Railway Track & Structures - November 2008 - (Page 33)

Figure 1, above, presents the forecast 30-year tie requirements, by year. Figure 2, right, shows these future needs in a more specific format, showing forecast tie gang dates for each of the 200 miles of track in the segment, including the next and second (following) tie gang cycles. and develop tie replacement programs, which can calculate costs and prioritize the work, based on the available budget. Planning for tie replacement Railroads continue to move towards automated Maintenance-of-Way Planning using new-generation track component measuring and monitoring tools to provide track and individual track component condition data. The availability of accurate and specific condition information allows for effective and efficient planning of maintenance activities and/or component replacement. The ability to efficiently define and schedule maintenance and replacement programs can result in improved planning and budgeting, which is of growing importance in today’s environment of tight budgets, limited access time, and conflicting demands on maintenance and capital dollars, according to Allan M. Zarembski of ZETATECH Associates, Inc., an HTT business unit. “Crossties represent a major track component and cost area.” Zarembski said. “A key application of tie condition information is in planning future tie maintenance and forecasting future tie replacement needs. This has traditionally been an area in which lack of adequate data has prevented the development of effective long-term tie maintenance planning tools. By providing detailed tie condition data to the railroad, railroads can now extend their maintenance planning capabilities to the crosstie area and predict future maintenance requirements, as well as immediate maintenance needs.” Data that is now available includes the full range of tie deficiencies, as identified by the tie inspector using state-ofthe-art PDA-based tie-condition “mapping” systems such as the Tie Inspect® system. This data is further supplemented by such state-of-the-art tie-condition measurements systems as the Gauge Restraint Measurement System and evolving measurement systems such as prototype visual/optical tie condition measurement systems. This data allows for both short-term and long-term planning of tie requirements and tie maintenance activities. “In the short term, a detailed map of tie condition allows for the determination of ties to be replaced by a tie gang scheduled in www.rtands.com a shorter time horizon,” he noted. “This allows for not only a planned replacement of all ‘bad’ ties, but also for the use of optimized replacement logic that considers the distribution of tie conditions and defines the minimum condition to be left behind. “One such approach uses a decision matrix based on track class, curvature, and other relevant factors,” Zarembski said. “This tie-replacement logic allows the railroad to define tie replacement criteria based on a number of adjacent good and/or marginal ties, proximity to a switch, bridge, or crossing, and other similar parameters. This tie-replacement logic software then identifies the specific ties to be replaced based on a minimum acceptable condition left in track.” A recent Railway Tie Association study on approximately 300 miles (approximately one million ties) of main line Class 1 railroad track illustrates how such a mapping of tie conditions can be used to determine not only the number of ties to be replaced but also the specific individual ties to be replaced. Information used to determine “bad” ties included conventional visual inspection (using TieInspect recording and mapping) and visual inspection supplemented by track strength (GRMS) measurements to identify additional “weak” ties not spotted visually. “As can be seen from this table, use of an optimized replacement method reduces the number of ties from simply replacing all the bad and failed ties, with some of the individual bad ties left in track,” he pointed out. “This effectively extends the life of some ties, optimizes replacements and results in some economic savings that allow for the optimal distribution of resources. In the case of the 300 miles of track represented by Figure 1, there is a savings of more than 6,700 ties or approximately three percent of the ties to be installed. Other studies have shown this savings can be as high as 9 percent, depending on specific tie condition and replacement criteria.” Zarembski continued: “For a longer planning horizon, the detailed condition data can be used as input into tie life tie forecasting and planning models to predict future tie replacement requirements and future tie gang scheduling dates. These forecasting and planning models make use of the basic understanding of the degradation/failure rate of wood ties such as was originally developed by the U.S. Department of Agriculture’s Forest Products Laboratory in the 1950s and subsequently verified by the AAR in the 1970s and by The Railway Tie Association in a research study performed earlier Railway Track & Structures November 2008 33 http://www.rtands.com

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Railway Track and Structures Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D TrainingVvital in Shaping Future of Railroad Industry Switch Stands, Switch Machines Automation Offers Improvements in M/W Planning AREMA 2008 Conference Report Products and Literature People Calendar Advertisers Index Sales Representatives Website Directory Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - November 2008

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