Railway Track & Structures - June 2008 - (Page 58)

Grinding behind the maintenance plan) must take this interaction into account. Thus, rail grinding will reduce the need for rail replacement by correcting surface defects, reduce the rate of internal defect development, and (in some cases) reduce rail wear.1 Rail lubrication will likewise reduce the need for rail replacement by reducing rail wear. However, it can result in an increased need for rail grinding since data show that increased lubrication results in a reduced rate of metal removal from the gauge corner and top of rail, allowing fatigue damage to accumulate and defects to grow where they would otherwise be worn away. The optimum balance of grinding and lubrication would allow for the maximum in-track rail life and the minimum amount of rail replacement.2 Furthermore, while rail maintenance activities such as grinding and lubrication will extend the life of the rail and delay/reduce the need for replacement rail, they will not eliminate this need. Rather, they will change the time (or cumulative tonnage) necessary for rail replacement, in some cases extending rail life by 100 percent or greater 1 before it requires replacement. Ultimately, the proper match between grinding, lubrication and rail replacement is an economic costbenefit decision. However, experience on other railway and metro systems has shown that a combination of effective grinding, lubrication and inspection can extend rail life by 100 percent or greater, while maintaining a low risk of rail failure. This results in an optimized rail replacement plan consisting of: Curve patching to replace rail, based on wear, predominantly in curves. Out-of-face replacement of longer segment, based on fatigue (with wear segments in between). This rail replacement plan is, in turn, coordinated with the grinding, lubrication and rail testing plans. Figure 3. Sample SmartGrind QC output. ditions and wheel/rail conditions. Once the actual and desired profiles are matched, and the differences calculated, the analysis of grinding requirements to reach the required profile is performed. This includes definition of number of passes, patterns and grinding speed. The result is the development of detailed grinding plan as shown in Figure 2. Rail maintenance management While each of these elements is of direct value individually, collectively they can be integrated to allow for optimization of rail maintenance activities. This includes trade-off decisions as to relay the rail (rail replacement) or use a combination of maintenance activities (rail grinding, rail testing, and rail lubrication) to extend the life of the rail. It must be emphasized that these rail maintenance and replacement activities are mutually dependent so that any maintenance plan (and the analysis References 1. Zarembski, A. M., The Art and Science of Rail Grinding, SimmonsBoardman Press, Omaha, 2005. 2. Kalousek, J., and Magel, E. E., “Achieving a Balance: the Magic Wear Rate”, Railway Track & Structures, March 1997. www.rtands.com Figure 4. SmartGrind Quality Index behavior over time. 58 Railway Track & Structures June 2008 http://www.rtands.com

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Railway Track & Structures - June 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Grade Crossings Provide Interface Between Railroads, Public Grade-Crossing Equipment & Materials Guide Fastener Suppliers Getting a Grip Grinding Plays Part in Rail Maintenance Big Picture Products and Literature People Calendar Sales Representatives Website Directory Advertisers Index Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - June 2008

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