GOOD MOTORING
Shocking situation
Static electricity that builds up in a vehicle as well as the human body during winter can be dangerous while refuelling the car
H. Kishie Singh

In the universe, there are equal amounts of electrons (negative electrical charges) and protons (positive electrical charges). These always try and maintain a balance at all times, and in all places. These should remain static.

Static electricity is generated whenever two materials are in contact with one another. These exchange charge by moving from one material to the other.

This deposits an excess of negative charge on one material and an equal amount of positive charge on the other. As the two move apart (like you getting out of the car), they take their uneven charges with them.

In an attempt to equalise the charges, a spark jumps from one material (you) to the other (your car). If the materials can conduct the electricity generated away (like earthing it), the charge will dissipate and ultimately recombine to maintain a balance. However, if the materials or charges are separated faster, they can dissipate the uneven charge held by the materials, the electrostatic charge builds up. They have to be equalised. The equalising process is a spark.

During winter, air becomes dryer and static electricity in the atmosphere builds up. You can see this when you comb your hair. The plastic comb attracts your hair. When you take off your sweater, you hear a cracking sound. These are electrical charges being released.

The same thing happens when you get out of your car. The upholstery has a high synthetic content, which generates electricity. The slight friction caused by your clothes against the upholstery fabric is enough to cause a spark.

For sure, you have had a slight electrical shock as you get out of your car in the winter months. You may not see it but a small spark jumps from the metal of the car to your finger. When you get out of the car, and put your foot on the ground, you "earth" the change, completing the circuit, and hence the spark.

While sitting in the car, there’s friction between you and the car seat. As you step out, you take half the charge. The static electricity charge generated can be as high as 10.000 V. For most people, the threshold of shock is 2,000-4,000 V. Though you will not feel the spark but you may be able to see the spark. The spark can be very dangerous while refuelling.

During winter, petrol vapours do not dissipate as fast as in the summer.

In the days gone by, petrol pumps were in wide open spaces. New mantras of marketing techniques dictate a full, covered area with 6-8-10`A0pumps pumping petrol into as many cars. The quality of petrol has also improved, (higher octane content), which means that it vaporises faster. In such a completely covered place, petrol vapours will accumulate.

It doesn’t take a very vivid imagination to figure out what a spark will do to accumulate petrol vapours. The Big Bang! One way to make sure you don’t discharge this static charge while refuelling is to earth your car. It’s very easy to do. Take about 40-50 cm of good quality wire. Make a loop at one end, bolt this to one of the many earthing points in the engine bay.

Observe closely under the bonnet, and you will find a wire from the engine block to the car body. There can be more than one such earthing wire.

After bolting it on, make sure that the bolt is securely fixed. Let the rest of the wire just hang loose to the ground. This simple move will take care of the static charge that you and your car generate.

There has been much research into this problem of fires and explosions, read Big Bang, at petrol stations, in the USA. There were many instances where such accidents could not be blamed on smoking or refuelling with the engine on. A static electric discharge was found to be the culprit. Exhaust fans at roof level could be one solution.

May be, major companies will look into this aspect of a possible problem, before it becomes just that. In the meantime, you can also take some preventive measures. Earth your car. Happy motoring.