Golden Nuggets from the Steam Turbine Users Group: Part 1 – Combined Cycle Journal

Golden Nuggets from the Steam Turbine Users Group: Part 1

With the 2023 Steam Turbine Users Group (STUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website.

Major outages: Plan the work, work the plan

The best way to minimize outage time is to create a detailed, long-term maintenance plan for the unit, and an experienced turbine services firm can help. Tim Keen and Neil Jones, MD&A, take you through the obvious, like scope, schedule, and budget, but also overlooked factors like special tooling that may be required, structural steam-path audits, comparing clearances to those taken at the last outage, casing horizontal joint gaps and diameter out of roundness, valve operation, and coupling alignment.

“Outage Planning Focused on the First/Second/Third Majors”

Address past ‘pain points’ in future bid specs

The first 12 slides in this “big picture” presentation by Eric Prescott, EPRI, address the general industry landscape for future capacity options (more specifically, renewables) driving the need for flexible, dispatchable combined cycles, and the impacts on steam turbine/generators (ST/G). However, the meat of the message is how to incorporate experience with ST/G damage mechanisms into bid specifications.

Balance of the slides are a glimpse into the publicly available EPRI report (No. 1024903), “QA/QC Practices for the Procurement of Steam Turbine and Generator Equipment.”

Evaluating Equipment and/or Component Upgrades in Consideration of Future Operating Flexibility Challenges”

Heavy outage season—a tale of two vendors

The pride and joy of STUG are presentations like this one, in which a user with responsibility for dozens of ST/Gs in his company’s fleet dispassionately describes experience with two different vendors, not to throw shade but to work out how both vendor and user can improve the experience. One vendor was contracted for major outage work on two HP/IP turbines at different sites, the other for packing/seal replacements on two D11 units (from different suppliers) at different sites. The slides include a blow-by-blow account of how the work transpired and the all-important lessons learned. Among the major ones:

  • Insist on early data review between user and vendor before the manufacturing of packing rows begins.
  • Do not allow packing to be final-machined until opening data have been fully reviewed and the rebuild strategy for the machine is defined.
  • Best practice is to send a segment from each row to the packing vendor for reverse engineering.

But don’t deprive yourself of the details supporting these and other recommendations, especially if you are or will be soon undertaking the first major for an ST/G (the situation for two of the units described here).

“Vendor Shop/Field Considerations During a Heavy Outage Season” 

Watch this varnish vanish

If you are having issues with varnish in your lube or control oil systems, or if you never thought varnish was that important, then Axel Wegner’s (C C Jensen, Oil Maintenance) slide deck is for you. It serves as a quick primer on the topic, beginning with the claim that the company’s “varnish removal unit,” or VRU, is the safest and most efficient technology for dealing with the troublesome byproduct of circulating oil systems at elevated temperatures. Prevention through oil changes and bleed-and-feed strategies are only half the story.

C C Jensen’s VRU is described as a depth-filter absorption/adsorption process with advanced agglomeration, which can remove both soluble and insoluble varnish. Wegner also extols the benefits of online oil condition monitoring.

Sadly, Axel Wegner passed on May 5 (2023) at age 55. RIP.

“Demystifying Varnish Analysis and Mitigation” 

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