NS Air Brake Test flashcards
NS Air Brake Test · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Automatic brake valve
- The valve that controls brake pipe pressure, applying the train brakes by reducing pressure and releasing them by restoring it. It does not directly control locomotive unit brakes.
- Independent brake valve
- The valve that controls the locomotive's own brake cylinders directly, independent of the train brake pipe. It is used to hold or stop the locomotive without affecting train brake pipe pressure.
- Equalizing reservoir
- A reference volume the brake valve actually reduces; the brake pipe follows it through the relay or equalizing portion. Leakage between the two causes incorrect brake pipe pressure.
- Auxiliary reservoir
- A reservoir charged from the brake pipe that supplies air to the brake cylinder when brake pipe pressure is reduced. It recharges only when brake pipe pressure exceeds reservoir pressure.
- Control valve positions
- The control valve operates in release and charging, application, lap, and emergency conditions. These determine whether the auxiliary reservoir charges, feeds the brake cylinder, or is isolated.
- Two-way check valve
- A valve on multiple-unit locomotives that lets the higher of brake pipe or independent control pressure feed the locomotive brake cylinders, preventing independent release from overriding an automatic application.
- Class I brake test
- A full initial terminal test of the entire train's brake system, including inspection of brake rigging and piston travel, performed where the train is originally assembled.
- Class II brake test
- A test performed at a terminal or yard where the train is received in one piece. It verifies brake pipe leakage and application and release without the full inspection required for a Class I.
- Class III brake test
- A test performed after a stop en route when only part of the brake system changed, such as cars set out or picked up. It verifies the changed portion and brake pipe continuity.
- Piston travel limits
- Common freight limits are 7 to 9 inches for 8-inch cylinders and 6 to 8 inches for 10-inch cylinders. Travel outside these limits is a defect to be corrected.
- Brake test completion
- A brake test is complete only when brake pipe pressure is fully restored, brakes are released, and the leakage test has passed. Any failing car is bad-ordered.
- Leakage test procedure
- Charge the brake pipe, cut out the feed valve, place the brake valve in lap, and observe the brake pipe gauge. Freight leakage must not exceed 5 psi per minute.
- Why lap for leakage
- The brake valve must be in lap during a leakage test because in release the feed valve replenishes the brake pipe and masks the true leakage rate.
- Pressure retention test
- After a brake application, the brake valve is placed in lap and brake pipe pressure must not drop more than 5 psi in 60 seconds, confirming the control valves hold.
- Locating excess leakage
- When brake pipe leakage exceeds the limit, the source must be found and corrected before departure. Common causes are leaking angle cocks, hose gaskets, and control valves.
- Leakage gauge location
- Leakage is read on the brake pipe gauge at the head end. Large leakage can prevent the brake pipe from charging to full pressure at the rear of a long train.
- Minimum and full service
- Minimum reduction is typically 6 to 8 psi; full service is about 20 to 26 psi. Reductions beyond full service do not further increase brake cylinder pressure in standard freight systems.
- Avoiding undesired emergency
- Make brake pipe reductions at a controlled rate. Rapid or large reductions, especially on a slack-stretched train, can trigger an undesired emergency application.
- Release after recharge
- Release the brakes only after the brake pipe has had time to recharge. Releasing too early leaves auxiliary reservoirs low and reduces braking for the next application.
- Bailing off independent brake
- During a service application, bail off the independent brake to prevent locomotive wheel slide and to keep the locomotive brake from fighting the train brakes.
- Split reduction technique
- Reducing brake pipe pressure in stages lets the brakes set more evenly through the train, reducing slack action and the risk of an undesired emergency application.
- Bad order definition
- A car is bad-ordered when a defect makes it unsafe to move or violates inspection standards. It must be repaired or set out before the train proceeds.
- Common brake defects
- Frequent brake defects include piston travel out of limits, a stuck or leaking control valve, a broken or missing brake shoe, a defective angle cock, and leaking hoses or gaskets.
- Measuring piston travel
- Piston travel is measured with the brake applied and the car at rest, from the cylinder face to the piston rod end or reference mark per the railroad's standard.
- Cutting out a car
- A car that will not apply or release may be cut out or set out. A cut-out car must have its brake pipe angle cock closed and its reservoir air bled off.
- Bad order tag
- A tag applied to a car that cannot be moved safely. The car must be set out and the defect reported to the car department or appropriate authority.
- Qualified employee requirement
- The brake test must be performed by a qualified employee, and results recorded as required by the railroad's rules and applicable federal regulations.
- No departure before test
- A train may not depart until the required brake test is complete and brake pipe leakage is within limits. The test is repeated if the train is broken up.
- Class III en route pickup
- When a train picks up cars en route, a Class III test is required for the added cars, and brake pipe continuity must be verified before departure.
- Emergency application
- Made by a rapid brake pipe reduction or by opening an emergency valve. It sets the brakes at maximum and requires a full brake pipe recharge before movement resumes.
- Undesired emergency application
- An emergency application that occurs without intent. It is investigated for causes such as rapid reduction, a defective valve, or a brake pipe obstruction.
- Bleed before disconnecting
- Bleed off air pressure before disconnecting hoses or working on brake rigging. Trapped air can cause sudden movement or serious injury.