ECP braking gets results

Field trials in Canada and Australia are illustrating the benefits of electronically-controlled pneumatic braking systems.

By Fred Carlson and Brian Smith, TTCI, for Railway Age

	Quebec Cartier Mining-one of several railroads testing ECP brake technology-has performed the most comprehensive revenue service testing of wireline-based ECP brakes to date using a NYAB system. The data collected indicates that ECP brakes offer many economic and safety benefits over conventional brakes. Photo by New York Air Brake

The Quebec Cartier Mining (QCM) Railroad and the BHP Iron Ore Railroad in Australia have been operating electronically-controlled pneumatic (ECP) braked trains in revenue service for several years. Data collected from these operations is being used by Transportation Technology Center, Inc. (TTCI), Pueblo, Colo., to evaluate the economic benefits of ECP brake systems. Analyses of both systems indicate ECP brakes offer many economic and safety benefits over conventional brake systems.

The QCM experience has confirmed many of these benefits:

Continuous reservoir charging, which makes it harder to "run out of air" on descending grades.
Graduated release, which eliminates stalling on descending grades, enables running brake releases from any speed, and sharply reduces the need to power brake.
Reduced fuel consumption due to improved train handling and, to a lesser extent, reduced air demand.
Stop distances 30% to 70% shorter due to simultaneous application and release of brakes.
Reduced slack action due to simultaneous application and release of brakes.
Reduced wheel, brake shoe, and draft component wear due to reduced slack action.

The BHP Iron Ore system has been operational for a shorter time and the benefits are not well quantified yet. However, the expected improvements in stopping distance have been measured.

QCM's wireline-based ECP operation
QCM operates a 265-mile route north from Port Cartier, Quebec. The railroad profile is undulating, except for the southern 66 miles, which descends at a maximum grade of 1.35%. Since April 1998, QCM has been operating a wireline-based stand-alone ECP-equipped iron-ore train whose performance is being compared with conventionally-braked trains in the same service. The ECP equipment is comprised of pre-production engineering prototypes manufactured by New York Air Brake Co. (NYAB).

The train is not equipped with conventional service and emergency portions. Previous revenue service tests of ECP- equipped trains used overlay systems, which allowed operation as a conventionally-braked train. Some conventional operation always occurred with these trains due to shortage of ECP- equipped locomotives and trained crews. Such operation tended to make the test data questionable, since defects could not be attributed to one type of operation or the other. However, with the stand-alone ECP system, conventional operation is not possible. Therefore, defects and delays can be confidently allocated to either the ECP or conventional brake systems.

QCM has been recording operational and maintenance data like fuel consumption, wheel replacements, brake shoe life, undesired emergencies (UDEs), sticking brakes, broken knuckles, causes for train delays, and other ECP and conventional air brake component failures. This is the most comprehensive revenue service testing of wireline-based ECP brake systems to date.

ECP brake systems use less air per brake application than conventional brake systems because no air pressure is released into the atmosphere to control brake applications or to increase signal propagation times. This allowed QCM to eliminate a compressor repeater car from the ECP train in cold weather. In fact, on Jan. 2, QCM reported that an ECP train with 170 cars in 22 degree (F) weather showed 0.5 cubic feet per minute airflow and no measurable gradient. These results are typical of ECP winter operations. It also allowed an increase in the length of the ECP train from about 158 cars to 180 cars without changing the locomotive consist. Since January 1999, the average ECP lading tonnage per train has been 1,600 tons heavier than the conventional trains.

QCM fuels its locomotives only at the south end of the railroad at Port Cartier, and the locomotives will stay with the same train for the entire 530-mile trip to the ore mines and back. Thus, the fuel consumption of each ore train operated can be reliably obtained. Since the ECP train length was increased in November 1998, the fuel consumption of the ECP train has been 5.7% lower per MGT than the conventional trains (Figure 1, p. 51). The reduced fuel consumption can be attributed to reduced power braking due to graduated release and, to a lesser extent, a lower compressor duty cycle due to reduced air demand. The next task for TTCI is to analyze event recorder data to determine how much of the fuel savings is due to train handling, and how much is due to reduced air demand.

