DD158581A1 - METHOD AND CIRCUIT ARRANGEMENT FOR VIBRATION MONITORING OF ROTATING MACHINES - Google Patents

Abstract

The invention relates to broadband and selective vibration monitoring for diagnosing the mechanical condition and performance of, in particular, thermal turbomachinery. The aim of damage early detection is to use the complex character of the harmonic vibration components for the diagnosis in addition to the consideration of sum level values and harmonic vibration components. In terms of process technology, the invention substantially compares and evaluates the changes of the level sum values and the vector changes of the complex harmonic oscillations in the time interval compared to reference level values and complex harmonic reference portions. The circuit arrangement of the invention essentially comprises electronic means for conditioning and processing of vibration signals with a computer system and means for the metrological representation of procedurally interesting changes in the vibration pattern (vibration diagnostics).

Description

-ι- 229824 2

Title of the invention

Method and circuit arrangement for vibration monitoring of rotating machines

Field of application of the invention

The present invention relates to a method and a circuit arrangement for broadband and selective vibration monitoring for the diagnosis of the mechanical condition and the operating behavior of rotating machinery (machine vibration diagnostics), in particular thermal turbomachinery, with the aim of avoiding damage, early damage detection and prevention of consequential damage.

Characteristic of the known technical solutions

To determine the characteristic quantities for the assessment of the mechanical condition and the operating behavior of rotating machinery, methods have been developed which incorporate the measurement of the vibrations of the machine to be monitored and the comparison with vibrations of the same or similar kind or with vibrations of a model or knowledge from previous machine investigations and, where appropriate, international standards and guidelines. In general, four basic procedures are used for monitoring and diagnosis, and indeed the wide-volume measurement and ¹ observation dea Schwingung3-3um ~ menpegels (normal procedure), the measurement and monitoring of the vibrational total level of several interssierender narrow frequency ranges, the measurement and monitoring the

229824 2

Single level of several narrow frequency ranges and the selective measurement and observation of the levels of individual frequency components in a frequency range using a Spektralanalysiereinrichtung. The three last-mentioned procedures are hitherto scarcely widespread, since the expenditure on conventional electronics is relatively large. Experience has shown or it can be determined through a series of special investigations that certain defects or defects of a particular machinery leave "traces" (changes) in the spectral image which can be found by means of selective measuring instruments (eg narrowband electronic filters) without the sum level often changing noticeably. For this reason are the. Procedures that identify and account for the amounts of individual vibration components for assessing the mechanical condition and performance of rotating machinery, clearly outperforming the procedures that monitor the level values of frequency ranges. In the prior art diagnostic methods, vibration components of interest are detected by means of special arrangements (filters), their amounts are determined and compared with reference values (new or normal values) and limit values, whereby the presence of various deficiencies and errors can be determined. In the most modern arrangements it is realized that the filters are automatically adjusted exactly with their center frequency to the rotational frequency of the machine or its higher harmonics (tracking filter). From the frequency mixture thus dependent on the speed of the machine dependent vibration components are screened and their amounts displayed. Such an arrangement is known from DEVOS 2315 806 in IPK G 01 N, 7/00 *

In this approximate solution, which corresponds to the state of the art, it is a prerequisite that the amounts of normal and new vibration components (reference values) that are typical for errors and defects must be negligibly small compared with those due to defects and defects. Because of the harmonic vibration components

229824 2

are complex sizes, resulting in failure to meet the above requirement in the hitherto usual pure quantitative observation of the vibration components only inaccurate

Diagnoses * -: ...--.

Neglecting the phase information, the variations of harmonic vibration components are associated with an unknown error between 0 and 200 <%> of the values of the reference values. Consequently, these statements are not sufficient for comprehensive machine diagnosis, especially in thermal door machinery.

In the prior art methods and devices, depending on the magnitude of the amounts of the reference values, it is left to chance (type of vectorial change) whether minor damage and defects as well as early damage can be detected.

Object of the invention.

With the solution according to the invention, a more meaningful assessment of the mechanical condition and the operating behavior of rotating machines, in particular of thermal turbomachines, should generally be achieved, as was possible with previous methods and devices for continuous monitoring of the vibration of the vibrations and machine diagnosis. Specifically, the solution according to the invention should be suitable on the one hand to give the operating personnel more precise information about the operating behavior and developing faults and damage, in order to avoid damage, to reduce consequential damage as far as possible and, on the other hand, to offer the possibility of directly inserting into the existing automatic protective device. and monitoring procedures.

Explanation of the essence of the invention

In order to achieve the objective, the task is to take account of the complex character of the harmonic vibration components and the resulting increased information gain from vibration measurement signals in addition to the diagnosis based on the sum of the sum values and amounts of "harmonic vibration components".

