Gas turbine high vertical vibrations at 1X

[edison123]

5100 RPM (85 Hz) GT driving a 3000 RPM (50 Hz) generator via a gear box is showing high vertical vibrations during startup (after a year-long shutdown) in GT front bearing (NDE) as below. GT rear bearing (DE) also showing similar high vibrations.

Both GT and generator white metal bearings are new ones supplied by OEM.

Overall GT vibrations increasing from 5 mm/sec to 20 mm/sec within 10 minutes at rated speed of 5100 RPM.

Generator excited to rated 10.5 KV but not synched (due to high GT vibrations). Generator vibrations are stable at less than 1.0 mm/sec from unexcited to excited.

Vibration probes are mounted on the bearing housing tops at 90 deg for both GT and generator.

Any idea why GT vertical 1X (85 Hz) is so high?

GT NDE Vertical

GT NDE Horizontal

GT NDE Axial

Muthu

http://www.edison.co.in

 

[1503-44]

No way to know without an inspection.



--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Strong]

If bearing vibrations are normal in the horizontal and axial/thrust direction and only high in vertical direction,then possible causes are: excessive bearing clearance or resonant structure. The resonant structure hypothesis can be verified by variable speed (run up) test and/or impact-response test. Were any of the bearing housing supports/covers removed or loosened for the bearing replacement or other repairs?

Walt

 

[1503-44]

Go.
"Both GT and generator white metal bearings are new ones supplied by OEM."

--Einstein gave the same test to students every year. When asked why he would do G like that, "Because the answers had changed."