Concrete Rail Seat Repair

Transcription

1 Concrete Rail Seat Repair Mark Austin CSX Transportation 500 Water Street J350 Jacksonville, FL (O) Maintenance October 7, ,062 words Abstract Starting in the early 1980s, CSX has been using concrete crossties as a means to reduce infrastructure expenses. Concrete crossties, if used in the right application, are projected to have a longer life cycle versus wooden crossties. Despite their expected longer life, concrete crossties are not without their own issues. As some of the concretes crossties have aged, these crossties in limited cases have affected track geometry in a negative manner. Upon further investigation, we discovered the geometry issues were generally associated with rail seat abrasion. From this, repairs were made using the materials and repair methodology available at the time. The first generation repair method was limited by the speed to which the repair material could be applied. The second generation repair method was a significant improvement over the first generation but later developed issues. What would become the current repair method had a rather steep learning curve. These various repair methods taught CSX the root causes of concrete rail seat abrasion as well as introduced a technique to prevent concrete rail seat abrasion. Background Since the early 1980s, CSX has installed over 2 million concrete crossties spread over 21, 317 miles of main track. Concrete crossties were installed in the early 1980s to reduce expenses by using the lowest total cost long term track construction. Concrete crossties are expected to have a much longer life than wooden ties. Concrete crossties are not unfailing. Over time, the rail seat for some locations deteriorated to a point of causing geometry exceptions. Geometry exception reports that include rail cant defects aid in identifying locations that have potential concrete rail seat abrasion. Division personnel typically verify the existence of concrete rail seat abrasion following a track geometry car inspection. Once the location of rail seat abrasion is determined, division personnel ascertain the severity and scope of the needed repairs. Based on this analysis, repairs are either made by division or system teams. If the abraded crossties are in a small area, division personnel make the repairs. Larger repair projects more commonly require the help of system production rail teams to repair concrete rail seats. Over the course of the years, several repair methods have been used at CSX to extend the life of concrete crossties. AREMA

2 Initial Repair Method CSX used repair teams nicknamed sunshine gangs to address the initial onslaught of rail seat abrasion. The repair material used an epoxy that could only be applied during dry weather, hence the reason for the repair team s nickname. In the end, this particular repair method did not address or remediate issues associated with rail cant. Second Repair Method Starting in the mid-1990s, CSX employed a system using a cast plate to bridge over the affected areas of rail seat abrasion. The driving factor of using the cast plate was to restore rail cant. To reestablish proper rail cant, the cast plate would sit on virgin concrete material. To fill the gap between the cast plate and the worn concrete rail seat, a polyurethane material would be injected onto the abraded surface before installing the cast plate. The setup time was minimal. Not long after the polyurethane material had hardened, the rail team could soon install the patch rail. This repair method had several drawbacks. First, the repair was dependent on the repair team to properly apply the polyurethane compound. Upon investigating failed or cracked cast plates, many rail seats did not have an even application of the polyurethane compound. Many rail seats had X s or Z s. This can be seen with past applications of polyurethane compound with an X or Z pattern. See photos below. Photo 1 Typical use of polyurethane AREMA

3 Photo 2 Typical application of polyurethane Photo 3 Typical application of polyurethane on concrete rail seat AREMA

4 Photo 4 Polyurethane abraded the concrete rail seat area The above photos illustrate the polyurethane compound creating an abraded X pattern into the concrete crosstie. This results from a concentrated load being transferred through the polyurethane compound material to the concrete crosstie. Photo 5 Too little polyurethane was applied to the abraded rail seat AREMA

