US3621179A

US3621179A - Cleaning metal surfaces to remove grease films

Info

Publication number: US3621179A
Application number: US11817A
Authority: US
Inventors: Jozef K Tylko
Original assignee: Tetronics Research and Development Co Ltd
Current assignee: Tetronics International Ltd
Priority date: 1970-02-16
Filing date: 1970-02-16
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

A method of treating a wearing surface of a railhead to remove an oil film and improve traction of a locomotive thereon in which effluent from a plasma jet torch is applied to the surface.

Description

[56] References Cited UNITED STATES PATENT 2,787,968 4/1957 Luvisi 2,819,681 1/1958 Luvisi 2,890,970 6/1959 Allen 2,906,858 9/1959 Morton, Jr 3,050,616 8/1962 Gage 3,140,380 7/1964 Jensen 3,336,460 8/1967 Hauck et 211.. 3,352,997 ll/1967 Butler 3,378,392 4/1968 Longo 2,824,526 1/1958 Nohejl Primary Examiner-J. V. Truhe Assislan! Examiner-George A. Montanye Attorney-Townshend & Meserole ABSTRACT: A method of treating a wearing surface ofa railhead to remove an oil film and improve traction of a 1ocom0- tive thereon in which effluent from a plasma jet torch is applied to the surface.

11 Ill" Illll PATENTEDNBV 16 l97l FIG. 5.

CLEANING METAL SURFACES TO REMOVE GREASE FILMS This application is a continuation-in-part of my prior U.S.

application Ser. No. 702,864, filed Feb. 5, i968 for Cleaning 5 Metal Surfaces to Remove Grease Films.

This invention relates to a method of treating rails to remove oil films and to a method of retarding the establishment of an oil film on a treated rail.

Although in many mechanical devices the provision of an 10 oil film between two coacting surfaces can be advantageous, where a tractive effort is to be applied to one of the surfaces then any slip between the two surfaces will lead to a loss of efficiency. An example of this occurs when considering a railway locomotive tractive wheel and the surface of the railhead of a railway line. In service the wheel and/or the surface upon which it runs can become coated with a film of oil which will act as a lubricant and permit slipping between the wheel and the surface. This coating may be only of molecular thickness but it can still cause substantial loss of tractive effort between the wheel and the surface. This loss can be appreciable particularly when a locomotive is accelerating from rest and it has been stated that as much as 1 percent of the total mileage covered by a locomotive is travelled under conditions of unsatisfactory wheel/rail adhesion.

Removal of the contaminating film by special chemical and mechanical methods has been proposed but this is expensive and capillary and allied effects will frequently cause the cleaned surface to be quickly recontaminated by the spreading of an oil layer from adjacent uncleaned parts of the metal surface.

Recent research in rail adhesion implicates boundary lubrication phenomena as one reason for a low value of wheel/rail adhesion. These phenomena cause the metal surface to actually react with the surface contaminants forming tenacious and strongly adhering films.

According to the invention there is disclosed a method of treating a wearing surface of a railhead to improve traction of a locomotive thereon by removing an oil film from the wearing surface comprises directing a gaseous effluent from a plasma jet torch onto the surface, the exposure to the effluent being short enough to have no deleterious effect on the railhead.

The method of the invention is to be distinguished from prior art methods of cleaning a rail to dry the rail and to remove oil films in which an intense flame from a suitable chemical burner is applied to the railhead. The action of the flame is to heat a portion of the railhead and when the temperature of this has reached a sufficiently high value the thin oil film is burned off. This method necessitates the raising of the temperature of the rail into the region where an adverse effect on the original heat treatment of the rail will be caused. In addition since the rail acts as a heat sink only a small proportion of the applied heat will actually have any action on the oil film. This inherent inefficiency of the thermal method of destroying the film will cause the cost of using the method to rise sharply if it is required for operation on a locomotive that is running at 5 or 10 mph. The cost of providing any significant thermal heating of the railhead when running at 50 mph. may well prove more objectionable than the original losses due to wheel slippage.

Although hitherto the plasma jet torch has been used as a source of intense heat in welding and cutting operations, it is not this property of the torch which plays a significant part in the present invention. The plasma torch can also act as a rich source of ions and free radicals and other highly reactive substances and these can be carried in a fast-moving gaseous stream to the railhead where they will have an effect directly on the oil film contaminating the metal surface without the need to transfer a substantial amount of thermal energy into this surface to cause an appreciable rise in its temperature.

The chemical reactions leading to the destruction of the thin film contaminating the railhead takes place instantaneously and the kinetic energy of the plasma jet helps to remove the reaction products. producing in the railhead surface a state of considerably increased frictional properties.

