Blade Vibration Monitoring (BVM)
http://www.hoodtech.com
Blade Vibration Monitoring (BVM)
Hood Technology Corporation is a small, innovative engineering company located in Hood River, Oregon, USA, specializing in blade vibration & monitoring (BVM) for rotating machinery (e.g., gas turbine engines, turbochargers, steam turbines, compressors).
Blade Vibration Monitoring (BVM), also named as Blade Tip Timing (BTT), Non-intrusive Stress Measurement System (NSMS), refers to measurements made on rotating machinery using sensors that do not make contact with the rotor blades. A BVM system has a number of advantages over the traditional turbo-machinery measurement method (strain gages): data for each blade is acquired in a measured stage, and the instrumentation is non-contacting, which means that no slip rings or telemetry systems are required and the sensors can be replaced, if necessary, without dismantling the machine or even stopping the machine in some installations. Hood Technology has been designing and building blade tip timing systems since 1999 and has supported more than 200 tests on devices ranging from 5cm-diameter turbochargers to 4m-diameter steam turbines.
BVM is usefully applied in the following three areas:
Vibration Characterization
Hood Technology’s BVM can compare the actual performance of turbine blades with those predicted by theory, addressing extraordinary conditions such as extreme surges that are not adequately addressed by theoretical models.
Risk Mitigation
Unique to Hood Technology’s BVM is the ability to monitor blade vibration in a jet aircraft (either manned or unmanned) while in flight. Risk mitigation is used to avoid flight conditions that could lead to premature engine failure, thereby risking aircraft and personnel loss.
Failure Prediction
Hood Technology’s BVM offers turbine operators the unique ability to interpret data predicting incipient failure of turbine blades, which could lead to catastrophic failure of the turbine stage and extensive damage to the turbine.
System description
Hood Technology’s blade vibration monitoring system consists of the following parts: sensors, preamplifiers, data acquisition console, and software.
Sensor
Sensors generate analog pulses each time a blade passes in front of them.
More.
Preamplification
A preamplifier is located near the rotor under test and connects to the sensors. For optical sensors, a laser and photodiode are contained in the preamplifier. The preamp is powered by the data console through a 9-pin sub-D cable. The buffered output can drive cables (up to 80m - 150m) without signal degradation. It can also act as a signal repeater for longer spans of cabling to the data console.
More.
Data acquisition console
The data acquisition console takes the analog signals from the preamplifiers and turns them into timing data which can be interpreted into useful information. There are two families of Hood Technology Corporation’s BVM data acquisition consoles. The first is the model 8030, mounted in a self-contained 19” instrumentation rack. The newly developed model 4016C has integrated preamplifiers, a much smaller form factor and all solid state components. Versions of this system have been used in flight testing.
More.
Software
The data acquisition console operates Hood Technology Corporation’s Acquire Blade Data software. Hood Technology’s software has been developed to meet the full range of BVM demands, from receiving and interpreting signals from the tip sensors (as processed by the pre-amp through the data console) to full-time monitoring of turbine system performance, including remote communications.
More.
Blade Vibration Monitoring (BVM), also named as Blade Tip Timing (BTT), Non-intrusive Stress Measurement System (NSMS), refers to measurements made on rotating machinery using sensors that do not make contact with the rotor blades. A BVM system has a number of advantages over the traditional turbo-machinery measurement method (strain gages): data for each blade is acquired in a measured stage, and the instrumentation is non-contacting, which means that no slip rings or telemetry systems are required and the sensors can be replaced, if necessary, without dismantling the machine or even stopping the machine in some installations. Hood Technology has been designing and building blade tip timing systems since 1999 and has supported more than 200 tests on devices ranging from 5cm-diameter turbochargers to 4m-diameter steam turbines.
BVM is usefully applied in the following three areas:
Vibration Characterization
Hood Technology’s BVM can compare the actual performance of turbine blades with those predicted by theory, addressing extraordinary conditions such as extreme surges that are not adequately addressed by theoretical models.
Risk Mitigation
Unique to Hood Technology’s BVM is the ability to monitor blade vibration in a jet aircraft (either manned or unmanned) while in flight. Risk mitigation is used to avoid flight conditions that could lead to premature engine failure, thereby risking aircraft and personnel loss.
Failure Prediction
Hood Technology’s BVM offers turbine operators the unique ability to interpret data predicting incipient failure of turbine blades, which could lead to catastrophic failure of the turbine stage and extensive damage to the turbine.
