GB2459193A

GB2459193A - Adhesion improver composition

Info

Publication number: GB2459193A
Application number: GB0906528A
Authority: GB
Inventors: Tanya Ball
Original assignee: Basic Solutions Ltd
Current assignee: Basic Solutions Ltd
Priority date: 2008-04-17
Filing date: 2009-04-16
Publication date: 2009-10-21
Anticipated expiration: 2029-04-16
Also published as: GB0807029D0; GB2459290A; GB2459193B; GB0906528D0

Abstract

An adhesion improver/friction modifier for improving the traction of a vehicle and, in particular to improve the traction of trains travelling along rails coated with fallen leaves. The adhesion improver comprises a mixture including sand, metal particles and a rheology modifier. The rheology modifier may be a hydrocolloid or a gum; and the matal particles may be steel shot. The composition may further include a suspension agent e.g. clay, a corrosin inhibitor etc. Another adhesion improver composition comprises a mixture including sand, a chelating agent and a rheology modifier. The chelating agent may be potassium hydroxide and/or phosphoric acid. Also shown is a method of increasing adhesion using the adhesion improver compositions.

Description

Adhesion Improver

Field of the Invention

The present invention relates to an adhesion improver/friction modifier and to a method of improving the traction of a vehicle. In particular, the present invention relates to an adhesion improver for trains travelling along rails coated with fallen leaves and to a method of improving the adhesion between a wheel of a train and the railhead.

Background to the Invention

Adhesion (or traction) between the wheel of a train and the railhead is required to propel the train forward and to enable the train to stop. The traction between the locomotive wheels and the rails is required to start or accelerate the train, to pull loads up gradients, or simply to maintain the required speed.

Rails that are located adjacent to trees and woodland may lose adhesion (or friction) and become slippy due to the fallen leaves. In particular, leaves on tracks are compacted by passing trains and form a smooth coating.

This coating is hard and reduces traction of the wheels with the rails and significantly reduces the effectiveness of the brakes on the train. The coating of compacted leaves thereby presents major problems for train operating companies and also presents significant safety issues. In particular, trains may not be able to stop in the required stopping distance and may overshoot p]atforms or the stopping positions for signals. Signals which when passed indicate danger are a significant hazard, and the inability to stop in a reasonable distance increase the chances of a collision. In addition, the acceleration of trains is affected and hindered, since the wheels tend to slip or spin relative to the tracks. Rails may also be contaminated by other matter as well as vegetative matter for example, water, rust, oil, solid particles etc. One cause of low adhesion between locomotive wheels and rails is due to the condition of the rails and, in particular, due to railhead contamination. Such contamination, and reduced adhesion, can result from water (for example, rain, dew, snow, ice or general moisture due to humidity), compacted leaves, rust, solid particles (for example, coal dust), fuel, oil, hydraulic fluid and other chemicals being present on the rails. These conditions can be worsened in certain weather conditions, for example, certain temperatures, humidities and atmospheric pressures.

Furthermore, a coating of compact leaves (which may produce a contaminant film) acts as an insulating layer and decreases the electrical conductivity between the wheels of the train and the rails. Accordingly, the train signal system cannot constantly locate and track the trains since the feedback of the location of the train is not gained. In addition, if the contaminant film acts as an insulator then this may produce a failure to activate track circuits which may lead to serious incidents or at least risk of such incidents.

Another problem connected with stopping trains, in particular when rails are slippery, is the damage caused to the surface of the whee]s. Such damage may inc]ude the creation of flat areas.

Various methods and systems have been used or proposed for cleaning rails and increasing the adhesion between the railhead arid a wheel. For example, the film or coatrag on the rail can be simply scraped off the rail. Other methods and systems include preventive methods (for example, leaf control), cleaning methods (for example, water jetting, scrubbing, etc) and/or the use of friction improvers (for example, sand) . The present invention relates to friction improvers.

Sand can be used to improve the traction between a wheel of a train and a railhead. However, dry sand is quickly dispersed from the rails and does not provide a prolonged increase in the traction. Therefore, it only provides a relatively instantaneous and temporary effect. In addition, dry sand does not increase the electrical conductivity between the wheels and the rails. Therefore, it may still be difficult to locate and track the trains.

