Breakthrough In Braking

Electronically controlled air brakes promise a safer, more efficient railroad world -- and they're delivering

By Greg McDonnell



Electronic Air Brake System

Phase I Present

Phase II Near Future

Phase III Future

Illustration of locomotive and freight cars shows the electronic and pneumatic components of TSM's Electronic Air Brake System (EABS). Three schematic diagrams of freight-car brake systems depict how EABS will be phased in over time, with CCU's eventually replacing brake valves, retainers being eliminated, and air reservoirs becoming single-chambered. Diagrams by Rick Johnson.


Standing beneath the palm trees that tower above the station platform at Needles, Calif., Santa Fe locomotive engineer Scott McDonald watches intently as his train, Chicago-Los Angeles stacker S-CHLA1-24, rolls into town on a warm spring night. Their red-and-silver Warbonnet paint glistening in the yard lights, C40-8W 887, SD75M 208, and C40-8W 849 strut through the yard and halt smartly in front of the depot at 1:07 a.m. Except for the business car tucked between the power and a seemingly endless string of containers, the westbound freight looks like just another intermodal train, and the passengers waiting for Amtrak train 3, the Southwest Chief, are none the wiser. McDonald, however, knows better.

Despite its outward appearance, the L.A.-bound stacker is no ordinary train, and McDonald has Bulletin No. 8207 addressed "To S-CHLA1-24 887 West at Needles" to confirm it: "Be governed by the following additional conditions: This train equipped with experimental electro-pneumatic equipment. When operated in EABS mode, air brakes are controlled with head end unit (HEU), not automatic air-brake valve . . . O.K. 10:50 p.m. PT. Dispatcher C.A.R."

Specifically, S-CHLA's 6362-ton, 6742-foot train consists of Burlington Northern business car Columbia River and 34 Gunderson-built, three-well/all-purpose BN intermodal cars fitted with an electronic air brake system designed and built by Technical Service and Marketing, Inc. (TSM), of Kansas City, Mo. The consist is one of three intermodal trainsets equipped with TSM's Electronic Air Brake System (EABS) and employed in revenue-service testing between Chicago and the Pacific coast.

As McDonald approaches the train, the nose door of the 887 opens and the inbound crew detrains. "Wonderful!" exclaims the arriving hogger. "That's a sweet ol' train . . . I can control it with my fingertips and keep the speed within a mile an hour right over the road." While still in the experimental stage, electronically controlled pneumatic brakes are expected to improve train handling and operations, safety and efficiency more dramatically than any development since 1869, when George Westinghouse convinced the Pennsylvania Railroad to equip a 4-4-0 and a couple of passenger cars with his new invention, the air brake.

Although hardware and appliances have improved significantly over the years, the basic principles of pneumatically controlled air brakes have not changed since the Rio Grande introduced the Westinghouse air-brake system on freight trains in 1878. Locomotive-mounted air compressors feed a system of pipes, hoses, reservoirs, cylinders, and valves with a supply of compressed air that operates the brake system. The brakes are applied by reducing brake-pipe pressure and released by restoring pressure to the system. Pneumatically controlled air brakes have served railroading very well, but Westinghouse never dreamed of 70-mph, 6500-ton stack trains, 15,000-ton coal trains, or 2-mile-long piggyback trains, and the technology has been pushed to the limit. Electronically controlled pneumatic brakes (ECP for short) employ microprocessors, digital communications, and electronically controlled, electrically operated valve assemblies to overcome the weaknesses and limitations of conventional pneumatic brakes. It sounds complex -- and it is -- but up in the cab of Santa Fe 887, it takes TSM Field Service Technician Craig Victor just a few minutes to brief McDonald on the new system and explain operation of the Head End Unit, or HEU, that supersedes the conventional brake valves on the locomotive's console control stand. After about five minutes, McDonald is EABS-qualified and anxious to put the new system to the test.

