An Underestimated (Ignition) Hazard: Electrostatic Charge
Published: Date, June 9, 2021
Position: Digital Marketer
Dissipation: An absolute must-have for conductive objects
To both avoid and safely dissipate hazardous electrostatic potentials, EN IEC 60079-32-1 „Electrostatic hazards, guidance“, NFPA 77 „Recommended Practice on Static Electricity“
and local technical regulations for hazardous substances contain a range of different recommendations and regulations. These relate to different aspects such as safe surface limits for insulating materials in hazardous areas, special requirements regarding pneumatically conveying bulk goods, recommended hose types for transporting liquids, the maximum permissible dissipation resistance of work clothing, and specifications for wet cleaning of surfaces. In this respect, the regulations for all conductive equipment and objects stipulate that grounding or potential equalisation connections must always be used, in order to restrict the charge to a non-hazardous extent. Electrostatic grounding is considered to be guaranteed if the resistance to ground is less than one MΩ.
Passive grounding – restricted safety for mobile containers
In principle, the required electrostatic grounding can be implemented using simple cables and suitable clamps. However, especially in areas where mobile containers such as tankers, tank wagons and FIBCs (Flexible Intermediate Bulk Containers, also known as “big bags”) of combustible materials are filled or emptied, passive grounding is not without risks. Frequent connection and disconnection of the clamps, grinding contact with the floor or accidentally rolling over the electrical lines in a vehicle can all subject the components to high mechanical load. Even minor damage to cables or contact elements can render the safety devices ineffective. Furthermore, corrosion, dirt or coatings can impair the conductivity between the clamp and object to be grounded. In the case of passive – i.e. not actively monitored – grounding, however, there is a significant risk of interruptions in the dissipating connection going unnoticed, meaning that safe dissipation of electrostatic potentials cannot be guaranteed.