1. Field of the Invention
The present invention relates to a system and method for addressing a pneumatic emergency initiated in a helper locomotive and, more particularly, to a system and method of improving braking safety and reducing brake system recovery time in an electronically controlled pneumatic (ECP)-equipped train after transmission of a brake pipe emergency dump command message by the helper locomotive associated with the train.
2. Description of Related Art
The air brake system on a train includes a brake pipe which extends the length of the train. The pressure is maintained in the brake pipe by the lead locomotive except when the engineer in the lead locomotive applies the brakes by releasing air pressure. The drop in air pressure propagates down the brake pipe causing brakes to be applied by the locomotives and all the cars in the train. With the advent of two-way end-of-train (EOT) units, an emergency braking event can be initiated by the engineer by causing air pressure to be vented simultaneously at the front and back of the train. The EOT unit is mounted on a coupler of the last car of the train, and specific coupler mounts have been designed to allow a helper locomotive to couple to the last train without damaging the EOT unit.
A helper locomotive may provide additional braking or motive power to the train. For example, in a train a mile long, a consist having three locomotives may provide sufficient power for a run along average grade terrain. However, a run over an above-average grade may require additional power in the form of a helper locomotive being attached to the end of the train just before traversing the increased grade. Once the train has cleared the increased grade, the helper locomotive is disconnected and may return to its point of origin. Current brake pipes of helper locomotives are connected to the train in one of two manners: a direct physical connection or a virtual connection. With a physical connection, the brake pipe hose of a helper locomotive has a connection to the train. This makes the brakes of the helper locomotive respond like any other car in the train, thus giving control of the brakes to the engineer in the lead locomotive. Coupling and uncoupling of the brake hose of the helper locomotive to the train is accomplished manually. Both operations expose railroad personnel to risk of serious injury. With a virtual connection, the brake pipe hose of the helper locomotive is connected to special radio-based helper equipment and the brake pipe pressure is communicated between the train and the helper locomotive via the existing radio system. Therefore, a safer alternative in adding braking functionality to the helper locomotive that uses a virtual connection is found in electronically controlled pneumatic (ECP) trains.
An ECP-equipped train relies on electronic signals, rather than changes in brake pipe air pressure, to activate brake valves on individual freight cars. Because signal propagation from the first to last car is instantaneous, the rate of brake cylinder pressure buildup can be increased. With conventional pneumatic brakes, brake cylinder pressure buildup time is carefully retarded to prevent the last cars in a train, where the brakes have not yet applied, from running into the first cars with fully developed brake cylinder pressure. With ECP, cylinder pressure buildup is about 6 to 7 psi/second for both emergency and service brake applications. The brakes can be applied, partially released, and then reapplied as often as necessary, within the ability of the locomotive compressors to replenish reservoirs on the cars of a long train.
In the context of a helper locomotive with a virtual brake pipe connection, ECP-equipped trains do not require that a physical brake pipe connection be made between the train and the helper locomotive. Specifically, a system is provided for forming a virtual brake pipe connection between the head-end-unit (HEU) of the helper locomotive and the EOT unit of the train. Thus, the EOT unit reads ECP braking commands from the ECP trainline and translates them into radio messages, which are sent to the helper locomotive. The system then sets the braking on the helper locomotive to match that of the ECP braking application on the train. A commercial system that implements the aforementioned functionality is known as HelperLink™ by Wabtec Railway Electronics.
As is known in the art, the aforementioned system may also initiate braking in the context of issuing an emergency brake application to the associated train based on a pneumatic emergency experienced on the helper locomotive or if the engineer of the helper locomotive is aware of a situation affecting the train that would require an emergency brake application. In such an instance, the emergency brake application involves the transmission of a brake pipe emergency dump command from the helper locomotive to the EOT unit. Upon receipt of the brake pipe emergency dump command, the EOT unit would open the brake pipe dump valve, which results in immediate discharge of the brake pipe of the train, and an immediate application of the brakes on all cars to an emergency level. This sudden and non-graduated removal of air from the brake pipe increases in-train forces and results in depletion of all air, which requires a lengthy recharging and testing of the entire brake system before the train may continue its travel.
Thus, there is a need for a system and method that overcomes or addresses some or all of the limitations of the existing ECP train systems and arrangements.