With the development of the steam turbine generator set to the direction of high parameters and large capacity, the equipment has no leakage and a first-class work is carried out. The dynamic and static clearance of the high and medium pressure cylinders of the steam turbine is getting smaller and smaller, and the shaft seal, oil block and diaphragm seal are statically and statically touched. There are more and more opportunities for motorcycles. The seals of hydrogen-cooled generators and the shaft seals of steam turbine low-pressure cylinders often have static and dynamic rubbing. At this time, the vibration will change significantly. The speed of the lifting and lowering process is fast and the amplitude fluctuates under the working speed, which affects the safe and stable operation of the unit.
Classification of 1 unit static and dynamic rubbing For turbo generators, the parts that are prone to static and dynamic rubbing are mainly shaft seals, oil blocks, diaphragm seals, bushings and sealing tiles, which are mainly characterized by radial collision and friction. From the static and static rubbing parts and traces, it can be divided into: (1) the rotor part, the static part of the whole week; (2) the stator part, the rotor whole week; (3) the rotor and the stator are all the whole week. From the perspective of the degree of hazard and vibration, it can be divided into: (1) dynamic and static rubbing of the speed-up process, accompanied by elastic thermal bending of the shaft, permanent bending of the shaft occurs when it is severely out of control; (2) work Dynamic and static rubbing at speed is mainly manifested by amplitude fluctuations or slow vibrations.
1.1 The dynamic and static rubbing unit of the lifting and lowering process starts up after large and small repairs. Sometimes it is normally turned on for a period of time. The vibration of the lifting speed is fast and long, especially below the critical speed. The main component is the fundamental frequency vibration synchronized with the rotational speed. Due to the dynamic and static rubbing, the rotor generates elastic thermal bending. The length of the thermal bending is greater than the wear amount, and the rotor becomes more curved and curved, causing the vibration to be fast. Once the vibration is out of control, a large shaft bending accident will occur.
The dynamic and static rubbing of the speed-increasing process is easy to occur in the high and medium pressure cylinders, because the dynamic and static clearance is the smallest, the front and rear shaft seals and the oil block are the main objects of rubbing.
This year is more typical of Hancheng No. 3 and Pucheng No. 2 aircraft.
The early 125MW unit of Hancheng No.3 unit was started after overhaul this year. The medium-pressure cylinder was used to test the impulsive steam turbine. The maximum speed was 1540r/min, and the watts were vibrating. The shaft vibration of No. 2 was faster and the shaft was not stable. live. In addition to the power frequency, the vibration component has 2 times and 4 times frequency components. The vibration waveform has clipping phenomenon, and the 2nd wattage vibration and the shaft vibration speed-up curve are very different. The shaft vibration corresponding to the speed drop speed is much larger than the speed-up condition. This is a typical rotor hot bending fault characteristic, mainly due to The shaft rubs against the oil and shaft seals, causing the rotor to bend. The high-pressure rotor was bent more than 0.2mm in the state of the disc, and the severe partial grinding of the No. 2 tile oil-blocking furnace side verified this. The No. 2 tile has vibration divergence during several speed-ups after overhaul, and the root cause lies in dynamic and static friction. The main reason is that the low speed to constant speed is not fully considered. The 2nd watt shaft neck is offset to the furnace side by 0.12~0.20mm, and the upward floating height is about 0.30mm, so that the dynamic and static gap is too small, and it is difficult to grind it in place as soon as possible. After the electrical test, the vibration is unstable during the speed-up process, whether it is at 1000r/min or at 1400r/min and 30001/min. The vibration starts to be small, and the vibration rises faster with time. The 2nd watt shaft vibration is most sensitive up to 400Mm. The falling shaft seal is spot welded together with the adjacent shaft seal to eliminate the rapid divergence of vibration.
