PSM’s Johnston focuses on compressor solutions, field experience

SRO, standing room only, is no surprise when PSM presents at a user group meeting. Chris Johnston, a senior R&D manager, moved quickly through understandable technical detail in bringing users up to date on PSM’s 7FA compressor solutions and field experience with state-of-the-art parts for F-class engines.

This year’s 7F program accommodated three vendor presentations in each of two 45-min time slots between the user-only sessions and the vendor fair. The format was the same both Tuesday and Wednesday.

Johnston divided the compressor section of his presentation into four parts: R0, S0-S4, S13-16, and S17/EGV (exit guide vanes). PSM’s compressor solutions have been operating in the fleet for four years with parts installed in more than 30 units, he said, adding that fleet-leader sets have been validated by way of on-going in-situ, destructive, and dimensional inspections. The company’s redesigned R0 blade, which has a different airfoil shape than the OEM’s, is meeting expectations in units that fog and online water wash. Its R0 retention plug replaces the biscuit familiar to many users (Fig 1).

Success with the flared R0 airfoil prompted development of an unflared R0, the R&D manager continued. The new offering also operates without restriction and is now running in four or five engines. The development approach used PSM’s successful methodology: field assessment, problem identification, solution implementation, and validation.

1. PSM’s R0 retention plug

2. Corrosion resistant carrier ring segment for S0-S4 is designed for ease of installation and removal

S0-S4 field issues, including high cycle fatigue (HCF) and corrosion concerns, have been addressed with a redesigned S3 airfoil and corrosion resistant carrier ring (Fig 2). Johnston said PSM believes that the OEM’s S3 vane has the lowest design margin in this section of the compressor and required redesign to mitigate HCF failures initiating at its leading edge. OEM vanes in S5-S16 have a history of hook fretting and other hook-fit issues. PSM’s S5-S12 vanes remain stator singlets, redesigned to better accommodate the circular case. For rows S13-S16, the company’s “hook ring” packed design provides increased damping.

The second part of Johnston’s presentation concerned the 7FA GTOP3 upgrade. GTOP is the acronym for Gas Turbine Optimization Program. This enhancement incorporates PSM’s low-pressure-drop combustion system and redesigned first- and second-stage HGP buckets and nozzles. The upgraded components have been operating since 2005 and have accumulated nearly 100,000 service hours. They are interchangeable with OEM parts.

The higher firing temperature allowed by the redesigned standard-life (24,000 hours/900 starts) first- and second-stage turbine buckets and nozzles can increase power output of a simple-cycle engine by 5% and improve simple-cycle heat rate by 1.3%, while still achieving less than 9 ppm NOx and accommodating turn down to 50% of the full-load rating. Extended-life (32,000 hours/1200 starts) airfoils are compatible with a 2% increase in simple-cycle power and a 1% improvement in heat rate.

Johnston noted the 22-MW gain attributed to GTOP3 for the company’s first combined-cycle install at a 2 x 1 plant. PSM provided field services, the gas-turbine TFAs, and tuning services. Third-party performance testing conducted before and after the outage validated a 5.2% increase in power for one GT and 5.1% on the other. Efficiency gains were 1.6% and 1.5%, respectively.


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