Combined cycle |
incorrect implementation in the design can result in cracks in critical HRSG parts, causing unsafe operating conditions and unplanned outages. The workshop on attemperators served as a useful primer for those new to the industry as well as a valuable reminder to experienced plant personnel of the risks that they present to component integrity. The workshop narrative provided an overview of attemperator design principles and types, highlighted the potential for severe thermal transients due to shortfalls in design, control or maintenance, and explained upgrade options to combat some of these deficiencies.
● Safety valve vent pipe silencers are a critical yet often overlooked piece of equipment. A presentation highlighted the importance of through-life inspection and maintenance in managing the risks presented by atmospheric corrosion; this was reinforced with examples of debris being ejected and posing a potential safety hazard during safety valve lift events. ● An update was provided on
commissioning of an engineered system to automatically drain condensate from HP superheater and reheater harps during the pre-start purge using ultrasonic technology. The system is intended to minimise drum pressure loss and blowdown system damage while mitigating the risk of condensate migration and thermal shock of downstream components during start-up. It also shortens the delay in providing cooling steam to the HP superheater and reheater, hence shortening the startup.
● An update was provided on the industry exemption being sought from draft regulations that would prohibit the use of PTFE in expansion joints and bellows, along with the implications of each possible outcome.
● A presentation discussing the benefits and limitations of various HRSG layup methods (wet and dry) highlighted the importance of not overlooking this non-operating period responsible for many corrosion damage events. Discussions following the presentation noted a recently demonstrated procedure to electrically heat evaporator modules during wet layup to maintain moderate pressure in the HP drum at moderate cost, with benefits being faster startup, lower HP drum fatigue damage on startup, freeze protection, and corrosion protection in water-side and gas-side surfaces.
● European legislation, in particular PED and EN 12952, that will impose additional requirements for testing and certification of new combined cycle plants in Europe was discussed.
● Recent developments in non-destructive testing techniques were presented, including the ability to detect internal or external tube corrosion through external tube fins and
At EHF2026, flow-accelerated corrosion (FAC) was again identified as the most important and largest tube failure mechanism worldwide. Photos above show two phase FAC, photo below shows single phase FAC. Source: Dooley and Lister, PPChem 20 (4)
via use of a robotic crawler deploying tooling into evaporator/ economiser tubes from
inside the upper header.
● HRSG tube failures (HTF) remain the major reliability concern. Tube leak root cause assessment (RCA) and tube leak
management
(tube leak reduction programmes and procedures) are essential for reliable HRSG operation. The need for upper management’s declaration that all tube leak events will be followed by an RCA, the first step of which is removal of the failure site for metallurgical laboratory determination of the failure mechanism, was presented by a combined cycle plant general manager who has implemented an effective tube leak reduction programme. Among other tube failure related topics addressed: - FAC was again identified as the most important and largest tube failure mechanism worldwide and discussion included clarification of the effect of pH in addressing two-phase FAC and oxidising power in preventing single- phase FAC.
- Under deposit corrosion (hydrogen damage) was highlighted and related to the transport and deposition of corrosion products. Alleviation here relates directly to the removal of HP evaporator tubes and their analysis to identify heavy deposits as compared to the IAPWS Deposition Map.
- Some discussion was focused on 26 | July/August 2026 |
www.modernpowersystems.com
increased corrosion products relating to the use of a reducing agent in the cycle.
- An update on the application of film forming substances (FFS) (both amine (FFA) and non-amine (FFP) based) was provided.
- Information on the latest IAPWS cycle chemistry Technical Guidance Documents for combined cycle/HRSG plants was provided to illustrate that these address each Repeat Cycle Chemistry Situation.
● Also discussed were the latest developments in fireside cleaning, with case studies presented on ice blasting and pressure waves. These remain hot HRSG topics. For HRSGs with badly fouled finned tubes, cleaning delivers the fastest ROI for a combined cycle plant recovering generating capacity loss due to gas-side pressure drop.
● A conference dinner, generously hosted by Precision IceBlast, was held in the Conservatorio San Niccolo in central Prato.
Please contact Barry Dooley (bdooley@structint. com or
bdooley@IAPWS.org) or Bob Anderson (
anderson@competitivepower.us) with any comments and for further information. EHF2027 will be held in May 2027, also in Prato, Italy.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75