A mixture of sand, metal and clay has been historically applied to the rails to provide an adhesion improver which has a tendency to adhere to and remain on the rails.

However, during storage, such mixtures tend to settle such that the (sand and metal) particles fall to the bottom.

This mixture can then be difficult to handle and distribute from the storage tanks. In particular, the sand, metal and/or clay particles may block or jam the applicators while being applied to the rails.

During distribution of this sand, metal and clay mixture, the operator may believe that the mixture is being applied to the rails even though, in fact, a blockage may be preventing the application. Accordingly, a blockage and the non-application of the necessary material to the rails may only be discovered after a significant period of time.

Therefore, the vehicle applying the mixture is required to travel along the same route again in order to apply the mixture.

Prior art abrasive mixtures incorporating stainless steel, or other non-corrosive metals, can cause problems, since the metal particles may become lodged in points along the track and cause faults or other problems.

Prior art abrasive mixtures do not have effective carrier systems. These carrier systems do not allow the deployment of the mixtures at high speeds i.e. 60mph.

Prior art abrasive mixtures freeze at -2 deg C.

It is an aim of the present invention to overcome at least one problem associated with the prior art whether referred to herein or otherwise.

Summary of the Invention

According to the first aspect of the present invention, there is provided an adhesion improver for improving the traction of a wheel on a rail, the adhesion improver having a variable viscosity such that it has a high viscosity when no or very low shear forces are applied and a low viscosity when higher shear forces are applied.

Preferably, the adhesion improver comprises a rheology modifier to impart the variable viscosity. Preferably, the adhesion improver is pseudoplastic.

Preferably, the adhesion improver further comprises a mixture of sand and/or metal particles.

According to a second aspect of the present invention there is provided an adhesion improver to improve the traction of a wheel on a rail comprising a mixture of sand, metal particles, and a rheology modifier.

According to a third aspect of the present invention, there is provided an adhesion improver to improve the traction of a wheel on a rail comprising a mixture of sand, a rheology modifier and a chelating agent.

Preferably, the adhesion improver further comprises metal particles.

Preferably, the adhesion improver comprises a hydrocolloid i.e. pure and modified acrylic polymers, microbial produced gums.

Preferably, the rheology modifier comprises a hydrocolloid.

Preferably, the rheology modifier comprises a gum.

Preferably, the rheology modifier comprises a polysaccharide.

Preferably, the rheology modifier comprises an organic gum.

The gum may comprise xanthan gum.

Preferably, the rheology modifier is arranged, in use, to increase the viscosity of the mixture.

Preferably, the rheology modifier is there to improve the delivery of solids onto the railhead.

Preferably, the rheology modifier increases the yield of the adhesion improver.

The rheology modifier may be pseudoplastic.

The viscosity of the rheology modifier may be arranged to decrease with shear. The viscosity of the rheology may reduce when the rheology modifier is subjected to shear (i.e. the rheology modifier is agitated, for example, mixed, shaken etc) and may have an instantaneous increase in viscosity when the shear forces are removed.

Preferably, the adhesion improver has a viscosity similar to that of water at higher shear forces.

The viscosity of the adhesion improver may be arranged to decrease with shear. The viscosity of the adhesion improver may reduce when the adhesion improver is subjected to shear (i.e. the mixture is agitated, for example, mixed, shaken etc) and increases the viscosity when the shear forces are removed.

Preferably, the adhesion improver comprises a mixture which is substantially homogenous.

Preferably, the adhesion improver comprises a chelating agent. The chelating agent may comprise a combination of two or more agents. Preferably, the chelating agent comprises potassium hydroxide and/or phosphoric acid, more preferably a combination of the two.

The mixture may comprise a suspension agent.

The adhesion improver may comprise a suspension agent which acts as a first suspension agent and a rheology modifier which also acts as a second suspension agent.

The suspension agent may comprise a clay.

T h e cl a y ma y comprise smectite and, preferably, predominantly comprises smectite.

The clay may comprise magnesium aluminium silicate.

