Optimization of track geometry maintenance : a study of track geometry degradation to specify optimal inspection intervals

Railway infrastructure is a complex system which comprises different subsystems. Long useful life span is one of the important aspects of this prime mode of transport. The useful life length of its assets is highly dependent on the maintenance and renewal strategy used during its life cycle. Today’s demands on the railway industry call for increased capacity, including more trains, travelling at higher speeds with higher axle loads. This increased usage will result in higher degradation of railway asset and higher maintenance costs. However, due to the competitive environment and limited budgets, railway infrastructure managers are compelled to optimize operation and maintenance procedures to decrease operation and maintenance costs while meeting high safety standards. To assure track safety and maintain high quality, a cost effective track maintenance strategy is required, one based not only on technical and/or safety limits but also on cost-effective maintenance thresholds. RAMS (Reliability, Availability, Maintainability and Safety) and LCC (Life Cycle Cost) analyses, which are derived from reliable track condition data, provide an approach to specify cost effective maintenance strategy to lessen corrective maintenance actions and downtimes.One of the main parameters to assure railway safety and comfortable railway service is to maintain high quality of track geometry. Poor track geometry quality, directly or indirectly, may result in safety problems, speed reduction, traffic disruption, greater maintenance cost and higher degradation rate of the other railway components (e.g. rails, wheels, switch, crossings etc.). The aim of this study is to develop a methodology to optimize track geometry maintenance by using historical geometry data. The methodology is based on reliability and cost analysis and supports the maintenance decision-making process to identify cost-effective inspection interval. An important phase of track geometry maintenance optimization is to estimate the track degradation rate. Obtaining knowledge about degradation helps to properly schedule maintenance activities such as inspection and tamping.The thesis provides a methodology to identify a cost-effective inspection interval based on track degradation rate and cost drivers. It contains state-of-the-art track geometry maintenance optimization. It describes Trafikverket’s (Swedish Transport Administration) maintenance strategy regarding measurements, reporting on and improving track quality, and it evaluates the efficiency of this strategy. Finally, it includes a case study carried out on the iron ore line in north of Sweden that runs from Boden to Gällivare to evaluate track geometry degradation and analyze the probability distributions of failures. A cost model is developed in order to find optimal inspection interval.Keywords: Track geometry degradation, Track maintenance optimization, Maintenance planning, TampingGodkänd; 2011; 20110516 (iman); LICENTIATSEMINARIUM Ämnesområde: Drift och underhållsteknik/Operation and Maintenance Engineering Examinator: Professor Uday Kumar, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Adjungerad Professor, Per-Olof Larsson-Kråik, Trafikverket, Luleå Tid: Måndag den 13 juni 2011 kl 10.00 Plats: F1031, Luleå tekniska universitet</p

Cost-effective maintenance of railway track geometry : a shift from safety limits to maintenance limits

Railway infrastructure is a complex system which comprises different subsystems. Long life span is one of the important aspects of this prime mode of transport. However, the useful life of its assets is highly dependent on the maintenance and renewal strategy used during the assets’ life cycle. Today’s demands on the railway industry call for increased capacity, including more trains, travelling at higher speeds with higher axle loads. This increased usage results in higher degradation of railway assets and higher maintenance costs. Formerly, railway maintenance procedures were usually planned based on the knowledge and experience of the infrastructure owner. The main goal was to provide a high level of safety, and there was little concern for economic issues. Today, however, the deregulated competitive environment and budget limitations are forcing railway infrastructures to move from safety limits to cost-effective maintenance limits to optimise operation and maintenance procedures. The goal is to make operation and maintenance cost-effective while still meeting high safety standards.One of the main parameters to assure railway safety and comfortable railway service is to maintain high quality of track geometry. Poor quality of track geometry, directly or indirectly, may result in safety problems, speed reduction, traffic disruption, greater maintenance cost and higher degradation rate of the other railway components (e.g. rails, wheels, switches and crossings etc.). The aim of this study is to develop a methodology to optimise track geometry maintenance by specifying cost-effective maintenance limits. The methodology is based on reliability and cost analysis and supports the maintenance decision-making process. The thesis presents a state-of-the-art review of track geometry degradation and maintenance optimisation models. It also includes a case study carried out on the iron ore line in the north of Sweden to analyse the track geometry degradation and discuss possible reasons for the distribution of failures along the track over a year. It describes Trafikverket’s (Swedish Transport Administration) maintenance strategy regarding measuring, reporting on and improving track quality, and it evaluates the efficiency of this strategy. It introduces two new approaches to analyse the geometrical degradation of turnouts due to dynamic forces generated from train traffic. In the first approach, the recorded measurements are adjusted at crossing point and then the relative geometrical degradation of turnouts is evaluated by using two defined parameters, the absolute residual area (ARa) and the maximum settlement (Smax). In the second approach, various geometry parameters are defined to estimate the degradation in each measurement separately. It also discusses optimisation of the track geometry inspection interval with a view to minimising the total ballast maintenance costs per unit traffic load. The proposed model considers inspection time and the maintenance-planning horizon time after inspection and takes into account the costs associated with inspection, tamping and risk of accidents due to poor track quality. Finally, it proposes a cost model to identify the cost-effective maintenance limit for track geometry maintenance. The model considers the actual longitudinal level degradation rates of different track sections as a function of million gross tonnes (MGT) / time and the observed maintenance efficiency.Godkänd; 2013; 20130814 (iman); Tillkännagivande disputation 2013-08-26 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Iman Arasteh Khouy Ämne: Drift och underhållsteknik/Operation and Maintenance Avhandling: Cost-Effective Maintenance of Railway Track Geometry A Shift from Safety Limits to Maintenance Limits Opponent: Professor Peter Veit, Institute of Railway Engineering and Transport Economy, Technical University Graz, Austria Ordförande: Professor Uday Kumar, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Tisdag den 17 september 2013, kl 10.00 Plats: F1031, Luleå tekniska universitet</p

