In order and together with the Dutch company I METER the Eng.-Office IMBUS developed a new sonic nozzle test rig for diaphragm gas meters. This should be used for calibration and verification of meters in a manufacturing plant and be laid out for the meter sizes G1.6, G2.5, G4 and G6.
From these facts also the substantial premises for the development resulted. It should be possible a fully automatic and fast test procedure. The necessary times for the leak test were to be optimised and reduced, without injuring however the requirements of the PTB Testing Instructions Volume 25.
A substantial quintessential point was thereby the structure of the sonic nozzle standard. In that case, a complicated nozzle exchange system was not used. Special attention was taken to the requirement, that each nozzle is permanently checked also during the use for possible internal and outside leakages. For generation of the 3 flows of all 4 meter types altogether only 9 nozzles are necessary.
The leak test is divided into 3 check modes
- Examination of the meter bench with the connections
- Examination of the flow pipe work system in front of the meter bench.
- Examination âof the doubles block and bleed âvalve technology as well as the ânozzle bypassâ control
With dividing it was possible to limit the necessary leak test periods of 2 up to 4.5 minutes, depending of the meter type. A substantial point was the use of reference containers.
The test rig was then built in 2008 by the company Akhnaton Ltd. in Sofia. Akhnaton Ltd. took over also the programming of the system control.
The test stand became certified by the Dutch verification authority NMI. The test rig is located in Poland and the diaphragm gas meters, produced under license over there, will be checked in the context of an EU certification in accordance of the MID requirements.