Question

Which one of the following Mine explosions associated with backlash ?

• A. Fire damp explosion
• B. Coal dust explosion
• C. Spontaneous heating of coal
• D. Black damp explosion

Hint:

Think of the difference in burning speed.
A gas explosion is almost instantaneous, like a "bang," which creates a vacuum upon cooling.
A dust explosion is more of a "whoosh," a fast-moving fire that sustains pressure for longer.
The "bang" causes the backlash.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks which type of mine explosion is characterized by the phenomenon of "backlash".

Step 2: Detailed Explanation:

Backlash is the violent rush of air and gases back towards the origin of an explosion.
It occurs after the initial high-pressure shockwave has passed.
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Fire damp explosion: Firedamp is methane (CH\(_4\)).
When a methane-air mixture explodes, it burns very rapidly, creating a high-temperature, high-pressure wave.
Immediately after the combustion, the resulting gases (CO\(_2\), H\(_2\)O vapor) cool down very quickly and contract.
This rapid cooling and contraction create a partial vacuum or region of low pressure at the origin.
The surrounding air then rushes violently back into this low-pressure zone, causing the characteristic backlash.
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Coal dust explosion: This is more of a propagating deflagration (rapid burning) than a detonation.
It produces a sustained pressure wave that travels through the mine workings.
While there is air movement, it does not typically produce the distinct and violent recoil or backlash associated with a gas explosion.
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Spontaneous heating of coal is a process that can lead to a fire or explosion, but it is not an explosion itself.
-

Black damp explosion: Black damp is a mixture of nitrogen and carbon dioxide and is non-flammable. It cannot cause an explosion.

Step 3: Final Answer:
The backlash effect is a distinct feature of a fire damp (methane) explosion.
This corresponds to option (A).