Abstract

Studies of ESD (Electro static Discharge) fuel system in order to improve safety and regulatory level of domestic cars in Arvand Pishro Company:

Electrostatic phenomenon

The study of electrical loads and the forces acting between them in the science of physics is called the electrostatic phenomenon. This phenomenon is caused from the forces that exert electric charges on each other. The electrostatic forces are dominant forces in the interaction between particles at interatomic average dimensions. From another perspective, imbalance in surface charge of objects exhibit attractive or repulsive forces. This surface charge imbalance, which yields static electricity, by contact and then separating the two surfaces with different materials, can be generated by phenomenon of electrical contact charging and the triboelectric effect. Rubbing two nonconductive objects generates a large amount of static electricity. Usually insulators, e.g., substances that do not conduct electricity generate good surface charge and keep well. Examples of such materials include rubber, plastic and glass. Conductive material, except that, for example, a metal surface is affected by liquid or solid insulators, rarely generate charge imbalance. The charge that is transmitted during electrical charging is stored on the surface of objective. Electrostatic discharge is briefly called ESD.

The risks of electrostatic phenomena

The fuel system of vehicles is made up of different parts. The fuel tank, fuel filler pipe, fuel filter, fuel pipelines, steam discharge pipes, gas stations, etc. All of these parts have static electricity when the vehicle is moving and transporting fuel to the engine. Now the reasons for the creation of the electricity in the car are mentioned:

• Movement and the fuel flow within the fuel system
• Friction between the parts in the car
• induced charge by other parts being electrically charged

In 2010 in Germany and several neighboring countries, several fires of vehicle  during refueling took place that after the reviews conducted by automakers, it was revealed that the reason for the incidents was static electricity generated in the fuel system parts. When refueling, being close of the fuel nozzle to the vehicle frame causes the evacuation of the charge in inductive way (spark) that the  existence of large amounts of gasoline vapors around nozzle strengthens combustion and fire likelihood  and could lead to loss of human lives. Other factors that automakers discovered in their research and observations  was that the  number of accidents in winter is more than warm seasons. After Studies, they concluded that due to the high speed of static electricity on clothes made of wool and the use of these clothes in the cold season, the possibility of discharging to the vehicle and the ignition at refueling time is high. All these factors caused the automakers to design the fuel system in such a way that any static electricity  is discharged before refueling. So routes for the transmission of electricity to the points of “Connect to body of cars” should be used (For example, in cars, the whole static electricity generated to the car’s negative battery end is transmitted.) Due to all the above, in recent years, electrostatic  loads discharge has become  one of the most important issues of vehicle design and fuel systems and in various standards including Iran’s national standard the requirements have been set for it that some of these standards are as follows:

• _{–      PSA B220210}
• _{–      European Directive 2000/8/CE}
• _{–     SAE J 1645}
• _{–     ASTM D4865-98(2003)e1 Standard Guide}
• _{–     ISIRI 6480}
• _{–     ECE R34}
• _{–     ۷۰/۲۲۱/EEC} 

According to these standards, the upper part of the Fuel filler pipe should be made of conductive material to transfer the static electricity to connection points to the vehicle body. Also no contact between metal parts of fuel nozzle with vehicle is allowed.

According to the requirements of using Euro 4 fuel in the country and increased risk of fire by making these changes, lack of electrostatic discharge paths in the fuel system of cars is a threat to the lives and property of people and you need to do necessary measures to fix the problem on older cars as well as the design of current products should be updated.

The benefits of polymer tank than the metal tank

The fuel tank

Tank is called to petrol storage compartment in vehicles. This piece is in the lower part of the vehicle and is in the safety components family. This piece must have good mechanical resistance against impact and in the event of a disaster gasoline should not leak into the environment. Given the required performance, the fuel tank must have the following characteristics:

• A secure compartment for storing petrol.
• When filling petrol in this case it should not create sparks and flow.
• The case should accommodate a certain amount of gasoline without any leakage.
• Characteristics of tank volume than gasoline height should be considered.
• Tap and vapors route for arrival and departure of gasoline from the tank in this equipment should be considered.
• fueling the engine by a gas station is made from this compartment.
• It should have high resistance to environmental conditions as well as a variety of possible fuel quality and additives at the entire life of the vehicle. In the automotive industry two types of tanks are used in the design and manufacture of fuel systems. The first group is metal tank that produces the metal fuel tanks using sheet metal forming. The collection is made of stainless steel and connection of components is done with electrode welding. The second group is plastic fuel tanks. The production technology of these fuel tanks is «Blow Molding» and has different production methods. Plastic tanks are usually made of heavy polyethylene and components of these fuel tanks are connected by plastic welding.

Regarding the use of plastic and metal fuel tanks in both Europe and America according to available benefits use of metal fuel tanks in modern automotive design is outdated and almost entire of plastic fuel tanks are being replaced as new and original technologies and only in some cases that circulation of producing a type of vehicle is very low by taking specific measures and accepting limits on design and materials metal fuel tanks are used.