LEC Brake Systems & Safety 2 — Questions and Answers
Question 1: What is the primary purpose of the independent brake valve on a locomotive?
- Controls only the locomotive brakes without affecting train brakes (Correct answer)
- Controls all brakes simultaneously including the entire train
- Releases air from the brake pipe to apply brakes
- Charges the main reservoir with compressed air
Correct answer: Controls only the locomotive brakes without affecting train brakes
The independent brake valve controls only the locomotive brakes independently from the automatic brake system that affects the entire train.
Question 2: During a brake pipe reduction, what happens to the brake cylinder pressure in a freight car equipped with standard AB valves?
- Brake cylinder pressure decreases proportionally
- Brake cylinder pressure increases proportionally to the reduction (Correct answer)
- Brake cylinder pressure remains unchanged
- Brake cylinder pressure drops to zero
Correct answer: Brake cylinder pressure increases proportionally to the reduction
When brake pipe pressure is reduced, the AB control valve directs reservoir air into the brake cylinder, increasing pressure to apply the brakes.
Question 3: What is the minimum brake pipe pressure reduction required to initiate a service brake application under AAR rules?
- 2 psi
- 6 psi (Correct answer)
- 12 psi
- 26 psi
Correct answer: 6 psi
A minimum 6 psi reduction in brake pipe pressure is required to initiate a service brake application according to AAR standards.
Question 4: Which condition would cause a 'sticking brake' on a freight car?
- Brake pipe pressure fully charged to 90 psi
- A broken release spring in the brake cylinder (Correct answer)
- Excessive brake pipe leakage above 5 psi per minute
- High ambient temperature above 90°F
Correct answer: A broken release spring in the brake cylinder
A broken release spring in the brake cylinder prevents the piston from returning, leaving brakes applied even after the brake pipe is recharged.
Question 5: What action should a locomotive engineer take when a train experiences a 'dynamiting' (emergency) brake application due to a break-in-two?
- Immediately apply full throttle to keep the train together
- Place the automatic brake valve in emergency and protect the rear of the train (Correct answer)
- Release the independent brake and allow the train to coast to a stop
- Apply only the independent brake to slow the locomotive consist
Correct answer: Place the automatic brake valve in emergency and protect the rear of the train
When a break-in-two occurs, the engineer must place the brake valve in emergency and follow rules to protect the rear section of the train from following traffic.
Question 6: What is the function of the brake pipe equalizing reservoir on a locomotive?
- Stores emergency air supply for brake applications
- Ensures accurate and consistent brake pipe pressure reductions (Correct answer)
- Lubricates the brake valve moving parts
- Provides air to charge the auxiliary reservoir
Correct answer: Ensures accurate and consistent brake pipe pressure reductions
The equalizing reservoir works with the automatic brake valve to ensure that brake pipe reductions are precise and repeatable by equalizing pressure between it and the brake pipe.
Question 7: Under FRA regulations, how long must a locomotive engineer wait after a full service brake application before making another brake pipe reduction?
- Until brake cylinder pressure equalizes, typically 15-30 seconds (Correct answer)
- Exactly 60 seconds regardless of conditions
- Until the train comes to a complete stop
- No waiting period is required between reductions
Correct answer: Until brake cylinder pressure equalizes, typically 15-30 seconds
The engineer must allow time for the brake system to equalize and respond before making additional reductions, which typically takes 15-30 seconds depending on train length.
LEC Brake Systems & Safety 2
What is the primary purpose of the independent brake valve on a locomotive?