OEM hosts the only US user meeting focusing on V-frame engines

Music City or the Home of Country Music, whichever you call it, Nashville was the site of the 2017 Siemens V-frame Users Group conference, June 12 – 15. The meeting attracted attendees from across the world representing 37 power generation companies. As with previous meetings for this frame, the scope and design of the agenda provided a platform for sharing information among all parties.

Recall that the OEM accepted the financial and technical-program responsibility for the V-frame annual conference several years ago when users opted out of the work required to organize a successful meeting.

This year’s program focused on safety within the plant during all modes of operation, improvements to the reliability and efficiency of the equipment through improved maintenance processes and procedures, improved monitoring techniques (including new digitalization capabilities), and the implementation of new design components and upgrades to the operating systems.

Highlights of the Nashville meeting included:

      • Exclusive user-only discussion sessions integrated into the four-day program.

      • An exhibition that showcased products and services for V-frame engines offered by Siemens and eight vendor partners. The OEM’s display included its repair and service network and technologies, and cybersecurity solutions.

Fleet update. The conference opened with a V-frame fleet update that reviewed performance data for the SGTx-2000E (known previously as the V94.2x and V84.2x) and SGTx-4000F (known previously as the V94.3x and V84.3x) engines. Both fleets showed similar availability and reliability numbers above 95% with the SGTx-2000F units slightly higher than the SGTx-4000E in starting reliability.

Introductory speakers Thomas Schmuck, for the SGTx-4000F, and Bernd Vonnemann, for the SGTx-2000E, got the audience engaged with a review of user questions and comments extracted from previous-conference user surveys and Siemens responses. Both presenters also provided an overview of new product upgrades.

Siemens unveiled its Health Advisor as a part of the company’s expanding digitization efforts. The performance-analysis tool evaluates and prioritizes solutions by cost and availability and displays potential availability and reliability improvements in unit con?guration, diagnostic monitoring, operation, and maintenance. This helps owner/operators select options of greatest value to their plants.

The OEM’s Continuous Plant Monitoring System also was discussed. It remotely monitors units and develops O&M plans based on the data provided. Such monitoring can support operation and maintenance planning and help users manage their plants optimally.

A new field service tool introduced to the group is designed to measure and monitor combustion dynamics to analyze combustion-chamber frequencies and help minimize the potential for acceleration events.

Outage-related safety tools used by Siemens’ field service personnel were discussed next. They include a method for hand-turning and locking of the rotor during various stages of work—such as blade removal. This flexibility can allow sites with silo combustors to flip the combustion chamber in a controlled manner and allow for work to be performed in a different orientation.

Expanded combined-cycle solutions. While most V-frame users are familiar with Siemens products and services intended to improve plant startup metrics, the new Flex-Power Services™ product includes offerings for the entire powerplant, regardless of the equipment suppliers. Example: Services for the heat-recovery steam generator include water-chemistry consulting, inspections, spare parts, and advanced engineering studies to assess the effects of gas-turbine upgrades on the HRSG.

Case studies

Plant optimization experience. Siemens engineers explained how they developed a solution to reduce emissions during “hot starts” (restarts within 12 hours after an engine shut down), while keeping the equipment within the manufacturer’s startup recommendations for internal temperatures, steam pressures, and flows. This was accomplished with the following series of interconnected steps:

      • Tuning.

      • Control logic optimization.

      • Incorporation of logic improvements with CEMS.

      • Personnel training.

Result: A hot-start CO reduction of more than 40% and a startup time reduction of 35%, in round numbers.

Fuel-gas quality. The OEM discussed its view of the effect of the increase in the number of fuel-gas supplies (wellhead gas, shale gas, and LNG) on plant operations. Siemens believes this has led to fluctuating fuel-gas quality nationwide. The speaker said one reason for the quality differences, is that each supplier has its own processing steps which produce varying hydrocarbon and sulfur (H2S) contents.

Siemens’ experience has been that higher hydrocarbons can lead to a variety of problems—including clogged burners from coking. High levels of H2S also can clog burner nozzles and/or contribute to burner corrosion.

For the user, fuel-gas sources and their mixtures should be considered simultaneously; operation outside of the OEM’s fuel specs could lead to operational issues and void warranties. Fuel gases (mainly consisting of alkanes) may have the same Lower Heating Value (LHV) but a different Lower Wobbe Index (LWI). Among other adverse effects, gas with a low LWI has the potential to cause combustion instabilities; gas with high LWI can cause both combustion instabilities and higher NOx emissions.