System description
Hood Technology’s blade vibration monitoring system consists of the following parts: sensors, preamplifiers, data acquisition console, and software.
Sensor
Sensors generate analog pulses each time a blade passes in front of them.
More.
Preamplification
A preamplifier is located near the rotor under test and connects to the sensors. For optical sensors, a laser and photodiode are contained in the preamplifier. The preamp is powered by the data console through a 9-pin sub-D cable. The buffered output can drive cables (up to 80m - 150m) without signal degradation. It can also act as a signal repeater for longer spans of cabling to the data console.
More.
Data acquisition console
The data acquisition console takes the analog signals from the preamplifiers and turns them into timing data which can be interpreted into useful information. There are two families of Hood Technology Corporation’s BVM data acquisition consoles. The first is the model 8030, mounted in a self-contained 19” instrumentation rack. The newly developed model 4016C has integrated preamplifiers, a much smaller form factor and all solid state components. Versions of this system have been used in flight testing.
More.
Software
The data acquisition console operates Hood Technology Corporation’s Acquire Blade Data software. Hood Technology’s software has been developed to meet the full range of BVM demands, from receiving and interpreting signals from the tip sensors (as processed by the pre-amp through the data console) to full-time monitoring of turbine system performance, including remote communications.
More.
Sensors
BVM blade monitoring employs optical, eddy current, and/or capacitive sensors. Customer needs and the operating environment determine the choice of sensors. Considerations include operating temperature, the degree of optical interference from oils, dirt, and/or other obscuring substances, and physical configuration, as well as customer preferences.
Multiple sensors are standard for installations, and there is no practical upper limit to the type and quantity of sensors that can be employed. Hood Technology Corporation principally recommends two types: (1) eddy current and (2) optical. Standard-sized sensors are typically integrated into the customer’s test setup. Alternatively, Hood Technology Corporation’s engineers often work with the customer to customize the sensor housing to accommodate specific installation needs.
Fiber-Optic Sensors; Unlensed
Hood Tech builds optical sensors in a range of sizes and temperature capabilities. The most common sensor size of this type built by Hood Technology Corporation is shown below. It is designed to connect to Hood Technology’s optical sensor pre-amp (BV-OP). Laser light is emitted from the center fiber, reflects off each passing blade, and the reflected light travels back to a photodiode through the outer six fibers. Reliable signals can be achieved with sensor standoff distances up to 10mm.
Temperature limitations of the sensors are dictated by the optic fibers. Using high-temperature fibers, temperatures of up to 650C can be tolerated. With a small cooling manifold air-cooled optical sensors have been used to 1100C.
Another type of unlensed optical sensor is the Skewed Dual Light Probe (SDLP), shown below. This sensor consists of two seven-fiber probes mounted in the same housing at a skew angle with respect to one another. This creates a sensor pair, whose time-of-flight is a linear function of the distance between the sensor and the passing blade. In other words, this sensor measures the clearance of each blade as well as the time-of-arrival. SDLPs have the same temperature limitations (up to 650C uncooled).
Fiber-Optic Sensors; Lensed
Lensed optical sensors can make measurements over longer distances. A ‘long-shot’ sensor can be used to execute BVM from several meters distance. In these cases, the laser light is collimated and can travel long distances (up to 10m has been used). Reflective tape is applied to a stationary object (e.g. stator vane, case wall) and the passing blade acts as a ‘shutter’ blocking the returning light. Because of the physical and temperature requirements, these ‘long-shot’ sensors are typically only used on the first stage of an axial compressor, but they have the ability to measure several span-wise locations on the blades. They also allow the user to measure the leading edge AND the trailing edge of a blade with a single sensor. An example installation on a gas turbine fan is diagrammed below.
An alternative "shutter" implementation of optical sensors has been employed on interior stages in gas turbine engines, where the sensor is split into an optical "sender" and an optical "receiver", arranged so that the blade passes between them. The passing blade again acts as a shutter, interrupting the optical beam. Again, both arriving edge and departing edge of the blade can be measured. An implementation in an LP turbine stage of a gas turbine engine is diagrammed below. This implementation does not requires reflective tape, and therefore it can be used in high-temperature environments.
