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Operation of the device
5.3.4
Adjusting the roughness factor
The roughness factor compensates for the condition of the internal pipe wall, as a rough surface will cause turbulence and affect
the flow profile of the liquid. The unit of roughness is mm or inches, depending on the current setting. The value represents the
worst height difference between a pit and a peak in the pipe wall. In most situations, it is not possible to inspect the pipe internally
and the true condition is not known. In these circumstances experience has shown that the following values can be used for pipes
in good condition:
Pipe Material
Non ferrous metal
Glass
Plastics
Light metal
Drawn steel pipes:
• Fine planed, polished surface
• Plane surface
• Rough planed surface
Welded steel pipes, new:
• Long usage, cleaned
• Lightly and evenly rusted
• Heavily encrusted
Cast iron pipes:
• Bitumen lining
• New, without lining
• Rusted / Encrusted
When a new site is added to the system a default value for roughness will be set depending on the pipe material. With the system
running in FLOW READING mode:
40
7.
Change the calibration factor according to the error
calculated in step 3. For example, if the flowmeter was
reading 1% high, decrease the Calibration factor value by
approximate this amount. Since that start value is 1.00, the
calibration value should be 0.99. Conversely, if the reading
is 1% low then increase the calibration factor to 1.01.
8.
Press the ENTER key to apply the change and return to the
View/Edit Site Data menu.
Scroll down to select Read flow using selected sensor and
9.
press the ENTER key.
10.
Check the flow measurement against the reference flow
meter again.
Roughness Factor
0.01 mm
0.01 mm
0.1 mm
1.0 mm
1.
Press the ENTER key and select 'Yes' to confirm that
you want to exit the Read Flow screen. The Main Menu is
displayed.
2.
Select View / Edit Site Data.
3.
Use the UP/DOWN arrow keys to select Roughness factor.
Press the ENTER key.
4.
Change the roughness factor according to the pipe
material and condition as described above.
5.
Press the ENTER key to apply the change and return to the
View/Edit Site Data menu.
6.
Scroll down to select Read flow using selected sensor and
press the ENTER key to return to the Read Flow screen.
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