- Email: [email protected]
Stress corrosion cracking detection
in the system' has the capability of looking outside the transducer array. In extreme cases where complexity or acoustic velocity may preclude the normal techniques of source location, 'touch and learn' software may be
Source location algorithms and software is available as standard to deal with fiat plates, cylinders and spherical surfaces. Particularly difficult structures having limited access can be tackled as the software employed
employed. Checks concerning legal transducer sequence, algorithm fit and statistical analysis have been employed to eliminate the 'clutter' effect normally associated with source location systems.
Fibre composite stress wave factor determination Acoustic Emission Technology Corporation's model 206AU AE/ultrasonic analyser has been designed to determine the stress wave factor in fibre composite materials.
T
Acoustic emission bursts
+ Q.
E
The instrument is made up of a pulser system, an AE section and a display section. The pulsar section transmits ultrasonic pulses into the material to produce simulated stress waves similar to AE events. A transducer then receives the signals which are processed in the AE section of the instrument and displayed as continuously repeating burst on the oscilloscope display.
e-O3
a Acoustic emission bursts "O
~_ O. E
The instrument features AET's patented automatic threshold system which automatically measures the continuous noise produced by the system and adds this to the threshold noise level voltage. This means that a fixed deadband results which allows the threshold noise level to be held as close to the background level as possible at any fixed gain value. This allows the system a higher gain than would be obtained if
-G ~?5
+
Thr sh I
b Fig. 4 (a) AET's patented automatic threshold method (b) the fixed threshold m e t h o d
the threshold remained constant. (see Fig. 4). The system can be used to evaluate the
effect of misaligned and broken composite fibres, microvoids, debonding and interlaminate failures.
Microprocessor controlled continuous leak monitoring Acoustic Emission Leak Locators Corporation's AELL-3000 microprocessor-controlled instrument is designed for continuous leak monitoring and identification of leak location. Sensors mounted on the surface of components detect AE signals which are generated by the leak source and transmitted through the structure. These signals are generated by the turbulent pressure forces present at the leak source. The standard AELL-3000 instrument provides eight indivi?~ual sensor channels able to monitor eight separate locations. This capacity can be expanded to include over 100 channels to provide full leak monitoring detection. The microprocessor incorporated into the instrument is programmed to carry out automatic computational analysis. The functions performed by the analyser include determination of leak locations, verification of leak signatures, setting of alarm levels to each channel
and data logging. During system set-up the microprocessor is also used to obtain acoustic background .loise spectrums and to measure the transmission efficiency of calibration leak signals between each sensor. This information is used to optimise the processing signals for each sensor location and is stored for later verification of leak signatures. Applications of the instrument include
detection of leaks in buried pipelines, process system piping and hydraulic systems. Acoustic Emission Leak Locators Corporation also operate a leak detection service which offers a 24 hours on call service, scheduled periodic visits to customers facilities and installation of acoustic waveguides for monitoring of relatively inaccessible locations or thermally hot components.
Stress corrosion cracking detection The Unit Inspection Company Limited have installed Dunegan Endevco's DART 144-transducer AE monitoring system on four hot blast stm es at British Steel's Redcar iron works to detect and locate stress corrosion cracking in the stove domes (see front cover). From the results of a feasibility study conducted prior to installation, it was concluded that a 32-sensor matrix would be adequate to cover one stove
NDT INTERNATIONAL. OCTOBER 1980
dome except for the crown nozzle. It is proposed to cover this are and the lower transition welds at a later date. Dunegan Endevco's DART (Distributed Acquisition Remote Test) signal conditioning equipment, installed at the plant, gives amplitude, rise time, duration and ring down counts on all 32 channels of the sensor matrix. Knowledge of the of the event ampli-
239
Source location algorithms and software is available as standard to deal with fiat plates, cylinders and spherical surfaces. Particularly difficult structures having limited access can be tackled as the software employed
employed. Checks concerning legal transducer sequence, algorithm fit and statistical analysis have been employed to eliminate the 'clutter' effect normally associated with source location systems.
Fibre composite stress wave factor determination Acoustic Emission Technology Corporation's model 206AU AE/ultrasonic analyser has been designed to determine the stress wave factor in fibre composite materials.
T
Acoustic emission bursts
+ Q.
E
The instrument is made up of a pulser system, an AE section and a display section. The pulsar section transmits ultrasonic pulses into the material to produce simulated stress waves similar to AE events. A transducer then receives the signals which are processed in the AE section of the instrument and displayed as continuously repeating burst on the oscilloscope display.
e-O3
a Acoustic emission bursts "O
~_ O. E
The instrument features AET's patented automatic threshold system which automatically measures the continuous noise produced by the system and adds this to the threshold noise level voltage. This means that a fixed deadband results which allows the threshold noise level to be held as close to the background level as possible at any fixed gain value. This allows the system a higher gain than would be obtained if
-G ~?5
+
Thr sh I
b Fig. 4 (a) AET's patented automatic threshold method (b) the fixed threshold m e t h o d
the threshold remained constant. (see Fig. 4). The system can be used to evaluate the
effect of misaligned and broken composite fibres, microvoids, debonding and interlaminate failures.
Microprocessor controlled continuous leak monitoring Acoustic Emission Leak Locators Corporation's AELL-3000 microprocessor-controlled instrument is designed for continuous leak monitoring and identification of leak location. Sensors mounted on the surface of components detect AE signals which are generated by the leak source and transmitted through the structure. These signals are generated by the turbulent pressure forces present at the leak source. The standard AELL-3000 instrument provides eight indivi?~ual sensor channels able to monitor eight separate locations. This capacity can be expanded to include over 100 channels to provide full leak monitoring detection. The microprocessor incorporated into the instrument is programmed to carry out automatic computational analysis. The functions performed by the analyser include determination of leak locations, verification of leak signatures, setting of alarm levels to each channel
and data logging. During system set-up the microprocessor is also used to obtain acoustic background .loise spectrums and to measure the transmission efficiency of calibration leak signals between each sensor. This information is used to optimise the processing signals for each sensor location and is stored for later verification of leak signatures. Applications of the instrument include
detection of leaks in buried pipelines, process system piping and hydraulic systems. Acoustic Emission Leak Locators Corporation also operate a leak detection service which offers a 24 hours on call service, scheduled periodic visits to customers facilities and installation of acoustic waveguides for monitoring of relatively inaccessible locations or thermally hot components.
Stress corrosion cracking detection The Unit Inspection Company Limited have installed Dunegan Endevco's DART 144-transducer AE monitoring system on four hot blast stm es at British Steel's Redcar iron works to detect and locate stress corrosion cracking in the stove domes (see front cover). From the results of a feasibility study conducted prior to installation, it was concluded that a 32-sensor matrix would be adequate to cover one stove
NDT INTERNATIONAL. OCTOBER 1980
dome except for the crown nozzle. It is proposed to cover this are and the lower transition welds at a later date. Dunegan Endevco's DART (Distributed Acquisition Remote Test) signal conditioning equipment, installed at the plant, gives amplitude, rise time, duration and ring down counts on all 32 channels of the sensor matrix. Knowledge of the of the event ampli-
239