SK5670Y1 - System for contactless diagnosis turbines, especially the individual blades of steam or gas turbine power plants - Google Patents

Abstract

Operating system for contactless diagnostics of turbines, in particular, individual blades of steam or gas turbine power plants, including one or more paddle wheels, mounted on a common shaft by a technical solution to the static portion of the turbine vane wheel from the outside, after circuit, arranged in the vicinity of the turbine blades at least one sensor (2, 3, 4) position with the shaft rotating blades, which is its output connected to the evaluation unit (5) for processing and storing signals from the sensor (2, 3, 4) the location and time of passage of the rotating blade and its variations and detecting deflection blades, their stress, vibration and vibration in vibration spectrum, and may include additional sensor (1) to identify specific blades and vanes synchronization, situated on the turbine shaft.

Description

The technical solution relates to the arrangement of a system for contactless diagnostics of turbines, in particular individual blades of a steam or gas turbine in power plants.

BACKGROUND OF THE INVENTION

Turbine blades in power plants are currently being checked by non-destructive diagnostic methods during turbine generator shutdown. Their operational diagnostics is not performed, while the inspection of the blades during operation of the turbine is able to detect their displacement or release. By observing the static deviations of the blade position, their possible cracks can be detected, and their vibrations can be controlled by monitoring the vibration frequencies of the blades and their deviations before the turbine crashes. When starting up the turbine, contact methods are used to monitor the turbine. Sensors, e.g. strain gauges. Such an apparatus transmits non-contact signals from the rotor, but uses contact sensors that are placed in demanding physical conditions of temperature, humidity and acceleration. For example, if the vibration of each blade should be monitored, up to 90 sensors would be required. The lifetime of such sensors is in the order of days to months, while their repair is not possible, it would mean shutdown of the turbine. Disadvantageous is the impossibility of measuring the dynamic monitoring of the turbine at an overheating speed, for example 1600 rpm, which is very close to the unfavorable speed in terms of vibration of the turbine blades. From the current turbine generator vibration and displacement measurement system, the vibration of the blades cannot be identified. Therefore, information about the dynamic behavior of the turbine generator is missing for qualified decision making to ensure safe and long-term operation.

The essence of the technical solution

The object of the technical solution is to provide a system for non-contact operational diagnostics of a turbine, in particular individual blades of a steam or gas turbine in power plants, comprising one or more impeller wheels mounted on a common shaft. The principle of the technical solution consists in that in the static part of the turbine, at least one position sensor with a rotating blade shaft is arranged on the periphery of the impeller around its periphery near the turbine blades, which is connected to an evaluation unit for processing and storing signals from it. a sensor indicating the position and time of passage of the respective rotating blade and its deflections and detecting blade deflection, stress, vibration and vibration vibration spectrum. The evaluation unit can be connected to a computer or modem or display.

The precise positions of the blade passages are thus read out by means of sensors. Positions are evaluated by analogue comparator or several comparators, eventually digitally after sampling by analogue-digital converter, when it is possible to distinguish partly shorter and longer blades according to amplitude and to specify their time positions. The information on the position and time of blade passage and monitoring of their deviations is used to determine blade deflection, stress, vibration and vibration spectrum of vibration.

The system may also include an additional sensor for identifying specific blades and blade synchronization located on the turbine shaft. To read the shaft twist, load or instantaneous turbine power, the system is arranged on at least two impellers or blades. turbine sections, where the individual position sensors with the rotating blades of each impeller are connected to the evaluation unit by their outputs.

Sensors are selected from the group consisting of a single or differential coil, a sensing induction coil or coils operating in a static magnetic field or a dynamic field excited by an auxiliary coil or an auxiliary coil assembly, based on a megnetoresist, Hall effect, and laser sensors or optical sensors operating on the principle of reflection of the beam from the blade. The turbine blades are magnetized or the sensors are equipped with an auxiliary magnetic field, a permanent magnet, an electromagnet or a combination thereof.

The system allows dynamic sensing of blade positions on the turbine shaft by evaluating amplitude and time differences, evaluating the trend of blade variations over time and load, evaluating blade vibration on the shaft, bending and torsional oscillations of blades and shaft, oscillations at transient external modes, and the determination of the amplitude and frequency of the individual blades. It allows long-term monitoring of vibration of individual blades as they approach the phasing revolutions. From the measured deflections it is possible to estimate the stress of the blades at selected locations, provided the system is calibrated. It is possible to determine the least favorable regimes from a perspective

SK 5670 Υ1 dynamic strain of the blades, in these modes the limits for the machine operation can be defined.

