CNG Dispensers

​In 2015 APLMF agreed to summarise the test procedures used in each APLMF training course and then to survey its members to validate the test procedures and to provide some quality control. The validated test procedures will be later used to develop eLearning modules. 

The summary test procedures are provided to guide economies wishing to follow OIML recommendations. They contain abbreviated terms and formulae which are defined in the relevant OIML recommendation.

Information relating to bulk fuel meters:
​​SUMMARY OF TEST PROCEDURES USED TO VERIFY CNG DISPENSERS
​Test Name
​Procedures Description
Verification of CNG Dispenser
​Process to inspect whether they comply with the approved pattern, to test to ensure that they are operating within the maximum permissible errors and finally to certify by marking them with a seal. 
Test Method​ 
​While gravimetric testing of CNG dispensers is sometimes used for verification, the disposal of the dispensed gas after testing presents a problem and this method of testing requires the transport of heavy and bulky test cylinders and calibrated scales.

If a master meter in series with the existing dispenser meter is used to meter the gas into a vehicle, the problem of gas disposal and the need to transport test cylinders and scales can be eliminated. The following information describes the master-meter method of CNG dispenser testing.
General safety requirements
Due to the highly flammable nature of the CNG and the movement of vehicles during the test, the following preparation is recommended, as to reduce potential risk, before any testing is commenced:
  1. Ensure that a suitable fire extinguisher is available.
  2. Keep ignition sources away e.g no smoking, engine and cell-phone off.
  3. Allow proper ventilation at the vicinity of the test site
  4. Position safety cones or bollards at suitable position at the test site
  5. Ensure proper grounding if portable cylinder is used
Required equipment​
The following equipment is required to carry out verification of a CNG dispenser.
  1. Master meter, having a valid calibration certificate and traceable to the National Metrology Institute.
  2. Data sheet, calculator
  3. Appropriate hoses and fittings
Visual Inspection​
  1. Check that access to the metrologically affected working parts, adjustments and programming are effectively prevented by sealing arrangements as approved by the authority
  2. Check that the dispenser is using the International system of units for the register or display. The display of total delivery, total sale and unit price shall be fully visible.
  3. Check that the hose is in reasonable condition and is not badly chafed, split, worn, collapsed or bulging.
  4. Check that the dispenser is clearly and indelible marked in such a way as to be easily readable and the following information should be included:
  • manufacturer’s name or registered  trademark
  • model or type designation
  • serial number
  • approval number
Performance test procedure​
  1. ​Turn the master meter on and allowed to warm up for about 15 minutes. 
  2. Check and adjust the master meter zero. Zero the dispenser totaliser by pushing the reset button on the display.
  3. Plug the dispenser nozzle into the master meter
  4. Fill the next vehicle available
    1. Note: minimum size of fill for a test is 3 kg
  5. Record the measured value displayed on the dispenser and the value indicated by the master meter. Calculate error for dispenser as follows:
    1. \[Error (E)=\frac{M_d-M_t}{M_t}x100\] ​​​
      1. Md  = mass of CNG indicated by master meter (kg)
      2. Mt = mass of CNG indicated by dispenser ( kg)
  6. Take at least 4 reading (4 runs); the minimum size of fill for a test is 3 kg.
    1. The error must be within  + or - 2.0 %. If the dispenser flowmeter is to be adjusted, the new frequency (or K-factor) can be calculated using the following formula:
\[New frequency = old frequnecy  X \frac{average (mass  indicated  by  master  meter)}{mass  indicated  by  dispenser}\] ​​
SUMMARY OF ECONOMY REPORTS
This report is unavailable for CNG Dispensers. 
​​ SURVEY RESULTS ON ADOPTING CNG DISPENSERS TEST PROCEDURES
Test name
Total economies surveyed
Adopted
Not implemented
Economies not responded
1. Verification of CNG Dispensers
19
13
1
5
2. Test Method
19
13
1
5
3.General safety requirements
19
14
1
5
4. Required equipment
19
13
1
5
5. Visual Inspection
19
14
5
​6. Performance test procedure
19
12
2
5
​Economies responded
Australia, Canada, Cambodia, DPR of Korea, Hong Kong  China, Indonesia, Japan, Malaysia, Mongolia, New Zealand, Singapore,       Chinese Taipei, Thailand, Vietnam

Economies not responded
China, Philippines, Papua New Guinea, Republic of Korea, United States of America