A comparative study of the gamma and Wiener processes for track geometry degradation modeling

Dans cette communication, nous proposons une comparaison des processus stochastiques gamma et Wiener pour la modélisation des défauts de géométrie de voie. A partir de mesures relevées sur plusieurs sections, les deux processus sont estimés et simulés. Les deux modèles obtenus sont alors comparés sur base de l’évolution de leur espérance mathématique et de leur variance. Finalement, un modèle de durée de vie résiduelle est proposé pour ces deux processus en calculant la distribution des temps d’atteinte d’un seuil critique de dégradation de géométrie de voie. Les implications pratiques de cette étude viseront à émettre des recommandations sur le choix d’un processus stochastique pour modéliser des dégradations de géométrie de voie.The purpose of this study is to compare the gamma and Wiener stochastic processes to model the track geometry degradation. Firstly, both the gamma and Wiener processes are estimated from field data. After that, the mathematical expectation and the variance of the aforementioned models are compared. Finally, a mean residual life model is proposed for both models by computing the distribution of the hitting times of a given track geometry degradation threshold. Practical implications of this study will consist in giving guidance for the choice of a stochastic process to model track geometry degradation

Från mätdata till underhållsbeslut : hjulslitage och spårkrafter

Denna rapport beskriver resultaten från projektet ”Från mätdata till underhållsbeslut” där avdelningen för drift och underhållsteknik/JVTC vid Luleå tekniska universitet på uppdrag av MTAB följt hjulslitaget på två malmvagnar under ett års tid. Under perioden har vagnarnas rälkrafter registrerats vid JVTC:s forskningsstation i Sävast.Godkänd; 2011; 20131121 (mikpal)</p

Selection of maintenance strategy, using analytical hierarchy process

Selection of appropriate maintenance strategy is key to economic viability of aviation and manufacturing industries. The study discusses and presents an approach to facilitate the selection of the most appropriate maintenance strategy on the basis of the cost-benefit analysis by using Analytical Hierarchical Process (AHP). The goal is to select the most cost-effective alternative, among Run-To-Failure (RTF), Preventive Maintenance (PM), incorporating Prognostic Health Management(PHM) capability, or any possible Design-Out Maintenance (DOM) strategies, which positively affects on aircraft operational availability. In this paper we proposed a stepwise algorithm to guide the selection process, based on two criteria of operational availability (benefit) and cost of failure.Godkänd; 2009; 20090912 (aliahm)</p

Condition monitoring of train wheel wear and track forces : a case study

One of the major failure modes in the railway industry is wheel wear. Wheel wear affects the dynamic characteristics of vehicles and the dynamic force impact on the rail, and can in worst cases scenario cause derailment. The wheel conditions also influences the wear and required maintenance on the rail. In this paper the correlation of wear rate and dynamic force between wheel and rail is studied to specify the most costeffective wheel maintenance interval. Two cars, total of sixteen wheels, were selected. In order to calculate the wear trend, measurements have been performed, by MiniProfTM, for a period of 12 months with the cars in traffic. During the same time period, the trend of track forces from the two cars has been obtained from the research station, outside Luleå, Sweden. Using the trends from wheel wear and track force in combination to form maintenance planning for wheels are discussed.Godkänd; 2010; 20100823 (ysko)</p