229824 2

In realization of the procedural side of the task, while acknowledging the prior art that certain filtered-out vibration components of the vibration a spectrum are electronically processed and compared to a reference signal, the invention features that the broad banded sum levels of the frequency ranges filtered out, the amounts of the Rotational frequency harmonic vibration components and the phase positions of distinctive points of the time waveforms of the harmonic components to a reference signal corresponding to a certain radial rotor position, the changes in the cumulative values and the vector iellen changes of the complex harmonic components, both in the time interval (transients) and reference level values and complex harmonic reference parts of the same order, which correspond to the hay or normal state at certain operating parameters, determined, brought to display, with limits compared and warning signals are derived when exceeding limits. To carry out the method, the schaltsteohnische solution of the problem consists essentially in that one or usually several vibration sensor for generating electrical signals in accordance with the machine vibrations during their rotation are present, the electrical signals either directly to a controllable Meßstell enumsoha It er or via measuring signal processing modules of a known broadband vibration monitoring system, two controllable Meßstellenumschaltern be forwarded, with the through rectified sum level signals directly and the AC signals via a low pass filter with controllable cutoff frequency to a switch and from there via a controllable normalization amplifier to the input of an analog-to-digital converter reach. It is also the analog-to-digital converter via a switch either by a derived from a Drehfrequenzaufnehmer, normalized in a pulse shaper as and multiplied by a frequency converter and a bistable memory stocky, speed-dependent and phase locked coupled to the rotor rotation Ecequence signal or by one of a

229824 2

In addition, "special" control circuits are provided, which are used for switching the Meßstbllen- and other switches and for controlling the influence of the low-pass filter and the Serve normalizing amplifier. The control modules are the input side, the analog-to-digital converter and the frequency converter output coupled via an interface to the bus system of a computer. The bus system is connected to memories for recording the control and processing programs of the constant and variable parameters of the measured and diagnosed values as well as devices for outputting the measurement and diagnostic results in analog and digital form and a keyboard for communication with the system.

Further features relating to the configuration of the circuit arrangement are mentioned in the corresponding part of the invention claim and explained in the following embodiment.

With the fulfillment of this objective, it is now possible that

an exact determination of the mast rotation frequency,

a determination of the complex harmonic components of vibration (amounts and relative phase angles) with rotational frequency and their multiples at any rotational speed of the machine,

a determination of the vectorial changes of the individual complex harmonic components, both in the time interval (transients) and in relation to complex harmonic reference components of the same frequency, which correspond to the new or normal state under certain operating parameters,

- a conversion of the amounts of the complex harmonic wave and bearing vibration components by numerical integration or differentiation into any same measured variable and the formation of the ratios shaft to bearing vibrations and

229824 2

- a "comparison of the current values with limits and a signalization of excesses

can be carried out.

embodiment

With reference to the drawings, a preferred embodiment for the solution according to the invention is shown below.

The drawings show:

1 shows the perspective measuring point arrangement on a turbine set (upper part) in connection with a block diagram of a broadband vibration monitoring system (middle part) and a simplified block diagram of the vibration monitoring system according to the invention (lower part);

2 shows a detailed block diagram of the vibration monitoring system according to the invention;

3 is a graph showing the complex vibration components to be monitored according to the invention.

The vibrations of a rotating machine to be monitored and diagnosed are detected by a plurality of vibration sensors 1a. The vibration sensor 1a can be mounted on the bearing housings piezoelectric accelerometer or electrodynamic speed sauf participants and / or non-contact Wellensohwingungsaufnehraer working on capacitive, inductive or based on eddy current loss en measuring method. The electrical output signals of the vibration sensors 1a or of the vibration sensor 1a associated with the matching components 1b reach the amplifier 2 of each vibration sensor 1a assigned and completely independent broadband vibration monitoring device. In FIG. 1, only one measuring channel is shown for the sake of simplicity. The monitoring devices realize in analogue measured value processing the international standards corresponding broadband real-time monitoring of a specific measurand to limit value overflow,

229824 2

The monitoring devices have an almost independent of the transducer type basic structure. Slight differences are possible due to possible electrical signal integration in bearing vibration transducers and band-pass filtering of the measuring signal.

