A tank truck is often the largest potentially isolated conductor which is brought on site and if incorrectly grounded, may pose a significant ignition risk.

When filling and emptying tank trucks, both CLC/TR 50404 and NFPA77 recommend that fully interlocked static grounding systems are used (see CA09 - Grounding of a tank truck). However, in cases where an interlock is not possible, a self-testing clamp unit provides operator feedback via the LED indicator, ensuring that a low resistance ground connection has been made through paint or rust etc. to the metalwork of the truck chassis. For remote working areas or infrequent operations, battery powered versions are preferred, while if frequent grounding operations are involved, a mains “line voltage” powered unit (fed via a certified Power Supply/Intrinsically Safe Interface Unit) is recommended, and several Monitoring Units may be fed from a common PSU.

BS5958 states that: During loading the vehicle should be grounded .... so that the resistance to earth is at all points less than 10 Ohms (7.2.1)

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