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34 brake benefits to different values of coefficient of friction between the tank car and the ground. The range of values of coefficient of friction used in this sensitivity test will be based [on] the results of full-scale tank car sliding tests on different ground conditions (specified later in this plan). Plan to measure force required to drag tanks with various loads across various surfaces. 2.2 DOT-117 Puncture Resistance The HHFT RIA used a histogram of impact forces and the puncture resistance of different types of tank cars to calculate the number of punctures and to determine the benefits of ECP brakes. As part of meeting the FAST Act requirements, DOT will use a histogram of impact forces calculated using the structural properties (stiffness, mass, etc.) of a DOT-117 tank car and then applied to the calculated puncture resistance of the same type of car. DOT will calculate the puncture resistance, stiffness and other required properties of a DOT-117 tank car from a finite element model of the car. DOT will validate the model from full-scale impact tests (speci- fied later in this plan). Test complete. Model was validated. Puncture predicted at 13 to 14 mph. Prelimi- nary test results showed ânear punctureâ at 13.6 mph. Currently no plans for a second puncture test. 2.3 Curved Track DOT will calculate the benefits of ECP brakes on curved track that is representative of the distribution of curves on the rail network. Using LS Dyna simulations with a revised initial condition at derailment to reflect negotiating a curve. 2.4 Derailment Initiation The HHFT RIA used the results of modeling with derailment initiated by a lateral force applied to the leading truck of the first car to be derailed. As part of meeting the FAST Act requirements, DOT will analyze alternative derailment initiation events to determine additional scenarios to the lateral force that was modeled for the HHFT RIA. Initiation events will include broken rails, broken wheels, bearing burn offs, wide gage, and track buckles. DOT will model the additional scenarios if they are found to be significantly different in nature to an applied lateral force. 2.5 End-of-Train Device vs. Distributed Power DOT will compare the sequence of events in a derailment of a train fitted with an end-of-train device to that of a train outfitted with distributed power at the front and rear. The events will include brake pipe pres- sure changes throughout the train, emergency brake applications and locomotive engineer responses. DOT will develop and model scenarios that describe these events. 2.6 Model Validation DOT, with support of its contractors, will model a sample of previous derailments. DOT will compare the results from the modeling to what happened in real life. The comparison will include, but not be limited to, the number of punctures, distances traveled by cars from derailment to rest, the ratio of cars derailed to those that stay on the track, the ratio of head to side impacts and punctures. In progress with preliminary results presented [to the committee on October 14, 2016]. 3. TEST PLANS The following are high level specifications for the planned tests. The contractor conducting each test will develop a detailed test plan as an early contract deliverable.
35 3.1 Coefficient of Friction-(Post derailment tank car kinetic energy dissipation) The contractor will perform a full-scale test to determine the coefficient of sliding friction between a tank car and the ground. The contractor will perform testing with the tank car on its side. The contractor will repeat the test on a variety of different ground conditions including those representing wet, dry and frozen agricultural land, and ballast. Plan for testing at TTCI [Transportation Technology Center, Inc.]. Will pull an empty and partially loaded tank car across the ground with a bulldozer or equivalent. 3.2 DOT-117 Puncture Resistance The contractor will conduct full-scale impact tests to provide data to validate the computer model of a DOT-117 tank car. The tests will be conducted against the crash wall at FRAâs Transportation Technology Center in Pueblo, Colorado. The contractor may perform two tests: one that does not cause puncture and one that does. Test completeâ¦preliminary results appear to validate simulations.
36 Appendix F Test Rack Results This appendix presents the test rack data that were received at the committeeâs request from New York Air Brake (NYAB) and Wabtec to illustrate the propagation of brake pressures over time in the event of a derailment. The graphs compare brake pipe pressure (BPP) and brake cylinder pressure (BCP) as a function of time. The test rack data represent the response of trains equipped with ECP braking systems and that of trains equipped with pneumatic brakes alone and with DP configurations or EOT devices. The data were developed from tests that the companies had conducted on their 150ârail car test racks with 90-psig BPP and minimum leakage as prescribed by AAR Standard S-464, Test Rack, 150-Carâ Performance Testing Procedure. The data and discussion focus on the cars of a loaded unit train that travel on the rail toward the POD immediately following the first car to derail. The separation and consequent drop in BPP initiate the emer- gency braking on the whole train, including the cars that would remain on the rails traveling toward the POD. (A separation in the BP hoses is assumed to occur at the POD.) The test rack data for ECP-only brakes from NYAB were generated by manually synchronizing the simultaneous separation of the car-to-car electri- cal coupling and the air hose. The results are presented in three sections in the order in which they were submitted to the committee. The first section presents test rack data on ECP-only and pneumatic braking systems that were submitted to the committee by NYAB in October 2016. The second section comprises test rack data from NYAB that were submitted in December 2016 to illustrate the effects of a software modification of the ECP-only brak- ing system. The third section shows test rack data provided in December 2016 by Wabtec simulating its pneumatic and ECP-OL brake systems. TEST RACK DATA RECEIVED FROM NYAB IN OCTOBER 2016 The test rack data from NYAB for a train in pneumatic brake mode were generated by separation of the air hoses at the point of interest. The test rack data for ECP-only brakes were generated by manually syn- chronizing the simultaneous separation of the car-to-car electrical coupling and the air hose at the POD. The times reported in this section have not been corrected according to the test rack results submitted by NYAB in December 2016. Data Representing a Train with ECP-Only Braking Figure F-1 shows a BPP drop for the first car trailing the POD, denoted as Car 1. The CCDs detecting a loss of BPP broadcast a critical loss message (due to loss of BPP) on the ECP electric line. As soon as two CCDs validated a loss in BPP, they initiated the process of an emergency brake application approximately 1.5 seconds after the BP hose separation (see below). Figure F-2 indicates that the approximate time from detection of BPP loss to sending of an electronic signal for emergency brake application was 1.5 seconds. Note that the ECP emergency brake application process is designed to begin when the ECP control system senses that the BPP has dropped to less than 50 psig. This test rack run exhibited a measureable response at about the same time that the BPP reached 0 psig. During the next 1.5 seconds, the BCP equalized at about 5 psig throughout the train, as the BC pistons were extended and the slack in the brake rigging was taken up to bring the brake shoes against the wheels.