Specifically, for a monitoring device other than the vibration sensor 1a, the following elements are typical:

- Amplifier 2

- Integrator 3, if necessary, to convert the measured signal into the monitored

one or more bandpass filters 4 to suppress unimportant parts of the spectrum

Rectifier 5 for the quantification of the AC signal (a DC signal proportional to the peak, peak or rms value is formed)

- Pointer instrument 6 or numeric display for displaying the parameter to be monitored \

- Signal evaluation modules 7 (threshold value switch) for the classification of the operating state and for the derivation τοη control and warning signals

- Blocks 8 for the realization τοη warning signals and protective measures

- Test oscillator 9 for calibration of the entire Messeinriohtung. , '

According to the system according to the invention for diagnosis-appropriate further processing, the measuring signals supplied by the Sohuvungsaufnehmer 1a are fed to the rectifier 5 a Meßstellenumschalter 10. The alternating voltage signals to the amplifier 2 or to the integrator 3 or after the bandpass filter 5 reach a Meßstellenumschalter At the same time analog signals for measured variables of various technological parameters (eg., Active power and excitation current generator, storage temperatures, absolute and relative strains of turbines) that are relevant for the interpretation of diagnostic parameters.

229824 2

Depending on the position of a changeover switch 13, either the switched from Meßstellenumschalter 10 signal passes directly or durohgeschalteten from Meßstellenumschalter 11 signal via a controllable (preferably digital) low-pass filter 12 to a switch 13 and from there via a normalization amplifier 14 with controllable gain for Meßsignalnormierung the different Signal level to the analog-to-digital converter 15, where there is a controlled digitization of the analog signal. By means of known control circuits-16; 17; 18, which are connected via an interface 19 (ijusanpassung) to the bus system 50 of a computer 51, preferably Mirkrorechner, are switching the Meßstellenumschalter 10; 11 to certain analog Singangskanäle, the switching of the switch 13; 34, the switching of the gain of the Wormierverstärkers 14 and the control of the low-pass filter 12 realized. In cooperation with the "computer 51, bus system 50 and interface 19 takes over the acquisition of the digitized measured values from the analog-to-digital converter 15 via the computer 51 in a memory 52. In addition, the acquisition of the set to a frequency converter 32 MuIt iplikationungsfakt. ors by the computer 51 »For the determination of the exact machine speed for controlling the low-pass filter 12 and the Meßgrößenumrechnung and as a rotor-fixed phase reference for the control of the analog-to-digital converter 15 for phase-locked sampling of the vibration signals are from the machine rotor rotational frequency signals (1 pulse per rotor revolution) derived by means of a photoelectric reference sensor 30 (scanning a light or dark mark), eddy current or Induktivaufnehmers normalized in the pulse shaper 31 and multiplied in the frequency converter 32 · These Inipulssignale be reduced in a bistable memory 33 and depending on the position of the switch 34 used for phase-locked with the rotor rotational movement scanning the voltage applied to the analog-to-digital converter 15 analog AC voltage signals.

The switch 34 also allows a conversion of all applied to the analog-to-digital converter 15 Gleioh- and? / Echselspannungssignale with a computer side programmable

22 9824 2

constant timing. For their generation, the computer clock frequency § in the frequency converter 35 is reduced in the ratio 1: i and counted into the counter 36. The counters 36; .38 can be designed as a gate or backward counter, which is always assumed to be the same in the further explanation. In counter 36, a count Z is written, the desired cycle time

T = Z · I ^l

for the signal conversion in the analog-to-digital converter 15 corresponds. When STulldurchgang of the counter 36, a pulse is derived, which controls the analog-to-digital converter 15. This process is repeated continuously.

The speed of the machine is determined by means of the frequency converter 35, the counter 36, an electronic gate 37 and the counter 38 in connection with the computer 51, the bus sy st em 50 and an interface 39 in the following manner: The frequency converter 35 and the As previously explained, counters 36 generate a desired cycle time which is used to control the gate 37. At the zero crossing of the counter 36, the electronic gate 37 is opened or closed.When the electronic gate 37 closes, the pulses multiplied in the frequency converter 32 decrease the counting value set in the counter 38 until the electronic gate 37 is opened again.The difference of the counter readings A Z is obtained by calculation with the computer 51 according to FIG

^{f =} Λ Z or η = Λ Ζ , 60 T '± _Ζ / ± _Λ T.

the rotational frequency f or rotational speed n to be determined. In the practical embodiment, frequency converters 35, counters 36; 38 and interface 39 expediently realized by a highly intergrated timer counter circuit 41 * For phase-locked with the rotational movement of the machine coupled query the analog-to-digital converter 15 is connected to the bus system 50 bus-matched interrupt logic 40 in

229824 2

used such a link that at the beginning of each selective signal processing triggered by the 31 Pulse generator interrupt signal INT 1, the program start for the first (definition of rotorfesten phase reference) and a bistable memory 33 triggered interrupt signal ICT 2 the current query, acquisition and storage of the applied to the analog-to-digital converter 15 digitized analog values implemented.

