Does a sudden increase in the turbine speed have an impact on the bearing shells?
Thread Content
We have a turbine here, and its speed suddenly increased during the warm-up process. Within 3-5 seconds, the RPM increased from 580 to 6240, causing an overload shutdown. In this case, does it affect the front and rear bearing shells as well as the thrust bearings? What other factors are related to such speed violations, in addition to the control system? Urgent!
Check whether the temperature and vibration of the bearing shells are within normal limits; if the lubricating oil pressure is adequate, then there is no problem with the bearing shells. This situation is usually caused by a problem with the control system. Also, check the speed control valve, throttle valve, and hydraulic oil system.
There are no issues with vibration, oil temperature, or oil pressure; the bearing shells should be fine
How is it possible for the rotation speed to increase from 580 to 6240 in just 3 to 5 seconds?
1. First of all, jumping out of the vehicle at high speed is the better of two bad options; if one really drives at high speed without jumping out, the engine is likely to be damaged beyond repair. A chain stop can help reduce the risk of equipment damage. 2. Determine whether the rotational speed is accurate or not by examining the power steam consumption and the opening degree of the GV valve, as well as the bearing temperature, vibration, and displacement. If the rotational speed really increases to such a high level, then there will definitely be significant increases in the amount of power steam required, as well as in the opening degree of the GV valve, bearing temperature, and vibration displacement. Conversely, it can be considered that the rotational speed is false. 3. If the rotational speed is accurate, then such a sudden increase in speed has an impact on both thrust bearings and radial bearings. If the warm-up time is short, it will result in insufficient expansion of the motor’s moving and stationary components, which in turn will affect the clearances between these components. If the steam turbine is suddenly supplied with such a large amount of power steam, it will inevitably lead to an increase in the axial thrust on the turbine; naturally, the axial displacement of the turbine as well as the bearing temperatures will rise significantly. In practice, it is necessary to consider the temperatures of the radial and thrust bearings, as well as the trends in shaft vibration and displacement. If these parameters do not reach the set threshold values, the machine can be restarted once the fault causing overspeed and shutdown has been identified and resolved; the speed can then be increased to the rated level, with continued monitoring of the bearing temperatures and vibration/displacement levels. 4. As for the reasons, it is possible that there is a fault with the speed display; furthermore, it is likely that the turbine throttle valve has failed and is fully open. Considering these factors, the probability of a fault in the control system is quite high.
Checking issues with central control operations and automatic control?
This can be carefully examined and analyzed. If it’s truly possible to achieve instant speed increases, and if this technology can be replicated, it would be a significant advancement. For example, applying it to other engines, etc.
A sudden increase in rotational speed of that magnitude can easily lead to uneven expansion of the clearance between the moving and stationary parts, resulting in contact between them and excessive vibration; check the control system.
The instrument check showed that there was no problem with the center console. The preliminary inspection revealed rust on the top of the throttle knob, as well as rust marks on the valve stem. It is suspected that sticking in the operation of the valve stem caused a sudden rise in the secondary oil pressure. It is the reason for the sudden increase in rotational speed.