Different Fire Indices || overman examination || Mine Environment

*Important fire Indices For Overman exams*

1. Grahm’s Ratio-:

CO produced
——————————-
O2 consumed

Index value:-
Less than 0.5% :- Normal
More than 0.5% but less than 1% :- Existence of Fire
More than 1% but less than 2%:- Fire in advance stage
More than 3%:- Active fire



2.Young’s Ratio:-

CO2 Produced
—————-
O2 consumed

Index value:-
Less than 25:- Normal
25-50:- superficial heating
More than 50:- heating


3.Oxides of Carbon Ratio :-

CO
——
CO2

Index value:-
More than 2:- Normal
2- 13Superficial Heating
More than 13:- Blazing Fire

4. Willet Ratio :-

CO produced %
——————————-
Black Damp + combustible Gas

Index value :-
Ratio increases with increase in temperature


5. Justin & Kim’s Ratio(Hydro Carbon Ratio) :
{1.01(THC)-CH4}1000
———————————-
THC+C

{ THC= Total Hydro Carbon in ppm,CH4 in ppm,C=0.01ppm}

Index Value:-
0-50 :- Normal
50-100:- possible spice of Heating
More than 100 :- Hot Zone



6.Jones & Tricket Ratio :-
[CO2+0.75CO-0.25H2]%
————————————
[(0.265 X N2) -02]%

Index Value:-
Less than 0.4 :- No Fire
0.4 -0.5 :- Methane burning
0.5-1.0 :- Coal,Oil,Rubber is burning
0.9-1.6 :- Timber is Burning
More than 1.6 :- Error in Analysis



7.Carbon-Hydrogen Ratio( C/H ratio) :-

3[CO2+CO+CH4+2C2H4]
————————————- X
0.265N2-O2-CO2-0.5CO+0.5H2+CH4+C2H4

Index Value:-
0-2.0 :- Normal
3.0-4.0 :- superficial fire
More than 5 :- Active Fire
More than 20 :- Blazing Fire