Old Truth Stands no Longer: How dangerous is splash filling really?
Coming Full Circle
This is where everything comes full circle in relation to the already mentioned IEC 60079-32-1 Table C2: Single splash filling by itself in the liter-range will not create any electrostatic ignition hazards due to the splashing process.
However, it has to be taken into consideration that precharged splashing liquids do in fact very well create ignition hazards, as they may build up charged slugs of conductive liquids — a phenomenon that was clearly established by the splash filling experiments. Consequently, for a risk evaluation, especially in the Chemical Industry the electrostatic charge generated in filters, pumps, and pipes must be taken into account and evaluated.
A Matter of Scales
Accordingly it can be readily deduced that all liquids in amounts up to at least ten liters, if not precharged by any previous action, will not generate any dangerous discharges when falling down up to three meters by means of gravity. But it is essential to note that the bucket is made of conductive material and reliably earthed.
So the investigations of electrostatic liquid charging by free fall through air are finished in the range of milliliters and liters. The researchers plan to continued them in the range of hectoliters but because of the elaborate process this cannot be scheduled at the moment.