EABS-equipped trains are currently outfitted with ECP components in an "overlay" installation. That is, the electronically controlled pneumatic equipment is installed on each car along with the standard air-brake system. The braking systems on these trains can be operated electronically or pneumatically, but when functioning in ECP mode, the electronic equipment overrides the standard air-brake control system. "Stand alone" ECP equipment is expected to begin testing at the Association of American Railroads' Pueblo (Colo.) test track in fall 1996.

In electronic mode, all braking functions are controlled from the HEU, which sits atop the console control stand on the locomotive. The HEU features a liquid-crystal display screen that provides the engineer with system and train-status information, while a series of buttons replace the familiar brake handles, levers, and valves that have been found in locomotive cabs since George Westinghouse went railroading. And, since the HEU is connected to the brake system electronically, the brake pipe no longer exhausts air into the cab, eliminating a significant source of noise and dirt. Indeed, in ECP operation, the brake pipe, or train line, serves only as a reservoir-charging system.

Relieved of its control functions, the brake pipe keeps air reservoirs throughout the train under constant charge, while the HEU communicates through a 230-volt D.C. power cable that parallels the brake pipe to send digital signals to every car on the train. In contrast to conventional air brakes, where brakes apply and release from front to rear, and brake-signal propagation takes 15 to 20 seconds (and sometimes as long as 90 seconds) to reach the last car on a long train, ECP brake action is instantaneous and uniform throughout the train.

Instantaneous signal propagation, uniform braking power, and continuous reservoir charging produce some of the greatest advantages of electronically controlled air brakes. Stopping distance for ECP-equipped trains has proven to be 30 to 70 percent less than that for pneumatically controlled trains, depending upon gradient, tonnage, and other factors. Train handling is vastly improved, slack action is substantially reduced, and the potentially dangerous loss of air -- and with it, brake effectiveness -- on long, steep descending grades is eliminated.

Every car in one of TSM's EABS consists is outfitted with a Car Control Unit (CCU), a high-tech appliance, not much bigger than a shoe box, that effectively gives the car's brake system an electronic brain which is connected to the HEU and all other CCU's on the train via the power cable that parallels the brake pipe for the length of the train. The CCU controls all brake functions of the car to which it is attached and engages in two-way communication with the HEU. At the heart of the CCU is a neuron chip programmed with the reporting marks and road number of its car. This chip not only gives the CCU its unique identification, but allows the device to communicate the status and health of the car's braking system to the HEU when polled, or contacted electronically.

Once every second, whether the system status changes or not, the HEU issues a brake command which is received and processed by the CCU of every car on the train. At the same time, the HEU conducts a diagnostic poll of all cars on the train, querying the status of one car per second. If the CCU of a car does not respond, the HEU informs the engineer by reducing the percentage of operative brakes readout on its display screen. A touch of the info key on the HEU provides details on the problem, including the reporting marks and number of the offending car or cars. The engineer is alerted if the percentage of operative brakes drops below 85 per cent. An additional benefit of the polling function, which includes brake-pipe, reservoir, and cylinder pressure of each car, is early detection of brake-pipe restrictions or blockages, which will help avert runaway incidents similar to recent occurrences on Cajon, Tennessee Pass, and Seventeen Mile Grade.

The CCU of the last car on a train performs additional functions, and its capabilities are expected to eventually eliminate the use of the radio-equipped end-of-train device (though a simple marker device may still be required to indicate the end of the train). Once per second, the CCU of the last car transmits the end-of-train brake-pipe, brake-cylinder, and reservoir pressures to the head-end unit. If the HEU fails to receive three consecutive transmissions from the last car, it will assume the train has broken in two and initiate an emergency brake application. At the same time, the CCU's on the disconnected portion of the train, having missed three consecutive messages from the HEU, will each make their own emergency application.

