Are your compressor rotor-blade spacers migrating?
by Team CCJ | May 16, 2012 10:53 am
Immediately following the announcement of the 7F User Group’s new website, Chairman Ben Meissner polled the more than 250 attendees in the Westin La Cantera’s ballroom to learn more about them. About half of the audience, by show of hands, said this was their first 7F meeting. Well over half the group had at least two years of experience operating and maintaining the GE engine, with 40% saying they had participated in at least one major inspection. Units in peaking, cycling, and base-load service were represented about equally. The starts leader in the room was over the 3000 mark; six engines were said to have recorded more than 100,000 operating hours. More than half the group had GE long-term or parts services agreements; about 30% self-performed maintenance.
The first user to present said he was concerned by the migration of compressor rotor-blade spacers discovered on two 7241s during their second HGPs. The units had about 1800 starts each but were transitioning from a starts-based regimen to base-load service. The units’ first majors would probably are two years off. This owner/operator was not sure what should be done to address the migration issue, if anything, and asked his colleagues in the audience to share relevant experience.
Not to worry. His investigation revealed no vibration problems resulting from spacer migration. In fact, calls to several users before making the trip to San Antonio did not uncover any vibration issues in the fleet that could be linked to spacer migration. The OEM’s response, he said, was “don’t worry.” However, GE expressed some concern that if the migration had occurred in rows 7 and 8, where the spacers align, a combined migration of the two rows could happen in the future.
Four attendees said spacer migration had occurred on their machines but there had been no negative effects. One of these users said he used to work for the OEM and had seen many instances of migration but no problems resulting from that movement. Yet another owner/operator had experienced migration on Frame 5s and 7EAs and thought it might be the result of poor craftsmanship—specifically, poor staking.
Someone else said that if just one or two spacers migrate it’s one thing, but if several in a small section of the rotor move, then you could throw the unit out of balance. He reported seeing this on peaking machines and attributed the migration to “thermal ratcheting.” A few others confirmed this based on their experiences with 7B-EAs. The OEM reportedly did field restaking for one user to correct for movement of one spacer.
Source URL: http://www.ccj-online.com/are-your-compressor-rotor-blade-spacers-migrating/