Greetings all,
During our T&I inspection, the turbine shell (casing) was removed for some job (not related to 1st stage nozzle). We found the 1st stage nozzles (S1N) at 9 & 6 clock positions have their trailing edge melted to some degree with TBC removed also from trailing edge. the leading edge is intact. S1N at other location like 12 and 3 clock are in good condition.
As per GE engineering, this could be due blocked cooling holes in the nozzles. Also they said the unit can run up to the next outage in this condition.
What makes this assumption valid (blocked holes) is that the compressor and the turbine stages were dusty compared to sister units. But I bore-scoped the nozzles from inside (since they are hollow from inside) and didn't find the cooling holes to be blocked. Further I blew some air to resemble the cooling process, and the air came out through the holes which suggests they are not blocked.
During normal operation, S1N are cooled from CPD directly, while S2N are cooled from stage 13 extraction, and S3N are cooled from stage 9 extraction.
Is there any possible reason other than blocked cooling holes to be investigated?
Regards
During our T&I inspection, the turbine shell (casing) was removed for some job (not related to 1st stage nozzle). We found the 1st stage nozzles (S1N) at 9 & 6 clock positions have their trailing edge melted to some degree with TBC removed also from trailing edge. the leading edge is intact. S1N at other location like 12 and 3 clock are in good condition.
As per GE engineering, this could be due blocked cooling holes in the nozzles. Also they said the unit can run up to the next outage in this condition.
What makes this assumption valid (blocked holes) is that the compressor and the turbine stages were dusty compared to sister units. But I bore-scoped the nozzles from inside (since they are hollow from inside) and didn't find the cooling holes to be blocked. Further I blew some air to resemble the cooling process, and the air came out through the holes which suggests they are not blocked.
During normal operation, S1N are cooled from CPD directly, while S2N are cooled from stage 13 extraction, and S3N are cooled from stage 9 extraction.
Is there any possible reason other than blocked cooling holes to be investigated?
Regards