Piston Travel and a Leaking Release Valve at Car 47
At an intermediate inspection point, you walk 60 cars of a 110-car manifest. On car 47, a loaded 100-ton covered hopper, you find the brake cylinder piston travel at 9.5 inches and a steady leak at the brake cylinder release valve. The brake shoe on the same car is worn to about 1/4 inch. The car is not equipped with a slack adjuster. The train is 6,800 feet long, and the next repair track is 85 miles away. The car inspector is 30 minutes out. The train has already received its initial terminal test and is on the main line. The dispatcher wants to know if the car can move. Temperature is 25°F; you hear air leaking from the valve and have a flashlight and gauge.
1. Is this car safe to move? Identify the defects and the risk of each.
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No. Three defects matter: piston travel at 9.5 inches is beyond the allowable range, commonly 7 to 9 inches for this cylinder type per your rule book, so brake force is reduced and the push rod may over-travel; the brake shoe at about 1/4 inch is worn out and can damage the wheel or fail; and the leaking release valve can prevent the brake from releasing, causing a dragged brake, overheated wheel, and fire. The leak also wastes brake pipe air and can affect the whole train. A car with a known sticking brake cannot be moved in revenue service without repair or proper cut-out and tagging.
2. If the car is cut out, what must be done before departure, and what limits apply?
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If the car is cut out, close the branch pipe cut-out cock, bleed the brake cylinder, secure the hand brake as required, and tag the car as bad order. Notify the dispatcher and car inspector, and follow the rule for the number and position of cut-out cars; a cut-out car has no air brakes and must not be treated as providing braking force. Because the next repair track is 85 miles away, the safer move may be to set the car out at the next siding rather than move it cut out over the road, especially with a worn shoe and a leaking valve. Do not release the train until the cut-out is documented and the brake test reflects the change.
3. What if the release valve leak stops after cycling the brake, but piston travel remains 9.5 inches?
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Cycling the brake and having the leak stop does not cure the excessive piston travel. The piston travel is a mechanical defect and remains out of adjustment; the release valve may also stick again. The car must be adjusted or repaired, or cut out and tagged. A temporary stop in leakage is not evidence of repair, and departing with 9.5 inches of travel leaves the car with reduced braking and a high risk of a dragging brake. Treat the car as bad order until the travel is within limits and the valve is repaired or replaced.