Static Electricity Basics
Where does the static electricity come from?
Static electricity is generated when a low conductivity fuel like petrol flows in a non-conductive pipe. Negative charges accumulate on the pipe wall and positive charges are carried away with the fuel. This charge separation is a similar to what happens when two non-conductive materials are rubbed against each other. Try rubbing a balloon against your skin or hair to experience electrostatic charging.
Since the non-conductive pipe cannot dissipate or lead away the charges they accumulate on the pipe wall. More charges are generated with low conductivity fuels, high flow velocities, turbulence cause by elbows, flame arrestors, filters etc. and by any impurities in the fuel. Tests on non-conductive pipes have shown that charges of 90,000 V can occur.
Click to play the animation of charge generation – Principle 1
The charges are not evenly distributed along the pipe wall, but dependent on the fuel flow and turbulence in the pipe. Discharges can occur between the pipe wall and a grounded object (metal flange or similar), between the pipe wall and the fuel or between differently charged areas on the pipe wall.