While the SGTx-2000E and SGTx-4000F designs can operate over a range of conventional and unconventional liquid fuels, an automatic tuning system is available to accommodate changes in fuel-gas quality. The system can include, among other components, a fuel gas analyzer, liquid separation, coalescing filter, fuel gas preheating, aluminized burner and control logic upgrades to automatically adjust for changes in the LWI.

Generator update

Generator Frame Owner Scott Robinson presented research results that concluded that multiple emergency starts from a standstill without lift oil in operation can potentially damage bearings. Inspections are recommended, based on the number of emergency starts.

Robinson also discussed new products and services, developed based on customer inputs, to help reduce outage duration and/or costs—including:

Ultra-low clearance inspection robot equipped with a high-resolution video can eliminate the need to remove rotors for major inspections. Stator slot wedge tightness, in-situ stator core tests, and retaining-ring inspections also can be performed. Field removal still may be necessary based on findings from the robotic inspection.

High-frequency loop test. Siemens has developed tooling and processes to perform the loop/thermographic inspection of stator cores without the need for a plant-supplied 4160- or 6900-Vac (100 to 700 amp) connection.

GVPI. The differences between the current, new-build generator manufacturing process of Global Vacuum Pressure Impregnation (GVPI) versus single VPI generators were discussed next. Since the global VPI manufacturing process was introduced in 1988, Robinson said, more than 1650 stator windings have been delivered and amassed 25.5-million operating hours, plus 322,000 combined start/stop cycles. To date, the frame owner continued, no stator failures attributed to insulation issues on Siemens generators have been reported to the company.

Robinson concluded his presentation with a review of the benefits and reasoning behind the modular design of the GenAdvisor™ Monitoring Platform. These include:

      • The ability to monitor partial discharge, endwinding vibration, inter-turn short-circuit monitoring, and rotor shaft voltage and shaft grounding current.

      • The allowance of concurrent monitoring of multiple generators and connection to the OEM’s Power Diagnostics Center.

      • Providing real-time information about the machine condition during operation (difference to offline tests).

Cybersecurity

Cyber attacks, past and current, were reviewed with an eye on how new international standards and government policies are helping to address increasing attacks via industrial devices connected to the OT environment. This was followed by a presentation on Siemens comprehensive cyber security portfolio approach to combatting hacking was presented.

A case study of Darktrace technology, which uses artificial intelligence systems to identify and respond to in-progress cyber threats followed. In the presentation, the Siemens team discussed how they attempted to bypass the Darktrace technology by using a registered, properly configured company laptop. As reported, within seconds of connection, the technology recognized the authorized, but unfamiliar, presence of the laptop and logged an alarm.

Within a short period of time, the technology learned that the computer was new to the network but was properly authenticated and was performing the same tasks as the other computers already on the network and lowered the threat severity level to less than 5%.

Engineering session

RCIE update. Siemens reviewed the 100,000-EOH (equivalent operating hours) Rotor Casing Inspection and Evaluation findings aggregated from overhauls of more than 100 SGTx-2000E and 48 SGTx-4000F gas turbines since 2009. Evaluation of these findings produced the following conclusions:

      • Statistical results have shown that, in some cases, there is a potential to reduce the component replacement scope at an RCIE outage.

      • Component-specific recommendations at an RCIE may change based on changing electricity markets and more demanding operating regimes.

      • Inspection programs are updated based on experience and the latest analytical results.

      • Siemens has an established materials ageing strategy designed to determine the mechanical properties of aged materials and work toward extending the RCIE of 2000E baseload units to 200k EOH.

      • Flexibility in timing of the RCIE and adaptation of the outage scope is possible and has been successfully implemented.

Repair update. A discussion of various state-of-the-art and/or patented repair processes available at the Winston Salem Service Center was conducted. In some cases, the repair technology was transferred from the 50-Hz to the 60-Hz design. These processes are focused on improving technologies to meet customer needs and meet or exceed the original component design criteria. Components that can benefit from these processes include:

      • Refurbishment of blades and vanes. Inspection and repair using welding, blending and/or brazing, recoating of the airfoils, and final inspection which now includes rigorous cooling-hole measurements.

      • R1 blade tip repair uses a patented, precise, automated laser welding process for tip findings and an automated laser re-opening process for cooling-air flow. The repair includes an improved coating designed to avoid spallation of the thermal barrier coating (TBC).

      • R1 and R2 vane repairs. Advanced brazing processes reduce scrap rates. These components may also benefit from the implementation of an upgraded TBC coating.

      • SGTx-2000E Si3D components. Updated repair techniques can increase inspection intervals up to about 41k EOH and 1500 starts.

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