In addition to basic safety features, the ECP concept has been developed with a fail-safe system that ensures that every imaginable defect, fault, or failure initiates a full service or an emergency brake application to stop the train. Furthermore, EABS eliminates the occurrence of undesired emergency brake applications resulting from faulty brake valves or "kickers," one of the most frustrating and time-consuming operational headaches associated with standard pneumatically controlled air brakes. At the least, emergency brake applications can subject equipment and track structures to considerable stress; worse, they can damage cargo and, under extreme conditions, result in derailment.

Just west of Summit, Calif., the track seems to drop out from under the 887 as the S-CHLA1-24 begins its descent of the legendary Cajon grade. Despite the enthusiasm of TSM's EABS Operations Manager Robert Lambrecht, CHLA's engineer McDonald is conservative, even skeptical that ECP can tame the storied hill. However, with Lambrecht watching over his shoulder, he gives the new technology a shot. As the train creeps downgrade with dynamics howling and a minimum electronic brake application set, TSM's apparatus does its stuff -- and EABS makes another friend.

One of the greatest limitations of simple pneumatically controlled air brakes is that once a brake application is set, it cannot be reduced without first releasing the brake fully. To do so on any descending grade, let alone one as steep as Cajon, would be an invitation to disaster. However, with electronically controlled air brakes, it's not only possible, but practical. Taking advantage of ECP's graduated-release feature, the engineer was able to adjust the train's speed by slightly increasing and decreasing the electronic brake application a pound at a time. Deftly manipulating the black "mushroom button" on the HEU, electronic braking's newest convert triumphantly brought the S-CHLA off the hill, the speedometer holding steady and the train tightly under control.

According to Lambrecht, crew response to the EABS-equipped trains has been phenomenal. The equipment is simple to operate, and train crews have high praise for the handling characteristics of EABS trains, especially its rapid release times, quick response, uniform braking power, slack reduction, graduated-release capabilities, and reduced stopping distances.

The long-term economic benefits of ECP operations have yet to be determined, but TSM cites among the immediate gains reduced maintenance costs, longer brake-shoe life, and a 30 to 50 percent reduction in wheel damage. One of the most interesting benefits though is the increase in fuel efficiency, as illustrated by an AAR simulation of a loaded coal train descending Tennessee Pass with three C40-8 diesels, 110 cars, and 14,721 total tons. Employing conventional brakes and using the dynamic brake as the priority train-handling brake, the simulated train averaged 27 mph and consumed 258 gallons of fuel over 1 hour, 27 minutes. The same train, still employing the dynamic brake as the priority train handling brake -- but with ECP brakes and graduated release -- averaged 29 mph, covered the same distance in 1 hour, 20 minutes, and consumed just 51 gallons of fuel.

Besides fuel economies, EABS opens the door to increased speed limits. BN Santa Fe officials see the system's shorter-stop capabilities as crucial to raising the 70-mph lid on intermodal trains to 79 -- a necessary advance if the company is to stay competitive.

The AAR has been involved with research, continuing development and implementation of electronically controlled pneumatic brakes for several years, but Technical Service and Marketing, Inc., has been the true pioneer. TSM began work on the ECP brake concept in 1991 and debuted its EABS equipment in revenue service in fall 1993, outfitting a 65-car Burlington Northern coal train operating in captive assignment out of Beardstown, Ill. After two years of revenue service, the prototype EABS equipment was shipped to Pueblo for continued evaluation on the AAR test track.

TSM expanded its revenue-service tests in August 1995, with a TTX trainset of 25 EABS-equipped, Thrall-built, five-well cars assigned to Chicago-L.A. double-stack service on Union Pacific. By January 1996, two 35-car BN trains of EABS-equipped, Gunderson-built, three-well/all-purpose cars (capable of loading containers or trailers) were in stack-train service between Chicago and the Pacific coast, and TSM's books were filling with orders for EABS equipment.