37 FIGURE F-1 Brake pipe pressure drop for an ECP-only system after air hose separation 75 cars from the rear of a 150- car test rack. Car numbers refer to the car position trailing the POD. Car 1 is the first trailing car. BC = brake cylinder; BP = brake pipe. FIGURE F-2 First 3 seconds for an ECP-only system after air hose separation 75 cars from the rear of a 150-car test rack. Car numbers refer to the car position trailing the POD. Car 1 is the first trailing car. BP = brake pipe; BC = brake cylinder. 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Pr es su re (p si g) Time (sec) Car_1-BP Car_1-BC Car_35-BP Car_35-BC Car_71-BP Car_75-BC 5 C
38 The control valve for the ECP-only system is different from the conventional brake control valve. That results in different air flow restrictions as compressed air flows to the BC from the auxiliary and emergency reservoirs. The resulting difference in the buildup of BCP over time can be observed by comparing the pres- sureâtime histories indicated in Figures F-1 through F-3 with those of Figures F-4 through F-6. The data indicate that beginning 3 seconds after air hose separation, all brakes on the trailing cars expe- rienced a constant rate of increase in BCP until 75 psig was reached approximately 11 seconds after air hose separation at the POD. See Figure F-3. AAR Standard S-4200 requires that the emergency brake application be completed in not more than 12.0 seconds and not less than 7.0 seconds from the time of initiation. The test rack data indicate that approx- imately 9.5 seconds was needed from the start of the emergency brake application until its completion. The test rack data for ECP brakes provided to the committee represent a POD between the 75th and 76th cars on a test rack of 150 cars. The legends in the figures presented here have been renumbered to indi- cate the position of trailing cars relative to the POD. The change in BCP as a function of time should look the same for ECP regardless of where the hose separation occurred. The differences in the responses of Cars 1, 35, and 75 in Figure F-3 are likely not meaningful; instead, they are likely due to variability in the re- sponse of physical components (control valves and cylinders). FIGURE F-3 ECP-only brake system was fully actuated 11 seconds after air hose separation 75 cars from the rear of a 150-car test rack. Car numbers refer to the car position trailing the POD. Car 1 is the first trailing car. BP = brake pipe; BC = brake cylinder. 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Pr es su re (p si g) Time (sec) Car_1-BP Car_1-BC Car_35-BP Car_35-BC Car_71-BP Car_75-BC 5 C
39 FIGURE F-4 First 1.5 seconds for a pneumatic system after air hose separation 75 cars from the rear of a 150-car test rack. Car numbers refer to the car position trailing the POD. Car 1 is the first trailing car. BP = brake pipe; BC = brake cylinder. Test Rack Data Representing a Train in Pneumatic Brake Mode Figures F-4 through F-6 illustrate the case of an air hose separation between the 75th and 76th cars on a 150-car train equipped with pneumatic brakes. The brakes on the first car following the POD actuated emer- gency application before BPP reached 0 psig. See Figure F-4. BCP should be between 12 and 18 psig within 1.5 seconds.1 In addition, on the assumption that the drop in BPP traveled in a pneumatic wave through the BP at approximately 980 fps, emergency brakes would have begun setting on approximately 29 cars behind the POD within the first 1.5 seconds after hose separation. The buildup of BCP over time for conventional pneumatic brake control valves (DB-60) differs from that of ECP brake valves because the air flow characteristics differ. The emergency portion on the conven- tional brake control valve is triggered at approximately 45 psig, which is earlier in the drop of BPP relative to ECP brake application. The data indicate that the BCP on the first car trailing the POD reaches approxi- mately 20 psig within 1.5 seconds after air hose separation (see Figure F-4). Figure F-5 indicates that the 35th car beyond the POD will have a BCP of approximately 17 psig 3 seconds after air hose separation. The propagation of emergency braking reached beyond the 58th car (not shown in the figure) during that 3- second period. In Figure F-6, each BC reaches about 90 percent of the final maximum pressure, 67.5 psig, within 8 to 12 seconds.2 Maximum pressure on the 75th car from the POD is reached within 16 seconds after air hose separation. 1AAR Standard S-461, Single-Capacity Freight BrakesâPerformance Specification, 2002 revision, Paragraph 3.4.3. 2AAR Standard S-461, Single-Capacity Freight BrakesâPerformance Specification, 2002 revision, Paragraph 3.4.3.
