Technical Committee Process Safety

Explosive Gas Area Classifications at Storage Tanks

In this report a scientific investigation on the emission behavior of a single-hull floating-roof tank for commercially available gasoline is documented. The tank has a capacity of 12.000 m3 and stores the blend Super E5. Since the tank is not a closed system the non-zero probability of the formation of ignitable concentrations of flammable gases results in accordingly classified explosion zones for the tank and surrounding area. The actual explosive gas area classification conformable to TRGS 509 represents the state of the art. A representative single-hull floating-roof tank was monitored using a network of IR-transmission detectors. Using the API 2517/2519 and the VDI 3479 standard, an emission expectation was estimated. The aim of the project is to measure the actual emissions for verifying, if the explosive gas area classification is plausible or overly conservative. From an evaluation of the measured data it can be concluded, that the explosive gas area classification seems overly conservative, especially in the retention area and at the dike which are classified as zone 1.