GB2274712A

GB2274712A - Non-destructive testing of composite conductor rails

Info

Publication number: GB2274712A
Application number: GB9301214A
Authority: GB
Inventors: David Julian Hartland
Original assignee: Brecknell Willis and Co Ltd
Current assignee: Brecknell Willis and Co Ltd
Priority date: 1993-01-22
Filing date: 1993-01-22
Publication date: 1994-08-03
Anticipated expiration: 2013-01-22
Also published as: DE4401484C2; DE4401484A1; GB2274712B; GB9301214D0

Description

Non-Destructive Testing of Composite Conductor Rails

Field of the Invention

This invention relates to a method for the nondestructive testing of composite conductor rails and to equipment for carrying out this method.

Conductor rails are used in electric railway systems and in other transportation systems such as overhead railways.

Composite conductor rails normally comprise a main body of aluminium and a wear-resisting facing layer bonded or otherwise fixed to the main body. A number of methods of producing composite conductor rails have been developed and one such method is described in British Patent Specification No. 2 231 544, to which reference should be made.

The facing layer, which is normally of steel, needs to be bonded effectively to the aluminium main body and, as part of standard quality control procedures, the effectiveness of the bond needs to be checked.

Traditional methods of testing have involved cutting a section from the end of a conductor rail and then carrying out a destructive test on this section. Such methods have obvious limitations and can provide no indication as to any variation in the effectiveness of the bond along the length of the conductor rail.

It is accordingly a specific object of the present invention to provide a method for the non-destructive testing of a conductor rail which is such that the effectiveness of the bond between the facing layer and the main body can be tested at a plurality of positions along the length of the conductor rail.

Another object of the invention is to provide a method for testing the effectiveness of the bond between the facing layer and the main body of a conductor rail, which method has cost-saving advantages as compared to existing methods of testing.

A further object of the invention is to provide equipment for the carrying out of this method.

Summary of the Invention

According to a first aspect of the present invention there is provided a method for the non-destructive testing of a conductor rail comprising two different components bonded longitudinally together, said method comprising:- a) moving a first probe or probe assembly into contact with one of the components, b) moving a second probe or probe assembly into contact with the other component at substantially the same position along the length of the rail, c) obtaining a reading which relates to the electrical resistance of that part of the rail between the probes or probe assemblies.

d) comparing said reading with known data to obtain an indication of the effectiveness of the bond between the two components at that position. and c) repeating the operation at a plurality of positions along the length of the rail.

Probe assemblies, each comprising a pair of probes, may be used. Each pair of probes may be spaced a short distance apart. for example, a few millimetres. A first pair of probes will be moved into contact with the first component whilst the second pair of probes moved into contact with the second component. The probe assemblies are preferably connected to a processor which includes a facility for providing a numerical reading indicative of the applied voltage divided by the current flowing through the rail, said numerical reading thus W being proportional to the resistance between the probe assemblies.

The pairs or sets of probes are preferably mounted on a trolley on which the processor is also mounted, the trolley being provided with wheels positioned in dependence on the profile of the rail so that the trolley can readily be moved along the rail so as to facilitate the taking of a plurality of readings at positions spaced along the rail.

The probes are preferably carried by an arm which is pivotally mounted on the trolley. One pair of probes are carried by the arm by means of a spring mounting in a location such that they engage the facing layer at a position generally centrally of the conductor rail and the other pair of probes are carried by the arm, again by means of a spring mounting, in a location such that they engage a preselected part of the main body. The arrangement is such that the arm is movable between a raised position, in which the probes are clear of the conductor rail so that the trolley can be moved along the rail, and a lowered position, in which the probes engage the rail so that a resistance reading can be obtained.

The resistance between the selected point on the facing layer and the selected point on the main body will depend on whether the measurement is taken at the end of the rail or at a position spaced from the end of the rail. When, therefore, a reading is obtained as a result of a measurement taken at the end of the rail, that reading is compared with one set of data whereas, when a reading is obtained as a result of a measurement taken within the main length of the rail, that reading is compared with another set of data.

According to a second aspect of the present invention there is provided equipment for use in the carrying out of the method defined above, said equipment comprising a first probe or probe assembly movable into engagement with a selected part of the facing layer, a second probe or probe assembly movable into engagement with a selected part of the main body of the rail, said probes or probe assemblies engaging the rail in substantially the same plane longitudinally of the rail, and processor means for providing a reading related to the electrical resistance of the conductor rail at the position at which it is engaged by the probes or probe assemblies.

0 The probes or probe assemblies and the processor means may be mounted on a trolley which is provided with wheels whereby it can be moved along the rail.

