Presidential Committee contradicts natural law of hydrocarbon explosions.
Posted on December 21st, 2021

Lankaweb

The Committee appointed by President Gotabaya Rajapaksa to probe the recent gas explosions, concluding that the change in the composition of gas was the primary reason for the recent gas-related explosions.

But this conclusion contradicts the basic law of gas explosions. Here is a simple demonstration.

DO NOT TRY THIS AT HOME. The demonstration was carried out in the safety of our workshop in Northolt (UK).

Here is an entertaining example of the effect of the composition of an inflammable gas and air (Oxygen) with (sort of) explosive results.

Before combustion can occur, three conditions must be met simultaneously. A fuel (ie. flammable gas) and air must exist in certain proportions, along with an ignition source, such as a spark or flame. The ratio of gas and oxygen that is required for combustion varies with each type of gas.

Visual example to show where on the scale % of LEL is measured

The minimum concentration of a particular gas necessary to support its combustion in air is defined as the Lower Explosive Limit (LEL). Below this level, the mixture is too lean” to burn. The maximum concentration of a gas or vapour that will cause an explosion is defined as the Upper Explosive Limit (UEL). UEL of Propane is 9.5% Volume while UEL of Butane is 8.4% volume and LEL of Propane is 2.1%volume and LEL of Butane is 1.8%volume hardly any practical difference between propane and butane when it explodes.

Above this level, the mixture will burn, providing oxygen is available, until the concentration reduces to the upper explosive limit. At this point the remaining gas or vapour will ignite, causing an explosion. The range between the LEL and UEL is known as the flammable range for that gas.

This demonstration is used as an example of what can happen in a domestic gas explosion. When the mixture of natural gas and air reaches the correct composition (between 5% and 15% gas) any spark or flame is enough to create a violent gas explosion.

It is the responsibility of the Gas Stove manufacturer to provide safe facilities to prevent a gas explosion in the gas stove. A wide range of propane -Butane compositions are used in the world.

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