5 Another drawback was that if the rail team applied too much polyurethane, the stack height would be negatively affected. Not only did this stack height issue make applying fasteners an issue, stack height also made applying the insulators an issue. Many of the insulators had to be installed by the team s quality inspection personnel resulting in delay and loss of productivity. In August 2011, CSX began studying the underlying issues associated with cast plates and to find a solution. Not long after the study, representatives from Transportation Technology Center Incorporated (TTCI) approached CSX to conduct a joint study on behalf of the Volpe National Transportation System Center. Effects of Rail Seat Abrasion In 2012, CSX conducted field observations jointly with TTCI to study the patterns and environment associated with rail seat abrasion. The study consisted of evaluating six curves with repeated repair projects involving a system production curve patch team. The degree of curvature ranged from two degrees to as high as fifteen degrees. The study was conducted on CSX s Coal River subdivision near St. Albans, West Virginia. This area has relatively high moisture content, with an average precipitation amount of 43 inches per year (1). Data collected inspecting rail seat abrasion depth on Coal River suggests (site specific to CSX): 1. As rail seat abrasion depth increases, so does rail cant. 2. Rail seat abrasion was not uniform from tie to tie. 3. On curves, all cant due to rail seat abrasion was outward. 4. There exists a close correlation with position in curve and rail seat abrasion depth. a. More curvature results in more rail seat abrasion depth and cant. b. Typically, at the tangents there was little or no measured rail seat abrasion. c. Rail seat abrasion depth gradually increased through the spiral. d. Rail seat abrasion depth remained generally uniform through the body of the curve. e. A few isolated locations of deeper rail seat abrasion did not correlate with variations in measured track geometry or predicted wheel/rail forces. These locations tended to be near grade (highway) crossings or areas where previous repairs had failed (1). Trying a Different Approach To continue employing the same repair method in the hopes of alleviating the issues associated with rail seat abrasion is pointless. CSX had to do something different to address rail seat abrasion. A short term repair method was developed but a new, long term repair method was needed to properly counter this recurring problem. The short term repair method was simple. Two tabs were added to the field side of the cast plate along with injection holes to allow for the injection of polyurethane. These two tabs would sit on original or non-abraded concrete material. By having these tabs sit on original concrete material, the proper rail cant could be reestablished. The advantage of using the tabs removed the dependence on repair teams to reestablish the proper rail cant using polyurethane alone. The downfall to this method is the reliance on repair teams to apply sufficient amounts of polyurethane beneath the cast plate in the abraded concrete rail seat area. Should there be an insufficient amount of polyurethane beneath the cast plate, the two field side tabs would be overloaded and could break. During the analysis of the root causes for the failures of the cast plate system, a product from Amsted came onto the market. AREMA

6 Photo 6 First generaion of Macro Armor repair plate The first iteration of Macro Armor plates experienced failures, based on the mistaken belief that since Kevlar was bullet proof, it would be railroad proof as well. In May of 2013, the first signs of trouble appeared. After further investigation, missing fasteners were attributed to be a secondary cause of failure for the first iteration of the Kevlar system not the primary cause. The primary cause was the inability of the Kevlar fabric to withstand the severe lateral load environment as depicted in photo 7. Photo 7 Kevlar shoulder unzipped AREMA

7 The second iteration involved using nylon insulator on the gage side and hybrid system consisting of nylon and Macro Armor material. This design also experienced failures, as shown below. Photo 8 Hybrid Kevlar shoulder with damage Current Repair Method CSX is now using Macro Armor plates and traditional nylon insulators for both the gage side as well as the field side. After applying the polyurethane material, a plate positioning tool assists in the proper positioning of the Macro Armor plates by using the undamaged bearing surface on concrete crossties to reestablish cant and elevation of abraded rail seats. The plate positioning tool can be used for concrete crossties that have either e-clip or fastclip fasteners. AREMA

8 Photo 9 - Macro Armor plate positioning tool The current repair process is as follows: 1. Place Macro Armor plates onto rail seats, 2. Inject polyurethane compound onto rail seats using the provided injection holes on the plates, 3. Place plate positioning tool onto seat using embedded cast shoulders as a guide and press plate positioning tool down onto Macro Armor plates, 4. Move to next rail seat with plate positioning tool and remove excess polyurethane from insulator, clip, and rail seat regions of the assembly. Where there is little to no rail seat abrasion observed during the pre-trip inspection, a Macro Armor Protector plate is to be used. Looking Ahead Prevention is one option in the battle against rail seat abrasion. Water mixed with fines proves detrimental detramental to the life of concrete rail seats. By providing a barrier between the concrete rail seat and foreign matter that damages the rail seat, a prolonged of the life of the rail seat can be expected. Starting in mid 2015, CSX adopted using the practice of applying a thin layer of polyurethane to the concrete rail seat. The targeted thickness of the polyurethane material is sixty thousandth of an inch. Tests of varying thicknesses were conducted. These tests analyzed the feasiblity of applying rail fasteners without overstressing them. There are perceived advantages to applying a thin layer of polyurethane to the concrete rail seat. The thin layer of polyurethane will provide a watertight enironment. By having a watertight environment, the introduction of fines can be reduced if not permanetly eliminated. Water and fines together produces a sanding pad effect. Another perceived benefit is the locking down of the abrasion pad. The thin layer of polyurethane tightly secures the abrasion pad to the concrete rail seat. This adhesion is more of a mechanical adhesion versus a more traditional glued adhesion. Using hands alone will not be enough to pry off the abrasion pad from the polyurethane coated concrete rail seat. AREMA

