The 12th IAPWS European HRSG Forum, EHF2026, met May 19-21 at Monash University in Prato, Italy, with Barry Dooley of Structural Integrity, UK, and Bob Anderson of Competitive Power Resources, USA, serving as co-chairs. The forum remains one of the more concentrated technical exchanges for combined-cycle users, suppliers, consultants, and HRSG specialists because it stays close to the failure mechanisms operators see in the field.
The event was developed and supported by the International Association for the Properties of Water and Steam and held in association with the Australasian Boiler and HRSG Users Group. Mecca Concepts, Australia, organized the meeting, which included 15 sponsors and a program built around 20 presentations, open-floor discussion, and a mini-workshop on attemperators. The agenda covered materials, cycle chemistry, operation, tube failures, controls, valves, inspection, fireside cleaning, layup, SCR retrofits, and balance-of-plant equipment tied to HRSG reliability.
Session highlights
Dooley opened the technical thread with the latest international statistics on HRSG cycle chemistry. The database, developed over more than 20 years from more than 400 HRSGs worldwide, continues to show repeat cycle-chemistry situations that are familiar to many combined-cycle plants. The figures cited at EHF2026 were blunt: 85% of plants have ineffective corrosion-product monitoring programs, 77% have less cycle-chemistry instrumentation than recommended by IAPWS, 80% do not monitor drum carryover, and about 74% are not challenging the status quo. IAPWS plans to incorporate these results into a benchmarking process in 2026 so plants can compare their chemistry and flow-accelerated corrosion programs with peer facilities.
Anderson’s update on HRSG thermal transients showed a similar pattern. The international database, collected since 2009, indicates only moderate overall improvement. Most damage remains associated with attemperators and drains. Only 21% of plants routinely inspect attemperator hardware; 86% experience leaking attemperator spray water; 93% of those plants use block-valve/control-valve sequencing logic that encourages leakage. The same dataset shows attemperator overspray in 39% of superheaters and 17% of reheaters, manual attemperator control at 29% of plants, and effective HPSH/RH draining during startup at only 35% and 41%, respectively.
The Day Two mini-workshop on attemperators was therefore well placed. Oliver Selzer of IMI reviewed attemperator designs and useful field modifications, while Anderson addressed damaging thermal transients associated with attemperator operation. The practical message was direct: steam-temperature control hardware that is poorly designed, poorly maintained, or badly sequenced can crack critical HRSG components and produce unsafe conditions or forced outages. The workshop also gave newer personnel a primer on basic designs and gave experienced users a structured review of where the failure pathways start.
Several presentations dealt with life assessment, inspection, and retrofit work. Quest Integrity, Baker Hughes, addressed life assessment of Alloy P91 used in HRSGs and boilers. TesTex reported on inspection techniques for HRSGs, including methods intended to detect internal or external tube corrosion through external fins and robotic tooling deployed into evaporator or economizer tubes from the upper header. GE Vernova covered HRSG upgrades tied to gas-turbine upgrades, and NEM-Energy addressed SCR retrofits in existing HRSGs.
The program also returned to pressure-part management during startup and layup. Anderson reported on full-performance commissioning of automatic HPSH and reheater control using ultrasonic technology to drain condensate from harps during the pre-start purge. The system is intended to limit drum-pressure loss and blowdown-system damage, reduce the risk of condensate migration and downstream thermal shock during startup, and shorten the delay in getting cooling steam to the HPSH and reheater.
Chemistry remained a major portion of the program. Azito O&M presented operating feedback and procedural improvements from cycle-chemistry management at Azito CCPP, listed in the agenda as 460 MW plus 253 MW. Aquatech International addressed silica management using new-generation high-flow EDI stacks. Kurita Europe discussed Cetamine application in cyclic operation. Dooley also reported on film-forming substances and the latest IAPWS activities, while the highlight discussion linked under-deposit corrosion, hydrogen damage, corrosion-product transport, and deposition directly to HRSG tube integrity.