Brake shoe life on the ECP train has increased by 25.8% over the conventional trains. The increased brake shoe life can be attributed to the reduced need for power braking due to the ability to graduate the ECP brake applications. Another factor is the uniform brake cylinder pressures throughout the ECP train. This type of savings has not been experienced on intermodal trains, where the ECP brake is used often for slight speed corrections at high speeds where dynamic brakes are not fully effective.

The ECP brake system has eliminated the occurrence of UDEs, while the conventional trains have experienced one UDE every 11 roundtrips. QCM data does not differentiate between valve-caused and slack adjuster-caused sticking brakes, but no sticking brakes due to ECP faults have been reported.

Through December 1999, the ECP train experienced a 28.7% improvement in car-miles between coupler knuckle failures, even with longer train lengths. However, for unexplained reasons, the car-miles between coupler knuckle failures have been about equal since January. The pre-2000 trend indicates, and the operating crews confirm, that the brake-induced slack action in the ECP train is sharply reduced. This reduction is due to the simultaneous application and release of the brakes on all cars. Reduced slack action should result in a substantial reduction in loss and damage claims in conventional and intermodal freight service. In addition, QCM feels that cracks occurring in their car structures are the result of severe slack action and could be reduced through the use of ECP brakes.

Wheel data collected from QCM is inconclusive. QCM maintenance policy requires removal of wheels from service for 2mm or more of hollow tread wear. These wheels are then turned and placed back in service on any car-ECP or conventional. Wheels are often removed from service before any brake-related tread defects have a chance to develop.

Trainyard car handling presents some uncertainties. Conventional cars are equipped with empty/load valves, but this equipment was removed from the ECP cars. When an ECP train is initialized, it is set electronically to either empty or loaded, and the ECP system modulates the brake cylinder pressure accordingly. When the ECP train was moved through the dumper, the brakes were sometimes in a pneumatic backup brake application. Without empty/load valves, the braking on the empty cars is excessive, so the cars were experiencing stopped or sliding wheels. Due to these factors, the wheel data from QCM has proved to be unusable.

Initially, the ECP train delay minutes per car-mile were significantly higher than the conventional trains. This was due to a number of factors all having to do with developmental problems using engineering prototypes in regular railroad service. The delays are those caused by UDEs, connector separations, and failures of car control devices (CCDs), car ID modules, power supplies, and head end units (HEUs). Train delays due to hose separations, sticking brakes due to failed slack adjusters, and coupler knuckle failures are ignored since these failures are common to both train types. Coupler knuckle failures are also ignored because the severity of the delay depends on where in the train the failures occurred and because an unknown number of failures occurred when the trains were in stretched condition. Now that the initial bugs have been eliminated, the ECP train has proven to be extremely reliables.

BHP Iron Ore's radio-based operation
On the radio-based ECP front, GE Harris has had equipment in operation at BHP Iron Ore in revenue train operation since August 1999. BHP Iron Ore operates nine trains per day between Port Hedland on the Western Australia coast and the mines at Yandi (roundtrip of 390 miles) and Jimblebar Junction. Typical trainsets at BHP consist of two groups of two locomotives and 110 cars operating in distributed power (DP) mode for a total of four locomotives with 220 cars. Trains are sometimes operated with up to 240 cars with four locomotives (37,500 tons loaded) and potential plans include trains of around 300 cars. The BHP operation currently moves over 50 million tons of iron ore per year.

Data supplied by GE Harris shows one of the basic, expected benefits of ECP braking in the reduction in stopping distance of both empty and loaded trains. Data for the empty trains shows an approximate 53% reduction in stopping distance. Data for loaded trains shows an approximate 49% reduction in stopping distance (conventional train: 220-car, four-locomotive DP; ECP trainset: 240-car, four-locomotive), even with a longer, heavier train in ECP mode than the conventional DP train. It should be noted that the conventional DP train already has improved braking performance over a conventional train without DP. GE Harris also reports a reduced trip time from mine to port of approximately 30 minutes for the ECP train vs. the conventional DP-train's trip time of 7.6 hours.

GE Harris is collecting data to quantify other improvements from ECP implementation, including fuel consumption and brake shoe wear. TTCI plans to follow the progress of the BHP trainsets directly with BHP in the future to be included in the economic analysis being generated for ECP brakes.