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Keller pressure measurement technology makes empty tanks a thing of the past

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article image The GSM-3 comprises of a modem and the SB box, to which as many as three Keller pressure transmitters can be connected.

Measurement technology from Keller AG für Druckmesstechnik was employed by a leading filling station operator in Switzerland to update their remote monitoring EasyOil system.

AVIA Osterwalder St. Gallen AG operates more than 120 filling stations in eastern Switzerland, and also sells and distributes motor vehicle and other fuels to corporate and private customers. The company has for several years, deployed the EasyOil system to offer its customers a practical method for remote monitoring of filling levels in oil and gasoline tanks.

To assist with the recent re-launch of the EasyOil system, AVIA called on the measurement technology expertise offered by Keller.

EasyOil comprises of a measurement system that determines the filling level in the oil tank, together with a GSM modem to transmit the filling levels via the mobile telephone network once they have been ascertained. In collaboration with Fredell GmbH Informatiklösungen, an IT solutions provider based in Widnau, AVIA developed the software that enables contracting customers to call up current filling levels and previous purchase orders for their tank installations. Customers are also alerted via SMS or email if the filling level falls below a certain pre-defined limit. By replying to these messages, customers can immediately trigger purchase orders to AVIA.

This service offers far more than convenience for busy private customers who might find themselves returning to an unheated home after a long working day because they forgot to place their fuel order. Most of all, the system offers major economic benefits to facility managers in companies, and for real estate managers who have to coordinate fuel supplies for multiple properties. Gas station operators and their suppliers can also benefit from a system such as EasyOil.

Since the system was launched on the market about 10 years ago, EasyOil has proven to be a win-win model for all, with customers appreciating its convenience and transparency, and AVIA benefiting from long-term customer loyalty in the fiercely contested fuel market.

As part of the technology upgrade, AVIA sought a suitable supplier that could deliver the measuring probes as well as the GSM transmission module, and found Keller, a company that operates across the globe and earns about 10% of its sales revenue from applications that use pressure probes to measure filling levels.

While developing the proposed solution for AVIA, Keller’s pressure measurement experts were able to draw on experience garnered from customers in the water management sector, where similar concepts are used to monitor groundwater and river water levels.

Since the underlying technology is developed by Keller in-house, it is possible for the company to develop special solutions for customers with great flexibility and speed. For AVIA, Keller is producing the GSM-3 variant (modified at the customer’s request), which also offers the option of SMS communication with consumers. Customer surveys have confirmed that this is the most reliable version, and the one preferred the most by customers. SMS messages guarantee that customers are informed promptly; they are also spam proof and can be clearly personalised.

The GSM-3 comprises the modem and the safety barrier (SB) box, to which as many as three Keller pressure transmitters (with voltage outputs of 0,5…4,5 V) can be connected. The box contains three built-in safety barriers. These circuits also make it possible to process the electrical measurement signals to gas stations, where an electrical spark could cause an explosion due to the gases contained in the atmosphere. This is why any pressure transmitter that performs measurements in such environments must be intrinsically safe. The safety barrier limits the electrical power produced by the measurement system within the area subject to explosion hazards (EX area).The GSM-3 may only be installed outside of the EX area. As part of the complete package, Keller also supplies the level sensor cables used to transmit the measurement signals.

Keller uses its intrinsically safe 26 Y Ei level sensor for EasyOil systems at gas stations, whereas the conventional version is used for heating oil tanks in locations not classified as EX areas. Similar to all of Keller’s pressure measurement equipment, the transmitters in these devices are based on the piezo-resistive silicon measuring cell invented by the company’s founder and CEO, Hannes W. Keller.

The slight mechanical deformation caused by the pressure on a piezo-resistive element in the sensor triggers a change in resistance which, in turn produces the electrical voltage that is used as the measurement signal. In Series 26 Y, which includes the level sensor, the temperature error (as it is known) is compensated electronically.

Thanks to Keller’s long years of experience and its highly mature product range, the company can produce the pressure transmitters for the EasyOil system with an excellent cost-to-benefit ratio along with long service lifetime, even in an aggressive medium such as gasoline, because of their robust stainless steel IP68 housing and the silicon measuring cell protected against the measured medium by a stainless steel diaphragm.

Depending on the location where each EasyOil system is deployed, AVIA purchases either the conventional 26 Y level sensor or the intrinsically safe 26 Y Ei version from Keller, together with the GSM-3 transmission unit and the cables. 

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