GB2459290A

GB2459290A - Adhesion improver composition

Info

Publication number: GB2459290A
Application number: GB0807029A
Authority: GB
Inventors: Tanya Ball
Original assignee: Basic Solutions Ltd
Current assignee: Basic Solutions Ltd
Priority date: 2008-04-17
Filing date: 2008-04-17
Publication date: 2009-10-21
Also published as: GB2459193A; GB2459193B; GB0906528D0; GB0807029D0

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. The composition may further include a suspension agent e.g. clay, a corrosin inhibitor etc. Also shown is a method of increaring adhesion using the adhesion improver.

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 locomotive wheels and rails is required to start or accelerate a 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. This coating of compacted leaves thereby presents major problems for train operating companies and also presents significant safety issues. Rails may also be contaminated by other matter as well s.

as vegetative matter for example, water, rust, oil, solid particles etc. In particular, leaves on tracks are compacted by passing trains and form a smooth coating.

This coating is hard and reduces the traction of the wheels with the rails and significantly reduces the effectiveness of the brakes of the train. S. *

* *: In particular, trains may not be able to stop in the required stopping distance and may overshoot plafforms or the stopping positions for signals. Signals passed at 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 effected and hindered since the wheels tend to slip or spin relative to the tracks.

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.

These conditions can be worsened due to the weather conditions, for example temperature, humidity and atmospheric pressure.

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 and the rails. Accordingly, the train signal system io 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 a 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 wheels and such damage may include the creation of flat areas. * ** * . S * S*

Various methods and systems have been used or proposed for cleaning rails and increasing the adhesion between the railhead and a wheel, for example, the * S.. S. * film or coating on the rail can be simply scraped off the rail. Other methods and *SSS** * systems include preventive methods (for example, leaf control), cleaning methods :r (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 and only provides a relatively instantaneous effect. In addition, dry sand does not increase the electrical conductivity between the wheels and the rails.

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, such materials 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 although, in fact, a blockage may be preventing the application. Accordingly, this blockage and the non-application of the necessary material may only be discovered after a significant period of time and requires the vehicle applying the mixture to travel along the same route again in order to apply the mixture.

Prior art abrasive mixtures incorporating stainless steel or non-corrosive metals, can cause problems with the metal particles which may locate in points along the track and cause faults or other problems. * ** * S * * *.

** Prior art abrasive mixtures do not have effective carrier systems that maximize the amount of sand I metal that can be deployed onto the railhead.

S.....

* These carrier systems do not allow the deployment of the sand / metal at high S.....

* speeds i.e. 60mph. S... * I...

Prior art abrasive mixtures freezes 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 a first 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.

Preferably the adhesion improver comprises a hydrocolloid i.e. pure and modified, 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.

S..... * S

The rheology modifier may be pseudoplastic. S... *S S * S S

* 25 The viscosity of the rheology modifier may be arranged to decrease with higher shear rates. The viscosity of the rheology modifier 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.

The viscosity of the adhesion improver may be arranged to decrease with higher shear rates. 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.

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.

The clay may comprise smectite and preferably predominantly comprises smectite. * ** * * S * SS

*:::: The clay may comprise magnesium aluminium silicate.

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*5SISI * The clay may comprise, prior to use, granules.

55.555 * S *:* Preferably the clay comprises a bentonite clay. ***. S. * SI

* 25 Preferably the metal comprises a corrosive metal.

Preferably the mixture comprises a pseudoplastic mixutre.

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 and preferably comprises between 30% to 50% by weight of sand and more preferably comprises 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. * * *

S.....

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

* 25 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 modifier and preferably comprises between 0.1% to 2.5% by weight of the rheology modifier.

Preferably the mixture comprises water and 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 arranged, in use, to increase the electrical conductivity between a rail and a wheel.

According to a second aspect on 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. * .*.

I * *.*

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

I... .1 * I S.....

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

* 25 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.

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. * S00 * I S. *

The preferred embodiment of the present invention provides a mixture that *00SS0 * is designed to improve wheel to rail adhesion and, in particular, to improve S.....

* (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 signaling circuits by increasing the conductivity between the rails and the wheels. However, it is currently believed that the 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 modifier. 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 sand 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. *�.. ****

: 25 The steel shot is corrosive and, once exposed, the steel shot corrodes and deteriorates. Accordingly, in time, the steel shot will eventually be dissipated.

