408
V. V. Bardakov et al.
Table 35.2 Damage levels of
columns
Damage level of column
Existing defects
Heavy
Destruction of concrete protection
layer
Concrete corrosion
Cracks with a width up to 6 mm
Intermediate
Partial destruction of concrete
protection layer
Cracks with a width up to 7 mm
Minor
Minor cracks in concrete
protection layer
Support columns of cooling tower which have been operated since the second
half of the last century were tested. Summary 3 columns with different damage
levels—heavy, intermediate and minor were investigated (Table 35.2).
3 AE sensors with operation frequency band from 30–300 kHz were mounted on
each column at a distance of 1 m between each other. The duration of data acquisition
was about 15 h. This time period included day-night and night-morning temperatures
changing which were used as a load in additional to the static load.
First of all noise level was investigated. This type of object has high level of
acoustic noises in sound range due to falling water and strong wind flows, but in
the frequency band from 30 to 300 kHz the noise level is low enough and does not
exceed 30 dB.
Figure 35.7 shows the dependence of cumulative hits on air temperature over 15 h
period for the most active channels of each column.
Fig. 35.7 Dependence of cumulative hits on air temperature for most active channels for 3 columns
with different damage levels (blue—minor, red—intermediate, green—heavy)
V. V. Bardakov et al.
Table 35.2 Damage levels of
columns
Damage level of column
Existing defects
Heavy
Destruction of concrete protection
layer
Concrete corrosion
Cracks with a width up to 6 mm
Intermediate
Partial destruction of concrete
protection layer
Cracks with a width up to 7 mm
Minor
Minor cracks in concrete
protection layer
Support columns of cooling tower which have been operated since the second
half of the last century were tested. Summary 3 columns with different damage
levels—heavy, intermediate and minor were investigated (Table 35.2).
3 AE sensors with operation frequency band from 30–300 kHz were mounted on
each column at a distance of 1 m between each other. The duration of data acquisition
was about 15 h. This time period included day-night and night-morning temperatures
changing which were used as a load in additional to the static load.
First of all noise level was investigated. This type of object has high level of
acoustic noises in sound range due to falling water and strong wind flows, but in
the frequency band from 30 to 300 kHz the noise level is low enough and does not
exceed 30 dB.
Figure 35.7 shows the dependence of cumulative hits on air temperature over 15 h
period for the most active channels of each column.
Fig. 35.7 Dependence of cumulative hits on air temperature for most active channels for 3 columns
with different damage levels (blue—minor, red—intermediate, green—heavy)