BS/EN 13231-5-2018 pdf download.Railway applications – Track – Acceptance of works Part 5: Procedures for rail reprofihing in plain line,switches, crossings and expansion devices.
life span, which makes it more economic to maintain them in an appropriate manner to extend their life rather than to change them.
Management of rail proflie and condition is therefore a prerequisite for safe and cost effective operation of railways. Predictable work – at least in a medium time horizon – organized in a strategic way needs to be defined to extract the maximum benefit from existing technologies and to guide the industry for future development. However, it is essential to ensure that the chosen approach provides enough flexibility to adapt to changing situations in both senses: increased requirements for maintenance due to higher loads and dynamic forces, reduced requirements for maintenance due to lower loads (improved vehicle characteristics) and better performing rails (reduced fatigue development).
The life expectancy of a rail is influenced by its interactions with the other parts of the train track system. The faster and more frequent train services, higher axle loads and new generations of vehicles with greater primary yaw stiffness have significantly increased the critical track forces that promote more rapid degradation of the rail (and wheel) leading to more frequent and costly maintenance interventions and even rail renewal. Significant research into rail metallurgy has resulted in the development of rail steels with much higher resistance to wear and RCF. Nevertheless rail maintenance by reprofihing is an essential requirement for efficient and safe functioning of railway track The combination of rail grade selection and maintenance strategy considering local track and traffic characteristics ensures effective control of any kind of rail surface defects.
42 Background of rail reprofihing
Reprofiling strategy is a planned maintenance activity usually defined by the infrastructure maintainer. In theory it is independent of available technologies, but in practice it is often influenced by the equipment that is easily accessible to or proposed by the contractors.
Work is programmed depending on damage having reached predetermined intervention thresholds such as corrugation depth, deviation from the transverse profile and depth of cracks.
Alternatively work is executed in cycles which are derived from experience and influenced by availability of machines, track possession times and similar factors such as traffic, usually expressed in mega gross tonnes (MGT), months, seasons, etc. Often work Is combined with other maintenance activities (e.g. after rail replacement, after tamping or when the line is closed for other work, etc.).
Before the execution of rail maintenance work, specifications (i.e. the results that need to be achieved) shall be defined for:
— detect repair (metal removal);
— longitudinal profile (tolerance);
— transversal profile (target and tolerance);
— surface condition (roughness, facet widths, etc.).
Shorter reprofihing intervals result in smaller metal removal requirements, consequently in such short periods the development of RCF and irregularities such as corrugation and resulting track deterioration is limited.
NOTE For some Infrastructure Managers in Europe, the preferable strategy is preventive cyclic reprofiling with small metal removal requirements applying profiles with moderate gauge corner relief. If the interval between reprofiling cycles is appropriately matched with the initiation and subsequent growth of cracks, metal removal can be adlusted for a one pass regime which Is operationally the best option.
In order to maintain RCF-sensitive sections economically, a certain damage level can be accepted (as intervention threshold or as remaining depth after treatment). However, this damage needs to be kept low enough to be removed pre-emptively and thereby avoiding safety issues. A rail reproliling strategy requiring metal removal rates of up to 0,6 mm at the critical gauge area and a maximum of 0,2 mm in the centre of the rail head shall be programmed.
Several Infrastructure Managers (lMs) utilize these metal removal specifications to control HC in standard carbon rail (R260) based on reproilling cycles at 15 MGT for curves and 45 MGT for tangent track. For harder heat treated rails (e.g. R35OHT) the intervals may be doubled depending on track and traffic characteristics.
If squats need to be controlled in tangent track due to traffic and vehicle characteristics (stiffness, traction and braking) shorter cycles may be required.
The reprofihing interval and the related average metal removal should depend on actual HC measurements which need to be checked again during reprofiling work. Such a policy optimizes the magnitude of artificial wear by reproilling and hence prolongs rail life.
5 Rail surface defects
5.1 General
Each irregularity causes a higher dynamic load on the surface of the rail and consequently an impact occurs at each wheel passage. Consequently the rail is subjected to high stresses and the damage often progresses at a significant rate.
Not only is the rail affected but also the whole track system. As the rail cannot always absorb the energy from the impact, the shock load continues further into the track. Local damage to fastenings, pads and sleepers may result. Ultimately the ballast becomes locally overloaded and disturbed and the stability of the track can no longer be ensured.
5.2 RoIling contact fatigue.BS/EN 13231-5-2018 pdf download.