Turbine Vibrations

Not sure why you are telling us this as you have not asked a question. I would suggest that you stop the machine and check the bearing. Depending on the size of this thing (which you do not mention), the shaft may be moving more than the bearing clearance which is never a good sign. If it is a big machine, start looking at all those pretty pictures that the online monitoring system draws for you.

TGIF

Thank You. The Steam Engine is QJPS from china, It was commissioned at last feb.09. Last five is working good condition load up to 10MW. Turbine rear side vibration is normal 60- 70micron. Trip is 400 micron. Now last week go up to 450micron., Now the main steam line spring supports are

1. Do you have any boroscopes? check up in case any blade started getting dislodged. Just we had a review meeting where it came up. The blades started getting dislodged, not enough to start breakin itself and others, but enough to start the vibration increase.

2. Check the foundation fasteners, have they yielded?

400 Microns against what specified value?

Have you talked to manufacturer? is there any provision of putting counterweight for dynamic balancing?

May be one or more of the blades at the rear side got damaged or lost some weight which is causing this.

Have you had a "bump" in the system? Could a coupling have slipped?

There are many possible causes for increased vibration. One of them is loss of coupling concentricity.

If this is indeed what happened to your unit, be prepared to have to drill-out a coupling bolt or two; they'll most certainly be seized in the bores. If you're lucky, you'll be able to split the coupling wide enough so that a saw blade can be passed through the gap.

To prevent further risks of coupling slip, use specialized bolts for this application. Conventional "fitted" bolts are a misnomer: As soon as they are tightened, they reduce in diameter, thus allowing possible coupling movement.

The suggestions already given should give you a starting point.

I would be interested in a little more data such as are you coming back from an overhaul?, The reason that is significant is; if the vibration doesn't represent a change in the vibration you may be looking at a balance shot.

If this vibration represents a change in vibration from good to bad then you should lean more heavily towards a part coming off. In this situation a step level increase in vibration would be an alert.

When you have gotten past this situation I would caution you that any change in vibration can indicate a problem. If a part comes off in the right place it can appear to make the vibration better.

Depending on the size of your machine turbine and generator temperatures can cause vibration, unbalanced generator cooler temperatures on large machines can cause large changes in vibration characteristics. Some bearings are very sensitive to temperatures.

The quickest way to check on a slipped coupling is to check with the operators and see if the machine has been brought in out of phase (if it was far enough out of phase the operator may remember changing his shorts).

If you don't feel comfortable with anylizing the vibration I would suggest you bring in someone with proper equipment.