The clay may comprise, prior to use, granules.

Preferably, the clay comprises a bentonite clay.

Preferably, the metal comprises a corrosive metal.

Preferably, the mixture comprises a pseudoplastic mixture.

Preferably the mixture comprises a gel.

Preferably, the mixture comprises a homogenous mixture.

Preferably, the mixture comprises a suspension.

Preferably, the mixture comprises a corrosion inhibitor.

Preferably, the mixture comprises a preservative, and preferably, comprises a preservative for the gum. The preservative may be arranged to prevent or inhibit fungal growth.

The preservative may comprise a fungicide.

Preferably, the mixture comprises a freeze point depressant.

The freeze point depressant may be non-corrosive and environmentally friendly. Preferably, the freeze point depressant comprises propylene glycol.

The mixture may comprise between 20% to 60% by weight of sand, preferably between 30% to 50% by weight of sand, and more preferably substantially 40% by weight of sand.

Preferably, the mixture comprises between 3% to 10% by weight of metal particles, and more preferably comprises between 5% to 8% by weight of metal particles.

Preferably, the metal particles comprise shot and more preferably comprise steel shot.

Preferably, the mixture comprises between 0.01% and 5% by weight of chelating agent, preferably between 0.05% and 3% by weight, and more preferably between 0.1% and 2% by weight of chelating agent.

The mixture may comprise between 0.05% to 5% by weight of the suspension agent, and preferably comprises between 0.1% to 2.5% by weight of the suspension agent.

The mixture may comprise between 0.05% to 5% by weight of the rheology modifer, and preferably comprises between 0.1% to 2.5% by weight of the rheology modifier.

Preferably the mixture comprises water. The adhesion improver may be made up to 100% by the addition of water to the other constituents of the mixture.

Preferably, the sand comprises fine sand.

Preferably, the sand particles have an average grain diameter substantially in the order of 0.25mm to 0.6mm, and more preferably in the order of 0.5mm.

Preferably, the metal particles have an average particle diameter substantially in the order of 0.5mm.

Preferably, the adhesion improver is alkaline.

Preferably, the adhesion improver has a pH of greater than 7, more preferably of greater than or equal to 10.

Preferably, the pH of the adhesion improver is in the range of 10.5 to 11.

Preferably, the adhesion improver is arranged, in use, to increase the electrical conductivity between a rail and a wheel.

According to a fourth aspect of the present invention, there is provided a method of increasing the adhesion of a rail for a wheel comprising applying a mixture to the rail wherein the mixture comprises sand, metal particles and a rheology modifier.

According to a fifth aspect of the present invention, there is provided a method of applying an adhesion improver according to either the first or second aspect of the invention to a rail, the method comprising the steps of: a) applying a shear force to the adhesion improver to reduce the viscosity thereof, and b)delivering the adhesion improver to the rail.

According to a sixth aspect of the present invention, there is provided a method of preventing or reducing adhesion of organic matter on a rail, the method comprising applying a mixture to the rail, wherein the mixture comprises sand, metal particles, a rheology modifier and a chelating agent.

Preferably, the viscosity of the adhesion improver increases upon delivery to the rail. This may be due to the removal of the shear force.

Preferably, the method comprises applying the mixture to a rail head.

Preferably, the method comprises adhering the mixture to the rail, and more preferably, to the railhead.

Preferably, the method comprises forming the mixture into a substantially continuous stream or fluid to be adhered to the rail.

Preferably, the method comprises applying the mixture to a rail from an applicator which is mounted to a vehicle, and preferably is mounted to a locomotive vehicle.

Preferably, the method comprises of increasing the amount of solids deployed onto the railhead.

Preferably, the method comprises increasing the electrical conductivity between the rail and the wheel of a vehicle.

According to another aspect of the present invention there is provided an adhesion improver to improve the traction of a wheel on a rail comprising a mixture of sand. and a rheology modifier.

The above features may be taken in any oombinaton and with reference to any aspect of the invention.

Description of the Preferred Embodiment

The present invention will now be described, by way of example only, with reference to the preferred embodiments.

