Units not in the rotor fault diagnosis
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Abstract: QNFS-generating units have a 50-2 type of abnormal vibration, the use of Henan lion-ting of Limited DCPS08A data collection and analysis system to detect, from the time domain and frequency domain wave spectrum features on the map , Diagnosed in the wrong unit of the rotor failure and a brief analysis of where the local oscillator.
Key words: generating units; abnormal vibration; DCPS08A; time-domain graph; frequency map; rotor misalignment
Key words: 0347.6 Document code: B
 
     QNFS-50-2-2 # generating unit is a limited liability company Lvdian Shenhuo major power plant equipment, early in March 2004 after the overhaul line put into operation, all of a sudden had a more unusual vibration. To find out quickly that the failure of generating units and local oscillator, to determine the severity of the need for an immediate shutdown and repair, we use the Henan Company Limited production of the lion-ting DCPS08A Data Acquisition and Analysis System was tested, and its generating set points Diagram in Figure 1. Turbine model for the N50-8.83-2, through the rigid coupling with the generator connected, the speed for 3 000r/min.
     First, comparative analysis of detection
     March 4, 2004, as shown in Figure 1 of the measuring point on testing, with units operating normally at the time of February 26, 2004 test results contrast, points 2 and 3 of the significant increase in the value of the vibration, and 3 vibration measuring point increase in value more than 2 points increase in the value of the amount of vibration. As a result, the election of the 3-point test results to be analyzed. In view of the 3 points of RMS velocity in the horizontal, vertical, the three axial direction, there is a V level> V axial> V vertical regularity, this special level of 3 points to the direction of the test results were compared Analysis.

     1. Time-domain analysis
     The normal operation of generating units, measuring 3-point field map shows the largest RMS velocity VRMS = 0.7mm / s, time-domain waveform for a comparison of the rules of sine wave; generating units running at the time of the normal rules of sine wave has been destroyed, its A wave rotor frequency ƒr and 2ƒr the wave superposition, the waveform on the week and a half has shown a clear-M, the largest RMS velocity VRMS = 5.6mm / s, is generating units at the normal vibration value of 8 times.

     According to the information, with the obvious characteristics of the wave can be directly used to determine an initial equipment failure. Analysis of the wave contribute to the failure to distinguish between different. In general, a simple imbalance of vibration is sine wave-like; not alone in the vibration waveforms relatively stable, smooth, repetitive, a "M" type; loose rotor components and dry friction arising from the vibration waveform comparison Mao Cao, imbalance, instability, the emergence of the phenomenon of clipping; and self-excited vibration, such as the oil film whirl, such as oil whip, vibration waveform comparison clutter, poor reproducibility, large fluctuations.
     Figure from Figure 2 and 3 of the time-domain waveform vibration and the speed of the RMS contrast, the combination of waveform analysis of characteristics of the law, the preliminary judge is not generating units in the rotor.
     2. Frequency-domain analysis
     The generator rotor frequency to work for ƒr = 48.8Hz (frequency resolution of 5Hz), the corresponding rate of RMS vibration VRMS = 0.3mm / s; 2 octave 2ƒr = 97.7Hz, its counterpart for the RMS velocity VRMS = 0.1mm / s; 3,4,5 high harmonics corresponding to the RMS velocity is less than 0.1 mm / s. Can be seen in Figure 5, the rotor 2ƒr, 3ƒr frequency, its corresponding RMS Vibration rate of increase for all VRMS = 1.3mm / s; in the frequency and ƒr Department 4ƒr corresponding vibration value of VRMS = 0.9mm / s. Can be seen when the rotor 2 abnormal vibration frequency vibration of the Office of the normal value is 13 times; other Department of vibration frequency value several times higher than normal.


     Not included in the rotor bearings and shaft misalignment wrong in both cases. Bearing in deflection in the journal called the wrong bearings, will not have its own vibration, the main impact on the film's good or bad performance. In the case of rotor imbalance, as no bearing on the uneven reaction to occur frequency radial and axial vibration. Units with the rotor coupling between the connection, if at all along the same line as the shaft misalignment. Generally means more in shafting not in the wrong. Rigid coupling connection with the rotor, not when there are parallel to the axis of displacement, and displacement point of view, the force suffered both radial and axial alternating power alternating power, and they may be radial frequency 2 With axial vibration and vibration frequency.
     Based on Figure 5 and 4 of the results of the comparison, not in light of the rotor failure of the vibration characteristics of the combination of generating units # 2 points 3 of the main characteristics of the spectrum for the performance of the rotor frequency to twice as much, and with a high harmonics Can not judge the generator rotor in the group.
     Second, the conclusions of the fault diagnosis and analysis of the local oscillator
     1. Conclusions Diagnosis
     Based on the above chart time-domain and frequency domain respectively, the comparison chart analysis, I gather that there is not generating units in the rotor fault, that is, the steam turbine generator rotor and the rotor shaft misalignment. In the light of ISO2372-1974 (E) vibration intensity assessment standards, the vibration of people pay attention to the value of inter-district, without an immediate shutdown maintenance, custody should be strengthened.
     2. Source analysis and verification
     Shaft caused by the wrong reasons in addition to the design and installation problems, in the operation of a number of factors will lead to the creation of a new right:
(1) run over by the crew changed the state power and thermal state;
(2) thermal insulation machine so bad on the basis of uneven deformation;
(3) changes in environmental conditions, such as the foundation by the impact of the rainy season and the drastic changes in ambient temperature, and so on;
(4) and soft feet, referring to the foot unit is not the same plane, or a fixed machine in the uneven floor, the bolts will be tightened after the deformation of the machine bearings and misalignment. After analysis, resulting in # 2 generating unit in the main rotor does not heat engine is so bad insulation on the basis deformation caused by uneven. Maintenance plan to use the opportunity of generating units to take the heat engine insulation measures, the elimination of local oscillator, the value of the vibration to significantly reduce the normal value.