Prior art non-corrosive or 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 inhibiter 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 I...

: quickly in the suspension whilst the water would accumulate and settle on the 25 surface ofthe 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, 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. ** S * * S

* *. 25 The rheology modifier increases the yield of the adhesion improver such that the maximum amount of sand and/or steel shot is more accurately and faster 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.

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 friction modifier 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 friction modifier does not include metal shot as it * *** can be used in the static units by the side of the rail tracks. *

*.S*.* * * 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 : 25 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.

The present invention provides a fast acting and easy 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 rallhead. The application may be arranged to immediately follow a cleaning method, for example a trainbone water jet may immediately precede the application of the adhesion improver.

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. * * *

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

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

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 according to claim I in which the rheology modifier comprises a hydrocolloid.
3. An adhesion improver according to claim 1 or claim 2 in which the rheology modifier comprises a gum.
4. An adhesion improver according to ciaim 3 in which the rheology modifier comprises an organic gum.
5. An adhesion improver according to claim 3 or claim 4 in which the gum comprises xanthan gum.

* **
6. An adhesion improver according to any preceding claim in which the rheology modifier is arranged, in use, to increase the viscosity of the mixture.
7. An adhesion improver according to any preceding claim in which the * :..: rheology modifier increases the yield of the adhesion improver. S...
8. An adhesion improver according to any preceding claim in which the . 25 rheology modifier is pseudoplastic.
9. An adhesion improver according to any preceding claim in which the viscosity of the rheology modifier is arranged to decrease with higher shear rates.
10. An adhesion improver according to claim 9 in which the viscosity of the rheology modifier reduces when the rheology modifier is subjected to shear.
11. An adhesion improver according to claim 9 or claim 10 in which the rheology modifier has an instantaneous increase in viscosity when the shear forces are removed.
12. An adhesion improver according to any preceding claim in which the adhesion improver comprises a mixture which is substantially homogenous.
13. An adhesion improver according to any preceding claim in which the mixture comprises a suspension agent.
14. 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.
15. An adhesion improver according to claim 13 or claim 14 in which the suspension agent comprises a clay.

* **
16. An adhesion improver according to claim 15 in which the clay comprises smectite. * *** 20
17. An adhesion improver according to claim 15 or claim 16 in which the clay comprises a bentonite clay.
18. An adhesion improver according to any preceding claim in which the *.: 25 metal comprises a corrosive metal.
19. An adhesion improver according to any preceding claim in which the mixture comprises a pseudoplastic mixture.
20. An adhesion improver according to any preceding claim in which the mixture comprises a gel.
21. An adhesion improver according to any preceding claim in which the mixture comprises a suspension.
22. An adhesion improver according to any preceding claim in which the mixture comprises a corrosion inhibitor.
23. An adhesion improver according to any preceding claim in which the mixture comprises a preservative.
24. An adhesion improver according to claim 23 in which the preservative is arranged to prevent or inhibit fungal growth.
25. An adhesion improver according to claim 23 or claim 24 in which the preservative comprises a fungicide.
26. An adhesion improver according to any preceding claim in which the mixture comprises a freeze point depressant. * **
27. An adhesion improver according to claim 26 in which the freeze **** point depressant is non-corrosive and environmentally friendly. *I..... * S
28. An adhesion improver according to claim 26 or claim 27 in which the freeze point depressant comprises propylene glycol. S...I **S.

*.. 25
29. An adhesion improver according to any preceding claim in which the metal particles comprise steel shot.
30. 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.
31. 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.
32. A method of increasing the adhesion of a rail for a wheel according to claim 31 wherein the method comprises applying the mixture to a rail head.
33. A method of increasing the adhesion of a rail for a wheel according to claim 31 or claim 32 wherein the method comprises forming the mixture into a substantially continuous stream or fluid to be adhered to the rail.
34. A method of increasing the adhesion of a rail for a wheel according to any one of claim 31 to claim 33 wherein the method comprises applying the mixture to a rail from an applicator which is mounted to a locomotive vehicle.
35. An adhesion improver to improve the traction of a wheel or a rail substantially as herein described. * *
36. A method of increasing the adhesion of a rail for a vehicle substantially as herein described.* a S.S* * a a *S * as a a S... S. * * as a.*