Flow Meter Calibration
To calibrate the flow meter is a simple but repetitive process that involves entering a ‘K-factor’ into the flow meter to ensure that the flow meter accurately displays the correct flow rate in litres per minute. The process is set up into Five main steps:
- Pipework preparation.
- Flow meter calibration.
- Current Loop set up - At thew flow meter
- Current Loop set-up - At the Smart Bilge+
- Testing.
Pipework Preparation
- The separator should be running at full capacity with the manual overboard valve locked closed (To ensure that no discharge can take place overboard) and the ‘test harbour valve’ set to divert all flow back to the bilge as indicated by the light blue line in the image below, this will allow the flow to pass the flow meter.
To identify the target flow rate, it is strongly recommended that the OWS is run, pumping the discharge water into a drum or tank of a known volume, from the harbour valve, to allow you to calculate the actual flow rate passing the paddle wheel flow meter.
- The cover should then be removed from the flow meter by removing the locking screw and turning the yellow bayonet type cover anticlockwise.
Once the cover is removed, you will see two small buttons (White and red) and an LCD display. The display is not backlit so a flashlight may be necessary to see the display if the flow meter is positioned in an awkward position. The flow meter is now ready for calibration.
Flow Meter Calibration
Calibrating the flow meter involves a series of small “trial and error” adjustments. If the Factor number is increased, the flow meter will display a low flow and vice versa.
- To calibrate the flow meter, you should hold the red button for 2 seconds and this will give you access to the menu. Using the white button scroll through the menu until “FACTOR” is reached then press the red button to adjust this setting.
- The screen will then change to a number, using the white button, this number can be adjusted up and down and the red button can be quickly pressed to move to the next digit to adjust. Once you have made a change, press and hold the red button for 2 seconds and you will be asked if you would like to save Y / N. using the buttons, select Yes.
- To exit all menus, press both buttons at once, to view the flow, hold the white button for 3 seconds.
- Further adjustments to the Factor should be made until the flow on the LCD Display matches the flow of the separator. Wait at least 1 minute between each change to allow the averaging to settle before you deem a change is necessary.
- Repeat testing should be carried out to ensure accuracy and reliability of the flow measurement.
- The Flow meter must be accurate to 5% or better, of actual flow rate.
- Record the Factor number in the service report.
The Calibration of the flow meter is now complete and the system is now ready for current loop set-up.
Current loop set up - At the flow meter
You must now set the 4-20 mA signal output of the paddle wheel flow meter. This will scale the current loop so that the SmartBilge plus can interpret the flow rate correctly.
- To adjust the 4mA output (Low end calibration) of the flow meter, you should hold the red button for 2 seconds and this will give you access to the menu.
- Using the white button scroll through the menu until “4 Set” is reached then press the red button to adjust this setting.
- The screen will then change to a number (Flow rate), This 4mA value must always be set to “0.0000L/M”. Using the white button, this number can be adjusted, and the red button can be quickly pressed to move to the next digit to adjust. Once you have made a change, press and hold the red button for 2 seconds and you will be asked if you would like to save Y / N. using the buttons, select Yes.
- To adjust the 20mA output (High end calibration) of the flow meter, you should hold the red button for 2 seconds and this will give you access to the menu.
- Using the white button scroll through the menu until “20 Set” is reached then press the red button to adjust this setting.
- The screen will then change to a number (Flow rate), This 20mA value must always be set the rated capacity of the OWS +10% and rounded up to the nearest whole litre.
For example, If a separator is rated to 1 Ton, This has a flow rate of 16.666 Litres per minute.
16.666 + 10% = 18.3326
Once rounded to the nearest litre, this gives a 20mA Flow value of 19 Litres per minute.
- Using the white button, this number can be adjusted, and the red button can be quickly pressed to move to the next digit to adjust. Once you have made a change, press and hold the red button for 2 seconds and you will be asked if you would like to save Y / N. using the buttons, select Yes.
- Refit the cover once the calibration is completed and the system is tested.
Current loop set up - At the Smart Bilge+
- Now the SmartBilge+ must have the “Flow meter” parameter activated, using the unique PIN number supplied by Rivertrace and the settings must be entered to match the paddle wheel settings, as below
- Settings for the flow meter parameter can be found within the “Accessories” menu under “Flow Meter”. The adjustable options for this accessory are:
- Set 4mA
This is the low-end scaling of the 4-20mA flow meter and must always be '0'.
- Set 20mA
This is the High-end scaling of the 4-20mA flow meter. This sets the span of the current loop between your Smart Bilge+ and Flow meter. This 20mA value must always be set the rated capacity of the OWS +10% and rounded up to the nearest whole litre, to match the 20mA (To match the value used in the flow meter current loop set up at the flow meter).
- Set Max Flow
This is the alarm point for the flow meter. If flow is detected above this rate, the alarm will be triggered, and discharge prevented. (Typically set to the maximum flow possible at the flow meter and rounded up to the nearest Litre).
- Set Flow Log interval
Whilst flow is detected, the Smart Bilge+ will record log entries periodically. If set to 0 seconds, this effectively deactivates periodic logging. For maximum flow recording accuracy, Rivertrace recommend setting this log interval to 10 seconds, meaning a log will be generated at 10 second intervals throughout the discharge. - The System is now ready for testing.
Testing
To test the flow meter set-up on your Smart Bilge+ you must continue to run the OWS in recirculation as described in the Pipework Preparation step.
- Whilst the OWS is running like this, enter the Smart Bilge+ Customer menu, find "View Inputs" and select.
- Scroll down to find "View Flow" .
- Check that the flow rate displayed matched the flow that is actually passing the paddle wheel flow meter.
- Vary the flow that is passing the paddle wheel flow meter and check that the flow rate displayed at the Smart Bilge+ remains accurate throughout testing to <5%.
- Stop the OWS, ensure all pipework is refitted back to working conditions, reseal the flow meter enclosure and tidy work area.
- Complete the Flow meter calibration certificate, supplied with your Flow meter kit.