Hello All,

Has anybody had much experience working with Woodward TG-13 governors? I've got a TG-13 governor on a steam turbine that's started to vibrate over the last couple of months. Overall vibration at the vertical point on the Governor is at 0.34 in/sec. The normal vibration is at about .20 in/sec. The vibration at the horizontal point is about 1/3 that of the vertical. Vibration on the turbine and pump is running at normal historical levels. The major part of the vibration is at 2xTS(6880rpm).

1xTS is at 0.12 in/sec
2xTS is at 0.32 in/sec
3xTS is at 0.04 in/sec.

I've checked phase across the coupling between governor and turbine and its about 30*-50*, so that doesn't seem to point to misalignment even though that's what the spectrum looks like to me.

Here's what we've done so far:
We replaced the governor.
We've replaced worn turbine bearings.
We've replaced the coupling between the governor and turbine.
We've aligned the Governor/Steam Turbine.
So far, nothing seems to change the peak.

I feel like I'm chasing my tail on this one. Does anybody have any ideas I could try?

Have you checked for possible resonance?
Look at spectrum in log format and see if "noise floor" around the 2 X TS is raised. This may be an indicator or resonance. Simple bump check may confirm suspicion.

Though this begs the question, "What changed from time it was normal @ a 'healthy' 0.2 ips"

Jim P

I hadn't thought about a resonance. Here's the same spectrum in log format. Is this the raised noise floor you were asking about?

As far as what's changed...everybody I talk to tells me the same thing...."Nothing"...

Mr Newbie,

Sure looks like a possible resonance near 2xSS. You could do two tests: a coastdown measuring speed, 2xSS amplitude and phase; impact tes with machine off. If you dare, you might check governor base bolt tightness while running.

Walt

I will do a bump test on the unit while it's running. Don't know if Operations will shut it down so I could do a Coastdown.

The governor is mounted horizontally on the turbine. I've checked all the bolts on it and they all appear to be tight.

Thanks for the advice.

Appearance of tightness is not a good criteria. If the governor housing is resonant, then bolt torque may have enough of a stiffness effect to change the natural frequency and vibration level. This won't be a cure, but it may help indicate what the problem is.


Walt

After completing the bump test, I did find a resonance at exactly 2 x Turning Speed of the governor. I've communicated to Maintenance what the problem is and offered solutions. Now the ball is in their court.

Thanks for the help!

Mr Newbie,

Telling the Maintenance Dept. that they have a resonance is a waste of time unless someone understands what it is and what to do about it. All maintenance folks that I deal with would not have a clue. If that's the case with your company, then the ball is really in your court to either accept the problem or to fix it.

Walt

When looking at a normal spectrum hi-res, does the unit seek? (hunting or seeking is speed changes). A coast down in peak-hold and storing data to present a cascade may shed additional light.

What is the full source of the 2X? All factors that can affect 2X - what are they - alignment OK? Good enough to have no 2X. Check all sources and eliminate them.