Eddy Current Sensors, Uncooled
The most common sensor size of this type built at Hood Technology is show in the figure below. In addition to a large number of gas turbine engines, this sensor has also been used with success in steam turbines, in each case on the final few stages of the LP turbine. For these steam turbine applications, the sensor housing is made with an erosion resistant material. Several eddy current sensor installations have been in continuous operation for over 2 years in gas turbine engines and steam turbines with no degradation in signal quality.
This sensor is used for time-of-arrival and for uncalibrated tip-clearance measurements
Eddy Current Sensors, Cooled
In turbines, we have operated such sensors with cooling airflow routed through the sensor in 1mm steel tubing, maintaining the sensor’s interior below 500C (see Figure below). We have used this approach with gas temperatures as high as 1000C.
Third Party Sensors
Hood Tech has used third-party sensors on many occasions:
- GDAIS eddy current sensors: Hood Tech has built custom interface amplifiers for the differential signals and connectors specific to GDAIS’ sensor interface unit (The SIU.)
- These interface amplifiers were embedded into the four 12-channel data consoles delivered to P&W in 2007.
- Qinetiq eddy current sensors
- Capacitec capacitive sensors
- BICC/Thermoheat capacitive sensors
- Thermocoax capacitive sensors with Fogale preamps.
- Aerodyne capacitive sensors
- Hamilton Sundstrand microwave sensors
- Polish Air Force Institute of Technology microwave sensors
- RadaTec/Vibrometer microwave sensors
- P&W optical sensors
- GE optical sensorsHood Technology’s data console has the front-end flexibility to accommodate any of these sensors as well as others not enumerated here.
Preamplification
Hood Tech manufactures preamps of two types: optical (BV-OP) and eddy current (BV-IND), both shown in Figure 1. Each preamp supports three sensors. Each preamp is about the size of a paper-back book and is powered by its own data cable (no power is required near the device under test.). It should be noted that the preamplifiers are required only when using model 8030 data acquisition console. The preamplifiers are integrated into model 4016C. This is described in more detail below.
1. Eddy Current Preamp (BV-IND)
The Hood Technology Corp. 3-channel eddy current preamplifier has three identical channels, each of which implements preamplification for any Hood Tech eddy current sensor. The preamp is powered by the data console through a 9-pin sub-D cable. Each channel has an easily adjustable gain up to 100X and an optional attenuator for occasions when the input signal is too large. The buffered output can drive cables (up to at least 150m) without signal degradation. It can also act as a signal repeater for longer spans of cabling to the data console.
2. Optical Preamp (BV-OP)
The Hood Technology Corp. 3-channel optical preamplifier has three identical channels, each of which has a 40 mW, 658nm class IIIb laser source and a photo detector. It is used with light probes built by Hood Technology Corporation using ST optical connectors. The preamp is powered by the data console through a 9-pin sub-D cable. The detector electronics have user selectable gains and filter settings. The buffered output can drive long cables (up to at least 80m) to the data console. The physical shape of the preamplifier mitigates the possibility of accidental laser exposure.
1. Eddy Current Preamp (BV-IND)
The Hood Technology Corp. 3-channel eddy current preamplifier has three identical channels, each of which implements preamplification for any Hood Tech eddy current sensor. The preamp is powered by the data console through a 9-pin sub-D cable. Each channel has an easily adjustable gain up to 100X and an optional attenuator for occasions when the input signal is too large. The buffered output can drive cables (up to at least 150m) without signal degradation. It can also act as a signal repeater for longer spans of cabling to the data console.
2. Optical Preamp (BV-OP)
The Hood Technology Corp. 3-channel optical preamplifier has three identical channels, each of which has a 40 mW, 658nm class IIIb laser source and a photo detector. It is used with light probes built by Hood Technology Corporation using ST optical connectors. The preamp is powered by the data console through a 9-pin sub-D cable. The detector electronics have user selectable gains and filter settings. The buffered output can drive long cables (up to at least 80m) to the data console. The physical shape of the preamplifier mitigates the possibility of accidental laser exposure.
The eddy current preamp (left) is used for Hood Technology eddy current sensors or third party sensors via a BNC input.
Optical preamp (right) contains lasers and photodiodes for Hood Technology BVM optical probes.
Optical preamp (right) contains lasers and photodiodes for Hood Technology BVM optical probes.
