Carry distance of top-of-rail friction modifiers

Abstract

Rail issues such as corrugation, rolling contact fatigue, noise and wear have been increasing with the increase in railway traffic. The application of top-of-rail friction modifiers (TOR-FMs) is claimed by their manufacturers in the railway industry to be a well-established technique for resolving the above-mentioned issues. There are various methods for applying friction modifiers at the wheel-rail interface, among which stationary wayside systems are recommended by TOR-FM manufacturers when a distance of a few kilometres is to be covered. TOR-FM manufacturers also claim that by using wayside equipment, the TOR-FM can be spread over a minimum distance of 3 km, over which it maintains a coefficient of friction of m ¼ 0.35 AE 0.05. To determine the carry distance of TOR-FMs, some researchers use tribometers to measure the coefficients of friction. However, moisture and deposits from the environment and trains can alter the top-of-rail friction and give a misleading indication of the presence of a friction modifier. Therefore, the coefficient of friction itself is not a clear indicator of the presence of TOR-FMs. In the present study, cotton swabs dipped in a mixture of alcohol and ester were used to collect surface deposits (a third body) from both the wheel and rail at various distances from the point of application. Subsequently, the third body collected on the cotton swab was analysed using an energy dispersive X-ray analysis. The results have shown that the maximum carry distance of TOR-FMs on the top of the rail is limited to 70 m when using a TOR-FM from one manufacturer and to 450 m when using a TOR-FM from another manufacturer. The carry distance on the contact band of the wheel is limited to 100 m and 340 m. The friction modifier on the edges of the contact band was detected over a distance of up to 3 km; however, this will not minimise the damage or friction at the wheel-rail interface.

Modelling of Frictional Conditions in the Wheel–Rail Interface Due to Application of Top-of-Rail Products

“…The predicted carry-on distance compares reasonably well with the experimental results from Khan et al [26] who observed carry-on distances between 70 m and 450 m for two different products on the top of the rail when they were applied by stationary wayside application equipment. Larger carry-on distances have been observed on the contact band on the wheel surface compared to the rail surface, which is also in qualitative agreement with the model predictions.…”

“…A dry layer of TOR-FM transferred from the wheel to the rail and vice versa at a low rate and was not squeezed out of the contact area. Khan et al [26] investigated Models describing the removal of contaminants from the wheel-rail interface and the associated change in the frictional condition have been published in the past. Allotta et al [22] modelled adhesion recovery from degraded adhesion conditions to recovered adhesion conditions by an exponential relationship based on the (instantaneous) value of the specific frictional work per unit rolling distance.…”

“…A dry layer of TOR-FM transferred from the wheel to the rail and vice versa at a low rate and was not squeezed out of the contact area. Khan et al [26] investigated the carry-on distance of TOR-FM at a Swedish iron ore line. Product was detected up to 450 m from the wayside application site on the rail surface.…”

Life cycle cost analysis for the top-of-rail friction-modifier application: A case study from the Swedish iron ore line

“…Based on the previous studies of the present authors 6–8 and the advice of experts belonging to the industrial partners, the following inputs were used for calculating the LCC. LCC period of 15 years, which is equivalent to the life of the rail on curves with a radius smaller than 550 m. The length of the curve = 450 m (assumption based on the average curve length on the IOL). The cost of a TOR-FM per litre = 160 kr (present average market price of the FM). The RCF reduction by using TOR-FM = 50% (assumption based on computer-based simulations.…”

“…5,17 The disposal cost = 10% of the purchase cost. For rail replacements, the disposal cost is 0 kr (according to Trafikverket). The man-hour cost for an authorised railway worker = 750 kr (according to Trafikverket). The lifespan of the wayside equipment = 15 years (assumption based on expert advice). The lifespan of the on-board system = 15 years (based on expert advice). An accumulated load of 20 MGT is equivalent to one year since the annual total load on the southern loop is 20 MGT. The total number of trains passing in one direction in a day = 14 (assumption based on the traffic on the southern loop of the IOL). The transportation cost per visit for repairs =1300 kr (standard charges in Sweden). The number of axles passing in one direction =1500 (assumption based on the traffic on the southern loop of the IOL). The installation cost of the system = two days (16 h) salary for an authorised railway worker (according to the manufacturer). The TOR-FM consumption in the case of wayside equipment (all curve radii) = 300 ml/1000 axles (manufacturer specification). The TOR-FM consumption in the case of an on-board system (all curve radii) = 30 ml/km/rail (manufacturer specification). The carry distance of the FM when wayside equipment is used = 450 m. 8 Issues other than wear and RCF such as corrugation, noise and energy consumption have not been considered in the present research. The reduction of wear and RCF on wheels could be an extra benefit, but not covered in the present research. In the present study, the focus is made on the curves and that short distance will not have any significant savings on the wheel. Assumptions and/or limitations: The tamping cost and other maintenance costs are not assumed in the maintenance cost. The reduction in damage other than wear and RCF, for example, corrugation, hunting, is not considered. The reduction in damage on the wheel by using a TOR-FM system is not considered. The typical life of a TOR-FM application system (both a wayside and an on-board system) can vary from 10 to 15 years, depending on the manufacturer and use.…”