Edit post

Edit your reply below.

Post Body
Enter your post below.
The TSB has provided a lot of insight into their thinking about train securement and the variable effectiveness of handbrakes in their report on the QNS&L ore train runaway at Doree, Quebec on 12/11/11.  It discusses handbrake torque, variation in force applied, lubrication, lever adjustment—all of which can cause variation in handbrake effectiveness.  This analysis seems to be the heart of the concern that the TSB has regarding train securement: <a href="http://www.bst-tsb.gc.ca/eng/rapports-reports/rail/2011/r11q0056/r11q0056.pdf">http://www.bst-tsb.gc.ca/eng/rapports-reports/rail/2011/r11q0056/r11q0056.pdf</a>   All of the following from the report: Hand Brakes The hand brake is a mechanical device allowing the brake shoes to be applied against the wheel treads to prevent the wheels from moving or to retard their motion. The force on the wheels is proportionate to the force exerted by the person applying the hand brake; however, other factors have to be taken into account such as hand-brake-gearing-system lubrication and lever adjustment. According to the Association of American Railroads (AAR) Manual of Standards and Recommended Practices Section S401 rules, to obtain an adequate braking force, the force applied to the wheels of a car by the brake shoes must be equal to about 10% of the car’s gross load (28 000 pounds for LIM cars) when a torque of 125 foot-pounds is applied on the hand brake wheel. Rule 13 of the Field Manual of the AAR Interchange Rules states that the hand-brake mechanisms and fittings must be inspected, tested and lubricated when a car is on a repair track or in a shop.   The locomotive engineer applied 35 hand brakes and a sample of 15 cars was selected to measure the braking efficiency using a torque wrench. The average torque was approximately 80 foot-pounds, while 2 of the 15 sampled hand brakes had a torque higher than 115 foot-pounds, the lowest value being 45 foot-pounds. Similar tests conducted as part of the accident that occurred in Edson in 1996 also determined that the torque applied to the hand brakes by an average railway employee could vary between 40 and 120 foot-pounds, with an average of 80 foot-pounds. These tests also revealed that, for a constant torque, for instance 80 foot-pounds, the applied force on the wheels varied between 12 000 pounds and 21 000 pounds. Concurrent with the tests conducted by the TSB at Sept-Îles, on 31 January 2012, Wabtec Corporation tested the force applied by the brake shoes on a sample of cars. These tests, which use brake shoes with strain gauges, were performed on 3 of the cars on LIM-55 and on another car not involved in the incident. They were conducted at room temperature, in a QNS&L shop and a LIM shop in Sept-Îles. The 4 cars failed the hand-brake tests, measuring just below the minimum 10% force required by the AAR. During these tests, it was noted that excessive force had to be exerted to apply the necessary tension on the hand brake chains of these 4 cars because the hand brake mechanisms lacked lubrication and the lever was out of adjustment. Wabtec Corporation performed single-car tests on the same sample of 4 cars. Two of these 4 cars passed the test in the empty mode and 3 of the 4 cars passed the test in the loaded mode, but just above the minimum threshold.   Hand-brake Condition The runaway train travelled almost 15 miles and reached a speed of 63 mph. In such a case, with the brakes applied, it would be expected that the wheels would have overheated and been damaged on the grade. However, examination of the 35 first cars on LIM-55 revealed no abnormal wear on the wheels and brake shoes even though the locomotive engineer indicated that he applied the hand brakes on them before the train ran away. The force on the wheels is proportional to the force exerted by the person applying the hand brake, but other factors also come into play, such as the lack of lubrication on the hand-brake mechanism and improper adjustment of its components. Each of these conditions, or a combination of these, could have given the operator the false impression that the brakes were sufficiently applied. The torque applied by the locomotive engineer was insufficient to effectively apply the brake shoes against the wheels and prevent their rotation. Wabtec Corporation had noted that excessive force was needed to apply the necessary tension to the hand-brake chain of the 4 cars tested in Sept-Îles because the hand-brake mechanisms lacked lubrication and the lever was improperly adjusted. Furthermore, when the LIM cars were single-car tested following the incident, the hand-brake mechanisms had to be lubricated and adjusted on all the cars. Hand-brake inspections required in accordance with Rule 13 of the Field Manual of the AAR Interchange Rules apply only when a car is on a repair track or in a shop. Therefore, these inspections would normally be performed at the same time as a single-car test. However, because single-car tests were not conducted on the vast majority of cars before they were put in service, the hand-brake defects were not identified. Train Securement between Bybee and Tika When a train stops in the slope between Bybee and Tika following emergency braking, it must be secured in accordance with CROR Rule 112 and related special instructions. Rule 112 special instructions specify the minimum number of hand brakes needed in general operating conditions, but do not give the number when specific conditions apply. It is up to the locomotive engineer to determine the number of hand brakes required. In this incident, for LIM-55, the locomotive engineer, taking into consideration conditions such as track grade and train specifications, determined that 35 hand brakes were sufficient. However, given the torque applied and the condition of the brakes, that number proved insufficient to prevent the train from running away. Employees rely on their personal experience gained in situations where cars have either not moved or ran away to determine the sufficient number of hand brakes to be applied. Standard operating practices do not take into account that hand brakes can be applied in varying degrees, depending on the wheel torque. Yet, the amount of torque that employees can physically apply to the wheel varies from one to the other. Torque variability is affected by the design, condition and maintenance of hand brakes as well as differences in physical capabilities among locomotive engineers. The car weight and type, track gradient where the cars are left and actual and possible wind speed and direction must also be considered when deciding the sufficient number of hand brakes needed to secure a train. Determining what constitutes a sufficient number of hand brakes requires more information than locomotive engineers may have available to them and a better comprehension of the relevant variables and their relationship. This means that each locomotive engineer is left with the decision to determine how many brakes should be applied and to what degree.   Locomotive engineers who apply hand brakes do not receive any definitive feedback to confirm that sufficient brake shoe force was attained. Furthermore, because it is impossible to verify hand-brake effectiveness by pulling or pushing cars on high grades, locomotive engineers cannot accurately know that management’s expectations have been met every time cars are secured in accordance with CROR Rule 112. Other railway companies in Canada have enhanced CROR Rule 112, on high-grade sections of track, by putting into place procedures detailing the application and the number of hand brakes required. Without specific instructions that take into consideration local conditions, there is a risk of underestimating the number of hand brakes required to secure a train on a steep grade such as between Bybee and Tika and consequently other trains could run away.
Tags (Optional)
Tags are keywords that get attached to your post. They are used to categorize your submission and make it easier to search for. To add tags to your post type a tag into the box below and click the "Add Tag" button.
Add Tag