Pucheng No. 2 introduced the Romanian four-cylinder four-disc 330MW steam turbine. Since the use of the adjacent furnace on October 22, it has been in the 800 400~1500r/min and 2500~2700r/min 1st, 2/3 watts. Absolute axis in the vertical direction. Eight northwest power technology 1 vibration is easy to reach 160 m, causing the unit to trip. In addition to the existence of a certain mass imbalance in the shafting system, the adjustment of the dynamic and static clearance at the shaft seal and the oil block is small, while the journal increases with the speed, rising upward by 0.17~0.30mm and offset to the east by 0.08~0.15mm. The static and dynamic friction occurs. Before the critical speed, the high and medium pressure rotors produce elastic thermal bending, causing the vibration to be fast. Thermal bending excites vibrations, which are typically seen twice. When the 1400r/min medium speed warms up, the vibration rises slowly, and finally reaches the jump value, which reflects the lighter static movement. It is the constant speed to do the electrical test. The vibration is fast and long when the speed is increased. The same speed corresponds to three different amplitudes. The later the time, the greater the vibration. The main reaction is in the high pressure cylinder. From the perspective of the long speed of vibration, it occurs. Severe static and static friction. The speed increase process and the center position of the intermediate pressure rotor journal vary with the speed. See details. In summary, the starting process should avoid static and dynamic rubbing below the critical speed to prevent permanent bending of the large shaft.
The position change of the 1-4 watt axis is 1.2 After the fixed speed of the turbine is under the working speed of the turbine, whether it is idling or adding or subtracting the load, the static and dynamic rubbing phenomenon will occur, and the vibration will fluctuate or be slow. Axial rubbing has limited impact on turbine vibration due to limited monitoring means and is not considered here. The blade or the shroud and the baffle seal are rubbed, and the vibration change is not necessarily obvious.
1 The vibration is slowly increasing during the load process. This phenomenon mainly occurs on the bearing bush supporting the medium and low pressure rotor, and the rubbing part is in the bearing bush or the low pressure cylinder. The vibration is slow and long, one is slightly rubbing; the other is that the shaft vibration of the rotor itself is too large, and the thermal bending length of the rubbing part is slightly larger than the wear amount. More typical are Pucheng No. 1 and No. 1 of Baoji.
Pucheng No. 1 and No. 2 are the same type. After starting on March 17 this year, the speed is fixed. With the load on the grid, the 4/5 watt shaft vibration climbs very slowly from 123m at constant speed. The second rise of 1m, and finally reached 173 ~ and there is no downward trend, and the brakes are stopped. The vibration is mainly based on the power frequency, and the speed is reduced to 2 500i/min, and the vibration is obviously reduced.
When the 4/5 wattage shaft is large, there is friction sound near the tile, and the bearing housing shell vibrates 30~39Mm. After checking the 4th watt, it is found that the east side of the upper tile is evenly ground, and the arc length is about 100mm. By repairing the rubbing part, the meter solves the problem by reducing the power frequency vibration with dynamic balance. In this regard, it is considered to be caused by static and light friction. In addition to the 4th tile, there may be some static and static friction in some parts of the low pressure cylinder.
The imported 300MW unit produced by Dongfang Steam Turbine Plant No. 1 of Baoji No. 2 Plant. In October 1999, when the machine was shut down, the 2nd watt of the partial wadding was replaced, the middle and low pressure rotors were turned to the center, and the 0.30mm cushion was added to the lower part of the 3rd watt. The 2nd wattage 3 watt was 0.450.50mm. On November 5th, the test boot was not connected to the grid normally. When it was turned on again on November 10, the 3000W/min idling under the 2nd watt X-axis vibration was large, and it was connected to the grid after the drop. The 2X axis vibration reached 140Mm, and then stabilized. After 90 Mm. from the load of 70 MW, with the load increase, the 2X axis is added, the load is between 220 and 240 MW, and the 2X shaft vibration exceeds 250 Mm to protect the jumper. The 3rd watt and 4th wattage height of the machine is the benchmark of the shafting system, and the 3rd wattage is raised by 0.30, which changes the center of the shafting. It is easy to generate static and dynamic friction and vibration climbing during operation. Then, in the lower part of the 3rd watt, the lower part of the 0.18mm2 watt was pumped out of the 0. 1mm mat, and this phenomenon did not appear again.