LII

In order to establish beyond any doubt that the method used in the present invention does not rely on thermal decomposition of the surface contaminants the following experiment was performed:

A plasma torch operating in a nontransferred mode and dissipating 25 kW. was suspended 8 cm. above a standard oil contaminated rail. After a lO-seconds-burst of a stationary plasma jet the surface temperature of the rail was measured by means of a precision surface temperature gauge and was found to be 82 C., while the body temperature of the rail, measured at a depth of 1 cm. below the surface, directly below the impinging plasma jet was found to be 61 C. These very low figures indicate that the decomposition of the oils and greases present on the surfaces of the rail could not have been accomplished by pyrolysis or any other form of thermal decomposition.

This point was further proved by exposing the same rail to a flame of a town gas torch, for a sufficiently long time to allow the surface temperature of the rail to rise to 280 C. Even at that temperature the contaminants were not decomposed and on subsequent measurement with a tribometer a low value of friction was obtained.

The plasma jet torch for treating the rail may conveniently be carried on the locomotive in a suitable position enabling it to be directed on to the rail surface. The torch might alternatively be positioned so as to treat a tractive wheel of the vehicle or possibly to treat both a wheel and the rail. The apparatus may be positioned on the locomotive so as to treat the rail ahead of the main direction of movement of the locomotive. The plasma jet may be also used to carry catalysts to the rail to promote the breakdown of the oil film. in addition to catalysts it is also within the scope of the invention to introduce into the plasma jet small quantities of substances or precursors of substances which will inhibit recontamination. Methods of providing such additives will be disclosed later in this specification.

An additional disadvantage of the former chemical and mechanical methods of cleaning a rail that have already been discussed is that a freshly cleaned area of the metal surface can become quickly recontaminated by a further oil film which spreads over the cleaned surface from adjacent uncleaned parts of the metal. it will be clear that even if the upper surface of the railhead has been thoroughly cleaned there will be quantities of oil on the sides of the rail that cannot be reached and in a matter of only minutes this will spread over the cleaned surface again so that the original condition is reestablished. The temporary cleaning effect that was produced by these former methods may thus be adequate for a single locomotive to pass over a given stretch of railway line but the tractive conditions will probably deteriorate considerably within a short time.

The present invention also comprises a method of retarding the recontamination of a cleaned area of the rail surface. Suitable inhibiting agents may be brought into contact with the treated surface, the agents acting to slow down the advancement of the oil film therealong so that the effect of the cleaning treatment will be prolonged. Conveniently the plasma jet torch may be used to convey the inhibiting agents to the metal surface. Examples of suitable inhibiting agents are given later in this specification.

By way of example, embodiments of the invention will be described with reference to the accompanying drawings in which,

FIG. 1 shows a tractive wheel of a locomotive on a rail,

HO. 2, is a cross section through the line ll-ll on FIG. 1,

FIG. 3 is an enlarged cross section through the line ill-lll on FIG. 2,

FIG. 4 shows a tractive wheel of a locomotive with ad jacently mounted plasma nozzle, and,

FIG. 5 shows a tractive wheel of a locomotive with plasma nozzle directed between the wheel and a rail.

When a tire I of a tractive wheel of a railway locomotive 1A is in contact with a rail 2 the actual area of contact is generally in the shape of an ellipse, 3. It has been shown that ifa tractive effort is applied to a wheel which is allowed to roll in the direction 4, a forward part 5 of the contact area of both bodies will remain rigidly together, while a rearward part 6 will experience relative slipping. A dividing line between the two parts will not be clearly defined but an increase in the tractive effort applied will result in an increase of the slipping rearward part of the area and the nonslipping forward area will be reduced. The forward area will eventually disappear and slipping ofthe wheel will take place.

The presence of contaminants on the coacting surfaces will generally cause a reduction of the adhesion between them. With a plasma jet nozzle 7, mounted ahead of the tire I a portion of the rail 2 can be passed through the jet before the rail comes into contact with the wheel. The plasma jet of elongated cross-sectional area which in operation issues from the jet is positioned so that its major axis is at right angles to a longitudinal axis of the rail. in this position, the shape of the jet as it impinges on the rail can be substantially the same as that of the ellipse 3. The combination of radiations from the jet, which as is well known to those skilled in the art, will produce further ionized particles, free radicals, and other highly reactive substances, and possibly also of the high kinetic energy of the jet stream have been found to have an adhesion increasing effect on the rail surface and to increase adhesion between the rail and the tractive wheel tire 1.

In a further example a plasma jet nozzle 7 as shown in FIG. 5 was mounted between the rail and wheel tire close to the point where these come into contact. The plasma jet is thus enabled to treat simultaneously the rail and tire surfaces.

A series of experiments was carried out using the plasma jet apparatus and details of the results obtained are given below:

A standard railway rail 5 yards in length was mounted horizontally and a plasma jet nozzle assembly carried on a tractor was positioned for movement directly above the rail. The distance between the nozzle and the upper surface of the railhead was made adjustable and could be varied between half an inch and 8 inches.

