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National Measurement Institute

Fuel instruments

The Licensing team is pleased to provide you with updates on topics relevant to your work as a servicing licensee.

We welcome your feedback and urge you to contact us with your ideas or queries. This will help us to prepare future updates. Contacting us is easy!
Simply call our hotline: 1300 686 664 (press option 2) to talk directly to one of our licensing officers or email us at

National trade measurement inspectors are currently not opening cabinets for fuel dispensers when conducting tests.  This means that if a fuel dispenser has been tested and subsequently taken out of service due to non-compliance such as being outside MPE (maximum permissible error), the inspector will not be able to remove the verification mark from inside the dispenser.

If you are contacted by a trader who has been advised that an instrument has been taken out of service by a National Trade Measurement inspector, please remove and destroy the verification label when rectifying the issue and reverifying the instrument.  A new verification mark will need to be applied. Please contact if you require further information.

Collapsed - Flow measurement and its impact on the fuel industry

Millions of dollars worth of hydrocarbon fuels, as well as other liquids and gases are bought and sold every day. The quantities of these commodities are usually measured by flowmeters as they flow through delivery pipes. The diversity of flowmeter types and the range of flow rates — from a few litres per minute to thousands of litres per second — make supporting Australia’s flow measurement infrastructure a major task.

Most flowmeters used with liquids are calibrated using a prover that passes a known volume of a test fluid with suitable properties through them. The prover volume is determined using water in place of the test fluid and the volume of this water — given the known density of water — can be measured by weighing.
Calibrating flowmeters for gases requires more complex approaches because of the low density and compressibility of gases.

To establish standards for gas flow, a bell prover is used to pass a known volume of gas at a known temperature, pressure and flow rate through devices known as sonic nozzles. These are smooth-walled holes and operate so that the velocity of the gas flow in the hole is equal to the velocity of sound. Under these conditions the flow rate depends only on the upstream temperature and pressure of the gas. Sonic nozzles calibrated in this way make excellent working standards for the calibration of other gas flow instruments, since larger gas flows with accurately known rates can be established using several nozzles in parallel.

Collapsed - Re-verification as a result of adjustment or repair

The information below will help verifiers to decide whether a measuring instrument needs to be verified after adjustment or repair.

Non-compliance issues that are not considered to affect metrological peformance of measuring instruments:   

  • Environmental parameters outside those permitted in the certificate of approval.
  • Faulty auxiliary indicating or printing device.
  • Faulty keypad buttons.
  • Faulty LCD displays - missing segments.
  • Incomplete details on instrument display (missing decals).
  • Incorrect, incomplete, illegible or missing data plate.
  • Unstable installation - instrument not securely fixed.
  • Faulty anti-drain valve.
  • Faulty delivery hose.
  • Faulty motor or pump.
  • Faulty nozzle. 
  • Faulty individual segments in a display (electromagnetic type).    
  • Instrument used on non-approved liquid.
  • Leaks in pipe work upstream of meter.

Re-verification will not be required. After repair the instrument can be used for trade.     


Non-compliance issues that are considered to affect metrological peformance of measuring instruments:

  • Faults in electronic circuit boards.
  • Faulty LCD displays - unreadable.
  • Incorrect software version in use.
  • Price computing errors.
  • Accuracy and/or air elimination in excess of the MPE.
  • Accuracy of preset incorrect.
  • Faulty interlock.
  • Faulty low-level device.
  • Faulty non-return valve.
  • Faulty conversion device.
  • Leaks in pipe work downstream of meter.
  • Meter creep.
  • Outside flow rate range.
Re-verification will be required. The previous verification mark must be removed or obliterated and after adjustment or repair the instrument must be re-verified.


Collapsed - Fuel dispenser serial numbers

NMI’s undertakes various compliance activities to help make sure fuel dispensers are providing accurate measurement.

When inspecting an individual instrument, there is a benefit in being able to review the performance history of the individual instrument.  Being able to identify the instrument and to record the results of the test against the individual instrument is therefore necessary to develop an instrument’s performance history.

Fuel dispenser manufacturers do not have an industry standard for fuel dispenser hose numbering. However every manufacturer does have a system for identifying individual fuel dispensers and the marking requirements are set out as part of the pattern approval process.

The Fuel Dispenser Numbering Guide outlines how to record measuring instrument serial numbers for various fuel dispensers depending on the manufacturers numbering system (as detailed in the guide). It is important that the recording of measuring instrument serial numbers is consistent amongst verifiers and inspectors as the data provided is used by NMI to identify instrument performance trends and plan inspection activities.

Collapsed - High flow fuel compliance

NMI has a number of programs in place to identify potential compliance issues with measuring instruments.

For example, NMI inspects high-flow fuel installations using NMI’s bulk flowmeter truck to assess the level of compliance for bulk fuel sales in local and accessible remote locations.

Generally NMI finds that flowmeters are measuring correctly.  However we do come across non-compliances such as not having leak detectors fitted on submersible pumps.  We also occasionally find control systems that are either not approved, have not been marked with a Pattern Approval number or have not been verified.

Please review your training and procedures to make sure equipment including control systems are being identified appropriately.  Some information is provided below about flowmeter safety features.

You can also contact the licensing team if you have any questions about the requirements

Collapsed - Use of flowmeter safety features not in certifications of approval

Some bulk flowmetering systems have safety features and devices that have been installed downstream of the meter or transfer point to comply with safety design standards or procedures.  However these features may not be described in the certificate of approval.

