I was interested to read about the functioning of the emergency brake safety loop circuit:
When the safety loop is opened due to an abnormal operating condition, the emergency brake solenoid valve is de-energised causing a maximum brake application.I wanted to know why the lead 3 car xtrap's emergency brakes didn't apply after the break. My understanding is if a loco-hauled train breaks apart at any point, brake pipe separates, emergency brakes come on on all wagons, both behind and ahead of the break.
In this instance, the uncoupling function was activated through an electrical circuit that was created by a wiring error in car 959M and the low IR of the uncouple solenoid of car 882M. This error resulted in the cab active relay, push button and the 3 km/h relay interlock devices being bypassed and allowing the unintended activation of the uncoupling circuit. The safety loop circuit on the lead car unit maintained the closed safety loop, hence emergency braking was not applied and it continued its journey until the driver realised that the trailing car unit had uncoupled, and brought the lead 3-car unit to a stop. As there were no active cabs in the trailing 3-car unit, the safety loop was opened, de-energising the emergency brake solenoid valves, resulting in the application of the emergency brakes on the trailing car unit bringing it to a stop.There's no analysis of whether the loops on the 2 3 car sets should be independent, whether losing air pressure should apply brakes on both sets, or whether the emergency brakes should have come on the lead car at all.
If a Comeng separates at the Scharfenbuergs while at speed, do the brakes come on on both sets?
Or is it a case that due to the wiring fault, the lead xtrap thought it was supposed to be decoupling - and the way you do that is by moving away from the other set - meaning emergency brakes should not be applied?