Rugged and Highly Accurate; Verification of Refueling Stations for Natural Gas

Natural Gas (methane) has developed to an attractive alternative vehicles fuel. Pioneering the development of a practicable distribution network of natural gas for vehicles (NGV) in Switzerland, Apex is providing consulting services, NGV refueling equipment and maintenance services. We have joined Ueli Oester - Founder and General Manager, Apex - on a planned verification and calibration of a nearby refueling station. On such a call, he relies on METTLER TOLEDO rugged high accuracy instruments.

After years of experience in the natural gas for vehicles (NGV) environment, Ueli Oester started a business in Switzerland as a supplier of NGV refueling equipment (compressors and dispensing systems) and as a service partner to the gas industry and the refueling stations operators. One important service provided by Apex is the verification and calibration of dispensing systems to bring them in conformity with national weights and measures legislation. The flow of gas dispensed to a car is measured using the Coriolis principle. Bringing the measurements of a mass flow meter in compliance with national and international standards (OIML /NTEP) requires a high accuracy scale and a set of approved calibration weights
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10:00 AM. We meet the weights and measures officer of the canton authorities in front of the dispenser. The service trailer of Apex contains 3 gas bottles made of high performance composite material, a KB60 scale and an IND429 display unit of METTLER TOLEDO.

Portability and Ruggedness
Mr. Oester explains: “Mobility is critical to us. The weighing system must be portable and it must be rugged. Our business is based on availability and proximity and it takes place independently of the weather; frequently this means wet and dirty conditions. Furthermore, the scale must be transported over kilometers of bumpy roads, packed, unpacked and installed, almost a 100 times per year”.

Accuracy and Scale Performance
Beginning with the verification process, the weights and measures officer verifies the KB60 using his own set of OIML/NTEP weights. Ueli Oester points at the stable weight value displayed on the IND429: “Check this! 6 years on the road and no deviation.” He explains that he verifies the scale regularly according to a procedure responding to the new GWP® guideline recently introduced by METTLER TOLEDO. Functional tests warrant reliable measurements.

The verification of the NGV dispensing system consists of 2 complete and one partial bottle filling. Once filled, the value displayed at the dispenser is noted. The bottle is placed on a small hand cart and transported to the scale that Ueli Oester installed nearby. Moving the filled bottle (60 kg) from the cart to the scale causes mechanical constraints that the scale is perfectly able to withstand. However, particularly when an instrument is submitted to varying conditions of usage or mechanical constraints, it is important to verify it on a regular basis.

Predictable Accuracy and Performance for High Availability
The General Manager of Apex explains that the verification of a NGV dispensing system must be fast: a refueling station that is unavailable, even for few hours, will cause customers to search the next refueling station around the block. This means lost business. One more reason for choosing METTLER TOLEDO’s KB60 with its rugged and easy to use design.

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