Development of RCP Vibration Monitoring System using Power Line Analysis Method 2002. 9. 2 정 재 천

Misalignment and Shaft Crack-Related Phase Relationships for 1X and 2X Vibration Components of Rotor Responses The most significant components of the rotating machine lateral vibration responses The synchronous vibration (1X) Due to rotor unbalance The vibration with twice rotative speed frequency (2X) Nonlinearity of the rotor/bearing stiffness characteristics Become important when the rotor lateral deflections are high. Asymmetry in the rotating system The different rotor stiffnesses in two perpendicular lateral directions “X” direction : nonrotating shaft is weaker, and deflects more under the given radial load force “Y” direction : the shaft is stronger, and defects less under the same n         다섯째 수준

Phase Rule Phase Rule The 1X phase The distance from the keyphasor pulse to the first positive peak of 1X time-base form where, = phase lag The 2X phase The distance from the keyphasor pulse to the first positive peak of 2X time-base form

Orbits Versus Lassajous Figures The Lissajous figure are particular cases of orbits A few examples of pure Lissajous figures The rotor horizontal motion is represented by a 1X component only where, = 0 In the rotor vertical motion, a 2X component is the dominant. where, = 2X component phase The value of the resulting orbits will have different shapes Introducing a 1X component in the “Y” wave with 90 phase different from the “X” wave. -         

Phase Marking of Waveform

The orbit from X-Y wave

Sources of 1X and 2X components The synchronous vibration (1X) Due to rotor unbalance The vibration with twice rotative speed frequency (2X) Shaft misalignment including gear mesh and belt drives and resulting radial preload, or radial preload generated by fluid flow -        

Case study of Shaft Crack Failure Comparison of the “Misalignment” and “Cracked Shaft” Related Orbits Misalignment case x,y responses are not matching Cracked Shaft Circular Orbits For the “Misalignment” case introduce a new variable Phase difference between 2X and 1X for the “Misalignment” case

The behavior of a rotor experiencing a shaft crack A model rotor system was designed which closely duplicates the system geometry of a Reactor Coolant Pump. “v” shaped cut to a penetration depth of 30% of the rotor diameter: 3% reduction in total stiffness of the rotor and bearing system stiffness Resonance : 2525RPM, Normal speed of RCP : 1190RPM

Initial side load (acting vertically downward) Initial side load (acting vertically downward) of 6kg

The side load of 8.3kg The side load of 8.3kg : Figure 3 and 4 The influence of the increased side load introduced a significant 2X vibration component.

4-point FFT flow graph Bit-reversed In-place input order Computations Butterfly -1

Savings due to FFT

Window Function Rectangular Window:

Window Function (cont’d) Hamming Window:

Time History Estimation Technique Figure. Current, Power and Torque Trend Mechanical and Electrical Failure of Machinery  Current, Voltage, Power and Torque Trend Monitoring  Correlation Method  Abnormal State Diagnosis

Frequency Domain Estimation Technique Torque Frequency Monitoring Normal State = Ws - [ Ws(1-S) + SWs] = 0 Single Stator Angular Frequency = -Ws - [ Ws(1-S) + SWs ] = -2Ws Single Rotor Angular Frequency = Ws - [ Ws(1-S)-SWs] = 2SWs Feature Frequency of Individual Abnormal State Rotor Misalignment ,

Feature frequency of MCSA technique Broken Rotor Bar State Bearing Defect State

Feature Extraction Algorithm Consist of; Data reduction block Feature data extraction block Data filtering and reduction block

Feature Data Extraction by Peak -picking Method and Interval Mean Technique Data reduction by interval mean technique Making 10X10 matrix

Abnormality Detection and Diagnosis Algorithm Calculation of sum of each row from reduced matrix Comparison of sum of each row to the normal state data Shaft Crack Detection adjustment of matrix reduction

Conclusion RCP VMS can be improved by adoption of power line signal analysis method The shaft crack detection can be possible by time-frequency analysis Matrix reduction by interval mean technique is proposed As a further study, the following activities will be performed Simulation by test bench Experiments by NPP test data of coast down and startup operation