Data Acquisition Console
The data acquisition console takes the analog signals from the preamplifiers and turns them into timing data which can be interpreted into useful information. There are two families of Hood Technology Corporation’s BVM data acquisition consoles. The first is the model 8030, mounted in a self-contained 19” instrumentation rack. The newly developed model 4016C has integrated preamplifiers, a much smaller form factor and all solid state components. Versions of this system have been used in flight testing. Table 1 highlights the major differences between the two models.
Table 1: Comparison of data console models 8030 and 4016C.
| Model 8030 | Model 4016C1 | |
| Timing Resolution | 80MHz, 12.5ns ~ 4um at 340m/s rim speed | 40MHz, 25ns ~8um at 340m/s rim speed |
| Data Streaming | ~1.5Mblades/sec | ~0.25Mblades/sec |
| Maximum Channel Count | 30 | 16 |
| Outer Dimensions | 650mmX900mmX1100mm | 222mmX465mmX199mm |
| Weight | ~130kg | ~10kg |
| Virtual Oscilloscope | Yes, up to 1.2Msamp/sec Fast refresh rate | Yes, up to 0.5Msamp/sec ~ 1 second refresh rate |
| Preamplifiers | Separate | Integrated |
| Power Consumption | 185 to 550W | 60 to 120W |
| Power Requirement | 110-240VAC | 24-35VDC |
| Thermoelectric cooling of laser diodes | No | Yes |
1. BVM Model 8030
A photograph of a 30-channel version of BVM model 8030 is shown below. This system hosts 1 to 10 BVSI modules, each supporting a Hood Tech preamp and 3 channels of sensor data.
Model 8030 data acquisition console. Standard 19 inch rack is soft-mounted. Console is on casters and has removable front and back lids for shipping and safe storage.
The Blade Vibration Sensor Interface (BVSI) unit, developed by Hood Technology Corporation ( Figure 2 ), conditions analog blade passage signals and converts them to a digital signal, which is precisely timed. The BVSI performs the following functions:
A photograph of a 30-channel version of BVM model 8030 is shown below. This system hosts 1 to 10 BVSI modules, each supporting a Hood Tech preamp and 3 channels of sensor data.
Model 8030 data acquisition console. Standard 19 inch rack is soft-mounted. Console is on casters and has removable front and back lids for shipping and safe storage.
The Blade Vibration Sensor Interface (BVSI) unit, developed by Hood Technology Corporation ( Figure 2 ), conditions analog blade passage signals and converts them to a digital signal, which is precisely timed. The BVSI performs the following functions:
- It provides power to Hood Technology's sensors, filters, repeaters and conditioning electronics.
- It allows one to determine blade passage on a repeatable feature of the analog pulses generated by the sensors.
- It provides a logic pulse indicating Time-Of-Arrival and an additional pulse indicative of pulse magnitude (i.e. tip clearance) which are timed by the National Instruments Timer Card.
- It communicates with Hood Technology’s Acquire Blade Data software, allowing the user to change BVSI settings (see in Table 2) via a graphical user interface
- It allows one to determine blade passage on a repeatable feature of the analog pulses generated by the sensors.
- It provides a logic pulse indicating Time-Of-Arrival and an additional pulse indicative of pulse magnitude (i.e. tip clearance) which are timed by the National Instruments Timer Card.
- It communicates with Hood Technology’s Acquire Blade Data software, allowing the user to change BVSI settings (see in Table 2) via a graphical user interface
Blade Vibration Sensor Interface (BVSI) conditions the analog blade passage signals and converts them into precisely timed digital signals.
Table 2: BVSI Parameters and their associated ranges or possible values.
| Parameter | Min Value | Max Value |
| Gain | -25 | 25 |
| High Pass Filter Cutoff | 0 Hz | 3397 Hz |
| Low Pass Filter Cutoff | 23 kHz | 1496 kHz |
| Offset | -7 V | +7 V |
| Arm level | 0.055 V | 4.995 V |
| Trigger Edge | Rising/Falling | N/A |
| Trigger Level | 0 % | 90 % of max value attained |
| Hold Off | 0.2 µs | 4984 µs |
| Decay Rate | Slow/fast | N/A |
2. BVM Model 4016C
Blade vibration monitor model 4016C was developed in 2008/2009. The cabling diagram, shown in Figure 3, is somewhat different than model 8030. The 4016C has all the features of the BVSI, BV-IND, and BV-OP integrated in a single box. In use, it would be located near the sensors. Rather than run cables with power and signal to the acquisition console, only an Ethernet cable is required to transmit data to a ‘ground station’, which could simply be a laptop computer running Acquire Blade Data. The figure also shows a flight-test implementation with a telemetry link. The first use of this system was in flight test of a military aircraft.
