When designing grounding for oil tanks, an issue of the requirements to the design and resistance of the grounding arrangement emerges. You should consider several rules at once which will be discussed below.
The resistance of the protective grounding shall conform to the requirements of the EIC, item 1.7.103, and shall not exceed 10 Ohm, and sometimes even 4 Ohm as per item 1.7.101.
Since the external lightning protection system is mandatory for oil tanks, an issue of choosing grounding system also emerges. In terms of design, according to GOST 31385-2016, item 18.104.22.168, a lower band of the tank wall should be connected via current collectors to the grounding arrangement installed at the distance of not more than 20 m around the wall perimeter but at least four, at equal distances.
The grounding electrode should have a cross-section of at least 80 mm2. Moreover, cross-sections and materials of grounding electrodes and arrangements considering corrosivity should conform to GOST R 50571.5.54-2013.
According to STO-SA-03-002-2009, item 14. 6, the tank protection from electrostatic induction and accumulation of static electricity is provided by connection of metal bodies of the equipment installed on the tanks as well as pipelines introduced to the tank, to the grounding electrode of protection against direct lightning strikes.
If you need to calculate and design the grounding arrangment for oil tanks, contact the ZANDZ Technical Center to obtain calculations free of charge!