Vibration Problems And Treatment Methods Of Turbine Generator Bearings

In general, there are three reasons for the large vibration of the turbine engine bearing:

1. Friction and vibration of moving and static parts;
2. The oil film is unstable or damaged, and the oil film vibrates;
3. The center of the shafting system is not at the same position, the quality of the shafting system is unbalanced, and the dynamic balance vibrates.

The main factors that cause the vibration of the first engine bearing are as follows:

(1) During installation, the gap between the dynamic and static parts is too small, mainly including the gap between the bearing bush and the bearing, the gap between the oil shield, the gap between the windshield of the generator, the gap between the blades of the steam turbine and the cylinder, the gap between the impeller and the stator of the generator, and the cavity of the steam seal gap;

(2) The cylinder is hindered by thermal expansion and tilted relative to the rotor.

The main factors that cause the vibration of the second engine bearing are generally as follows:

(1) The amount of lubricating oil supplied is too small;

(2) Unload oil from the oil hole of the oil pocket at the bottom of the bearing bush;

(3) The lubricating oil temperature is too high or too low;

(4) The oil quality of the lubricating oil is unqualified.

The main factors that cause the third vibration generally include the following:

(1) The alignment of the coupling is unqualified, and the center of the shaft system is inconsistent;

(2) The superheat of the inlet steam parameter is too low or changes frequently, and the center of the steam turbine rotor changes;

(3) Insufficient water drainage or insufficient warm-up time, and the expansion of the rotor and cylinder is not synchronized;

(4) The temperature of the steam seal is too high, the center of the dimple moves up, and the center of the shafting is destroyed;

(5) The vacuum and exhaust temperature are too high or too low;

(6) The bearing seat is loose;

(7) Bearing wear;

(8) The large shaft of the steam turbine generator set is bent;

(9) The counterweight of the coupling bolts is unqualified, and the mass of the rotor is unbalanced;

(10) Turbine loses blades;

(11) Generator rotor counterweight is loose or dropped;

(12) The mass of the steam turbine rotor is unbalanced;

(13) The mass of the generator rotor is unbalanced.

After testing, it is concluded that: the problem of large vibration of turbogenerator bearings is dealt with:

(1) When installing, the gap between the moving and static parts is too small

After shutting down, check and deal with all the gaps between the joints, bearing bushes and bearings, oil shield, generator windshield, steam seal and other dynamic and static parts. The size is within the range required by the manufacturer and there is no trace of rubbing.

(2) The cylinder is hindered by thermal expansion and tilted relative to the rotor.

During the flushing process, check that the axial and radial expansion of the cylinder is not hindered, and that the opposite side expands synchronously.

(3) Lubricating oil supply is too small

During the flushing process, the oil return temperature of each bearing pad meets the requirements. The highest temperature of the bearing pad is 61.06°C for the support bearing pad of #4 tile, and the highest oil return temperature is 57.44°C for #4 tile. Under the guidance of the manufacturer, the #4 The oil inlet orifice of the tile is enlarged from the original design value of 8mm to 10mm. The second start-up inspection: #4 tile bearing maximum temperature is 56.33°C, oil return maximum temperature is 52.65°C, no impact on vibration.

(4) Unload the oil from the oil pocket oil hole at the bottom of the bearing bush

During installation, all the oil holes of the oil pockets at the bottom of each tile have been welded dead, and the oil will not be unloaded.

(5) The lubricating oil temperature is too high or too low.

During the first flushing process, the oil temperature of the lubricating oil was adjusted several times between 32C~47°C. When the oil temperature of the main pipe was <43°C, the vibration of #4 dropped slightly by 8μm. After the subsequent flushing, the oil temperature of the main pipe was controlled Between 37°C and 41°C.

(6) Lubricating oil quality is unqualified

After shutting down, the lubricating oil tank was cleaned, and the tiles were turned over. Only slight wear marks were found on the #1 bearing, and the oil quality was checked by the production unit, which met the requirements.

(7) The alignment of the coupling is unqualified, and the center of the shaft system is inconsistent

Check the original construction record of the installation unit, which meets the requirements of the manufacturer. And check the tightness of the coupling bolts, no looseness.

(8) The superheat degree of the inlet steam parameter is too low or changes frequently, and the center of the steam turbine rotor changes

During the entire flushing process, the parameters of the incoming steam remain unchanged.

(9) Insufficient water drainage or insufficient warm-up time, and the expansion of the rotor and cylinder is not synchronized

The wall temperature of the drain pipe was measured on site, all > 110°C.

(10) The temperature of the steam seal is too high, the center of the dimple moves up, and the center of the shafting system is destroyed

The steam delivery temperature of the shaft seal is adjusted within the design value of 126°C~190°C, and the vibration of each tile remains unchanged.

(11) Vacuum, exhaust temperature is too high or too low

The vacuum is adjusted between the design value -60~-89kPa and the exhaust temperature is adjusted between the design value 56°C~78°C, and the vibration of each tile does not change.

(12) The bearing seat is loose

The tiles in the distance do not vibrate much, and there is no obvious vibration when measured and felt on the spot.

(13) Bearing wear

Inspection of tile turning, except for slight wear marks on #1 tile, other bearings have no wear, and after treatment after tile turning, the vibration of the second start-up has no obvious improvement.

(14) Coupling bolt counterweight unqualified, rotor mass unbalanced

Check the bolt counterweight record of the installation unit, which meets the requirements of the manufacturer.

(15) Turbine blades falling off

The steam turbine did not vibrate much, and no abnormal sound was heard on the spot.

(16) Generator rotor counterweight is loose or dropped

After running and stopping, open the end covers at both ends of the generator to check that the counterweight is not loose or falling off.

(17) Bending of steam turbine or generator shaft

The characteristics of vibration caused by thermal deformation of the rotor are closely related to the temperature of the rotor and steam parameters, and most of them occur in the load stage after the unit is started in a cold state at a constant speed. The vibration increases. However, the large vibration occurred in the running stage of the unit, so it can be ruled out.

(18) Mass imbalance of steam turbine and generator rotor

Set up a vibration analyzer to confirm that the vibrations of #3 and #4 bearings are all concentrated in 1 times frequency, that is, the bearing vibration caused by mass imbalance, re-balance the balance weight of the generator, and restart the machine. The maximum vibration value of each bearing does not exceed 70μm. It fully meets the requirements of the manufacturer and specifications, and can meet the needs of safe and stable operation of the unit.