Modelling For Optimizing Railway Maintenance Operations:Turnouts/switches

The importance of maintenance in the railway system cannot be over-emphasized.Construction of railway infrastructure involved a huge amount of investment,as such,it is important to maintain reliability,availability,and sustainability,to prevent unexpected/total breakdowns as much as possible.The purpose of this research is to provide a Mathematical model to minimize the cost of carrying out Preventive Maintenance(PM)system on Nigeria Rail line and achieve effective operational services.The focus of this research is given to the most important and delicate part of the railway system;"The Turnouts/Switches".The turnout comprises of infrastructures(i.e track),switches&crossings(S&C)which altogether requires persistent monitoring and maintenance because any failure/fault resulting from this component usually lead to a Train delay,cancellation,derailment and accidents which could result in death,or injury to railway users.Therefore,in an attempt to keep this equipment in a healthy condition there is an overall increment in the maintenance activities required,such as;inspections,services,tests,and restoring maintenance.However,Research has revealed that these efforts has,in turn,create a negative impact because the turnouts are no longer allowed to reach their maximum lifetime before they are replaced,and even before replacement,a lot of resources and money are wasted on what can be referred to as over-maintenance i.e.carrying out maintenance operation when it is not necessary.The result of which creates a huge maintenance cost for the overall railway annual maintenance budget.In summary,the will to prevent over-maintenance actions on Nigeria new standard gauge lines are the driver for the motivation of this research.The literature review provides a general overview of the research scope concerning Turnout PM and gives a holistic view of maintenance management.It is confirmed that Railway Infrastructure Management sees maintenance as an investment opportunity to be optimized and not a cost to be minimized.Therefore,researchers need to develop more effective and efficient maintenance methods for better optimization model based on a real-life situation.This study,therefore,creates a mathematical model referred to as MOM(Maintenance Optimization Model)for the use of optimizing PM activities on S&C components.MOM is an Integral Linear Programming(ILP)Problem which uses branch-and-bound procedure.The problem on a large scale is modelled and solved using the IBM ILOG CPLEX Optimization Studio.The software optimized the preventive maintenance activities on turnouts/switches by combining switches which have the same activities and scheduled them to be executed at the same period,resulting in the reduction of the number of times(frequency)activities are set-up on the turnouts/switches.The combination of these switches as well as maintenance types results in the reduction in manpower and logistics(or Set-up)cost which in turn,causes a decrease in the total cost required to maintain these switches.Most importantly,the method was tactically executed without compromising Railway safety and standard as specified by the manufacturers/equipment manual guide and the railway operational standards.The methods suggested in this research is formulated from real problems experienced by the railway Corporation in Nigeria.Thereby,using the Nigerian Railway maintenance system as a case study and the MOM model is tested using real cost data from the line while some missing data are randomly generated.The result produced excellent solutions in reasonable computation time.The performance of these model is then used to perform a sensitivity analysis and with the combination of the research from China railway maintenance practices(based on my knowledge)are used to offer recommendations on how Turnout/Switches maintenance system could be improved on Nigeria Railway Line in order to minimize total maintenance cost,reduce life-cycle cost and ensure the longevity of the S&C components.Inferences and conclusions from these solutions offer relevant insight for railway infrastructure managers to plan their maintenance operation,as combination analysis will call for a reduction in the overall cost of preventive maintenance while ensuring the component effectiveness and increased life expectancy.Finally,MOM flexibility creates a framework for easy application of the experiment on any Turnout/Switches with similar circumstances,allowing management to utilize their own specific conditions and methods.