Page 207 - CW E-Magazine (26-9-2023)

Special Report

Voltage(mV) vs Time(sec) <5> Powder(dB) vs Frequency(Hz) <5>
6000 65
5000 60
4000 55
3000 50
2000 45
1000
40
0
35
-1000
30
-2000
25
-3000
20
-4000
15
-5000
0 2m 4m 6m 8m 10m 12m 14m 0 100k 200k 300k 400k 500k
Fig. 8: AE Sensors characteristics
AE signal of lead break and corresponding Power spectrum.

Bridge cable
Sensor attached with magnet Pb blanket in nuclear applications

Waveguide rolling sensor produces by PAc
Fig. 9: Installation of Sensors on Structure
response – resonant and wideband. are shown in Figure-9 and described
Thickness of piezoelectric element below:
defines the resonance frequency of Glue (superglue type) is commonly

sensor. used for piping inspections.
Diameter defines the area over Magnets are usually used to hold

which the sensor averages surface sensors on metal pressure vessels.
motion. Grease and oil are then used as a
Another important property of AE couplant.
sensors includes the Curie Point – Bands used for mechanical attach-

the temperature under which ment of sensors in long term appli-
piezoelectric element loses perma- cations. Fig. 10: AE data Acquisition devices
nently its piezoelectric properties. Waveguides (welded or mechani- Different AE data acquisition

The Curie Temperature varies for cally attached) used in high tem- device are shown in Figure-10 and
different ceramics from 120°C to perature applications. described below:
400°C. There are ceramics with Rolling sensors are used for inspec- 16 bit, 10 MHz A/D converter.

over 1200°C Curie temperature. tion rotating structures.Special Pb Maximum signal amplitude 100 dB
blankets used to protect sensors in AE.
The AE sensor installation features nuclear industry. 4 High Pass filters for each channel

Chemical Weekly September 26, 2023 207

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