The computer system includes memories 52 for programs, parameters, measured values, reference values and limit values, as well as matching circuits 53; 54; 55; 56; 57 for output devices and these themselves as writing recorders 62, printer 58, display 59 and digital or alphanumeric displays 60 as well as for an operator keypad 61. All these system components are connected to the bus system 50.

The operation of the vibration monitoring system according to the invention can be summarized as follows: A pulse signal is generated with the frequency f which coincides exactly with the rotational frequency of a machine to be monitored. This pulse signal is multiplied in phase in the frequency converter 32 to the frequency N · f _n . The bearing and / or vibration transducers 1a provided at various points of the machine generate electrical signals in accordance with the vibrations generated in the machine due to their rotation. Low-frequency components of these signals are filtered out and sent for further processing.

The supplied in accordance with the rotation in the machine pulse signals with the frequencies f and N · .f are used as interrupt signals to control the analog-to-digital converter 15 in cooperation with the computer 51 so that the Schwingungssignäl phase-locked with coupled to the rotor rotational movement, scanned with the frequency Ii · f _n and at the same time a rotor-fixed reference point (zero point) is defined.

229824 2

Triggered by the interrupt signals and controlled by the programs of the computer 51, the digitized analog values are queried and averaged over each measuring cycle over a selected number of rotor revolutions, so that the averaged time course of the vibration signal in the memory 52 in discrete form with the supporting points £ \ «Is present. Since the edge of the pulse having the frequency f _n as the interrupt signal realizes the program start for the first interrogation of the analog-to-digital converter 15 at the beginning of each measurement cycle, the phase angle zero-degree is automatically assigned to the first averaged discrete sample. The averaged discrete samples are multiplied by discrete sine and cosine function values. One period of the angular functions corresponds exactly to one rotor revolution or one ga _; Number of times a rotor revolution. The subsequent summation of the products and division by half the number of samples yields the components % i and y ^ of the complex oscillation component A * (see Fig. 3) with rotational frequency or its harmonics

- N

vs ~ " ) * g _φ GOS C f ·" f * 3.}

i -.-- TT .JT ₁ j T ^

TJ -.

y. -I- y I. sin (£ JL j)

j = 1

The index i corresponds to the order of the harmonics, ie i = 1 means rotational frequency component; Έ means frequency multiplier factor . The conversion of the components χ ^ and y ^ into complex vibration vectors A ^ (polar coordinates) takes place according to the relation

and the conversion to the direction angle Cf £ of the vibration indicator Aj ₁ according to the relationship

a = arctane

The corresponding magnitudes for the vectorial change of the complex vibration component compared to a complex reference component of the same order (in FIG. 3 by the index sequence).

229824 2

draws) one gets out

or in meaningful representation

_{m arctan} f ^ 4

^ i ^x io)

The exact speed determination is carried out by means of timer and Zählerbaust a in cooperation with a microcomputer by counting the pulses with the frequency N · f during a certain period of time "from the difference of the counter counter" the speed is calculated.

By knowing the speed of the harmonic vibration components can be converted into any measured variable (error-free integration and differentiation), so that shaft and bearing vibrations and their changes can be compared in any selected measure.

Claims (13)