The rail was lightly wiped with an oiled cloth until its coefficient of friction fell from a value of 0.53 to 0.12. The tractor was started and the plasma nozzle assembly made to travel along the rail at speeds ranging from 0.1 to 20 mph.

ln a series of tests the nozzle was operated in a nontransferred arc mode. As shielding gas, mixtures of nitrogen and argon were used in ratios from 10:3 to 1:1 respectively. The volumes of total gas used varied with power consumption from 25 c.f.h. and 8 kw. to 150 c.f.h. and 24 kw.

The experiments were conducted using nozzles providing jets of circular and of elliptical cross section. The circular nozzles affected a zone of 3 cm. in width on the railhead when at a height of 5 inches above the rail. The nozzle providing an e1- liptical jet affected the whole flat portion of the rail that is about 5 cm. in width at the height of5 inches.

After carrying out one pass with the plasma jet the coefficient of friction of the rail was measured immediately after the treatment and was found to be of about 0.5 or higher. This high value of friction was retained for approximately 5 or 10 minutes without change, and then its value started to drop progressively, reaching 0.35 within 2 to 4 hours.

Additional mechanical cleaning of the rail was also tried by jetting finely powdered silica through the plasma jet at rates of from 0.1 to 12 g. per minute. It was found that the coefficient of friction was restored and remained restored for substantially longer periods which varied from 10 to hours in laboratory conditions.

Good results were also obtained when fine aqueous col-' loidal suspensions of silica were introduced to the plasma jet or alternatively when alkali or alkaline earth metal silicates were introduced through the plasma jet. The best results in this series of experiments were obtained with 1 percent w./v. aqueous solutions of potassium silicate which was introduced through the plasma jet at a rate of approximately 2 ml./min.

The above methods increased the time during which the plasma-treated oil contaminated surface of the rail retained its lgh frictional properties. A further increase In the frictional properties of the contaminated surfaces were obtained by depositing electrolytically or chemically layers of nickel, cobalt, rhodium and rhenium or alloys thereof in the arc-constricting passages of the plasma torch and also in the immediate vicinity of the arc exit, in the region known as the arc root zone and also in the arc chamber itself. These deposits, as was confirmed by spectroscopic measurements, are slowly ablated in the environment of the arc evolving their respective vapors in the region surrounding the plasma jet. It was found that the use of such layers increased frictional properties of the railhead surfaces even at substantially high velocities of plasma traverse, without the need of increasing the electrical power supplied to the plasma torch.

The foregoing descriptions of embodiments of the invention have been given by way of example only and a number of modifications may be made without departing from the scope of the invention. For instance, the stream of effluent emerging from the jet nozzle may contain additional or alternative gases to those specifically described. Ingredients such as water might be added to the jet to modify the effects of the plasma effiuent.

Use of the apparatus of the invention has been found to be particularly suitable on a railway locomotive of comparatively light weight such as a diesel-electric, electric or pneumatic locomotive. The reduction in gross weight of the locomotive can thus be effected without any tendency for increased slippage of the tractive wheels to occur.

lclaim:

l. A method of treating a wearing surface of a railhead to improve traction of a locomotive thereon by removing an oil film from the wearing surface, comprising the step of directing an effluent from a plasma jet torch onto the wearingsurface, the exposure to the effluent being sufficiently short in duration to have no deleterious effect on the wearing surface and to cause no appreciable rise in the temperature of said wearing surface, the destruction of the oil film being the result of a substantially instantaneous reaction between the constituents of said plasma and the oil film at a nonpyrolytic temperature for said oil film, and the removal of the products of said reaction from the wearing surface being effected by the kinetic energy of the plasma jet.

2. A method according to claim 1, in which a nozzle of the plasma torch is electrically connected for operation in a nontransferred arc mode.

3. A method according to claim 1, in which the plasma jet torch is directed into a space between the railhead and a locomotive wheel.

4. A method according to claim 1, in which silicon compounds are fed into the plasma torch for delivery to the surface.

5. A method according to claim 4, in which the silicon compound is silica.

6. A method according to claim 4, in which the silicon compound is potassium silicate.

7. A method according to claim 1, in which a catalyst selected from the group consisting of nickel, cobalt, rhodium, rhenium and alloys thereof is fed into the plasma torch for delivery to the surface.

8. A method according to claim 7, in which the catalysts are derived by ablation of a constricting member of the plasma torch.

Claims

2. A method according to claim 1, in which a nozzle of the plasma torch is electrically connected for operation in a nontransferred arc mode.
3. A method according to claim 1, in which the plasma jet torch is directed into a space between the railhead and a locomotive wheel.
4. A method according to claim 1, in which silicon compounds are fed into the plasma torch for delivery to the surface.
5. A method according to claim 4, in which the silicon compound is silica.
6. A method according to claim 4, in which the silicon compound is potassium silicate.
7. A method according to claim 1, in which a catalyst selected from the group consisting of nickel, cobalt, rhodium, rhenium and alloys thereof is fed into the plasma torch for delivery to the surface.
8. A method according to claim 7, in which the catalysts are derived by ablation of a constricting member of the plasma torch.