Gas Exam - Part 3

Question 1

What is the ignition temperature of CH4?

Answer 1

595 degrees

Question 2

What is the minimum amount of O2 required for methane explosion?

Answer 2

12.2 % O2

Question 3

What are the legal limits for CH4?

Answer 3

AUX FAN POWER TRIP	2%
DIESEL VEHICLE WITHDRAW	1%
DIESEL VEHICLE SHUT DOWN 	1.25%
NERZ/ ERZ1 INTERFACE TRIP	0.5%
NERZ/ ERZ1 INTERFACE ALARM	0.25%
SHEARER POWER TRIP	2% (CUTTERS @1.25%)
MEN WITHDRAW	2.5%

Question 4

What is the legal limit for CH4 in regards to the main fan?

Answer 4

Not stated in the Regs, but must be done by risk assessment to determine % and the time period that this can occur for. All headings into the main fan shaft must be monitored by CH4 sensor

Question 5

Is CH4 poisonous?

Answer 5

No, but becomes slightly narcotic at high concentrations

Question 6

What are the physical/ chemical properties of CH4?

Answer 6

COT

Slightly soluble in water

Question 7

What is the explosive range of CH4?

Answer 7

5-15 %

Question 8

At what percentage is CH4 most easily ignited on a heated surface?

Answer 8

5-6%

Question 9

What is meant by the term lag of ignition?

Answer 9

The time it takes for a gas to ignite after it has come in contact with the ignition source

Question 10

What is the lag time for 5-6% CH4?

Answer 10

2 seconds

Question 11

How is CH4 produced and where about is it found?

Answer 11

Methane is a seam gas and is liberated from the coal during the winning of coal during production. Also released from cracks, stress panes, slips and faults
Due to it being lighter than air, it is found on the roof and accumulate in high spots and cavities

Question 12

What is the effect of suspended coaldust on the LEL of CH4?

Answer 12

Can lower it from 5% to 0, depending on the coal dust concentration and the coals volatility

Question 13

At what percentage is CH4 most explosive?

Answer 13

9.46%

Question 14

What effect does temperature have on the upper and lower explosive limits of flammable gas/ air mixture?

Answer 14

As the temperature increases, the LEL decreases and the UEL increases

Question 15

What are the physical/ chemical properties of H2?

Answer 15

Colourless Odourless Tasteless

Not readily soluble in water

Question 16

Is H2 poisonous?

Answer 16

No

Question 17

Is H2 flammable?

Answer 17

Yes, flammable range between 4-75%

Question 18

Why is H2 most dangerous (X5) ?

Answer 18

Wide flammable range

Almost absence on the lag of ignition

Instantaneous build up to maximum pressure

Half initiation energy required for CH4

Low ignition temperature

Question 19

Where can H2 be found (X3) ?

Answer 19

Mine fires, Spontaneous combustion, advanced heatings, battery charging stations

Question 20

Where can H2S be found in a mine?

Answer 20

Seam gas where sulphides present in the coal

Stagnant water

Question 21

What is the highest concentration of H2S without causing death?

Answer 21

500ppm – Breathed without causing death. Within half an hour produces serious inflammation of the eyes, palpitations, fainting

Question 22

What are the physical/ chemical properties of H2S?

Answer 22

Colourless, Rotten Egg Smell, Sweetish Taste

Highly water soluble

Question 23

What are the effects that H2S has on humans?

Answer 23

Irritates the eyes & respiratory tract as well as the CNS. In high quantities death comes about through respiratory arrest

Question 24

Is H2S flammable?

Answer 24

Yes 4.3 - 45%