Preventing oil storage tank overfill hazards with a more reliable high level alarm: Application of the Month

Refineries take advantage of storage tanks of all shapes, sizes, and designs. The type of tank used is typically determined by what product is stored inside.

Floating roof tanks, for example, are commonly used to store large volumes of petroleum products with low flash points. The roof floats on the surface of the stored liquid, and the roof rises and falls with the changes in liquid level.

The tank’s floating roof helps to greatly reduce product loss from evaporation, reduce any harmful emissions or air pollutants, and prevent product contamination from outside sources. A floating roof has the added benefit of eliminating vapor space above the liquid, which reduces the chances of an explosion. A roof does not, however, prevent overfilling a storage tank.

Monitoring level to prevent overfilling in these tanks has traditionally been done manually with a person regularly inspecting the tanks or using a mechanical float system. Both methods work, but not without their troubles. People can’t single-handedly, constantly monitor the level in multiple tanks, and floats routinely get stuck, both of which result in all-too-familiar measurement errors. 

VEGA representatives have helped countless refineries avoid this scenario using non-contact 80 GHz radar. The VEGAPULS 64 uses a high-frequency, 80 GHz signal to measure continuous liquid level. The 80 GHz frequency delivers a narrow signal, allowing the radar to make an accurate measurement close to the edge of the tank and without the need to install target plates on the roof.

Mounting the radar near the edge of the tank makes for an easier installation, especially when swapping out a new radar where an old float used to be. Other radars using lower frequencies would need to be installed elsewhere since they’re more likely to experience interference from the tank wall while the VEGAPULS 64’s narrow beam can reach the tank roof without interruption.

Making refineries safer

Automating this measurement with a mA output from a transmitter tied to a high level alarm eliminates measurement errors and provides a reliable safeguard against overfilling, creating a safer environment for everyone.