Rail defect management

BS EN 17397-1:2020 pdf free.Railway applications – Rail defects Part 1: Rail defect management.
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/ohp
plain rail zone comprising all parts of the rail located away from the rail ends and the welding zones
rail end part of the rail located within the length of the flshplates
welding zone weld material itself plus 20 mm from each end of the weld collar (for aluminothermic welding and electric arc welding) or upset (flash-butt welding)
Note 1 to entry: Any defect occurring in this zone is classified as a welding defect.
defective rail rail which, for reasons of integrity or profile (including wear), requires management (examples in Annex A)
damaged rail rail which is neither cracked nor broken, but which has other defects
cracked area part of the rail with a localized material discontinuity
broken rail rail which has separated into two or more pieces (see Figure 1 and Figure 2) or any rail from which a piece of metal becomes detached from the rail head, with a gap of more than 50 mm in length and more than 10 mm in depth resulting in a running band less than 30 mm in width (see Figure 3).
rail surface defect defect which initiates on any of the surfaces of the rail.
rail head surface defect defect which initiates on or within 5 mm from the running surface of the rail.
rail internal defect defect which initiates from within the rail section but may grow to become visible on the rail surface.
NDT Method discipline applying a physical principle in non-destructive testing[SOURCE: EN 13938-5:2004, definition 3.2]EXAMPLE: Ultrasonic testing.
wheel/rail interaction effect of rolling and sliding contact and direct forces from the vehicle wheels which can cause damage to the rail.
environmental degradation damage to the rail caused by external environmental factors.
geometrical planes of the rail see EN 16729-3:2018, 3.10, Figure 4
infrastructure manager [IM] body or organisation responsible in particular for establishing and maintaining railway infrastructure,
as well as for operating the control and safety systems.
track maintenance engineer [TME] engineer with “safety of line” responsibility for a defined track area.
An infrastructure manager shall put a framework in place to monitor the condition of its assets. If the infrastructure becomes deteriorated, it needs to be renewed or repaired. This can be for economic reasons or, typically at a later state in the development and propagation of the defect, due to safety reasons.
There are a wide variety of rail defects that lead to damaged or defective rail. These defects can be grouped and categorized by a system.
The classification of the defect types along with the internationally widely used numbering scheme can be found in the Annex A of this document.
The IM shall implement a testing framework (appropriate NDT methods and inspection frequencies) to inspect rail to detect the defects considered relevant by the lM. The testing frequency should be designed to mitigate the risk that a detectable defect propagates to a critical size leading to failure.
The standard EN 16729-3:2018 describes how several of the most relevant defects can be detected using various methods of NDT.
Management of NDT inspection results
Actions shall be taken depending on the results of the inspection. Several limits can exist that lead to different actions. Immediate action has to be taken, if the defect has reached a safety critical size. Smaller detected defects shall be managed (by repair or removal) to prevent them from reaching a safety critical size.
The infrastructure manager shall record the lifecycle of each defect from detection, monitoring, to removal.
A methodology to analyse rail condition should take into account the economic optimum of reliability, availability, maintainability, safety (RAMS) and life cycle costs (LCC). Different infrastructure managers have different limits for these economic factors, based on various boundary conditions.
The larger a defect grows, the greater becomes the safety risk and this has to be balanced against the economic limits. The urgent removal of a safety critical defect is usually not the most cost-effective action with regards to LCC.
Definition of limits
A typical degradation curve is shown in Figure 4, together with an example of various limits for intervention.
Informative immediate action limits LIA for the most common types of rail defects can be found in Annex B. The IM may define more stringent limits based upon performance and overall risk management of the infrastructure.
Some defect types do not directly lead to cracks growing in the rail, but will affect the performance of the track system and need to be removed. For these defect types. end of economic maintenance limits LEJ is typically used. One example is corrugation, where the values presented in EN 13231-5:2018 represent end of economic maintenance limits LEI.
Risk management starts with the implementation of the track-testing framework, develops on the detection of a defect and ends with the actual removal of the defect. Upon detecting a rail defect and based on the actual circumstances in the track, a variety of measures should be considered in order to mitigate the risk of failure before the rail can be changed:
— reducing line speed;
— mounting fishplates, if feasible for that type of defect;
— increase the frequency of inspection, up to constant surveillance;
— restriction of the use for special types of railway vehicles;
— closing the track.
Several factors other than defect type and size shall be taken into account when assessing the risks that defects have on the structural integrity of the rail:
— line speed, category and type of traffic;
— multiple isolated defects within a short distance or cluster density of defects over longer length;
— expected crack growth until removal;
— location of the defect Site in the track;
— track condition including geometry;
— rail profile and current condition such as wear and corrosion;
— steel grade;
— manufacturing process;
— accumulated tonnage;
— site history;
— low rail temperatures causing tensile stress in the rail of continuously welded track.BS EN 17397-1 pdf download.Rail defect management