The cabling diagram of the BVM model 4016C is somewhat different than Model 8030, because the BVSI and preamplifier are integrated into one box that is located near the sensors. Data are streamed to disk, via UDP or TCP/IP. The “ground station” can be simply a laptop connected with an Ethernet cable.
External dimensions of model 4016C
Blade vibration monitor model 4016C was developed in 2008/2009. The cabling diagram, shown in Figure 3, is somewhat different than model 8030. The 4016C has all the features of the BVSI, BV-IND, and BV-OP integrated in a single box. In use, it would be located near the sensors. Rather than run cables with power and signal to the acquisition console, only an Ethernet cable is required to transmit data to a ‘ground station’, which could simply be a laptop computer running Acquire Blade Data. The figure also shows a flight-test implementation with a telemetry link. The first use of this system was in flight test of a military aircraft.
The cabling diagram of the BVM model 4016C is somewhat different than Model 8030, because the BVSI and preamplifier are integrated into one box that is located near the sensors. Data are streamed to disk, via UDP or TCP/IP. The “ground station” can be simply a laptop connected with an Ethernet cable.
External dimensions of model 4016C
Processing Software
Hood Technology’s software has been developed to meet the full range of BVM demands, from receiving and interpreting signals from the tip sensors (as processed by the pre-amp through the data console) to full-time monitoring of turbine system performance, including remote communications. The major components of BVM software from Hood Tech are:
ACQUIRE BLADE DATA (VER 9.X)
Acquire Blade Data software is used to capture non-contacting blade tip timing sensor data. Some features include:
ACQUIRE BLADE DATA (VER 9.X)
Acquire Blade Data software is used to capture non-contacting blade tip timing sensor data. Some features include:
- The software communicates with Hood Technology’s BVSI 5.x, integrated in BVM model 8030 and BVM model 4016C, allowing the user to view and change conditioning and triggering parameters for each sensor (gain, lowpass, highpass, arm, trigger, etc.).
- The Virtual Oscilloscope allows the user to view analog sensor signals and time of arrival while simultaneously adjusting conditioning and triggering.
- The time of arrival and the encoded blade pulse amplitude can be continuously streamed to disk (up to 1.5Mpulses/sec ~=6MB/sec for BVM8030 and 0.25Mpulses/sec ~=1MB/sec for BVM4016C).
- Up to 30 channels are supported (30 for BVM8030, 16 channels for BVM4016C).
- Multiple rotors are supported.
- Real-time displays include:
- The Virtual Oscilloscope allows the user to view analog sensor signals and time of arrival while simultaneously adjusting conditioning and triggering.
- The time of arrival and the encoded blade pulse amplitude can be continuously streamed to disk (up to 1.5Mpulses/sec ~=6MB/sec for BVM8030 and 0.25Mpulses/sec ~=1MB/sec for BVM4016C).
- Up to 30 channels are supported (30 for BVM8030, 16 channels for BVM4016C).
- Multiple rotors are supported.
- Real-time displays include:
- RPM
- Sensor Status (correct number of pulses, arrival variability).
- Generalized synchronous and non-synchronous amplitudes, including blade-by-blade and historical data.
- Circumferential Fourier fit (multi-sensor order tracking) with assumed response order.
- Synchronous Campbell diagram based on order scheduling.
- Blade-tip clearance from blade-pulse amplitudes or Skewed Dual Light Probes (SDLP), including blade-by-blade and historical data.
- Blade Stagger when two chordwise positions are available.
- All-blades FFT for non-synchronous events (flutter, rotating stall, etc.)
- Single blade non-synchronous amplitudes using scheduled nodal diameters.
- Interblade spacing as a potential indication of rotor cracks.
- Sensor Status (correct number of pulses, arrival variability).
- Generalized synchronous and non-synchronous amplitudes, including blade-by-blade and historical data.
- Circumferential Fourier fit (multi-sensor order tracking) with assumed response order.
- Synchronous Campbell diagram based on order scheduling.
- Blade-tip clearance from blade-pulse amplitudes or Skewed Dual Light Probes (SDLP), including blade-by-blade and historical data.
