3: Operating Procedures
20 Portaflow 220 User Manual
(Issue 1.0)
3.5.3 Adjusting the calibration factor
With the system running:
1. Stop (Stall) the Portaflow’s totaliser facility and zero it (Paragraph 3.6.1).
2. Run the Portaflow’s totaliser to measure the total flow over a 30-60 minute period, and note the total flow
indicated by the reference flow meter over the same period.
3. Calculate the % error between the Portaflow and reference meters. If the error is greater than ±1%
calibrate the Portaflow as detailed below.
3.5.4 Adjusting the roughness factor
The roughness factor compensates for the condition of the internal pipe wall, as a rough surface will cause
turbulence and affects the flow profile of the liquid. 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:
Key Point: In order to cancel any applied offset you must either read the flow via
Quick Start or switch the Portaflow instrument OFF & ON. Any value that you trim-
out using the offset adjustment will be added/subtracted from the flow reading
across the whole range.
Key Point: USE THIS FACILITY WITH CARE & ONLY WHERE NECESSARY
The Portaflow instrument is fully calibrated before leaving the factory and under nor-
mal circumstances does not require further calibration when used on site.
This facility can be used to correct the flow indication where unavoidable errors occur
due to the lack of a straight pipe or where the sensors are forced to be fitted close to
the pipe-end, valve, junction etc.
Any adjustment must be made using a reference flowmeter fitted in the system.
4. Press the Options key to access the FLOW
READING OPTION screen shown.
5. Scroll down and select Calibration
factor.
6. Change the calibration factor according to
the error calculated in step 3. For example, if
the Portaflow was reading 1% high then
increase the Calibration factor value
by 0.010. Conversely, if the reading is 1%
low then decrease the calibration factor to
0.990.
7. Press Enter to apply the change.
8. Select Roughness factor or Exit as
required.
FLOW READING OPTION
DD-MM-YY HH:MM:SS
Data review
Zero Cutoff (m/s) : 0.00
Set zero flow (m/s) : 0.00
Damping (secs) : 10
Totaliser : Run
Reset +Total
Reset –Total
Calibration factor : 1.000
Roughness factor : 0.01
Diagnostics
Exit
Pipe Material Roughness Factor
Non ferrous metal
Glass
Plastics
Light metal
0.01
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