Vibration limits for GE turbine generator 1

[eeprom]

Hello,
I am setting up a vibration monitor for a GE turbine/generator which has 4 babbitted bearings. I have some initial vibration limits of alarm at 3.5 mils, and trip at 5.0 mils. These values were given to me, but I don't know how they were derived. Can someone point me in the direction of some technical papers/articles which discuss setting vibration limits?

thanks

 

[WaterMan22]

ISO 7919 is a good source for understanding/setting vibration limits as it covers a wide array of machinery types. Depending on your machine there are 5 parts (1-General guidelines; 2-Large Steam Turbines; 3-Coupled Machines; 4-Gas Turbine Sets; 5-Hydro Turbines)

 

[snoopnoon]

These limits usualy come from the bearing clearance dimension. The criteria that I abide by is that vibration limit must be less than 75% of seal clearance. At the bearing location the amplitude must not exceed 3(12000/RPM)^.5

 

[rmw]

If I were going to go looking through GE stuff for this answer here is where I would start;

http://www.gepower.com/prod_serv/products/tech_docs/en/all_gers.htm

rmw

 

[WCFoiles]

Have you looked in the turbine manuals? Hopefully, you will have the resources of mechanical and vibration people to assist you.

You mention trip, which makes the monitor have a control function. This gets more serious than if it is just a monitor.

ISO may give some guidance, but you need to know the equipment more than it is a TG set, inclluding the available instrumentation, prox probes, shaft riders, dual probes.


Regards,

Bill

 

[eeprom]

Snoopnoon,
The 75% of clearance makes perfect sense. I figure that this should work as a logical baseline. But your equation appears to fit very well. Can you tell me how that equation was derived?

thanks

 

[snoopnoon]

EEprom, I hope i did not mislead you with that equation. That equation applies to me because of the unbalance weight i applied to the rotor at various locations (midspan & cplng). for midspan unbal use 16*weightrotor/RPm; for rigid cplng lp end unbal= -8*weightrotor/rpm; flex cplng @drive end=640*(1/2wghtrotor)/rpm. With these conditions my initial reply is valid. Obviasly if you place 50% of rotor weight for unbalance these values do not tread water. Apply each unbal case individually and check your clearances then. Hope this helps. Let me know if you need more in depth analysis as this is very vague.