LOKAL 400 Operating Manual
Page 18
7.6 Calibration of sound velocity
In rare cases, it might happen that the sound velocity of the pipe-section is not the same than the one
stored in the Lokal 400. The reason for this could be the age of pipelines (i.e. hardening of the material in
plastic pipes) or incrustations (i.e. corrosion on ductile or iron pipes). The same problem is faced if repairs
with different materials were not mapped or recorded (often not the same material gets used!!). A
difference in sound velocity is elaborate for the result of the correlation and could lead to miss digging in
the worst case. One option to check the sound velocity on the section of pipe you want to conduct the
measurement is to calibrate it. Please apply following procedure:
1.
Open outside of the measurement section a hydrant or wash out (or similar). Means, “behind” A
or B. Important: the sound needs to be greater than the leak noise itself. [Perhaps through new
positioning of the MB´s, the noise from the leak itself could be used to calibrate the sound velocity
for the section]
2. Type in the pipe parameters for the section into the Lokal 400 [refer to section 7.1.1]
3. Start a correlation and wait until a result (peak) is shown
4. Because the (main-) noise is now outside of the measurement section (between A and B) the
Lokal 400 will show a “leakage” directly on A or B (depending which one is nearest)
5. Now you can calibrate the sound velocity of the measurement section through pressing long onto
this button
. A multiple piep-
tone will be audible. You will find the “calibrated” (new) sound
velocity in the pipe parameter settings [see section 7.1.1]
IMOPRTANT:
This only works, if only one section is entered in the pipe parameter settings. As soon as
more sections are typed in, it does not work!
NOTE:
If you chang
e anything on the pipe parameters (i.e. dimension or material), the “calibrated” sound
velocity will be deleted and the stored velocity will be taken over automatically. It makes sense to safe the
calibration file for future measurements on this section in the device.