In the following description, numerous specific details are set forth in order to provide a thorough understanding. It will be apparent, to those skilled in the art, that the present invention may be practiced without limitation to these specific details. It will be appreciated that well known methods and structures have not been described in detail so as not to unnecessarily

obscure the description.

The preferred embodiment of the present invention provides a mixture that is designed to improve wheel to rail adhesion and, in particular, to improve (locomotive) wheel to (locomotive) rail adhesion where the rail is coated with a covering of organic matter, for example, a coating of compacted fallen leaves. The preferred embodiment aims to ensure a uniform spread or distribution of the adhesion improver (or friction improver) across the rail head primarily increasing the traction of a locomotive but possibly also helping to rupture and soften leaf film and allow passing wheels to remove the contamination easily from the surface. In addition, the preferred embodiment also improves traction where acceleration problems occur and assists with the operation of signalling circuits by increasing the conductivity between the rails and the wheels. However, it is currently believed that most significant advantages of the present invention relate to the effective delivery of the number of solids deployed onto the railhead and hence longevity of product on the track after many axial passes.

In particular, the present invention comprises an adhesion improvement mixture comprising sand, metal particles, and a rheology modifer. The rheology modifier is arranged to modify the fluid properties of the mixture and also to improve the suspension of the sand particles and metal particles in the mixture and to prevent settlement of those particles, particularly in storage. Accordingly, the rheology modifier also functions as a suspension agent.

In the preferred embodiment, the friction improver mixture comprises 40 by weight of sand. The diameter of the sand grains in substantially 0.5mm. The sand is graded such that approximately 98% of the sand grains have a diameter in the region of 0.25mm and 0.6mm. The average or mean grain size (diameter) is approximately 0.5mm. In particular, the sand may be graded such that the average diameter is substantially 0.355mm with 98% of the sane having a diameter in the range of between 0.25mm to 0.6mm.

The adhesion improver mixture comprises 5 by weight of metal particles and, in particular, of metal shot. This metal shot is electrically conductive and aids the electrical connectivity between the wheels of the train and the rail. In the preferred embodiment, the metal shot comprise steel shot with a diameter of substantially 0.3 - 0.5mm. The hardness of the steel shot is determined such that the wheels of locomotives travelling along the railhead will not be damaged.

The steel shot is corrosive and, once exposed, the steel corrodes and deteriorates. Accordingly, in time, the steel shot will eventually be dissipated. Prior art non-corrosive resistant metal additives can cause significant problems, for example, blocking points or joints along the rails. The present invention will reduce or eliminate such problems through the natural deterioration of the metal particles.

The adhesion improver includes a corrosion inhibitor to inhibit the formation of corrosion, for example, whilst the adhesion improver including the steel shot is in storage. The corrosion inhibitor may comprise Flotec 340.

The adhesion improver mixture also comprises a suspension agent comprising a clay in order to further suspend the sand and metal particles within the mixture. In the preferred embodiment, the clay comprises a bentonite clay.

The suspension agent comprises smectite. The suspension agent is a water swellable clay.

The clay is a swellable clay.

The clay is a magnesium based clay. The clay is a colloidal clay and, in particular, comprises an absorbent colloidal clay base material.

The clay is a salt tolerant clay.

The mixture comprises water and the mixture of the adhesion improver is made up to 100% by water in order for a suitable and preferred consistency of the adhesion improver to be achieved. The bentonite clay helps to suspend the sand and metal particles in the water.

However, a mixture solely of these three materials (sand, clay and metal) would not be stable over a prolonged period of time and the (sand and metal) particles would tend to fall and settle relatively quickly in the suspension whilst the water would accumulate and settle on the surface of the particles.

This settlement in storage can result in blockages to the pumping equipment during application, particularly in the deposit pipe since the particles are unevenly distributed in the mixture and the particles may tend to settle and block such pipes etc. In addition, such a mixture has slow viscosity build up after exiting the deposit nozzle and may deteriorate into droplets that are easily blown away from the rail edge during the application. In addition, even if the mixture is applied successfully to the railhead, a significant portion of the mixture will tend to flow over the railhead rather than remain on the upper surface of the railhead. Accordingly, this mixture is wasted and is not effective in improving the adhesion of the contact surface on the railhead.