Some examples of safety features may include pressure or thermal relief valves, debris filters and sample collection devices (this type of device can have an impact on the metrological performance of the instrument and must therefore be installed in a manner that does not allow for a sample to be taken at the same time fuel is being delivered to a purchaser). Safety features and other non-metrological features are often not covered by OIML recommendations or described in certificates of approval.

In some circumstances bulk flowmetering systems for liquid hydrocarbons can be installed with safety features which allow measured liquid to be diverted downstream of the meter without specific mention in the certificate of approval.  However any diversion of flow to an alternative outlet must be apparent. This can be achieved by using a physical barrier, visible valves or other indications as to which outlets are in operation.

In the case of pressure or thermal relief valves, the opening pressure must exceed the maximum approved operating pressure for the flowmetering system.

Bulk flowmetering systems tested in accordance with the relevant NITP shall be tested within the approved operating conditions and shall comply with all relevant criteria, including MPEs. Please contact the licensing team if you encounter a situation where non-NMI design requirements may have implications for the certificate of approval or test procedure and we will follow up for you.

Collapsed - Calibration of hydrocarbon flowmeters for the fuel industry

It is essential that flowmeters used for metering the flow of LPG, diesel and petrol are accurately calibrated so that fair and reliable transactions can take place at all levels throughout the distribution chain.

To assist in maintaining accuracy the National Measurement Institute's (NMI) facility at Londonderry, in Western Sydney, provides testing and calibration services for LPG, diesel and petrol flowmeters.

The Londonderry facility has the capability to circulate propane or butane through a 40 L piston prover at flow rates of up to 1700 L/min, and provides calibrations directly traceable to Australian primary standards for mass, density, temperature, pressure and time.
For petroleum meters, test fluids known as NORPAR and D130 (which have viscosities and densities similar to petrol and diesel fuel respectively), are circulated through a 60 L piston prover at flow rates of up to 4000 L/min.

Both the LPG and liquid hydrocarbon systems provide compensated flow rate uncertainties of under 0.03%. Gravimetric testing of driveway flowmeters is also conducted at the Londonderry facility. The capability to calibrate CNG flowmeters, at mass flow rates of up to 100 kg/min, will be commissioned in the coming year, depending on demand for this service.

The team at NMI is focussed on providing a complete service package which incorporates:
  • fast turn-around times
  • technical advice on flow metering issues
  • fully automated computer control, allowing rapid and extensive testing of repeatability and linearity
  • flow rates up to 1700 L/min for butane and propane and 4000 L/min for diesel and petroleum substitutes
  • measurement uncertainties as low as 0.03%
  • capability to control both the flow rate and the meter pressure independently and accurately, thereby allowing a thorough assessment of the meter performance
  • direct traceability to NMI’s primary standards of measurement of mass, density, temperature, pressure and time
  • gravimetric testing of driveway flowmeters
  • capability to calibrate CNG flowmeters at up to 100 kg/min.

For further information or advice

Calibration Coordinator
Phone: +61 2 8467 3836

Collapsed - Technology Profile: diesel exhaust fluid (e.g. AdBlue) dispensers

Newly manufactured diesel powered vehicles have a selective catalytic reduction (SCR) process to reduce the level of harmful nitrogen oxides being emitted.

Verifiers may be asked to verify the dispenser or bulk flow metre used to supply the diesel exhaust fluid (DEF) used in the SCR process.  DEF is widely available across Australia and is typically marketed as ‘AdBlue’, a solution of 32.5% aqueous urea and 67.5% demineralised water.

How does the SCR work?

A catalytic converter in the vehicle exhaust system mixes the solution and exhaust gases to convert the nitrogen oxides in the exhaust into nitrogen and water.

A gaseous reductant such as anhydrous ammonia, aqueous ammonia or urea, is added to a stream of exhaust gas and is absorbed onto the catalytic converter. Carbon dioxide is a reaction product when urea is used as the reductant.

With a product like AdBlue the aqueous urea vaporizes and forms ammonia and carbon dioxide. The nitrogen oxides are catalytically reduced by the ammonia (NH3) into water (H2O) and nitrogen (N2), and released through the exhaust.

DEF dispensers

There are various flowmeters approved to dispense DEF (fuel dispensers (5/6A/**) and bulk flowmeters (5/6B/**). Some of the approved patterns include the use of a coriolis type meter (mass flowmeter). Components are generally stainless steel to prevent corrosion.

DEF is generally stored in an above ground tank. The storage tank is filled via a camlock fitting inside the container. As it is not possible to return the product to the storage tank, the site controller should provide a suitable vessel (i.e. clean and empty (plastic) 200 L drum) to enable testing.

Generally, the dispenser nozzles are fitted with a magnetically operated valve in the spout to prevent accidental cross contamination with diesel fuel. In the case of filling a vehicle, the magnetically operated valve is opened once the nozzle passes through a magnetised fitting when inserted into the vehicle’s DEF tank. In the case of testing, a DEF adaptor is required to deliver product into a suitable volume measure (i.e. a 15 L stainless steel conical volume measure).

Testing DEF dispensers

Although DEF is not a petroleum product, the appropriate NITPs to use are 5.1 and 5.2.  A dispenser marked 5/6A/** should be tested in accordance with NITP 5.1. A dispenser marked 5/6B/** should be tested in accordance with NITP 5.2.

These instruments do not have a gas elimination system but rely on a low-level device in the supply tank to prevent air entering the system. NITP 5.1 does not make reference to how a low level cut-off test is performed.  If a verifier needs to assess whether the low-level device is working correctly, apply the test detailed in section 4.11 of NITP 5.2.

Licence class

A licensee only needs subclass 5.1 or 5.2 on their licence to verify diesel exhaust fluid measuring instruments, depending on whether it is a dispenser or flowmeter.