Old Truth Stands no Longer: How dangerous is splash filling really?

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DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

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Anders Thulin Consulting

Programmed to Receive

Discharges from a plastic box to an earthed probe were used to control if signals appear. It soon turned out that the antenna should be circular and about a meter in diameter. Fortunately this did fit into a test tank suitable for trials. Two different antennas with minor different characteristics were used to obtain reliable results. The test tank (which was 3.56 m high with 2.08 m in diameter) made of stainless steel was borrowed from a nearby chemical factory run by Akzo Nobel.

To calibrate the antennas a coulomb meter was used, installed at the bottom of the test tank. Objects (insulating or conductive) were electrostatically precharged and then lowered down to the probe of the coulomb meter. The readings of the latter were compared with the signals from the antennas and forwarded to the oscilloscope where they could be evaluated.

Setting the Stage

From a small storage metal vessel which was lowered down into the inside of the large tank with a rope, different liquids were allowed to fall down and splash from different heights. The experimental setup was checked by charging the storage vessel filled with conductive tap water to about 10 Kilovolts.

Then the water was allowed to splash 3.5 meters downwards through the antenna assembly and into the receiving vessel. Both one and 10 liters of pre–charged tap water showed strong electrostatic discharges (about 50 times above the sensitivity level of roughly 1 Nano-Coulomb).

Three different liquids were tested, one of them with low conductivity (transformer oil), one with high conductivity (tap water) and one intermediate medium (regular diesel fuel). In all of the 90 experiments with different volumes (one or ten liters), no discharge from the splash filled liquid could be detected. Therefore, the static charge generated by splash filling with a splashing height 3.5 meter must be below approximately 1 Nano-Coulomb, independent of the conductivity of the liquid.

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