1.2.2 Vibration fluctuations under load conditions Vibration fluctuations sometimes occur at the working speed. The probability of the low-pressure rotor is larger and the duration is longer. First, due to the low temperature of the low-pressure rotor shaft seal, the shaft diameter is large, and it is not easy to produce large-axis bending. Second, because the working speed is far from the critical speed, the mechanical lag angle is close to 180*. The unbalanced force automatically straightens the rotor for thermal bending. The essence is a Intermittent movements and rubbing.
Some units are prone to such phenomena due to structural reasons, such as the Luohe No. 5 machine.
The imported 300MW unit produced by Harbin Turbine Works of Luanhe No. 5 was started after minor repairs on November 1 this year. The amplitude of No. 3 and No. 4 watts fluctuated slightly. With the continuation of time, the vibration fluctuation of No. 4 tile became larger and larger. The frequency-frequency vibration varies from 112 to 169 Mm, and the power frequency vibration fluctuates with fluctuations. The fluctuation is related to the load change, and the fluctuation under the stable load is small. See the early introduction of the 300MW unit, which is prone to low-pressure after the cylinder dynamic and static rubbing. The No. 5 machine No. 4 tile is located on the low-pressure rear cylinder. After more than 10 days of rubbing, the machine The vibration tends to be stable.
3 The expansion of the unit is not smooth, causing the collision and friction of the cylinder of the steam turbine to expand and deflect, resulting in the reduction or disappearance of the static and dynamic gaps, resulting in collision and wear of the static and dynamic components. In severe cases, the vibration reaction appears to be instantaneous and fast, so that the tile is partially released; when it is light, the vibration rises faster. More typical are Hancheng No. 3 and Baoji No. 1 No. 1 aircraft.
Since the 1995 Hancheng No. 3 machine, the problem of poor cylinder expansion has been prominent. The front box 1 wattage is often lost, and the upper watts are partially removed from the furnace side. The machine has intermittent contraction during the shutdown process, and the start-up process has a twisting phenomenon, and the sound at the head is unpleasant, accompanied by a "sudden" sound. Normal peaking operation, see the side shaft vibration trend of No. 1 watt furnace. In the overspeed test, both the furnace side and the electric side exceeded 1 mm, and the monitoring found that the No. 1 watt shaft vibration had a good correspondence with the noise at the head. The No. 1 watt shaft vibration is seriously exceeded. In addition to the poor expansion of the unit, it is also related to the poor contact between the front and the sliding surfaces of the platen and the lack of stable support. The side of the platen gap of the machine head is 0, and the electric side is 0.30mm. This year, the sliding pin and the front box were thoroughly treated in the overhaul, and good results were obtained.
No.1 of Baoji No.1 Plant is a 25MW steam turbine produced in Czech Republic. The speed rise process is not strong before 2800r/min. After this speed, the vibration rises faster. After the vertical vibration reaches 50, the vibration continues during the load process. Climb up to 90Mm has tried to deal with the high-speed dynamic balance of the generator rotor and the opposite wheel, the effect is not great. The rear side of the cylinder is blocked by one side expansion. The 2nd tile upper tile is grounded on the steam side and the north side, and the lower tile is grounded on the electric side. After the bearing is moved to the north side by about 0.1 mm, the lower tile is pumped with a 0.05 mm mat, and the tile surface is properly shaved to eliminate the vibration. The reason for the vibration of the machine is mainly due to the unilateral expansion being blocked. The 2nd watt journal can not be in the proper position of the center position of the random group, and the journal and the tile are rubbed to cause the vibration to climb.
