Portable electronic gauging devices cut VOC emissions

Paul Boughton

Manual gauging is not usually associated with advanced technology nor with reducing VOCs emissions, but recent developments by one manufacturer working in this sector have taken the concept onto a different plane.
When they hear the word ‘manual’ in relation to tank gauging, most people would picture a traditional tape and bob assembly. Although relatively easy to operate, these traditional tape and bob assemblies cannot be used without opening the tanks, and therefore large quantities of VOC can escape during gauging. When tanks are inerted, the gas pressure shall be reduced prior to open the tanks for gauging.
‘Automatic’ equipment would suggest more sophisticated technology linked via remote control system to a computer, and working under closed conditions, ie without VOCs emissions.
The reality is more complex, however. State-of-the-art manual electronic gauges are highly accurate portable measuring instruments incorporating microprocessor control and reliable electronic sensors and can work under totally closed conditions.
The latest examples in the field even use digital signal transmission technology between the unit and the sensor head to improve immunity to electromagnetic fields.
Unlike automatic systems, portable electronic gauging devices (PEGDs) are designed to be used on many different tanks and can be checked in a laboratory independent of the tank geometry.
PEGDs are more reliable than other traditional methods (dipping tape with weight, dipping rods, water finding pastes, glass thermometers, etc), giving more repeatable results.
But until recently their weight was considered a disadvantage, they needed regular re-calibration to ensure that accuracy is maintained, and they were not immune to electromagnetic fields.
The new UTImeter from Enraf Tanksystem SA addresses these issues, and sets new standards in the technology of PEGDs.

No VOCs emissions

In recent years there has been growing concern over the release of volatile organic compound (VOC) vapours, with regard to both air pollution and occupational exposure. New vapour control systems that require closed operation to avoid VOC emissions have been developed and Enraf Tanksystem SA has responded by introducing gas-tight gauges which allow gauging to be carried out without releasing any vapours. The new HERMetic UTImeter is designed to offer fast, accurate and reliable gauging without any vapour release. A compact ball valve, specially designed, is permanently fixed on the tank. The UTImeter is easily connected to this valve via a quick coupler. Then a single penetration of the tank can establish ullage, oil/water interface level and product temperature. All along the gauging process, the system remains tight and the operator is never exposed to the VOCs.
Compared with the current models, the UTImeter is the first PEGD that allows the tape, the sensor or the electronic board to be simply exchanged with no effect on the accuracy of measurement.
The UTImeter does not require any subsequent calibration of the temperature function over time. Each sensor contains a high precision Platinum RTD element. The RTD element signal is digitised, and all errors (offset, non-linearity and drift) are corrected and compensated by a micro-controller directly located in the sensor probe itself. The UTImeter will give the same consistently accurate temperature readings over the life of the sensor.
Moreover, as the RTD element characteristics are stored in the sensor memory and are dedicated to each sensor, changing a sensor does not require a new calibration.
That means the units used onboard vessels by the crew, by vetting inspectors, or the ones used at terminals, will always give the same results. This should result in reducing the time consumed in reconciling figures between the different parties involved in cargo inspection operations.
This will also give the owners more flexibility to optimise their pool of PEGDs, as exchanging parts between units will not downgrade their individual accuracy.
It should be noted that PEGD accuracy should still be verified periodically where the equipment is operated within an ISO9001 or equivalent quality assurance system.
The UTImeter is light. Compared with the current units available on the market, the UTImeter weighs between 30 and 40percent less, and is 15percent to 25percent less bulky. Depending on the model, its weight varies from 3,4kg to 7,5kg.
To achieve these improvements Tanksystem has used technologies never used previously for PEGDs: the aluminium housing is injected instead of cast, a lot of parts are made in high tech plastics that are unaffected by contact with petroleum, solvents and chemicals, and the measuring tape is thinner than before, just to mention some of the improvements.
Tanksystem designed the UTImeter based on feedback from end-users, so it is lighter, easier to handle and operate, and simpler to clean and maintain, while still achieving the highest standards of measurement accuracy.

Immune to electromagnetic fields

Most PEGDs are not immune to electromagnetic fields, because the measuring tape can act as an antenna and the transmission of the signal from the sensor to the processor/display unit can be affected by interference.
Thanks to its new digitised transmission of the signal from the sensor to the display, and other protective special features, the new UTImeter fulfils the requirements of the EN50081 (emission) and EN50082 (immunity) standards for electromagnetic compatibility.

André Odermatt is with ENRAF Tanksystem SA is based in Bulle, Switzerland. www.tanksystem.com