HRSG User's Group: Improving steam-plant reliability, durability and profitability    

HRSG User’s Group Conference Notes, April 24-26, 2019

Edited by: Rob Swanekamp, PE

Copyright 2019 HRSG User’s Group

Welding Grade-91 steel Without Post-Weld Heat Treatment
William F. Newell, Jr., PE, PEng, IWE, Euroweld, Ltd

For more than a decade, the National Board of Boiler and Pressure Vessel Inspectors (NBIC) Code has required that weld-repairs to Grade-91 steel must be followed by post-weld heat treatment (PWHT), for the purpose of tempering the weld-metal and the heat-affected zone.

Case Studies on Operating HRSGs with Elevated Feedwater pH
Colleen Scholl, HDR, Inc.

In 2013 the Electric Power Research Institute (EPRI) updated its cycle-chemistry guidelines for combined-cycle power plants. Striving to minimize the flow-accelerated corrosion (FAC) that was plaguing heat-recovery steam generators (HRSGs), these 2013 guidelines elevated the recommended pH range for all-ferrous systems operating on all-volatile treatment (AVT). Specifically, EPRI elevated pH from the (9.2 – 9.6) of its 2006 guidelines, to (9.6 – 10.0).

Case Studies of Major Losses at Combined-Cycle Projects
Bob Sansone, Power Gen & Construction Practice, LLC

Modern steam turbines have redundant levels of protection from catastrophic overspeed, so overspeed accidents don’t happen in today’s modern times, right? WRONG! Overspeed accidents still happen in today’s power industry!

Recent NYC blackout highlights importance of NERC’s New Regulation
Scott Dude, Dude Testing, LLC

The North American Electric Reliability Corp. (NERC) recently issued a regulation for all power producers to test their electrical systems for proper coordination between protective relays. This protective-relay coordination standard number 27 (PRC-27) presents a big challenge for all power plants, but particularly for combined cycle/cogeneration plants, whose lean staffs lack the electrical engineering personnel needed to comply with it.

Next-Generation, Fast-Start HRSGs
Marlon Farquharson, Siemens Heat Transfer Technology

Today’s heat-recovery steam generators (HRSGs) are suffering reliability problems, mainly because they’re being operated in the cycling mode, instead of the baseload mode for which they were designed. The good news is, HRSG suppliers are adapting to the market-demands and are designing the next generation of HRSGs to have cycling-friendly—also called fast-start—features.

Upgrade duct-burner performance with advanced instrumentation
Roberto Roubicek, SEI

Many combined-cycle plants use duct burners to boost steam production (Fig 1). Unfortunately, the temperature instruments—or thermocouples—that control these burners typically are antiquated, causing such problems as flame instability, lost electricity sales, and HRSG damage by a phenomenon that the Techs wryly call ‘flame lick.’ Fortunately, these duct-burner problems can be prevented, and steam production can be maximized, by replacing these antiquated thermocouples with advanced acoustic pyrometers.

Dye-Penetrant Testing
Joe Frey, Joe W. Frey Engineering Associates, LLC

Dye-penetrant testing is one of the most popular non-destructive evaluation (NDE) techniques in power plants, because it can identify cracks and other defects in the smooth surfaces of all metals—including both magnetic steel and non-magnetic steel—as well as of most non-metallic materials.

Flow-Accelerated Corrosion and the use of Pulsed-Eddy Current for HRSG Inspections
Doug Hilleman, PE and Ryan Moore, Intertek Group, PLC

Flow-accelerated corrosion (FAC), and under-insulation corrosion (UIC) are two of the most troublesome damage mechanisms in HRSGs, because monitoring them typically requires a plant outage, and the laborious removing of insulation from pipes, or the shaving of fins from tubes. Fortunately, a new non-destructive evaluation (NDE) tool can monitor both mechanisms without any of that removing-or shaving-labor. You don’t even need to shut down the plant, thanks to this new NDE tool!

Replacement Projects for HRSG Tube-Modules
Max Begeman, NextEra Energy Resources, Inc.

Instead of patching up one individual tube leak after another, for a temporary repair, some users of aging HRSGs have opted to remove and replace their entire tube-modules, for a long-term repair.

How to Operate Baseload-Designed HRSGs in Cycling Service
Thamarai P. Chelvan — Sr. Key Expert, Fired Boiler, HRSG & BOPs, Siemens O&M Technical Support

Most of today’s heat-recovery steam generators (HRSGs) were designed for steady-state baseload duty, but are forced by market demands to operate in the cycling mode. As a result, HRSGs are failing at an alarming rate.