MSHA Explosives and Blasting 3

Question 1

Under MSHA regulations for underground mines, what must be done with all electrical power in an area before blasting begins?

Accepted Answer

Power must be de-energized and locked out in the blast area to prevent stray currents from triggering electric detonators

Answer

MSHA requires de-energizing and locking out all electrical power in the blast area before connecting electric blasting circuits to prevent stray electrical currents from accidentally detonating electric blasting caps.

Question 2

How long must miners wait after a blast before re-entering an area in an underground coal mine, according to MSHA standards?

Accepted Answer

At least 30 minutes, or until the ventilating current has cleared the smoke and fumes

Answer

MSHA requires miners to wait until the ventilating current has removed blasting smoke and fumes, with a minimum waiting period, before re-entering to ensure breathable air and to check for misfires.

Question 3

Which MSHA standard prohibits the use of non-permissible explosives in the working section of an underground gassy coal mine?

Accepted Answer

30 CFR Part 75 Subpart N

Answer

30 CFR Part 75 Subpart N specifically governs the use of explosives and blasting in underground coal mines, requiring permissible explosives in gassy or potentially gassy working sections.

Question 4

What is the purpose of a 'delay detonator' in a multi-hole blast pattern?

Accepted Answer

To fire individual holes in a timed sequence, reducing ground vibration and improving rock fragmentation

Answer

Delay detonators fire in a timed sequence (milliseconds apart), which reduces peak ground vibration, controls flyrock direction, and improves the efficiency of rock breakage compared to instantaneous detonation.

Question 5

Under MSHA rules, who is responsible for conducting a pre-blast inspection to ensure the blast area is clear of personnel?

Accepted Answer

The certified blaster in charge of the blast

Answer

The certified blaster in charge is responsible for ensuring that all personnel have been warned, all access routes are guarded, and the blast area is clear before initiating the blast.

MSHA - Mine Safety and Health Administration Practice Test

MSHA - Mine Safety and Health Administration Practice Test

MSHA Explosives and Blasting 3