Explosives and Blasting Flashcards
7 cards from real MSHA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Explosives and Blasting flashcards as text
Under MSHA regulations for underground mines, what must be done with all electrical power in an area before blasting begins?
Answer: Power must be de-energized and locked out in the blast area to prevent stray currents from triggering electric detonators
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.
How long must miners wait after a blast before re-entering an area in an underground coal mine, according to MSHA standards?
Answer: At least 30 minutes, or until the ventilating current has cleared the smoke and fumes
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.
Which MSHA standard prohibits the use of non-permissible explosives in the working section of an underground gassy coal mine?
Answer: 30 CFR Part 75 Subpart N
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.
What is the purpose of a 'delay detonator' in a multi-hole blast pattern?
Answer: To fire individual holes in a timed sequence, reducing ground vibration and improving rock fragmentation
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.
Under MSHA rules, who is responsible for conducting a pre-blast inspection to ensure the blast area is clear of personnel?
Answer: The certified blaster in charge of the blast
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.
What does MSHA require regarding the record-keeping of blasting operations?
Answer: Blasting records including the quantity and type of explosives used must be kept and made available to MSHA inspectors
MSHA regulations require that blasting records documenting quantities, types of explosives, and other relevant information be maintained and made available to MSHA inspectors upon request.
According to MSHA regulations, which of the following conditions requires that blasting operations be suspended immediately?
Answer: An approaching electrical storm or lightning
MSHA regulations require the suspension of blasting operations when a lightning or electrical storm approaches because lightning can induce electrical currents that could accidentally detonate electric blasting caps.