Best practices improved for in-situ blending, shim removal from Advanced Turbine Support

Continual improvement of O&M best practices is a goal of plant managers focused on keeping their employees safe and their facilities at the top of the dispatch list. The process of continual improvement also is embraced by equipment and services suppliers wanting to create or maintain a competitive edge.

Mike Hoogsteden, director of field services for Advanced Turbine Support LLC, called yesterday to tell the editors about advancements in the capabilities of the company’s technicians regarding in-situ blending and shim-extraction. The bottom line: What might not have been possible yesterday is today.

Blending. Hoogsteden said Advanced Turbine Support recently developed, patented, tested, and proved tooling that allows—depending on rotor stacking—expanded in-situ (no case removal) blending of compressor blades and stator vanes back to Stage 11. The blends can be analyzed by engineering to determine any associated risks both before and after the work is done. Advanced Turbine Support recommends attempting in-situ blends on rotating blades and stationary vanes (photo array) when engineering analysis confirms such repairs are preferable over immediate unit disassembly.

Shim extraction. Most owner/operators of GE Power E- and F-class gas turbines have heard about shim extraction without case removal. So, what’s new? Advanced Turbine Support now offers the capability—depending, again, on rotor stacking—to extract or blend shims back to Stage S-3. In certain situations, shim grinding is possible beyond S-3.

If shim extraction is new to you, consult GE Power’s Technical Information Letter 1562, “E- and F-Class Shim Migration and Loss,” which describes how to inspect for migration of shims between front-end compressor stator-vane segments. It says that once a shim has migrated to 50% of its height and is protruding into the air stream, the OEM no longer considers this a low-to-medium risk condition.

Hoogsteden said his company’s technicians have successfully mitigated migration risk for a decade now, by extracting without case removal S-1 and S-2 shims from E-class engines and S-0 and S-1 shims from F-class compressors. He added that Advanced Turbine Support recommends an in-situ extraction or blend to remove protruding stator-vane shim material once a shim has migrated 0.050 in. from the compressor case—this to prevent damage that could result from a shim liberation.

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