What you can expect to learn at the Power Users’ Combined Conference

Power Users group.3.20.15It’s difficult to gauge how much information of value a speaker will provide based on the title and presenter name in the agenda. Many commercial conferences offer enticing titles but the content disappoints. The Power Users’ Combined Conference is organized by users under a not-for-profit umbrella solely for the benefit of owner/operators; content providers are hand-picked by members of the steering committees. A speaker who dares to cross the invisible line between technology and sales pitch is not invited back.


To give you an idea of what you can expect to learn during the Tuesday afternoon (second half) track in the Combined Cycle Users break-out the editors compiled the following precis of the four presentations:

Planning for HRSG HP steam drum weld crack inspection and assessment, Lester Stanley, HRST Inc.

HP steam-drum weld cracks become more common in HRSGs behind F-class gas turbines as units age. Discovery of a drum weld crack during an inspection creates urgent and challenging questions for plant management to enable proper decision-making—including these:

      • How big are the cracks?

      • Can I delay repair or must I repair now?

      • How should I repair?

      • Will my current outage duration be affected?

      • How much will the repair cost?

The speaker will offer the benefit of his company’s experience on where cracks are being found today and examples of weld repair experience. In addition, outage planning steps will be described to assure proper inspection and immediate analysis of inspection results so “fitness for service” according to API 579/ASME FFS-1 can be applied and repair decisions made within hours of crack discovery.

The bottom line: This presentation will help you (1) identify problems early, (2) enable a “fitness for service” assessment to delay repairs, if possible, so they can be better planned and conducted during a scheduled outage, and (3) avoid rushed repairs that could result in re-cracking.

HRSG risks caused by low-load gas-turbine operation, Bryan Craig, HRST Inc.

An increase in gas-turbine low-load operation can create new risks for the HRSG. Assessment of HRSG predicted and actual performance at low loads provides valuable guidance on whether damage is a possibility. The speaker will present examples and consequences of low-load problems—including the following:

      • Low economizer water flow velocities, which can cause tube leaks.

      • Elevated superheater and reheater tube-metal temperatures, which can exceed design temperature limits and increase the creep damage rate—even when attemperator spray flow is properly controlled.

      • Strategic HRSG considerations for 2 × 1, 3 × 1, and 4 × 1 power blocks.

      • Attemperator spray-water overspray damage.

      • Reduced catalyst performance, resulting in emissions compliance challenges.

      • Acceleration of HRSG inlet-duct component damage because of higher turbine exhaust temperatures.

Attendees will come away with a greater awareness of checks that should be performed when shifting to increased low-load operation.

HRSG cleaning increases efficiency, decreases costs, increases output, Keith Boye, Precision Iceblast Corp.

Learn through a series of before/after photos the benefit of CO2 blasting for cleaning HRSGs in addition to generators, compressor blades, catalyst, inlet houses, inlet scrolls, etc. Speaker will walk attendees through the following in rapid order:

      • Types of buildup encountered in HRSG tube passages.

      • How to determine when cleaning is necessary.

      • Consequences of not addressing fouling in timely fashion.

      • Concerns to be aware of before engaging a cleaning contractor.

      • The risks/rewards of deep cleaning.

      • Case histories offering practical examples of as-found condition and results.

Impact of changing operating profiles on plant emissions and catalyst life, Andy Toback, Environex Inc.

Learn the following:

      • What happens to SCR and CO catalysts during startup.

      • How to accelerate removal of NOx and CO.

      • What happens to SCR and CO catalysts during low-load operation.

      • How to control NOx, ammonia slip, and CO emissions during low-load operation.


Here are key aspects of the content in three presentations that will be made to steam-turbine users on Tuesday afternoon:

Thermal distortion repair methodologies for steam-turbine diaphragms, Sean McLenithan and Mike Leigh, K Machine Industrial Services LLC.

      • Definition of terms (diaphragm parts) puts everyone on the same page.

      • Diaphragm dishing explained and failure modes described (there are several).

      • Post-mortem inspection helps attendees understand how poor welding, material choices adversely impact diaphragms in service.

      • Dishing repair example with proposed modifications. Excellent photography makes the presentation easy to follow.

Steam-turbine packing lessons learned, Donna Rambin and Vince Caudill, STAR & STAR Field Fit Inc.

      • Geometry of typical packing rings.

      • Retaining rings.

      • Anti-rotation pins.

      • What causes packing rubs.

      • Effects of rubs.

      • Types of distortion and how to address each.

      • Seal clearance measurements.

      • Roundness check.

      • Diaphragm dishing and creep.

      • Steam dams.

      • Alignment.

      • LP turbine gland issues.

      • Slant tooth versus inline teeth.

D-11 steam turbine O&M, Mark Cohen and Scott Cavendish, Independent Turbine Consulting LLC

Design features of the D-11 and the evolution of the machine’s design is important history for anyone new to F-class combined cycles. The consultants will open their presentation talking about the evolution in the steamers shell, LP exhaust casing, design backpressure, rotor span and critical speed, etc. Discussion of the Top 10 maintenance issues will be next, with rotor vibration at No. 1.

Alignment factors are next, with the presentation focusing on steam path, turbine shell support, LP casing, etc. Common startup problems associated with turning gear, steam seals and vacuum, and starting and loading follow. Then the subject shifts to rotor vibration—including diagnosis, trips, and restarts.

Turning gear and roll-off issues, steam seals and vacuum, drains and water induction, and valve maintenance issues, and thermal insulation issues round out the presentation.


Below are summaries of the take-aways you can expect from three presentations that will be made to generator users on Tuesday afternoon:

Hydrogen safety, Steve Kilmartin, Environment One Corp.

      • Why hydrogen as a generator coolant.

      • Safety concerns, including understanding hazardous areas.

      • Key components in the hydrogen cooling system.

      • Safe purging—including hydrogen leak detector, portable gas analyzer, personal LEL detector, use of non-sparking tools, etc.

      • Locating and qualifying leaks.

      • Training.

EMI testing, Paul Spracklen, Doble Engineering Co.

      • Condition-based maintenance (CBM) goals.

      • CBM online diagnostic methods.

      • Partial discharge analysis.

      • EMI as a test tool.

      • High-voltage discharge and arcing.

      • EMI diagnostics.

      • RFCT (radio-frequency current transformer)—including collection of frequency analysis, identifying areas of concern, and looking and listening to those areas.

Rotor thermal sensitivity, Howard Moudy, National Electric Coil.

      • Causes explained, including insufficient or unequal clearances, asymmetrical coil expansion, bound slot wedges, blocked ventilation passages, shorted turns.

      • Rings off rotor inspection.

      • Blocking design/end-turn blocking.

      • Case study on turn insulation migration.

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