Concerns and mitigations
HRSG tube failures remain the main reliability concern. The EHF2026 discussion again put root-cause assessment ahead of short-term patching. The recommended first step after a tube leak is removal of the failure site for metallurgical laboratory determination of the failure mechanism. One combined-cycle plant general manager described an effective tube-leak reduction program built around management’s declaration that every tube-leak event would be followed by RCA.
FAC was identified again as the largest HRSG tube-failure mechanism worldwide. The chemistry discussion separated the controls needed for two-phase and single-phase FAC, with pH affecting two-phase FAC and oxidizing power used to prevent single-phase FAC. The same operating thread addressed under-deposit corrosion, hydrogen damage, and heavy deposits in HP evaporator tubes, with tube removal and comparison against the IAPWS Deposition Map used to judge the severity of deposition.
Attemperators and drains remain high-risk components because their problems often appear as thermal transients rather than obvious equipment failures. The data on leaking spray water, overspray, manual control, and poor HPSH/RH drainage point to work that plants can check directly: hardware condition, valve sequencing, controls permissives, startup drainage, and operator practice. The workshop made clear that design changes and field modifications can help, but they do not substitute for disciplined inspection and maintenance.
Preservation and layup also received attention because many corrosion events begin while the HRSG is not operating. RINA Tech UK reviewed responsive and responsible preservation methods for different operating modes. The discussion noted a recently demonstrated procedure to electrically heat evaporator modules during wet layup to maintain moderate HP-drum pressure at moderate cost, with reported benefits including faster startup, lower HP-drum fatigue damage on startup, freeze protection, and corrosion protection on water-side and gas-side surfaces.
Vendor and OEM caveats
The supplier program was useful, but the takeaways should be applied plant by plant. Bang & Clean presented PressureWave+ DeepCleaning reference cases, and the highlight discussion noted continued interest in ice blasting and pressure-wave cleaning for badly fouled finned tubes. These methods can offer fast return on investment when gas-side pressure drop has reduced generating capacity, but the case for cleaning still depends on fouling condition, access, outage timing, and the value of recovered output.
SCR, catalyst, expansion joints, silencers, and inspection tools carried similar cautions. NEM-Energy discussed SCR retrofits in existing HRSGs, and Cormetech covered modern SCR catalyst. Dekomte addressed expansion-joint membrane developments and hydrogen readiness, including the implications of draft regulations that could prohibit PTFE use in expansion joints and bellows. Bremco’s presentation on HRSG steam vent silencers warned that through-life inspection and maintenance are needed to manage atmospheric corrosion and the safety risk from debris ejected during safety-valve lift events.
European code requirements were another caution for owners planning new combined-cycle projects or major HRSG work. TÜV Rheinland discussed requirements and tests at gas turbines for water-tube boilers under EN 12952-8, while the highlight discussion noted that European legislation, including PED and EN 12952, will impose additional testing and certification requirements for new combined-cycle plants in Europe. These requirements should be considered early enough to avoid late design or commissioning surprises.
Actionable takeaways
For users, the practical list from EHF2026 is familiar but still not broadly executed: benchmark the chemistry program, verify corrosion-product monitoring, check drum-carryover monitoring, inspect attemperator hardware, correct spray-water leakage and valve sequencing, confirm startup drainage, and stop allowing undocumented tube leaks to pass without metallurgical RCA. The data presented at the forum show that many plants still have room for improvement on basic practices.
The next step is to turn the forum statistics into site-specific work orders and management expectations. Plants should compare their chemistry instrumentation with IAPWS guidance, review FAC and deposition risk, audit reducing-agent use where corrosion products are elevated, evaluate layup practices for their operating mode, and review HRSG upgrade or retrofit work against code, catalyst, access, controls, and maintenance constraints. EHF2026 again showed that the same damage mechanisms keep returning. The plants that reduce forced outages will be the ones that treat those mechanisms as routine inspection and operating discipline, not as occasional conference topics. CCJ