229824 2 Invention claim 1. A method for broadband and selective vibration monitoring for the diagnosis of the mechanical condition and performance of rotating machinery, in particular thermal turbomachinery, wherein certain filtered out portions of the vibration spectrum are processed electronically and compared with reference variables, characterized in that the broadband sum level values of the filtered Frequency ranges, the magnitudes of the harmonic components which are harmonic to the rotational frequency, and the phase angles of salient points in the time lapses of the harmonic components to a reference signal corresponding to a given radial hotor position, the changes in the sum level values and the vectorial values   Changes in the complex harmonic vibration components, both in the time interval (Translenten) as well as against 3eVegelerten and complex harmonic reference components of the same order, which correspond to the new or normal state at certain operating parameters determined, * displayed, compared with limits and warning signals when exceeded derived from limits. 2. The method according to item 1, characterized in that the vectorial changes of the complex hormonal vibration components with rotational frequency, double rotational frequency and coupled network frequency are determined and observed. 3. The method according to item 1, characterized in that the simultaneous monitoring of bearing and wave oscillations, the time courses of the measured signals in the typical Aufnshmer-transducer combination typical measured variables discretely detected, the complex harmonic Signalantaile and their vectorial changes to complex harmonic reference signals the same frequency by numerical selective processing, the amounts   - these shares and their changes through integration 229824 2 or differentiation converted into any same measured variable and the ratios of shaft vibration components to bearing vibration components are formed and displayed. 4 · A circuit arrangement for broadband and Selective Sohvfingungsüberwachung for the diagnosis ^ ^it mechanical condition and the operational performance of rotating machines, in particular thermal turbomachines, for performing the method, wherein one or more devices for generating electrical signals in accordance with the vibrations of the engine during rotation thereof are provided ^ after point 1, characterized-characterized in that electrical signals either directly to a controllable Meßstellenumschalter (11) or via measuring signal processing modules of a known broadband vibration monitoring system two controllable Meßstellenumschaltern (10; 11) are zuleitbar that the carried-through rectified sum level signals directly and the AC signals via a low-pass filter (12) with controllable cut-off frequency to a switch (13) and from there via a controllable normalizing amplifier (14) to the input of an analogue Di. gital converter (15) are bar that the analog-to-digital converter (15) via a switch (34) either by a Referenzaufnehmer '(30) derived in a pulse shaper (31) normalized and by a frequency converter ( 32) multiplied and (33) stocky, speed-dependent and phase-rigidly coupled to the rotor rotation control signal or by a computer (51) derived by a ^ from a time- ber-counter assembly (via interface 39) emanating from a bistable memory controllable temporally constant clock frequency is controlled that special control circuits (16; 17; 18) are provided, which serve for switching over the changeover switches (13; 34) and the measuring point changeover switches (10; 11) as well as for controlling the low-pass filter (12) and the normalizing amplifier (14) and in that the control circuits (16; 17; 18) input- 229824 2 - Side, the analog-to-digital converter (15) and the frequency converter (32) on the output side via an interface (19) to the bus system (50) of the computer (51) are coupled to a memory (52) for receiving control and processing programs, of limit values, of constant and variable parameters as well as of measurement and diagnostic values, that means for outputting the measured and diagnosed values in analog digital form and that a keyboard (61) for communication with the system, are present over Matching circuits (53; 54; 55; 56; 57) are connected to the bus system (50). 5. The circuit arrangement according to item 4, characterized in that a generally known single or multi-channel vibration monitoring system is assigned and the signals for the selective Weit erverarbeitung after the amplifier (2) or after the integrator (3) or after the bandpass filter (4 ), and the signals for the ^s ummenpegelwerte after the rectifier (5) Meßstellenumschaltern (10; 11) are fed. 6 · Circuit arrangement according to item 4, characterized in that the phase-locked with the rotational movement of the machine coupled query the analog-to-digital converter (15) to the bus system (50) connected bus-matched interrupt logic (40) is provided in such a link that at the beginning of each selective measurement, an interrupt "* signal (INT 1) triggered by the pulse shaper (31) initiates the program start for the first and an interrupt signal (INT 2) triggered by the bistable memory (33), the current query, acquisition and storage the digitized analog values applied to the digital-to-analog converter (15) can be realized via the interface (19) in cooperation with the computer system. 7. Circuit arrangement according to item 4, characterized by that the low-pass filter (12) is a digital » 8. Circuit arrangement according to item 6, characterized in that the computer system is a microcomputer system. 229824 2 9. Circuit arrangement according to item 4, characterized in that for the generation of time-constant, quartz-stabilized clock frequencies for controlling the analog-to-digital converter (15) and for determining the engine speed as a timer counter modules a highly integrated timer counter circuit (41 ), which is connected via its ₍ internal interface (39) to the bus system (50) is arranged such that the pulses in the frequency converter (35) subscribed clock frequency (0) of the computer (51) are paid from a written into the counter (36) count backwards and at the zero crossing of the counter (36) each having a pulse derived that the output of the counter (36) is connected to the switch (34) and to the electronic gate (37), the electronic door (37) being opened or closed by the derived pulse, in that further counters (38) are coupled to the frequency converter (32) via the electronic gate (37) in such a way that, when the electronic gate (37) is closed, the counters are counted upwards in accordance with speed-proportional pulses. 10. Circuit arrangement according to item 4, characterized in that the timer counter assembly of a frequency converter (35) and two countdown counters 36; 38 exists. Circuit arrangement according to item 4, characterized in that the means for outputting the measured and diagnosed values consists of a printer (58), a display (59), a display (60) and a recorder (62). 12. The circuit arrangement according to item 4, characterized in that the matching circuits in particular those for a keyboard (53), for an analog output (54), for a printer (55), · for a display (56) and for an alphanumeric display ( 57). 229824 2 13. Circuit arrangement according to item 6, characterized in that the Hechner system consists of a bus system (50), the computer (51) and a memory (52). For this. JL side peats