4 The high and medium pressure leakage steam blows into the bearing housing, causing the high friction and medium pressure flange leakage to the bearing seat, causing the bearing box of the steel plate to be deformed, and the bearing height rises to cause wear. The wear and tear of Bao 2 No. 1 and Luohe No. 5 machine No. 2 are related to it. Bao 2 No. 1 machine is more serious. The front unit of the steam leakage has a stable load of 300MW and the vibration is small.
After the steam guide tube is sent to the Lancome steam, the vibration rises and the fluctuation becomes more and more serious. The two top shaft oil pockets are invisible after the 2nd watts are opened. Both of these faults occurred on the welded bearing housing. The adjacent low-pressure rotor weighed about 56t, and the No. 2 wattage height rose. A part of the load of the No. 3 watt was transferred to the No. 2 watt, resulting in the No. 2 watt overload grinding.
5When the working speed rotates the blade and the shroud of the moving and static rubbing turbine, after the overhaul of the cylinder, the rubbing marks on the blade top seal, the blade top and the shroud of the partition can be found, and sometimes the tip steam seal is even ground. Light. Due to the elasticity of the blade, the impact of the rubbing on the shafting vibration generally has little effect, and the typical one is the Luohe No.6 machine.
The condensate hardness is greatly stopped. Into the low-pressure cylinder inspection, it was found that the low-end rotor terminal end blade blade arched belt was almost completely worn away. The blade height of the last stage of the machine is 900mm, the top of the blade is the full circle of the arched shroud, and the radial clearance of the tip and the guide ring of the infrastructure installation is 7.2~7.4mm. Only one piece of the full-stage blade arch type does not fall off, 7 pieces of rivets Still, the rest of the belts are all falling off. The top of the leaf is about 3~4mm, and the guide ring is made up of a row of about 300mm from the center of the A. The guide ring has 6 positioning pins, 3 on the top and bottom, and the 3 positioning pins in the upper half are only intact at the top. From the point of view of static and dynamic rubbing, the fault belongs to the whole circle of the rotor and the local friction of the stator. The characteristics are classified into dynamic and static. There are few reasons for the vibration change: (1) the tip of the blade rubs against the stator and does not cause large axis bending; (2) the tip of the blade is relatively elastic, and some of the impact force and friction generated during friction are converted into elastic deformation force. That is, the part of the large bearing is not very strong; (3) the 3rd watt tile is tiltable tile, the upper tile is elliptical tile, the bearing damping characteristics are good, and this friction has a certain inhibitory effect.
1.3 The dynamic and static rubbing generators under the working speed of the generator have relatively less chance of static and dynamic rubbing. The main reason is that the hydrogen sealing tile is easy to rub, and the rear tile of the generator is easy to wear. The effect of rubbing on vibration at operating speed depends on both the degree of rubbing and the dynamic characteristics of the generator rotor. More typical are Pucheng No. 1 generator and Bao Er No. 1 generator.
Shortly after the full 300MW, the front axle of the generator was suddenly increased from 40Mm to 107Mm, and then stabilized at around 96,um. There are also some changes in other watts, the adjacent 8th watt shaft vibration rises, and the 10th watt shaft vibration decreases. Mainly due to the change of power frequency component, the unit runs continuously for 63 days, and the 9th watt shaft vibration changes at 90~104Mm, which is relatively stable. On June 28th, the speed drop exceeded the critical value of the No. 9 watt shaft vibration to 190Mm. It was found that the No. 9 tile side seal tile oil retaining edge was curled, the tile surface had a trace of scratches, and the No. 10 tile underwhat tungsten gold had a suede phenomenon. This vibration phenomenon has not appeared since then, and it is believed that it is mainly caused by the abrasion of the 9th tile side sealing tile and the 10th tile lower tile.
