STUG2017 addresses the tough issues facing steam-turbine users

Most readers are familiar with steam turbines; some believe they “know” steamers, some really do. But until you attend a meeting of the Steam Turbine Users Group (STUG) you can’t appreciate how much new there is to learn. Some of the material presented and discussed at last year’s meeting, reviewed here, should help you recognize the value of attending the 2017 Conference and Vendor Fair at the Sheraton Grand at Wild Horse Pass, Chandler (Phoenix), Ariz, August 28-31.

STUG was founded in 2014, making the upcoming annual meeting the group’s fourth. What began as a conference focusing on GE A10 and D11 steam turbines for combined-cycle plants is now a meeting covering steamers used in the production of electricity from every major OEM.

The group operates under the PowerUsers umbrella, an organization run by users for owner/operators to enable the sharing of experiences, best practices, and lessons learned via attendee-driven discussions focusing primarily on design, installation, O&M, overhaul, and safety. A quick look at the names and affiliations of steering-committee members in the accompanying box tells you if there’s one meeting that can get you “up to speed” on steam turbines, this is the one.

While you may think you’re already “up to speed,” don’t be so sure. There have been many design changes/enhancements in the last couple of years. At the 2016 meeting, a GE engineer compared designs of his company’s steam turbines (STs) both before and after the Alstom acquisition.

One change noted: Before Alstom, the D11 had high- (HP) and intermediate-pressure (IP) turbines of the impulse type. Today’s enhanced steam path features a reaction HP cylinder (IP turbine is still impulse).

The new HP rotor is made of 10Cr steel and is retrofittable. The upgraded material was said to add more stiffness to the rotor. Plus, the new rotor won’t grow as much at high temperature as the original did. J seals dissipate heat if a rub occurs; heat does not flow into the rotor.

Attendees were told that for an HP/IP shell (single casing, not the current two-casing design) in good condition, a steam-path upgrade can increase steamer output by up to 1.5% through the recovery of ageing losses and better technology—such as advanced Singlet™ high-efficiency diaphragms, abradable coatings and brush seals, modern N2 packing head, integral covered buckets, etc. A decrease in overhaul time is another benefit of the upgrade, the speaker said. In the illustration given, the outage was reduced from 60 to 37 days.

The HP/IP enhancements presented were said to solve the rotor bowing issue that had affected the fleet and to mitigate shell and packing-head cracking and diaphragm dishing. OpFlex steam-turbine agility was mentioned as a comprehensive system solution configured to improve ST starts through revised control settings. And a shell warming system described promised faster starts. [link to Arnold article]

So, you say, most if not all of this information is available on the OEM’s website. It is, but you don’t get to ask questions interfacing with a website and you don’t have the opportunity to poll your peers regarding their experiences with the enhancements promoted. Personal contact with the experts: That’s the value of attending user-group meetings. Register today. [link to STUG registration]

GE’s day-long 2017 agenda includes presentations on valves and actuators, “digital valve” packages, diaphragms and N2 packing head, structures, rotating components, electrohydraulic control oil fluids, repair technologies, outage strategies, etc.

Alternative vendors for turbine upgrades and major outage work presenting this year include Siemens, EthosEnergy, and MD&A. This gives you the opportunity to compare offerings in a dynamic environment. MD&A’s planned podium time in Phoenix is a solid two hours. Last year the company’s engineers provided critical thinking on valve issues and maintenance, diaphragm dishing, casing re-rounding, and rotor straightening—all hot topics for plant personnel.

Follow the “living” conference program posted on the STUG website to get the details as they become available.

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