Why does the tanker clip the electrostatic grounding clip after it arrives at the gas station?

The electrostatic clamp is used to conduct away static electricity to ensure the reliable grounding of the electrostatic conduction loop.

The explosion-proof electrostatic grounding system of the British Newsengel oil tanker can be adopted, which consists of an automatic monitoring interlocking control system, a portable hose continuity tester and other necessary accessories. Fully provide electrostatic safety protection for tanker and personnel. Beijing Ailida Technical Guidance