First- and second-stage distress in 7EA compressors a focus of borescope inspections

Owner/operators of 7EAs with more than a year or two of close association with this frame likely are aware of clashing and other damage associated with S1 (first stage) stator vanes. GE engineers reported at the morning session of the CTOTF™ spring 2015 E- & EA-class Roundtable that progress has been made in identifying the root cause of clashing and work continues in this regard.

In the afternoon, Mike Hoogsteden, field service manager for Advanced Turbine Support LLC, provided a background on S1 issues dating back to the inspection company’s first finding of clashing in 2006. It has worked closely with users since to make available data from its inspections important to problem definition.

The speaker began by discussing developments in inspection technology over the last decade and how they have contributed to a better understanding of the S1 findings and provided information of greater value for the resolution of issues. Follow this timeline: 2008, implementation of visible dye inspections; 2009-2010, measurements added to documentation; 2011-2012, inspection documentation with trending data reveal an obvious increase in damage year over year; plus implementation of eddy-current (EC) inspections suggests an elevated level of risk to owner/operators.

Continuing, in 2013 TIL 1884 recommends checking the suction side of stator vanes in the so-called area of interest; 2014, Advanced Turbine Support identifies by way of dye penetrant two cracked S1 vanes (same compressor) in the area of interest and confirms same with EC; January 2015, borescope inspection finds an S1 vane missing 1.25 in. at the tip of the airfoil; March 2015, EC inspection identifies suction-side cracks in 12 of 34 S1 vanes, only three cracks were confirmed with liquid penetrant.

Hoogsteden suggested to the users, “Although TIL 1884 recommends a penetrant inspection in the area of interest, our recent findings support performing an in-situ EC inspection to the trailing edges of all the R1 rotor-blade platforms, the leading-edge tips and entire suction side of every S1 stator vane each peak-run season or every six months.”

Access details on the foregoing by reading CCJ ONsite’s summary of Advanced Turbine Support’s state-of-engine presentation to the 7EA Users Group last fall as well as CCJ’s report on 7EA User Group activities published in advance of the organization’s 2014 meeting.

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