358
Y. Xu et al.
Table 30.1 The attenuation testing result of the waveguide rod
Location of the
analog source
10 mm sensor
edge
80 mm starting
point of thread
500 mm end of
thread
1000 mm 1450 mm
end point
Average
response
amplitude (dB)
94.5
83.9
85.5
80.5
84.1
Table 30.2 Comprehensive sound wave conduction on inner tank wall after installation of guide
rod
Response amplitude of
knocking near a certain
sensor
Triggered sensors and their response amplitudes
2#: 96 dB
9#: 71 dB
4#: 57 dB 5#: 56 dB 11#: 67 dB
5#: 98 dB
11#: 64 dB
4#: 58 dB 9#: 56 dB 1#: 56 dB
several times with a metal member like a screwdriver. If the adjacent sensor receives
the mechanical tap signals, it is considered that the waveguide rod is well coupled
with the inner tank wall, and AE signals from the inner tank can also be received.
Some conductivity test results are shown in Table 30.2. The results show that the
waveguide method basically meets the requirements for AE on-line detection of such
tanks.
30.3.2 Method Two: The Fixed Accessories of Storage Tank
[3]
Figure 30.4 shows the overhead foundation of an 8800 m
3 double wall cryogenic
storage tank (4118-v4) in a large petrochemical company in Zhejiang Province.
Through drawing review and site investigation, it is found that there are several
Fig. 30.4 Photo of 4118-v4
tank bottom