A digital flow meter turns an AdBlue® pump kit into a measuring tool. It shows how many litres went into each vehicle, helps you track use against diesel and makes leaks or waste easier to spot. But a meter that reads a few per cent out gives you misleading numbers every day. The good news is that most K24-type meters can be checked and calibrated on site in a few minutes.
How K24-type meters work
K24 has become a common shorthand for a style of compact digital meter used on AdBlue, water and similar liquids. Inside, liquid passing through the chamber turns a set of oval gears or a turbine. Each rotation produces a pulse, and the electronics convert the pulses into litres using a calibration factor.
That factor is set at the factory, but real-world conditions can shift it. Flow rate, liquid viscosity, temperature and the way the meter is plumbed in all affect how many pulses equal one litre. Field calibration adjusts the factor to suit your system.
Make sure your meter is made for AdBlue. The body and internals should be plastic or stainless steel, not aluminium, which corrodes in AdBlue.
When to check or recalibrate
- When the meter is first installed.
- After changing the pump, hose length, nozzle or filter, all of which can change flow rate.
- After the meter has been dismantled, cleaned or repaired.
- If recorded totals stop matching deliveries or IBC levels.
- As part of a routine check, for example every few months on a busy site.
A general calibration procedure
Button sequences differ between models, so always follow the manufacturer's manual for the exact steps. The general process is the same for most meters.
What you need
- A clean, dedicated container with an accurately marked volume. A graduated measuring vessel of 10 or 20 litres works well. Larger volumes give better accuracy.
- The meter's instruction sheet.
- A way to return the AdBlue cleanly to use, or a plan to dispose of it if there is any doubt about cleanliness.
Steps
- Bleed the air. Run AdBlue through the system until flow is steady and no bubbles are visible. Air in the line gives false readings.
- Check first. Reset the meter, dispense into the measuring container at your normal flow rate and compare the display to the actual volume. If it matches, you do not need to calibrate.
- Enter calibration mode. Usually by holding one or two buttons, as described in the manual.
- Dispense a known volume. Fill the container to the mark at your usual operating flow. Do not stop and start more than necessary.
- Enter the true volume. Adjust the displayed figure to match the actual volume in the container and confirm. The meter calculates a new factor.
- Test again. Reset and dispense another known volume. The reading should now match.
- Record it. Note the date, volume used and result, so you have a history for the meter.
Many meters let you return to the factory calibration if something goes wrong. Check the manual for how.
Keeping meters accurate
- Keep the flow steady. Meters are most accurate within their rated flow range. Very slow trickles or bursts can read differently.
- Filter upstream. Grit can jam gears. An inline filter, often around 10 micron, after the pump protects the meter.
- Stop crystals forming. AdBlue left to dry inside a meter forms urea crystals that can stick the gears. Keep the system full and sealed, and flush with demineralised water if it will sit unused.
- Replace batteries on time. Low batteries can cause blank screens or lost totals.
- Pulse meters for fleet systems. If the meter feeds a fleet management or card system, check the recorded volumes match the display after calibration.
One thing you can do today: dispense exactly 20 litres into a marked container and compare it to your meter's reading. If the difference is more than you are comfortable with, work through the calibration steps above.
How Liquidia can help: Liquidia supplies Piusi K24-type AdBlue meters and complete metered pump kits. See the accessories range for options, and use the AdBlue usage calculator to compare your metered figures against expected use.