufacturers of gas turbines and heat-recovery steam generators to push the designs of their equipment to limits unexpected a decade ago. Today, for example, you can buy a single-shaft combined cycle for 60-Hz service with an output of nearly 500 MW (about double the rating of a mid-1990s unit) and an efficiency of more than 60%. The engineering achievement is even more remarkable given renewables-era demands that these behemoths be able to start and ramp up and down quickly. more

HRSG pressure parts a top discussion topic

The first few minutes of the open discussion session on HRSG pressure parts at the 2012 AHUG conference last December were devoted to NFPA standards, before hardware took center stage. The subject of purge credit was introduced. Recall that NFPA required a pre-start purge prior to 2011, but changed that to allow a purge on shutdown provided a triple block/double bleed arrangement was provided on gas lines to the gas turbine and duct burners (if installed). more 

AHUG features presentations by top HRSG experts, vibrant open discussion

nullDon't delay. Make plans now to attend the fifth annual Australasian HRSG Users Group (AHUG) meeting, December 3 to 5, at the Brisbane (Australia) Convention & Exhibition Centre. This conference and its associated workshops are acknowledged by some industry observers as the leading public forum, in terms of content, for owner/operators of heat-recovery steam generators worldwide. more

Important to monitor iron transport in the steam/water circuit

Thermal Chemistry Ltd's David Addison, a globally recognized water consultant with years of experience in powerplant operations, says that accurate measurement of total iron in a combined cycle's steam/water circuit is critical to understanding the degree of effectiveness of the cycle chemistry program formulated to protect against corrosion and deposition. more

You don't have to like chemistry, but you have to respect it

Cycle chemistry demands particularly close attention for units experiencing weekday starts and weekend (or longer) shutdowns. Attendees at the last meeting of AHUG were polled regarding their two-shifting experience (shutdowns of four to six hours) and what return-to-service/standby chemistry issues they were facing (if any). One user said his 175-MW plant was designed for base-load service but had been two-shifting/peak-chasing the last five years. The 2 x 1 station has only one HRSG and it is of the once-through design. Thus its optimal cycle chemistry is different from that used in drum-type boilers. However, this plant also was dealing with chemistry issues and had suffered stress corrosion cracking in the steamer. more

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