Rear Brake Pipe Pressure Does Not Follow the Cab Reduction
During pre-trip inspection in the yard, you are on a 10-car train. The main reservoir gauge reads 140 psi, and the brake pipe gauge in the cab reads 70 psi. The rear car brake pipe gauge reads 58 psi and is slowly falling. When you make a 10-psi brake pipe reduction, the rear car gauge does not drop, although the brakes apply on the front cars. A maintenance tag on the trainline between car 5 and car 6 shows recent work. You have 20 minutes before your scheduled departure. The yardmaster wants the train out on time. No other brake defects are reported. You have a brake test form and a radio, but the mechanical crew is at the far end of the yard. The train is scheduled to make all local stops.
1. What is the most likely cause, and what checks should you perform?
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The pattern points to an isolated brake pipe, most likely a closed angle cock between cars 5 and 6. The cab brake valve is working because the front brakes apply; the rear gauge does not drop when brake pipe pressure is reduced, which means the rear cars are not seeing the brake pipe signal. The rear gauge is also lower and falling, consistent with trapped pressure leaking off or a partially closed or blocked connection. The recent work tag makes that location the prime suspect, but check both ends of the coupling, the brake pipe hoses, and the angle cocks. Also verify the rear gauge is not defective by comparing it with a known good gauge or the next car. Do not move the train until the cause is found. A brake pipe that is not charged and not applying on the rear cars means those cars may not brake, which is a train-level safety defect.
2. The angle cock is found closed and opened. The rear gauge rises to 70 psi. May you depart to protect the schedule?
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A rising gauge alone is not proof the brakes work. Even if the rear gauge climbs to 70 psi after you open an angle cock, you must perform the required brake test: make a brake pipe reduction and confirm the rear gauge drops and the brakes apply on the rear cars; then release and confirm recharge. If the angle cock was found closed, open it fully, check for leaks, and recharge before testing. The 20-minute departure time and the yardmaster's pressure do not justify skipping the test. If the test fails, notify the yardmaster and mechanical, and do not depart. The correct decision is to delay or replace the train, not to accept a gauge reading as evidence of safe braking.
3. The mechanical crew says to cut out the rear brake valve and depart. How do you respond?
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Do not accept a verbal shortcut that reduces braking without proper authority. Cutting out a brake valve is not a repair for a closed angle cock; it may leave the train with less braking and may violate the rulebook. Ask for the instruction in writing or through the proper authority, and confirm the train can be operated safely with the remaining brakes. If the defect is a closed angle cock, the proper fix is to open it and test. If mechanical cannot make the train safe, stay put. The operator is responsible for refusing to move an unsafe train, and schedule pressure from the yard does not transfer that responsibility to the person who gave the verbal instruction.