The preferred embodiment of the present invention comprises a rheology modifier to create a gel which strongly retains the sand grains and metal particles in the suspension. The preferred embodiment of the mixture is homogenous and exhibits characteristics similar to a colloidal dispersion rather than to a suspension and, in particular, the components tend not to settle or are at least very slow in settling. The adhesion improver comprises a hydrocolloid. The mixture is designed to flow easily through a pump and to be applied as a fluid to the railhead in a continuous linear coating.

The rheology modifier comprises a hydrocolloid which is an organic gum and, in the preferred embodiment, the rheology modifier comprises xanthan gum (a polysaccharide) . The xanthan gum greatly increases the viscosity of the mixture and aims to produce a liquid mixture which demonstrates pseudoplasticity. This means that when the mixture is the subject of a shear force i.e. during application to the rails, the mixture will thin out, but once the shear forces are removed the liquid will quickly thicken (i.e. once it has exited the applicator nozzle) . Accordingly, whilst in storage the sand and metal particles are maintained in suspension in the liquid but, when required, the liquid is still able to flow relatively easily in order to be coated onto the railhead.

The rheology modifier increases the yield of the adhesion improver such that the maximum amount of sand/or steel shot is more accurately and quickly deployed onto the railhead.

The xanthan gum also acts as a viscosity builder and binder to bind the sand and metal in the liquid mixture to produce a substantially homogenous material which does not appreciatively settle during storage.

The xanthan gum produces a synergistic effect with the bentonite clay in maintaining the sand and metal within the liquid and preventing settlement.

In the preferred embodiment, the adhesion improver comprises 0.61 by weight of xantham gum. The xantham gum is an organic compound. Therefore, its presence at a low level, for example 0.6% by weight, ensures that the beneficial rheological effects are seen in the adhesion improver whilst not providing the disadvantageous effects of the organic leaf film.

The preferred embodiment of the adhesion improver provides a preservative for the organic gum. Since the rheology modifier comprises an organic gum, this organic gum tends to deteriorate with time. The preservative is essentially a chemical agent which is arranged to destroy or inhibit the micro-organisms in the mixture. In the preferred embodiment, the preservative comprises panacide M at 0.5% weight in the formulation (30% w/v of dichloropen as the sodium salt) In one embodiment, the adhesion improver does not include a clay but consists of the rheology modifier which acts as the sole suspension agent. The adhesion improver may comprise 2% of rheology modifier (the hydrocolloid) In one embodiment the adhesion improver can include up to 7.5% by weight of propylene glycol to prevent the product from freezing, down to mm -7 deg C. In one embodiment the adhesion improver does not include metal shot as it can be used in the static units by the side of the rail tracks.

The preferred embodiment of the adhesion improver is a gel which is a pseudoplastic fluid. The adhesion improver can be easily and readily distributed to a railhead and coats the upper surface of the railhead rather than being blown away during application or flowing down the sides of the rails once coated. In addition, the sand and metal filings are suspended evenly in the adhesion improver mixture and the adhesion improver mixture will not appreciatively settle or deteriorate during storage.

In a further preferred embodiment of the adhesion improver, the mixture further comprises a chelating agent.

The chelating agent comprises 0.4% by weight potassium hydroxide and 0.8% by weight phosphoric acid.

The chelating agent acts to neutralise free iron on the railhead. Therefore, any iron oxide, or hydrated iron oxide, which would otherwise bond with organic matter, such as lignin, within leaves, is neutralised by the adhesion improver. The neutralisation of the iron on the railhead by the chelating agents makes the iron passive.

Therefore, the iron is unavailable for the bonding action with the organic matter in the leaves. Consequently, the chelating agents in the adhesion improver contribute to the prevention of bonding between free iron on the railhead and organic matter in leaves. This prevents the formation of a leaf film on the railhead.

Furthermore, the present invention provides an alkaline mixture. The adhesion improver has a pH of between 10.5 and 11. This high pH aids in dissolving the organic (leaf) matter bonded to the railhead. This works by dissolving the lignin contained within the leaves.

