gas turbine vibration

[bethw]

When up to operating speed, what might cause a gas turbine to vibrate slightly even though the rotor is balanced? I'm not talking excessive here, just enough to draw a small crowd.

 

[dgallagher]

Could be Bearings, blades, misalignment, foundation, piping, air flow, resonance, looseness, rub, just about anything on or near the turbine could be exciting some frequency. You'll need to take vibration readings and analyze the data to determine the problem and forcing function.

Dave G.

http://www.reliabilitydirect.com

 

[EnglishMuffin]

Does it have squeeze film damped rolling element bearings ? (Many do). If so, could be something wrong with that (oil pressure for example). And of course another possibility is that the bearing axis and the axis used for balancing may not coincide for some reason.

 

[borjame]

Bad bearings (the race, the bearings, or the track) could do it and so could a leak in the thrust balance system. You could have lost a blade (turbine or compressor) and that would imbalance the rotor. Are you seeing any drop in output or any temperature anomalies? How's TSFC?

 

[yates]

Bethw
You do not mention if gas turbine is driving a generator, pump or compressor. Depending upon application a reduction gear will probably be associated with the GT. Differing vibration amplitude readings at different locations should tell you if vibration is coming from GT shaft or from reduction gear. Analysis of primary vibration frequency will tell you if you have lost a blade as Borjame suggests, or if it is a more complicated problem. Is vibration amplitude speed-dependent or rather load-dependent ?. Your GT (and reduction gear) should normally be equipped with vibration sensors, so you can do a little rough analysis before placing your own sensors in strategic locations.

 

[FredGarvin]

You're not going to get anywhere without taking some meawsurements. Turbines "vibrate slightly" all the time. You need to understand what the vibration is. Then you can determine where it is coming from. Has the turbine recently undergone maintenence? Does the vibration seem to follow speed during the accel to max? If it doesn't, I'd tend to look for a resonance in the support structure or surroundings.

Get some accelerometers on the engine and maybe a couple on the surrounding structure to get some hard data to work with.

 

[rmw]

Are you operating at, or near a critical speed? And, by the way, at what speed is this occurring?
Did this come on all at once, or has it been so from day one?
Has the compressor been cleaned lately, or not??
Can you answer any of the questions in the previous replies?
Is it still vibrating, or has it shelled itself yet?