Why electrostatic charge should be prevented by a monitored grounding system? Understand electrostatic ignition hazards and avoid them in compliance with best practice. Download technical article now!
During loading and unloading of flammable liquids, atmospheres with explosive gas-air mixtures may arise in the working environment. Because of these hazardous atmospheres, precautions should be taken to, amongst other things, avoid the ignition risks of electrostatic charge.
The discharge resistance, i.e. the resistance of the earth connection of the object, has significant influence on the potential discharge energy of a possible spark discharge. This resistance must not exceed a certain maximum value, since otherwise a safety risk arises in the explosion-endangered area.
Based on scientific calculations, the limit value of the permissible discharge resistance is set at 106 Ω, accepted and implemented in the standards of TRGS 727, CLC/TR 50404 and IEC TS 60079-32-1:2013.
Assuming a worst-case scenario with the most unfavorable values of these variables, the maximum discharge resistance Rmax is calculated as follows:
The mere knowledge of the need for a discharge connection with a maximum resistance of 106 Ω is not sufficient to ensure safety in the working environment.
Accordingly, the mentioned policies and best practice recommendations demand for a monitored grounding solution (such as Grounding Control Device EKX-4) that checks the established connection during the entire process and ideally has electronic control outputs, to initiate countermeasures in dangerous situations.
You can download the entire article “Best Practice for protection against electrostatic charge” with illustrative example calculations and more detailed information on minimum ignition energies in potentially explosive gas atmospheres by clicking here.