NGWA questions with verified answers
After cutting several hundred feet of hard rock the rate has slowed
down. What is the probable cause? Ans✓✓✓ Bit wear or dulling,
reducing cutting efficiency.
Compare speed/feed relationships in hard rock drilling using roller cone
bits. Ans✓✓✓ Low RPM requires higher down pressure(feed) for
effective penetration.
High RPM with too much feed can cause bit wear or failure, while too
little feed can reduce drilling efficiency.
Explain the difference between high and low pressure air rotaries.
Ans✓✓✓ High-pressure air rotary: Faster drilling, better cuttings
removal, used in hard formations.
Low-pressure air rotary: Slower drilling, more controlled, used in softer
or unstable formations.
Explain the difference between high and low volume air rotaries.
Ans✓✓✓ High-volume air rotary: Moves more air, better for deep
holes or large cuttings removal.
Low-volume air rotary: Moves less air, suited for shallow holes or
smaller cuttings.
Explain these terms: misting, dusting. Ans✓✓✓ Misting: Injecting
water or fluid into the air stream to control dust and cool the bit.
After cutting several hundred feet of hard rock the rate has slowed
down. What is the probable cause? Ans✓✓✓ Bit wear or dulling,
reducing cutting efficiency.
Compare speed/feed relationships in hard rock drilling using roller cone
bits. Ans✓✓✓ Low RPM requires higher down pressure(feed) for
effective penetration.
High RPM with too much feed can cause bit wear or failure, while too
little feed can reduce drilling efficiency.
Explain the difference between high and low pressure air rotaries.
Ans✓✓✓ High-pressure air rotary: Faster drilling, better cuttings
removal, used in hard formations.
Low-pressure air rotary: Slower drilling, more controlled, used in softer
or unstable formations.
Explain the difference between high and low volume air rotaries.
Ans✓✓✓ High-volume air rotary: Moves more air, better for deep
holes or large cuttings removal.
Low-volume air rotary: Moves less air, suited for shallow holes or
smaller cuttings.
Explain these terms: misting, dusting. Ans✓✓✓ Misting: Injecting
water or fluid into the air stream to control dust and cool the bit.