Therefore, the adhesion improver of the present invention softens the organic matter deposited on the railhead, and reduces the thickness of the leaf film.

The present invention provides a fast-acting and easily applicable mixture for use when required and/or when adverse conditions are identified. The adhesion improver can be stored (without significant degradation) for prolonged periods.

The adhesion improver can be effectively used with known trainborne sanders without blocking the pipes and ensures a smooth flow through the pipes and out of the applicator.

The adhesion improver can be applied manually or using a trainborne sander (for example, mounted on a multi-purpose vehicle) . Since the adhesion improver emerges as a continuous flow of material without forming droplets or being easily blown away, the friction improver can be applied at greater speeds compared to known mixtures (for example, sandite) . This therefore improves the efficiency in applying the friction improver. The adhesion improver thickens as soon as the fluid emerges from the nozzle and before the fluid contacts the railhead. The application may be arranged to immediately follow a cleaning method, for example a trainborne water jet may immediately precede the application of the adhesion improver.

The rheology modifier in the adhesion improver of the present invention increases the tack of the adhesion improver. Therefore, the rheology modifier helps the adhesion improver to "stick" the solids to the railhead.

Therefore, unlike known adhesion improvers, which are easily removed from a track upon exposure to water because the clay suspending agent has no water resistance, the adhesion improver of the present invention remains stuck to the railheads. Therefore, the adhesion improver of the present invention provides longevity of the solids on a track in wet conditions.

The adhesion improver of the present invention also helps in the delivery of the adhesion improver to the railhead since the sand and metal particles are adhered to the track by the rheology modifier. This results in an increase in the mass of solids delivered to the railhead.

The increase in mass of solids delivered to the railhead is illustrated by the Examples given in Table 1 and described below.

Flow Rate Speed of delivery Mass of solids delivered onto

Example

(m3/s) train (MPH) railhead (units, e.g. kg/rn2) 1 3 60 0.80 2 1 40 0.63 3 1 60 0.19 4 3 40 2.40 2 50 0.85 6 1 40 0.57 7 3 60 0.84 8 3 40 2.33 9 1 60 0.11 2 50 0.75 A 3 20 4.92 B 2 40 0.23 C 2 40 0.22 D 2 40 0.32 E 2 40 0.34

Table 1.

Examples 1 to 10 use the adhesion improver of the present invention comprising 40% by weight sand, 5% by weight metal shot, 0.6% by weight xantham gum, 0.8% bentonite clay, 2% corrosion inhibitor and 0.5% by weight preservative. The composition is made up to 100% by weight with water.

Comparative examples A to E use an industry standard composition (Sandite) which comprises no rheo]ogy modifier.

In each of the examples and comparative examples listed in Table 1 above, a lm length of track was cleaned using a high pressure water jet system. The composition was then applied to the cleaned track from a rail head treatment train (PHIl) . The PHIl delivered the composition to the track at the specified speeds and flow rates.

The composition was then removed from the im length of track using pre-weighed paper towels and plastic pots.

The pots were allowed to dry for at least four days and then re-weighed to quantify the mass of solids collected from the lm length of track. This valus was used to determine the mass of solids delivered to the track in kg/m2.

As can be seen from the results given in Table 1, the adhesion improver of the present invention allows a higher mass of solids to be delivered to the railhead at lower flow rates and higher speeds.

The adhesion improver may simply be made by mixing the sand, steel shot, xanthan gum crystals together with granular bentonite clay (for example Van Gel B granules) and adding water to the required viscosity/consistency.

In addition, if required, the corrosion inhibitor and/or the preservative and/or freeze point depressant can also be added to the mixture.

In particular, the bentonite clay is hydrated by adding the granular claim slowly into water at 40°C. The hydrated clay is then homogenised for 20 to 30 minutes.

Next, a lower shear mixer is charged with water and the sand and xanthan gum are added and blended for 10 minutes.

The remaining ingredients, including the bentonite clay and any optional additives, are then charged into the low shear mixer and blended for a further 10 minutes. The resulting mixture is then transferred to a storage vessel and the viscosity is checked after 24 hours.

