Function of Spark Arrester for Fuel Tank of Diesel Generator

The fuel tank spark arrester is an important safety device installed on the fixed fuel tank of the diesel generator, which is generally used as a safety device to prevent the spark spread of flammable gas and flammable liquid vapor. Its function is to allow flammable and explosive gases to pass through, prevent external spark from entering equipment, pipelines and containers containing flammable and explosive materials, or prevent spark from spreading between diesel generator and oil pipeline.

1. Fire Arresting Principle of spark arrester

Combustion and explosion are not direct reactions between molecules, but are stimulated by external energy, causing the destruction of molecular bonds and the generation of activated molecules. The activated molecules then split into short lived but very active free radicals, which collide with other molecules to generate new products and generate new free radicals that continue to react with other molecules. When the combustible gas passes through the narrow channel of the spark retardant element, the probability of collision between free radicals and the channel wall increases, and the number of free radicals participating in the reaction decreases. When the channel of the flame arrester is narrow to a certain extent, the collision between free radicals and the channel wall is dominant. As the number of free radicals decreases sharply, the reaction cannot continue, so the combustion reaction cannot continue to spread through spark arrester.

When the flame passes through the narrow pores of the flame retardant core, the sudden increase in heat loss prevents the combustion from continuing and extinguishes it. Therefore, the factors affecting the performance of flame arrester are the size of the pores or channels of the flame retardant layer and the thickness of the flame retardant layer. To understand the basic principle of flame arrester, first of all, we should understand that the combustion of oil and its products, like the combustion of other substances, not only generates a lot of heat, but also generates flame. To cause combustion of combustible materials, not only must the three combustion elements - combustibles, combustibles, and ignition sources be simultaneously present, but each element must have a certain amount and interact with each other, otherwise combustion cannot occur. If the mixed gas is ignited and the heat generated by combustion is insufficient or dissipated too quickly (heat dissipation exceeds heat generation), the mixed gas cannot continue to ignite and the combustion flame will be extinguished.

For this reason, corrugated plate flame arrester is widely used. The corrugated plate type flame retardant core divides the pipeline cross-section into multiple triangular cross-sectional holes that allow gas to pass through but do not allow flames to pass through. The effective fire resistance function of corrugated plate flame arrester mainly depends on the size and length of the hole (i.e. the thickness of the flame retardant core) and the propagation speed of the explosion flame. Well designed flame arrester should have low flow resistance and high fire resistance performance.

2.Type of spark arrester

The spark arrester equipped for the oil tank of diesel generator can be divided into deflagration spark arrester to prevent the spark from propagating at subsonic speed and detonation spark arrester to prevent the explosion spark from propagating at sonic speed and supersonic speed according to their performance.

According to the place of use, it can be divided into vent spark arrester installed in the oil tank vent of diesel generator and pipe spark arrester installed in the closed pipeline system. The venting spark arrester is divided into tube end type and ordinary type, and the tube end type venting spark arrester is deflagration resistant type.

According to its structure, it can be divided into metal mesh spark arrester, liquid seal spark arrester, plate spark arrester, filled spark arrester and corrugated spark arrester. Since the 1950s, metal mesh spark arrester have been widely used. However, this type of spark arrester has a weak ability to extinguish the flame. Only when the number of layers of metal mesh reaches 10~12 can they achieve their expected fire prevention ability. At present, they are rarely used.

The flame arrester is divided into upper and lower shells, and the flame retardant core is placed between the two shells. The shell is cast from aluminum alloy and should have sufficient strength to resist the pressure generated by micro detonation impact. The fire resistance core of corrugated flame arrester is a disc shape composed of thin stainless steel corrugated pipe and flat belt. The fire resistance ability of the triangular hole formed by the corrugated is not only determined by the size of the hole in the section and the thickness of the fire resistance layer.

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