Long-term acquisition and storage of measured data and the possibility of their evaluation for various modes of turbine operation are advantageous. The measurement extends a lot of knowledge about the tuning of the blades in real operating conditions, based on the evaluation of data from the permanent monitoring system, it is possible to identify problematic areas in operation. From the deviations from the initial state, it is possible to analyze the operating mode with increased strain on the blades as well as possible suspicion of beginning damage to the blade. There is a possibility to draw different warnings for a given phase when starting a turbine generator. Thus, the risk of blade breakage during turbine operation can be expected to be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution will be explained in more detail by means of the attached drawing and will be described in more detail in the following. The drawing shows schematically the basic arrangement of the system for contactless diagnostics of turbines with three transducers of moving turbine blades in their area, which are situated on the casing respectively. in the static part of the turbine and with one sensor located on the turbine shaft for identifying specific blades and synchronizing the blades. Eight sensors are shown schematically in the static part of the turbine.

Examples of technical solution

The system for non-contact turbine diagnostics consists of the measured turbine, sensors 2 to 4, evaluation unit 5, or computer 6, modem 7, display, etc.

To monitor the dynamic parameters of the blades of the steam turbine impellers, diagnostics based on the contactless sensing of transitions with the shaft of the rotating turbine blades is utilized by means of one or more sensors 2, 3, 4, located on the casing respectively. in the static part of the turbine near the blades, that is outside the turbine. The sensors may be formed by a single or differential coil, a sensing induction coil or coils operating in a static magnetic field or a dynamic field driven by an auxiliary coil or an array of auxiliary coils. They can sense differences in the magnetic field when passing turbine blades on the principle of megnetoresistor or Hall effect. The system may be supplemented by at least one additional sensor X located on the turbine shaft to identify particular blades in the blade wheel and to synchronize the blades.

The X-4 sensors for measuring blade positions operate on any of the following principles:

- inductive, in which they consist of a single or differential coil. When passing the blade around the sensor there is induced voltage in the coil;

- inductive, consisting of at least two single or differential coils. As the blade passes the sensor, an induced voltage is generated in each of the coils, which are used independently to increase reliability; for sensitivity autocalibration, a pulse or continuous test signal may be transmitted to at least one coil;

- inductive active when there is at least one coil (single or differential) to which a continuous or pulsed signal is fed and its amplitude or frequency changes are monitored due to the passage of the blade, which affects the dispersion field of the sensor;

a sensing induction coil, wherein the coil assembly is configured to increase the angular sensitivity of the sensor and to suppress the influence of blade variations from the sensor;

a sensing induction coil (s) operating in a static magnetic field or a dynamic field, excited by an auxiliary coil or a set of auxiliary coils to increase sensitivity;

- sensors which detect differences in the magnetic field when passing through the blades on the principle of a magnetoresistor, Hall effect, operating in a static or dynamic magnetic field. The sensors can also work with the residual blades' magnetic field or can be magnetized for this purpose by blades;

- laser sensor respectively. optical sensor, working on the principle of reflection of the beam from the blade.

The individual sensors X to 4 are connected to an evaluation unit 5 comprising an external or internal preamplifier, at least one comparator (multiple comparators serving several different signal amplitude levels), a reader array for measuring turbine blades timing transitions, and an imaging and archiving unit that displays , processes and archives the readings of the individual time intervals and further transfers them according to specific requirements using commercial technologies such as computer 6, modem 7, display and the like. Readers are best implemented using a gate array to minimize the number of parts.

SK 5670 Υ1

In another possible embodiment of the present invention, the comparator is replaced or supplemented by an analog-to-digital converter, the sensor signal being sampled and processed digitally to refine the time readings of blade passages around the respective sensor.

Twisted pair or fiber optic comparators and drivers can be moved to suppress interference to preamplifiers and together as close as possible to sensors J to 4. Analog-to-digital converters can also be moved directly to preamplifiers and the logic circuit can evaluate the blade passage position at either analogue or in the evaluation unit 5.

The system can also be suitably complemented by a synchronization mark on the turbine shaft, or it can be mounted on at least two impeller wheels. This also makes it possible to evaluate the rotation of the turbine shaft when, due to its high rotational speed, the shaft is subjected to a torsional (tensile) stress so that the individual impeller blades move slightly angularly towards each other. In this case, the individual shaft position sensors 2, 3, 4 of the rotating blades of each impeller are connected by their outputs to an evaluation unit 5 which evaluates the angular displacement of the individual impeller and the shaft twist.

The turbine blades are either magnetized or sensors 1 to 4 are equipped with an auxiliary magnetic field formed by a permanent magnet, an electromagnet or a combination thereof. An alternating electric signal can be used for the auxiliary magnetic field.

When the turbine blade passes in the region of the sensors 2 to 4, the sensor carries information about its position and time of transition, which is evaluated either analogously by means of an amplifier and comparator, or by digital sampling and evaluation of the shape of pulses. The information about the position and time of the blade passage and the monitoring of their deviations is used to determine the blade deflection, stress, vibration and vibration spectrum at vibration.

If the system is placed on two or more turbine sections, the rotation of the shaft, its stress and the instantaneous power of the turbine can also be read.