The xanthan gum and bentonite clay produce a synergistic effect in retaining the sand and metal particles.

These chemicals also give an ideal viscosity profile that greatly improves the delivery of solids onto the railhead.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features

disclosed i n th i s specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims 1. An adhesion improver to improve the traction of a wheel on a rail comprising a mixture of sand, metal particles and a rheology modifier.
2. An adhesion improver for improving the traction of a wheel on a rail, the adhesion improver having a variable viscosity such that it has a high viscosity when no or very low shear forces are applied and a low viscosity when higher shear forces are applied.
3. An adhesion improver according to claim 2, wherein the adhesion improver comprises a rheology modifier to impart the variable viscosity.
4. An adhesion improver according to any of claims 2 and 3, wherein the adhesion improver further comprises a mixture of sand and/or metal particles.
5. An adhesion improver to improve the traction of a wheel on a rail comprising a mixture of sand, a rheology modifier and a chelating agent.
6. An adhesion improver according to claim 5, wherein the adhesion improver further comprises metal particles.
7. An adhesion improver according to any of claims 1 or 3-6 in which the rheology modifier comprises a hydrocolloid.
8. An adhesion improver according to any of claims 1 or 3-7 in which the rheology modifier comprises a gum.
9. An adhesion improver according to any of claims 1 or 3-8 in which the rheology modifier is arranged, in use, to increase the viscosity of the mixture.
10. An adhesion improver according to any of claims 1 or 3-9 in which the rheology modifier is pseudoplastic.
11. An adhesion improver according to any preceding claim in which the adhesion improver comprises a mixture which is substantially homogenous.
12. An adhesion improver according to any preceding claim in which the mixture comprises a suspension agent.
13. An adhesion improver according to any preceding claim in which the adhesion improver comprises a suspension agent which acts as a first suspension agent and a rheology modifier which also acts as a second suspension agent.
14. An adhesion improver according to claim 12 or claim 13 in which the suspension agent comprises a clay.
15. An adhesion improver according to any preceding claim in which the metal comprises a corrosive metal.
16. An adhesion improver according to any preceding claim in which the mixture comprises a pseudoplastic mixture.
17. An adhesion improver according to any preceding claim in which the mixture comprises a corrosion inhibitor.
18. An adhesion improver according to any preceding claim in which the mixture comprises a preservative.
19. An adhesion improver according to claim 18 in which the preservative comprises a fungicide.
20. An adhesion improver according to any preceding claim in which the mixture comprises a freeze point depressant.
21. An adhesion improver according to claim 20 in which the freeze point depressant comprises propylene glycol.
22. An adhesion improver according to any preceding claim in which the metal particles comprise steel shot.
23. An adhesion improver according to any preceding claim, wherein the adhesion improver is alkaline.
24. An adhesion improver according to any preceding claim in which the adhesion improver is arranged, in use, to increase the electrical conductivity between a rail and a wheel.
25. A method of increasing the adhesion of a rail for a wheel comprising applying a mixture to the rail wherein the mixture comprises sand, metal particles and a rheology modifier.
26. A method of applying an adhesion improver according to either the first or second aspect of the invention to a rail, the method comprising the steps of: a) applying a shear force to the adhesion improver to reduce the viscosity thereof, and b) delivering the adhesion improver to the rail.
27. A method of preventing or reducing adhesion of organic matter on a rail, the method comprising applying a mixture to the rail, wherein the mixture comprises sand, metal particles, a rheology modifier and a chelating agent.
28. The method of any of claims 25 to 27 wherein the method comprises applying the mixture to a rail head.
29. The method of any of claims 25 to 28 wherein the method comprises forming the mixture into a substantially continuous stream or fluid to be adhered to the rail.
30. The method of any of claims 25 to claim 29 wherein the method comprises applying the mixture to a rail from an applicator which is mounted to a locomotive vehicle.
31. An adhesion improver to improve the traction of a wheel or a rail substantially as herein described.
32. A method of increasing the adhesion of a rail for a vehicle substantially as herein described.