Boasting five years of ECP experience and proven equipment with several million car-miles of service (and acquired in mid-July 1996 by Rockwell International's Railroad Electronics unit), TSM is not just the uncontested leader in the field, but the only supplier to have electronically controlled air-brake equipment in revenue service. New York Air Brake expects to have a basic ECP system on the road by early 1997, while Pulse Electronics (the leader in EOT devices), a division of Westinghouse Air Brake since 1995, and Zeftron are also reported to be working on the development of AAR-compliant ECP standards, especially for communications software and connectors.

The logistics of converting the North American freight-car and locomotive fleets to ECP braking are mind-numbing. Most industry sources predict that during the transitional period, two classes of service will evolve. High-utilization equipment such as unit coal-train cars and intermodal cars will be converted on an aggressive schedule, while the emergence of ECP-equipped general-service freight cars could take years.

Railroading stands to reap untold side-benefits from the growth of ECP technology, particularly from opportunities created by the presence of CCU's on every car and the existence of a communication cable along the length of the train. TSM has already successfully tested distributed-power operation with ECP trains, utilizing the EABS train line as a communication and multiple-unit cable linking the lead unit with locomotives positioned throughout the train. Furthermore, TSM is actively developing additional features to be incorporated with EABS technology on future ECP trains, including brake-cylinder and hand-brake position sensing, bearing-temperature monitoring, hot-bearing detection, G-force monitoring, and derailment detection.

While TSM is recognized as the ECP pioneer, Burlington Northern Santa Fe's championing of the new technology should not be overlooked. From BN's role in testing the original EABS equipment on its Beardstown coal train, to BNSF's operation of EABS-equipped stack trains in the Chicago-Seattle and Chicago-Los Angeles corridors, the company has played a key role in testing, development, and acceptance of ECP technology. Delivered in late 1995, the 70 BN EABS-equipped three-well intermodal cars are the first railroad-owned, ECP-equipped cars in revenue service. Since then, TSM has retrofitted several hundred BNSF cars, including 241 coal hoppers, 120 grain cars, and 90 iron-ore cars with EABS equipment. In addition, TSM is equipping 200 BNSF diesels for EABS operation: BN SD60M's 9200-9298 and 1991 (for Montana coal service), along with Santa Fe C44-9W's 600-699 (for intermodal and grain train service).

Conrail has introduced EABS operation to the East; 120 hoppers, 5 SD60M's, and 2 SD40-2's in assigned helper service have been retrofitted with EABS equipment for unit-coal-train service between the former Monongahela Railway and eastern Pennsylvania. A number of other railroads, including Canadian Pacific and Union Pacific, have expressed interest in EABS equipment. In fact, UP has requested that all new locomotives be equipped for ECP operation and that the HEU functions be incorporated in the integrated cab electronics (ICE) screens on the locomotive control console. The ECP revolution is clearly gaining momentum.

TSM President Doug Klink, inventor of the EABS "Disk," the interface between the pneumatic and electronic portions of the brake equipment, is enthusiastic about the effects of ECP technology and its potential to allow railroads to operate trains faster -- and safer. In his 15 years of work in the railroad industry, ECP has provided the greatest satisfaction, he says, "because of the positive impact it will have on people's lives. . . . It will give a guy a better chance of coming home alive at the end of his work day." George Westinghouse, meet Doug Klink.

Easing the S-CHLA1-24 to a passenger- train-style stop at Hobart Yard in Los Angeles, engineer Scott McDonald turns to TSM representative Craig Victor and poses the question most commonly asked by train crews who have operated EABS trains. It's not a technical or operational query, though. "When can I buy stock in this outfit?" he wants to know . . . and that could just be the most positive EABS endorsement of all.


GREG McDONNELL is a special correspondent for TRAINS. He thanks Fred Carlson of AAR, and Craig Victor and Robert Lambrecht of TSM, for their assistance. Tennessee Pass simulation data is from "Electronically Controlled Pneumatic Brakes -- Implementation Through Cooperation," by Frederick G. Carlson and Alfred J. Peters, 1996.

This article originally appeared in the November 1996 TRAINS
14 October 1996


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