Class I Test With DPU Leakage Near the Limit
You are the conductor on train 18N, a 112-car manifest, 4,800 tons, 7,200 feet, with two head-end units and one DPU on the rear. It is 35°F at the initial terminal. After charging to 90 psi and waiting the required time, the head-end leakage gauge shows 4.5 psi/min and the DPU telemetry shows 4.8 psi/min at the rear. During the walk-around, you find a leaking brake pipe hose gasket at car 63. The yard has a carman available, but the train is already 20 minutes past its departure slot. The dispatcher asks if you can depart with the leak as-is and re-check en route. Your railroad's rule requires a Class I initial terminal brake test before departure. You have a calibrated gauge at the head end; the DPU readout comes from the rear unit's display.
1. May the train depart as-is? Explain the leakage standard and what the two readings mean.
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Not as-is. The 5 psi/min figure is a maximum allowable brake pipe leakage for the train, not a target, and a known leaking hose gasket is a defective brake pipe component that can fail completely or worsen as the train flexes and temperature changes. The head-end gauge reading of 4.5 psi/min and the DPU telemetry of 4.8 psi/min are both under the limit, but the DPU reading is not a substitute for the required calibrated leakage test, and a single known leak at car 63 makes the train non-compliant with the intent of the initial terminal test. Have the carman replace the gasket, or set the car out if repair cannot be made, then re-charge the brake pipe, re-measure leakage with a calibrated gauge, and complete the Class I test, including observation of brake application and release. Do not accept the dispatcher's 're-check en route' proposal: en route leakage checks cannot cure a known defect.
2. If the gasket is replaced but leakage remains 5.6 psi/min at the head end, what must you do before departure?
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The train cannot depart. The rule is a hard limit: brake pipe leakage must not exceed 5 psi/min for the train, or the applicable limit in your rule book, before the initial terminal test is complete. You must continue troubleshooting: isolate cars by closing cut-out cocks or angle cocks in sections, and check for leaking hoses, gaskets, pipe unions, dirt collector, and the rear DPU. If a defective car is found, repair it or set it out; if the leakage is distributed and cannot be brought under the limit, the train must not leave until the condition is corrected. Do not split the difference by departing with 5.6 psi/min and hoping the DPU can hold pressure-brake pipe pressure loss can cause unintended applications or failure to release. Document the retest and notify the dispatcher.
3. What documentation and communication are required for this defect and repair?
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Record the initial and final leakage readings, the car number and defect, the repair performed, and the name of the carman. Notify the dispatcher that the train is being held for a brake defect and give an accurate delay estimate. If the car is set out, update the train list and brake test documentation, and note any change in train length or tonnage. The Class I test must be completed after the repair; a test performed before the repair does not cover the corrected condition. Keep the radio communication factual and avoid speculation.