STUG 2015 OEM presentations: Siemens

Steam-turbine maintenance and upgrade technology, Jim Auman

Slides illustrating stationary and rotating components—including details on integral shrouds, several airfoil shapes, different types of roots, control-stage technology, blade locking screws, seals (brush, abradable coatings, retractable), etc—would be of particular value to employees not having intimate knowledge of steam turbines.

Several slides familiarize users with mods and upgrades and their value. Capacity increases—as much as 6% in some cases—can be achieved via technology and flow upgrades, typically possible during an outage of from four to six weeks. Inspection recommendations and service bulletins addressing side-entry integral shroud looseness and the migration of free-standing L-1R were included. Access presentation.

Steam-turbine upgrade technology and recent project experience, Mike Smiarowski

Siemens has responded to demands placed on customers for increased cycling and load-following with new components offering upwards of a 25-year lifetime, higher reliability, major inspection intervals for retrofits of 100,000 equivalent operating hours, partial-arc design for HP retrofits, etc.

The speaker reviewed some design features conducive to higher output—including improved inter-stage shaft sealing, twisted three-dimensional shaped drum blades, improved blade profiles, and changes to the shape and size of the last stage. Also mentioned were upgraded replacement steam chests and valve parts made of improved materials. Mods recommended for LP turbines include upgraded blade carriers, single-piece inner casing, optimized exhaust flow guide, integrally shrouded L-2R, and freestanding L-0R and ILB L-1R blades.

Benefits of ST and condenser upgrades for units rated between 200 and 900 MW are these, with the expected heat-rate benefit (typical) in parentheses: HP turbine (1.5%-2.5%); HP/IP (1.5%-3.0%); IP (0.2%-0.5%); LP (0.5%-2.0%); condenser (0.2%-1.0%).

The speaker also presented thumbnails of several rotor overhauls and the performance benefits gained, closing by stressing that advanced planning is critical to success. Access presentation.

Generator Footprint™ replacement, Greg Palubin

Generators can suffer all manner of wear and tear over their lifetimes. For units owners want to keep in service, but would require serious work to assure long-term reliable service, a total generator replacement may make best sense. Siemens offers a program whereby it will drop in a machine from any manufacturer provided its footprint is compatible with the foundation for the generator being removed. The company has experience in this regard, reporting success in more than 35 plants.

Here’s how the process works:

1. Siemens engineers perform a site walk-down to collect electrical, mechanical, and foundation information.

2. The OEM’s engineers analyze the data collected in the first step—that is, axis height, turbine thrust, foundation interfaces, etc.

3. Siemens collaborates with the customer to optimize the machine for future operation.

4. Siemens can support the project with service, project management, and parts from proposal to end-of-life.

Other presentation highlights included details on the company’s Micalastic® insulation system, which is characterized as having high thermal stability and other benefits; global vacuum pressure impregnation (GVPI); rotor cooling scheme contributing to uniform temperature distribution and higher efficiency, etc. Basics of excitation systems, and cooling systems relying on direct/open air, totally enclosed water-to-air, and totally enclosed air-to-air heat transfer, were presented in a few slides. Access presentation.

Siemens Flex-Plants™, Jacki Engel

If you want to learn about the advantages of Siemens’ fast-start/fast-ramp offerings for new combined cycles, this presentation satisfies that need. Access presentation.

Steam-turbine field service capabilities, Gene Morgan

More than half of Morgan’s presentation discusses the company’s processes to maximize safety, quality, productivity, and human performance; reviews its district office network; how Siemens works with owners as a partner; personnel capabilities and craft labor resources; and foreign-material exclusion program. Remainder offers one-slide service summaries for generators, valve refurbishment, fluid systems, NDE activities, lifetime assessments, and steam turbine and generator inspection, followed by similar capsules of capabilities in training, tooling, supply of critical parts, etc. Access presentation.

Steam-turbine factory service

This summary of shop capabilities focuses on the company’s Charlotte facility, offering snapshots of products and services, lean manufacturing, workforce development (apprenticeship program, training, etc), tooling, and centers of competence for stationary parts, valves, rotors. About 30% of the presentation discussed factory service for gas turbines. Access presentation.

Combined-cycle generator fleet topics, Scott Robinson

If generators are among your responsibilities, this presentation is worth reviewing. Robinson stressed in his opening remarks that generators are designed to be very reliable; however, regular maintenance is required.

He reviewed industry-wide generator issues, including these:

Stators: End-winding looseness, cracks in copper bars caused by vibration, core looseness, damaged wall insulation in windings, hot spots in stator core.

Rotors: Damaged inter-turn and core slot insulation, cracked turns in end windings, rotor tooth top cracking, cracks in rotor wedges, J-straps, and poll crossover.

Next, Robinson showed users how to optimize outage intervals to achieve lowest maintenance expenses. Packaged in this section of the presentation were the work-scopes for minor, medium, and major inspections and sample schedules for integrating gas-turbine and generator outages.

What may be of particular interest to users experienced in generator overhauls is that Siemens may have updated the maintenance recommendations they have been following for years. For example, wedge tightness testing has been removed from the minor-inspection scope, as have some electrical tests; a bearing insulation test has been added. For the medium inspection, bearing condition exams have been added and the bump test removed.

Siemens’ Generator Lifetime Assessment was introduced to the group and described as a proactive outage planning partnership between the customer and OEM. Two important benefits are a reduction in the risk of experiencing an unplanned outage and optimization of technical and customer needs.

The focus of Robinson’s discussion of top NDE solutions for combined-cycle generators was the company’s FAST Gen(SM) program involving high-resolution visual/video inspection; stator-slot wedge tightness test; and Siemens multi-frequency core assessment service.

An advantage of FAST Gen is its use of robotic inspection for proactive planning of generator maintenance and the gathering of inspection data for assessments, trending, predictions, and recommendations. Robots were said to reduce inspection time by up to 50% because disassembly is minimal. Retaining-ring inspections also can be performed in-situ with robotic tooling provided there is sufficient access space.

Robinson closed out his presentation with an overview of online monitoring and diagnostics capabilities—including such standalone instruments as a fiberoptic vibration monitor for end windings (now on nearly 200 units), radio-frequency monitor to warn of electrical arcing (now on over 300 units), and an active shaft grounding system (on 21 units). The company’s power diagnostics center provides remote monitoring and daily analysis of any deviations. Access presentation.

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