Sub synchronous peaks at gearbox of steam turbine

Dear All,

Good day!

We are experiencing high vibration problem at gearbox of 10 MW steam turbine (GE made) during start-up condition. Spectrum is showing sub-synchronous peaks (0.2 X, 0.4 X, 0.6X and 0.8 X) during start-up only which disappear when machine gains full speed. Amplitude of these peaks are up to 28 microns and is directly related to rpms of machine. Never seen anything like this before.

Expert opinion is required please.

Best Regards,

 

Original Post

Dear John

Thank you for your response.

Details of gearbox are as follows:

No. of Teeth on pinion = 28

No. of Teeth on Gear = 109

Pinion RPM  = 7007

Gear RPM = 1800

Double Helical Gears

Bearing types = Sleeve bearings

Spectrum of gear side bearing is attached, where sub synchronous vibration was found.

X-section drawing of gearbox is not available.

Attachments

Photos (2)

Just looking at the plot you provided (Bearing 5-79YD,  gear low speed "blind") it appears as if you have a major peak (almost 10 µm) at a very low frequency that is likely part of the total amplitude shown of 12.63 µm.  The frequency is low enough that it "hugs" the left vertical scale.  Is this data perhaps from an accelerometer or a velocity transducer and it is then integrated into displacement units?

Can you add a similar plot with the frequency scale in Hz (or CPM) but only out to about 100 Hz?

The data you have presented is at 1831 but this is a generator.  Was this taken unloaded and before synch to the grid?  If so what is the behavior when loaded?

 

 

JR RE posted:

Dear All,

Spectrum is showing sub-synchronous peaks (0.2 X, 0.4 X, 0.6X and 0.8 X) during start-up only which disappear when machine gains full speed. Amplitude of these peaks are up to 28 microns and is directly related to rpms of machine. Never seen anything like this before.

Expert opinion is required please.

Best Regards,

 

The one plot you attached does not support the 0.2X, 0.4X, 0.6X and 0.8X and in general, components near those fractional orders have small amplitudes.Untitled

Attachments

Photos (1)

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