Baoji No. 1 Machine In August 1999, the unit's fixed speed was normal, and it was ready to carry out the false synchronous test. At this time, the generator was obviously added whether it was shaft vibration or vibration. 5th watt, 6th wattage shaft plus about 50Mm6 wattage plus 40Mm 5th wattage reduce 10Mm abnormal before 5th, 6th wattage reverse phase 180* anomaly 5th, 6th wattage phase When the difference 220* speed exceeds the critical speed of 1380r/min, the 6th wattage reaches 150, um, but before this vibration phenomenon is less than 30Mm, the hydrogen seal is worn after the inspection.
2 Identification of static and dynamic rubbing and countermeasures Dynamic and static rubbing has many symptoms, and the dynamic response changes are complicated. Turbine generators are prone to static and static friction. The main components are bearing bush, shaft seal, oil block, sealing bush and diaphragm seal. The corresponding rotating parts are journal, shaft and blade. Other mechanical faults cause the static and dynamic gaps to disappear, and static and dynamic rubbing occurs. It is a follow-up fault and usually cannot be spontaneously generated. The main faults causing static and dynamic rubbing are: (1) improper adjustment during maintenance, dissipating motion and static, and the rotating shaft is in an extreme position; (2) the shaft vibration caused by other causes is too large; (3) the dynamic and static gap adjustment is too small; (4) The cylinder deviation and the temperature difference between the upper and lower cylinders are large; (5) the leakage steam blows to the bearing housing, causing the deformation of the welded bearing housing and the elevation of the bearing bush, and overloading the grinding tile. Dynamic and static rubbing involves collision and friction between the rotor and the stationary component, which produces both an impact effect and a frictional effect. The friction effect causes the temperature distribution of the radial section of the rotor to be uneven, causing the rotor to bend thermally. The thermal bending produces a new imbalance force acting on the rotor to cause vibration.
In summary, when identifying the static and dynamic rubbing of a turbo generator, it should first be clear that the rotational speed is before, after or after the critical speed of the corresponding rotor. In the low speed and cranking state, it is possible to judge whether there is friction sound by means of a conventional listening stick, or to use an eddy current sensor with an angle of 90* (X, Y direction) to observe whether the shaft center position is bouncing and whether the journal is raised. Before 600~800r/min, the lubricating oil film is generally not formed completely. When the journal is not jacked up or the top shaft oil pump is stopped at a lower speed, it is easy to grind down the tile, which is in the low pressure rotor and the generator rotor. It often occurs on the bearing pads. The softening point of the bearing tungsten gold is 110 ° Q - the temperature of the tungsten gold rises faster or rises, indicating the bearing wear.
After the unit is speeded up, the vibration information can be used to identify the static and dynamic rubbing.
Through the comprehensive analysis of the vibration spectrum, waveform, Bode diagram of the lifting speed, trend graph and axis trajectory, it can be judged whether the static and dynamic rubbing has occurred, and it is difficult to determine the specific part of the rubbing.
The dynamic and static rubbing occurred before the critical speed is caused by improper or small adjustment of the dynamic and static gaps, and the temperature difference between the upper and lower cylinders is large, mainly in the high and medium pressure cylinders. The vibration spectrum is more single-frequency, the vibration rises faster, and the shaft vibration can react with the vibration of the vibration. The same speed of the Bode diagram is increased more than the speed-up amplitude after the gate is opened. Or curved) indicates excessive.
