WTUI 2024: Highlights, Challenges, and Best Practices in Running GE Aeroderivatives

The 33^rd annual Western Turbine Users Inc. (WTUI) conference took place in late March 2024 in Palm Springs, CA. Almost 1,100 attendees were welcomed by WTUI President Ed Jackson, Plant Manager at Missouri River Energy Services’ Exira Generating Station in Brayton, Iowa.

“A strong user group like WTUI challenges OEMs and equipment suppliers to improve their products as we demand new uses and extend the lives of our equipment,” said Jackson.

He introduced the authorized service providers for LM turbines: IHI Power Services Corp., MTU Maintenance, and TransCanada Turbines—each briefed the audience on their service offerings. Clive Nickolay, CEO of GE Vernova’s Aero Business Line, then addressed various deficiencies in the supply chain for vital components and repairs. He laid out a few details of ongoing reorganization efforts that are taking place to speed up delivery, debug parts availability, and reduce the time taken to return a unit to the customer.

“Demand for materials, components, and engines is exceeding supply across the aero-engine space,” said Nickolay. “We are maximizing the reuse of existing materials and components, beefing up our supply-chain options, and working out ways to increase the repairability of parts. We are also lowering lead times by placing stock in the right places within the supply chain, so they are closer to our depots and end users.”

Jim Vono, President and CEO of FieldCore and One Field Services Leader at GE Vernova, followed up by explaining the top factors being worked on to further upgrade field-service safety. He named turbine lifting operations as the highest risk area.

“We are finding better ways to lift turbines safely,” said Vono.

Hydraulics and pneumatics represent another area of high risk. If the turbine is running and these systems fail, there is a risk for those in the line of fire.

BREAKOUT SESSIONS

A big reason for WTUI’s continuing popularity is the level of detail provided on every possible aspect of maintenance for LM2500, LM6000, and LMS100 units. Even the LM5000, which has reached its end-of-life, merits its own discussion forum during the event. After all, there are some of these units still running in the field. Despite the OEM no longer supporting it, the user community meeting provides valuable insight into how to find LM5000 parts and fix problems, and offers advice on workarounds to keep these machines running.

For three days, the event featured breakout tracks for each LM engine. The LM2500 track, for example, was guided by Garry Grimwade, who has operating and maintenance responsibilities for four LM6000s, four GE 10s, and an LM2500-powered combined-cycle unit at Riverside Public Utilities in California. Over the course of the week, he MC’d user discussions and had representatives from GE Vernova brief users on various problems and their recommended fixes. Turbine operators asked questions and heard from their peers about how they solved different challenges.

HRSG MAINTENANCE

Jack Odlum, an engineer at the heat recovery steam generator (HRSG) inspection and repair firm HRST, led a session on the basics of HRSG maintenance. The theme was how to use planning to prevent unnecessary delays during outages. After all, aging HRSGs experience problems such as pitting, creep, and fatigue. He recommended that inspections be done ahead of any major outages and covered the different ways to conduct them. Non-destructive examination (NDE) techniques, he said, include the use of sophisticated camera equipment to detect what the eyes might miss or cannot see. Here is a list of common types of NDE techniques:

• Ultrasonic thickness (UT) is used to determine the thickness of a specific component. This is a good way to check for corrosion.
• Phased array ultrasonic testing is used to identify any inside diameter cracks or weld voids as well as find other subsurface issues. For external cracking, though, dye penetrant tests and magnetic particle techniques can be employed.
• Pulsed eddy current (PEC) determines the relative thickness of ferromagnetic material underneath coverings such as stainless-steel bellows and insulation.

• Replication copies the grain structure to identify signs of material creep.
• Hardness testing is used to understand material properties.
• Infrared imaging (FLIR or IR) reveals the operating temperature on seals, casings, and other surfaces.

Alternatively, borescopes are used to inspect tubes, piping, and other internals inside HRSGs. Drones can also be used to view elevated components.

“Drones are a good way to avoid the need for scaffolding, but they can also spot problems where scaffolding will be required,” said Odlum.

The presentation laid out what to look for while inspecting different HRSG components, such as economizers, steam drums, superheaters, and evaporators. Economizers heat water to near saturation before it goes to the evaporator. This increases the amount of steam production. A common issue is flow-accelerated corrosion (FAC). Borescopes and UT are good inspection techniques for FAC. PEC inspection can also be used to inspect what might be happening underneath insulation, such as the presence of drain corrosion.

Odlum provided an example. Operators knew there was an economizer leak but didn’t know the precise location. This leak eventually caused a drain failure. When the failed drain was found and replaced, an inspection of the other drains detected extreme corrosion that needed extensive repair. In turn, engineers then checked a sister unit using PEC to see if it suffered from similar corrosion issues. No leaks were found; however, three pipes were identified that needed to be replaced to prevent future leakage issues.

Odlum recommended spot-checking high-risk FAC areas such as tube inlets and headers before or during any outage window. He offered LM turbine users further tips related to the typical kinds of damage that might impact HRSG evaporators and steam drums as well as the best inspection methods and repairs to address them.

DRY LOW EMISSIONS CONTROLS

Next up, Marc Forget of the European Maintenance Support Aero Department at Engie Electrabel, delved into the intricacies of dry low emissions (DLE) controls for GE LM-series machines. He said DLE is all about reaching a compromise between NOx and CO emissions. If you lower the flame temperature, the CO rises, but a higher flame temperature leads to more NOx.

“You have to find the sweet spot within the thermal limits of the unit,” said Forget. “The use of a premix system helps to ensure combustion is as complete and as lean as possible.”

When a premix combustion system is involved, it causes humming and vibration of the flame. This excites the mechanical components of the engine. Good monitoring and appropriate controls are needed to compensate. Forget stressed the need for accurate temperature controls and the right combustion system design.

He demonstrated his long years of experience and expertise with DLE systems as he explained the dos and don’ts of instrumentation related to DLE systems, such as gas quality and combustion stability measurement tools. There is a lot to know about how to measure different parameters, calculate fuel-flow rates, and maintain DLE combustion systems. He told attendees about various gotchas when removing delicate sensors and instrumentation components, such as Honeywell gas pressure transducers and Woodward fuel metering valves.

“A good wear-mitigation technique is to power down fuel metering valves when the gas turbine has been stopped,” said Forget. “Also, you should track valve run hours and protect them against water ingress to avoid problems.”

EXCITATION CONTROLS

Another vendor presentation came from Ian Golightly, Senior Controls Engineer at BRUSH (part of Baker Hughes). He discussed the elimination of obsolescence and unscheduled outages by upgrading excitation controls. Older GE aeroderivatives often use analog controls, such as the modular automatic voltage regulator (MAVR), the MicroAVR, and the Prismic A30. These systems sometimes struggle on modern grids where the presence of renewables necessitates fast response and accurate measurement.

“Modern digital AVRs and protection relays can better support and more rapidly synchronize with modern power grids,” said Golightly. “Excitation performance on analog controls may not be compliant with the latest NERC regulations.”

He explained how to protect relays so they don’t trip generators before the AVR limiters operate, as well as the kind of generator protection systems that can adequately prevent damage if turbine operating conditions exceed capability or stability limits.

The 2025 WTUI conference will be held in Long Beach, CA, March 30 – April 2.

Drew Robb, former editor of Turbomachinery International, is a freelance writer specializing in engineering and technology. Email Drew at drew@robbeditorial.com.