Older Petrol-trucks were supplied with a chain or strap to discharge static electricity; this was because natural rubber-tires manufactured prior to the mid 1940's would generate a powerful static charge on the chassis of the vehicle which caused numerous fires during fuel transfer operations.
Modern "Synthetic Rubber-Tire" actually have enough Carbon in the rubber compounds so they conduct enough electricity and any static electrical charge is dissipated back to the road surface directly through the tires. Now therefore there is no longer any need for a dissipation-strap or a Grounding-Chain".
A tanker is used to transport the Petrol from storage tanks to the petrol station.
Tank, Tanker or a Canister.
The flow of petrol
Most likely, this is to discharge any static electricity that the tanker may have accrued during its journey. Such static can be dangerous because it may cause the petrol to ignite; therefore, the wire 'grounds' the tanker (i.e. it allows the electricity to pass harmlessly into the ground) and removes this threat.
It is a ship known generally as a tanker.
Because even if there's a slight static charge in the tanker, it could ignite the petrol and explode. If it's connected to the ground by a wire, then all the static charge in the truck is removed (ie grounding the truck).
I am not sure, I wrote tanker.
it depends on the tanker but usually about 9300 gallons
The oil company who provided the gas/petrol. However, the police would probably guard the tanker until another driver arrived.
Sure, just change the tank and all the plumbing. If you were trying to re-purpose the tank, no, the tank has to survive a 300 psi pressure test
Road tankers are large lorries that carry large tanks that can hold bulk liquids or powder. A milk tanker will carry milk. And an oil tanker will carry petroleum products - petrol, diesel, oil, etc.
I assume you meant measuring the level in an oil tanker making a delivery to a petrol station? The driver uses long metal rods that are dipped through opened caps on the top of the tanker to check the level inside. Note: I assume the metal rods are non-ferous and won't cause a spark, but I'm not sure!