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The year of the electronic air brake

01 Feb 1998

INTRO: North America is grasping the benefits of electronic brake application on long freight trains; with over a dozen pilot projects clocking up more than 160 million wagon-km in revenue service, 1998 may be a turning point in braking technology

BYLINE: Doug Klink

Vice PresidentTSM Inc

Electric control from the driver's cab of air brakes on each car has been commonplace for many decades in multiple-unit and fixed formation passenger trains. The advantages of applying the brakes simultaneously on all vehicles in a train are well known. Yet freight trains have grown many times longer and heavier than passenger trains without the benefit of electro-pneumatic brakes. Freight suffers to a far greater extent than passengers the economic penalties - and dangers - of sequential brake application through exhausting the train pipe at the head-end only.

Where radio-controlled locomotives are cut into heavy haul trains in order to limit coupler forces, this provides the opportunity to exhaust and recharge the train pipe at intermediate points as well as from the head end. Otherwise, some 2 min can elapse between operation of the brake control valve on the leading locomotive of a 150 car unit train and the application of brakes on the last car.

Conventional EP brakes require a number of wires along the train which directly energise solenoids on each car. These operate valves which admit air stored in reservoirs to the brake cylinders, and exhaust it to release the brakes. The reservoirs are recharged from a train pipe, which can also be used to apply and release the brakes if the electrics fail.

Aside from a few special applications such as mail trains, EP brakes have never been considered economic for freight. This is changing with the introduction of electronic control. Data messages are transmitted by wire or radio from the locomotive to a microprocessor on each car, where battery powered air valves create and hold exactly the desired pressure in each brake cylinder. The battery is trickle-charged by small generators built into the axle bearings in the case of radio, or via control wires through the train where these are used.

Electronically controlled pneumatic (ECP) brake technology has some way to travel before it can begin delivering the productivity benefits promised for railways, independent car owners and consumers worldwide. But if current trends continue, the industry may well remember 1998 as the year of the electronic air brake.

With the broad operational benefits well understood in North America today, suppliers are forecasting a significant increase in revenue service applications of ECP technology during 1998. On October 8, for example, electricity generator Southern Co of Atlanta, which receives low-sulphur coal from Wyoming in unit trains, ordered over 2500 EABSTM ECP kits from TSM. The decision followed successful trials with 250 cars during 1997 (see green route on Fig 1, p97). Co-operation and strategic alliances between brake and component manufacturers, independent car owners, railways and government agencies will facilitate the process.

The trend is expected to accelerate worldwide over the coming decades, driven by the demand for more efficient rail transport. In the US today, for example, many trains do not run at full line speeds simply because they can't stop fast enough in relation to the spacing of signals. This will continue to be an operational and economic constraint until braking distances are shortened. Electronic control has been shown to reduce braking distances by 30% to 70%.

The benefits summarised in Table I all contribute to raising productivity, and this is the key factor that will drive the adoption of ECP brakes.

Four years' experience

It was TSM Inc of Kansas City which installed the first ECP brakes on a Burlington Northern train carrying coal in 1993. Since then, more than a dozen trials with our EABS