According to the rotor dynamics theory, the larger the angular acceleration is, the faster the rising speed is, the smaller the resonance peak is; the smaller the damping is, the larger the bearing gap is and the worse, the more obvious the effect of the fast over-critical speed; staying at the critical speed Since the axis is moved outward by the Archimedes spiral with time as the variable, the longer the time, the faster the vibration amplitude and the unstable resonance occurs. However, this is not advisable for the first launch of the unit after trial operation and maintenance. This is because the vibration is very sensitive to the change of the imbalance near the critical speed. Once it is rubbed, it is easy to make the vibration out of control and cause the permanent bending of the large shaft. If the fundamental frequency before the criticality is large, mainly caused by imbalance, the dynamic balance should be considered first. The large imbalance will cause the dynamic and static rubbing to occur in advance, which will aggravate the degree of wear and expand the critical speed region. When the rubbing occurs, the vibration spectrum is dominated by frequency conversion or a wide frequency band occurs due to collision. The wide frequency band includes subsynchronous vibration components, supersynchronous vibration components, side frequencies and harmonic components, and the vibration waveform is distorted and clipped, and the long speed of vibration quickly.
After the unit is fixed at a constant speed, the dynamic and static friction during the grid-connected load-carrying process and normal operation rarely occurs. The general performance is as follows: (1) amplitude fluctuation, the fluctuation period is a few seconds faster, and the slow is 1; 2) The vibration is slow and long. During the expansion process, the high and medium pressure cylinders have a short duration of motion and static friction due to cylinder deviation and slippage of the sliding pin system. The dynamic and static rubbing time of the low pressure cylinder is longer and more stubborn. The wear of the hydrogen sealing tile will increase the vibration by one step, then fluctuate slightly at the new vibration level, and experience a stop opportunity, and the vibration will return to normal again. The vibration spectrum is mainly based on the power frequency, accompanied by a certain harmonic vibration component. When the working speed is much higher than the first-order critical speed, the accurate half-frequency component and the appearance of the half-frequency (25 Hz) 1~7 times component are discriminated. Whether the working speed is an important basis for dynamic and static rubbing.
Measures to prevent large-axis bending and large vibrations of the turbine generator from static and dynamic rubbing: (1) When adjusting the clearance of the moving and static components during maintenance, in addition to considering the upward movement of the journal when raising the speed, the journal should be considered to follow the steering. The resulting offset, except for tilting tiles, can be considered from 0.08 to 0.20 mm. (2) The first time after the overhaul, it is not advisable to quickly rush the critical speed to avoid permanent bending of the large shaft. (3) Below the critical speed, confirm that there is a significant imbalance in the rotor, and dynamic balance should be performed. A large mass imbalance in the rotor will cause the rubbing to occur prematurely and the resonance range to expand. (4) Fully chasing the vehicle to eliminate the hot bending of the rotor and then increase the speed. (5) Eliminate the poor expansion and deviation of the cylinder as soon as possible, and avoid the excessive temperature difference between the upper and lower cylinders. (6) The medium-speed warm-up machine should select the speed-insensitive warm-up machine according to the actual speed-up vibration characteristics of the unit. (7) Monitor the shaft vibration and control the shaft vibration as much as possible to prevent permanent bending of the large shaft.
3 Conclusion The dynamic and static rubbing of steam turbine generator is a complex dynamic process, which includes the collision and impact of static and dynamic components, as well as the friction of static and dynamic components, random group structure, rubbing speed, rubbing position and operating conditions. Different, sometimes there is a big difference in the form of expression. Nevertheless, the most important effect of the shaft and the bearing bush, the shaft seal, the oil block and the sealing tile on the unit is the thermal bending effect, which causes the rotor to generate an additional synchronous vibration component. The hazard to the unit is different at different speeds.
The vibration spectrum, the waveform clipping, the vibration difference of the speed-up and acceleration process, the rapid length of the synchronous vibration component, and the amplitude fluctuation can be used to identify whether the static and dynamic rubbing has occurred. Transient rubbing produces a wide-band spectrum, and the appearance of precise 1/2-frequency octave components is an important basis for judging dynamic and static rubbing.
Dynamic static rubbing is another successor to the mechanical failure that makes the static and dynamic gap disappear. Reasonable and effective dynamic and static clearance and control of the relative vibration of the rotor can not only ensure the economical efficiency of the unit, but also prevent the permanent bending of the large shaft.
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