Monday, October 27, 2014

Overview About The Detonation Arrestor

By Young Lindsay


Basically, hydrocarbons are flammable but the levels in which they burn can be figured and calculated and thus it may be controlled as well with the appropriate ratio of it mixed in with air. With this in mind, combustion may be stopped depending on the environment it is in. This process may be called as deflagration which means burning down the flames.

The Clean Air Act of the United States have pushed industries to properly contain the combustion of gases and liquids in their factories. They need to have it controlled and ensure safety for managing these hazardous materials. With this, the invention of a detonation arrestor is made to provide for this.

Nicholas Roussakis in 1990 was able to invent these Flame Arresters or Arrestors as the initial device. Its mechanism would burn down the ignition that happened in a tank or pipe to prevent it from going further to the source, therefore, preventing it from any huge explosions and damages. Although the detonator is different from a regular flame arrester.

For the detonation, it is built in order to manage high pressures like 1,500 psi or 10 MPa and that it travels through the pipes in a supersonic speed which is about 2,500 meters per second. Generally this works by placing this device in between pipes to make a demarcation in cases of ignition on either side and to stop it from further burning. Although it still allows flow of the gas between the two sides.

This device is passive and the parts it has are non moveable which means that when it is installed, it would work right away. The core of the device is made of thin layers of metal ribbons that are fashioned in waves and crumples. What it does is extinguish the flames in those tight spaces but still lets gas to freely flow.

There are studies on the limit of these hydrocarbons up until which point of the ratio between them and the air composition for them to burn and stop. This is called their Lower Explosive and Upper Explosive Limits or LEL and UEL. The tests conducted would help determine up to which point to the metal ribbons should be compressed in order to work.

The LEL is the first start of the hydrocarbon and air composition where it starts small and increase and up to which percentage it would begin burning, while the UEL is the percentage to which it stops after increasing it further. So the air and the hydrocarbon percentage would be recorded appropriately depending on which point it burns and stops. With these calculations, the arrestor is made according to it.

In an example with Methane gas, the LEL it has is about five percent. This means at five percent methane and ninety five for the air, it starts burning. This then stops when it reaches fifteen percent. But there are cases where the gas would still combust even with zero oxygen composition in the air.

The use of this device with its mechanism is highly important in industries where they are dealing with dangerous gases and liquids. These industries call it their vapor control system. This makes sure that the safety of everyone working and the surrounding area would be maintained.




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