The orientation and determination of a particular blade can be ensured by placing an additional sensor or sensors on the turbine shaft, for example, a bore, a projection, a mark. Refinement can be achieved by applying multiple marks to several sectors along the circumference of the shaft. The system can also send a warning signal when the turbine is in unsafe mode.

The signals generated by the sensors 1 to 4 when the individual turbine blades and reference marks pass on the turbine shaft are amplified, compared analogously and digitized and then processed and stored in binary form in the evaluation units 5 as files carrying both time information with resolution 10 ns, and second, information about the place (origin) of the time event. In the control program, all functions of each channel can be set, such as the active edge of the signal (lead-in, descending or both), edge insensitivity to suppress error events, measurement or test mode, and other functions. The control program of the evaluation unit 5 stores the data in files either continuously or in cycles with a set block length and a recording period. The monitor displays on-line information about the frequency of events at each input, which allows to verify the function of all sensors and individual channels of the evaluation unit 5.

The diagnostic and evaluation program for data transformation and analysis always processes a continuous block of data from a sufficient number of turbine revolutions and performs statistical data processing. The optimum block length for processing appears to be 100 turns. The block contains sufficient data for analysis and the analyzed event can be considered instantaneous and will not be averaged over a long period of time. The time data generated by the blade transitions around the individual sensors 2 to 4 is transformed into standardized vectors describing the sequence of transitions of the given blade around the subsequent sensors. Eight reference marks on the turbine shaft calculate the time differences to the nearest reference mark, which makes it possible to eliminate shaft unevenness. The values are normalized according to the actual speed and circumference of the turbine and correction is made for the time shift caused by the different shape of the blade impulses. The time difference between the blades is converted to instantaneous deviations from the center position in mm. Data can be analyzed from one sensor, using all eight sensors extends the frequency band from 25 to 200 Hz and allows analysis of components induced by turbine rotation. Subsequent frequency analysis leads to better separation of the components of the spectrum. The transformed data can be exported as ASCII vectors, for example, in CSV format.

The transformed data can be analyzed sequentially, and the required calculation (histogram and FFT) is performed for each blade. The blades are searched for blades with the highest statistical displacement. For these blades (or for a blade preset by the operator), a histogram of the blade amplitudes and FFT amplitude frequency in mm are calculated and displayed. Based on the previous calibration, the vibration at the root of the vane can be estimated at the resonant frequency of the vane. The operator does not have to interfere with the program. The data file on the disk will store data that will define the limits of the specified limits. The operator can edit this data. If a limit is exceeded, this information will be shown on the display and stored in a summary table on the disc that can be retrieved by the operator.

The verification of the function of the software is as follows. During the measurement, the frequency of events on individual inputs is displayed on the monitors of the evaluation units 5 and it is possible to check the correctness of the sensor function4

SK 5670 násled and subsequent input circuits. Furthermore, each channel of the evaluation units 5 can be software switched to a test mode, whereby a test signal is generated instead of the measured signal. In this way, the operation of the entire software chain (or hardware, including sensors) can be verified. Data analysis software verification is performed using a special data file (data simulator). In addition, the blade deflection histograms shown provide an immediate overview of not only the deflections but also the correct operation of the system, including the software.

PROTECTION REQUIREMENTS

Claims (6)

A system for the non-contact operational diagnostics of a turbine, in particular individual blades of a steam or gas turbine in power plants, comprising one or more turbine wheels mounted on a common shaft, characterized in that in the static part of the turbine At least one turbine blade position sensor (2, 3, 4) with a rotating blade shaft connected to an evaluation unit (5) for processing and storing signals from the sensor (2, 3, 4) of the position and time of passage of the respective turbine blade. the rotating blade and its deflections, and detecting blade deflection, stress, vibration and vibration vibration spectrum. System according to claim 1, characterized in that it comprises an additional sensor (1) for identifying particular blades and synchronizing the blades situated on the turbine shaft. System according to claim 1 or 2, characterized in that, for subtraction of the shaft spinning, its loading or the instantaneous power output of the turbine, it is arranged on at least two impellers or blades. turbine sections, wherein the individual shaft position sensors (2, 3, 4) of the rotating blades of each impeller are connected to the evaluation unit (5) by their outputs. System according to one of claims 1 to 3, characterized in that the sensors (1, 2, 3, 4) are selected from the group consisting of a single or differential coil, a sensing induction coil or coils operating in a static magnetic field or a dynamic field, excited by an auxiliary coil or an array of auxiliary coils, based on the principle of megnetoresist, Hall effect, and laser sensors or optical sensors operating on the principle of reflection of the beam from the blade. System according to one of claims 1 to 4, characterized in that the turbine blades are magnetized or the sensors (1, 2, 3, 4) are equipped with an auxiliary magnetic field formed by a permanent magnet, an electromagnet or a combination thereof. System according to one of claims 1 to 5, characterized in that the evaluation unit (5) is connectable to a computer (6) or a modem (7) or a display. 1 drawing