- Blade Stagger when two chordwise positions are available.
- All-blades FFT for non-synchronous events (flutter, rotating stall, etc.)
- Single blade non-synchronous amplitudes using scheduled nodal diameters.
- Interblade spacing as a potential indication of rotor cracks.
- Test monitoring and data management features include:
- Select manual data acquisition and RPM-dependent acquisition.
- Circular buffer streams all data, so that data can be recovered if tagged (to be saved) by other events (e.g. high non-synchronous vibration, pretrigger).
- Automatic folder creation for long term testing.
- Data can periodically saved for long-term tests (months and years).
- Creates an ASCII information file (*.inf) containing all pertinent information.
- Notes are automatically appended to *.inf.
- Supports the use of visual and audible alarms for excessive synchronous and non-synchronous vibration, tip clearance, and blade stagger angle.
- Circular buffer streams all data, so that data can be recovered if tagged (to be saved) by other events (e.g. high non-synchronous vibration, pretrigger).
- Automatic folder creation for long term testing.
- Data can periodically saved for long-term tests (months and years).
- Creates an ASCII information file (*.inf) containing all pertinent information.
- Notes are automatically appended to *.inf.
- Supports the use of visual and audible alarms for excessive synchronous and non-synchronous vibration, tip clearance, and blade stagger angle.
Multiple screen captures from Acquire Blade Data software
ANALYZE VIBRATION (VER 6.X)
Analyze Blade Vibration is used to analyze data gathered with non-contacting blade-tip sensors. Some features include:
- Sensor Location Determination, based on user configuration, interblade spacing, or a combination of the two.
- Supports multiple rotors and chordwise sensor positions.
- Quick view of RPM-run history.
- Quick view (aggregate) of synchronous / non-synchronous vibration with synchronous order determination.
- Synchronous Analysis:
- Supports multiple rotors and chordwise sensor positions.
- Quick view of RPM-run history.
- Quick view (aggregate) of synchronous / non-synchronous vibration with synchronous order determination.
- Synchronous Analysis:
- Circumferential Fourier fit (i.e. Order Tracking) using 3 or more sensors.
- Single Degree of Freedom fit for each sensor or for combinations of times-of-flight.
- Blade-by-blade viewing or stack plots.
- Results can be exported to a Campbell Diagram and to Excel and Word formats.
- User-configurable data smoothing and processing features.
- Single Degree of Freedom fit for each sensor or for combinations of times-of-flight.
- Blade-by-blade viewing or stack plots.
- Results can be exported to a Campbell Diagram and to Excel and Word formats.
- User-configurable data smoothing and processing features.
- Non-synchronous Analysis
- Waterfall display.
- Nodal diameter and true frequency determination of non-synchronous events.
- Non-integral Circumferential Fit performed for single blade amplitudes.
- Results can be exported to a Campbell Diagram and to Excel and Word formats.
- Blade Stagger Angle Analysis
- Blade-Tip Clearance Analysis
- Supports two types of sensors: (1) skewed dual light probes (aka V-probes, SDLP) and (2) sensors whose blade pulse voltage is a function of clearance.
- Calibration can also include tip speed.
- Calibration utility allows for qualitative results when no calibration exists.
- Results can be exported to Excel and Word formats.
- Nodal diameter and true frequency determination of non-synchronous events.
- Non-integral Circumferential Fit performed for single blade amplitudes.
- Results can be exported to a Campbell Diagram and to Excel and Word formats.
- Blade Stagger Angle Analysis
- Blade-Tip Clearance Analysis
- Supports two types of sensors: (1) skewed dual light probes (aka V-probes, SDLP) and (2) sensors whose blade pulse voltage is a function of clearance.
- Calibration can also include tip speed.
- Calibration utility allows for qualitative results when no calibration exists.
- Results can be exported to Excel and Word formats.
Multiple screen captures from Analyze Blade Vibration software
MONITOR
Monitor software operates in conjunction with Acquire Blade Data software (and therefore without a generic user interface) to perform long-term trending on synchronous resonance, asynchronous phenomena, and blade lean, which can indicate the presence of a crack. In order to maximize the efficacy of Monitor Software, the data are distilled using experience to identify expected cracks and models of blade-lean behavior. In addition, Monitor Software can automatically generate reports and publish them to a website and/or email them to addressees. Monitor Software currently requires a small amount of customization for each application.
