Level measurement inside the Rock

Saab Tank Control has completed the supply and installation of its latest Rex Radar Level Gauges on fuel storage cells located within the Rock of Gibraltar.

The cells, which were dug out of the rock several decades ago, are lined with steel and used to store fuel for the strategic military base. The largest cell is 405m in length and 18m deep.

Precision measurement is vital for this kind of application and Saab claims that TankRadar Rex is the first radar level gauge in the world to be approved according to the new international recommendations for custody transfer OIML R 85 (E) by an accredited laboratory.

The tests undertaken according to OIML R 85 cover a range of issues and are the most arduous performed for a tank gauging system. Accuracy requirements are within +/- 1mm. The performance is also checked under disturbed conditions such as high temperature, thermal shock, effect from hysteresis, EMC disturbances and power interruptions.

The Rex gauges utilise different types of antennae dependent upon the application. For the Gibraltar installation, the latest parabolic antenna was used as this provides a more focused beam thus giving minimum disturbances from the cell walls.

To improve accuracy further, the linearity of the radar sweep is controlled by a digital reference circuit. When measuring under conditions such as those experienced within the Rock, the gauge also uses advanced digital filtering and FFT calculations of the cell profile to deal with poor reflections and disturbances.