9 Going further on the mechanical adhesion, preliminary tests have shown that the abrasion pad makes an impression caused by the surface dimples. These surface dimples help secure the abrasion pad from moving laterally and longitudinally. By preventing the movement of the abrasion pad, the sanding pad effect is also reduced if not completely eliminated. This practice of using a thin layer of polyurethane is for all new concrete crossties, including concrete crossties used in maintenance repairs. Photo 10 Polyurethane coating to protect concrete rail seat area Lessons Learned During the course of studying rail seat abrasion, CSX has learned several recurring themes. 1. Rail seat abrasion occurs more frequently near road crossings 2. Rail seat abrasion occurs more frequently as the degree of curvature increases 3. Severity of rail cant correlates with the severity of rail seat abrasion (1) Conclusion The development of viable repair methods has proven beneficial for CSX, TTCI, suppliers, and the industry as a whole. We have benefited by gaining a better understanding of the root causes for concrete rail seat abrasion. From these efforts, repair and mitigation techniques can be further pursued. Despite the best efforts of CSX Engineering personnel and various suppliers, rail seat abrasion is still an issue for CSX. To do the same repair method year over year is unacceptable. New methods and materials still need to be developed and tested. Time will tell if the current repair and prevention methods will be successful for the long term. References Federal Railroad Administration. (2012). Assessment of Rail Seat Abrasion Patterns and Environment. AREMA

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11 AREMA 2015 ANNUAL CONFERENCE Background First installation in early 1980s Over 2 million concrete crossties spread over 21,317 miles of main track Expected to have longer life than wood crossties Reduce operating expenses using lowest total cost long term track construction Background Rail cant defects help identify locations with rail seat abrasion (RSA) Division managers ascertain severity of RSA System rail teams repair concrete rail seats on a large scale AREMA 2015 ANNUAL CONFERENCE First Repair Attempt First repair teams nicknamed Sunshine teams Epoxy could only be applied in dry weather Limited repair application Second Repair Attempt Cast plates introduced in early 1990s Cant deficiencies addressed Polyurethane introduced in 2003 all weather repair! Minimal setup time AREMA 2015 ANNUAL CONFERENCE Second Repair Attempt Dependent on proper application Second Repair Attempt Cracked plates were not supported properly AREMA

12 AREMA 2015 ANNUAL CONFERENCE Second Repair Attempt Abrasion became deeper Second Repair Attempt Stack height issue with too much polyurethane Installation of insulators is difficult Virgin material became scarce AREMA 2015 ANNUAL CONFERENCE Second Repair Attempt Installation of new clips is difficult Plates with tabs only bought time Production slows New repair method is needed! Joint Study with Volpe Center Coal route in a high moisture environment Conducted with help from TTCI Analyzed six curves ranging from 2 to 15 degrees Theory was put to fact AREMA 2015 ANNUAL CONFERENCE Joint Study with Volpe Center Site Specific to CSX: As rail seat abrasion depth increases, so does rail cant Rail seat abrasion was not uniform from tie to tie All cant due to rail seat abrasion was outward Joint Study with Volpe Center Site Specific to CSX: A close correlation with position in curve and rail seat abrasion depth, More curvature results in more rail seat abrasion depth and cant, Typically, at the tangents there was little or no measured rail seat abrasion, Rail seat abrasion depth gradually increased through the spiral, Rail seat abrasion depth remained generally uniform through the body of the curve, A few isolated locations of deeper rail seat abrasion did not correlate with variations in measured track geometry or predicted wheel/rail forces. These locations tended to be near grade (highway) crossings or areas where previous repairs had failed AREMA

13 AREMA 2015 ANNUAL CONFERENCE Taking a Different Approach Taking a Different Approach Employing same method with no gains is pointless Macro Armor was something new, something different Kevlar may be bullet proof but not railroad proof! AREMA 2015 ANNUAL CONFERENCE Taking a Different Approach Current Repair Method Second attempt also had trouble Using Macro Armor and traditional nylon insulators Using positioning tool AREMA 2015 ANNUAL CONFERENCE Current Repair Method Looking Ahead Using Macro Armor and traditional nylon insulators Using positioning tool Prevention is another tool in the bag Abrasive fines and concrete do not mix! AREMA

14 AREMA 2015 ANNUAL CONFERENCE Lessons Learned Concrete Rail Seat Repair RSA occurs more frequently near road crossings RSA occurs more frequently as the degree of curvature increases Severity of rail cant correlates with the severity of rail seat abrasion THANK YOU! AREMA