While loading or unloading of inflammable hydrocarbon products, it is required to maintain an equal potential between the filling structure and the vehicle body, in order to avoid spark hazard due to electrostatic charges. Grounding Unit checks and ensures that proper grounding of vehicle body is maintained throughout the loading or unloading process.
It consists of a rugged flameproof enclosure, with electronic circuit in it and a crocodile clamp, which is connected to the vehicle. Green and red indicating lamps show the proper or improper grounding condition. Potential-free relay contact outputs from the unit are connected to the local/remote loading control system.
When crocodile clamp of the Grounding Unit is connected to the metal surface of the vehicle body, the device checks the capacitance and resistance of the vehicle towards earth. If the grounding resistance is within the safe limits, the red lamp switches over to green, signifying proper grounding and the internal relay is switched to give potential-free contact outputs to the local/remote loading control system.
In case the grounding loop breaks at any time during the loading operation, the green lamp switches over to red and the internal relay is de-actuated, signalling to the loading control system to stope operation in order to avoid safety hazard.