Brief Description of the Drawing

The drawing shows the cross-sectional configurations of a number of conductor rails, these being examples of the rail configurations to which the invention is applicable.

Description of the Preferred Embodiment

Each of the conductor rails shown in the drawing comprises a main body 10 of aluminium and a steel facing layer 11 bonded to the main body 10. The facing layer 11 may be formed by welding together two longitudinal steal strips with the welding operation being carried out with the steel strips in contact with the main body. This method of production of the conductor rail is described in detail in Patent Specification No. 2 231 544, to which reference should be made.

The conductor rail has a low longitudinal resistance. The resistance depends on the cross-sectional configuration of the main body 10, with the rail which has the largest dimensions having a longitudinal resistance of 4 milliohms per kilometre and with the rail which has the smallest dimensions having a longitudinal resistance of 20 milliohms per kilometre.

The electrical pick-up shoe contacts the facing layer 11 and it is thus important that there should be a low electrical resistance between the main body 10 and the facing layer 11. The resistance will be low if the facing layer 11 is bonded tightly to the main body 10 and there are no gaps or nonconductive inclusions between the facing layer 11 and the main body 10. The resistance will also depend on the position along the length of the rail at which any resistance measurement is taken. The maximum resistance, assuming uniform bonding, will be at the ends of the rail.

Equipment for use in obtaining a measurement indicative of the electrical resistance of the rail comprises a trolley which has wheels which run on the presented surfaces of the main body 10 so that it can readily be moved along the lenath of the rail. On the trolley, there is a pivotally mounted arm which carries a pair of probe assemblies.

Each probe assembly consists of two probes which are spaced a short distance apart, for example, 5 millimetres apart. The probes are carried on the arm by spring mountings with one probe assembly movable into engagement with the facing layer 11 at a position on the centre line of the conductor rail and with the other probe assembly movable into engagement with the upwardly facing surface of the base of the main body 10. The probe assemblies are arranged so that they engage the conductor rail in substantially the same plane longitudinally of the rail.

The probes are connected to electrical test equipment mounted on the trolley, the test equipment including a processor which provides a reading indicative of the electrical resistance of the rail at the position at which the measurement is being carried out. The electrical circuitry of the test equipment may be such that one probe of the probe assembly in contact with the facing layer forms part of a first test circuit which also includes one probe of the probe assembly in contact with the main body. this first test circuit being utilised to determine the voltage drop between the two probes.

The electrical circuitry of the test equipment may further be such that the other probes of the two probe assemblies are contained within a second test circuit which is utilised to determine the current flowing between the two probes.

The reading can be displayed on a counter or like display and the displayed reading is then compared with known data so that an assessment may be carried out as to whether or not the facing layer 11 is effectively bonded to the main body 10. As mentioned above, different data apply to measurements taken at the ends of the rail as compared to measurements taken along the main length of the rail.

It is to be appreciated that. as the method of testing is totally nondestructive and as readings can rapidly be carried out at different positions along the length of the rail. quality control procedures can be improved and cost-saving advantages obtained.

The testing of the rails can be carried out not only as part of the manufacturing process for the production of the rails but also when the rails are in use. This allows the bonding to be checked periodically during the anticipated forty-year life of a conductor rail.

The method of testing and the equipment can thus be used as part of a conductor rail maintenance or replacement programme.

Claims

Claims: -

1. A method for the non-destructive testing of a conductor rail comprising two different components bonded longitudinally together, said method comprising:- a) moving a first probe or probe assembly into contact with one of the components.

b) moving a second probe or probe assembly into contact with the other component at substantially the same position along the length of the rail, c) obtaining a reading which relates to the electrical resistance of that part of the rail between the probes or probe assemblies, d) comparing said reading with known data to obtain an indication of the effectiveness of the bond between the two components at that position, and e) repeating the operation at a plurality of positions along the length of the rail.

2. A method as claimed in Claim 1, which includes the use of probe assemblies, each assembly comprising a pair of probes spaced a short distance apart. one pair being moved into contact with the first component whilst the second pair are moved into contact with the second component.

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3. A method as claimed in Claim 2, in which the probes are connected to a processor which includes a facility for providing a numerical reading indicative of the applied voltage divided by the current flowing between the probes, said numerical reading thus being proportional to the resistance between the probes.

4. A method as claimed in Claim 1, and for testing a conductor rail comprising a main body and a facing layer bonded to the main body, in which the probes or probe assemblies are mounted on a trolley provided with wheels positioned in dependence on the profile of the rail so that the trolley can readily be moved along the rail so as to facilitate the taking of a plurality of readings at positions spaced along the rail.

5. A method as claimed in Claim 4, in which the probes or probe assemblies are carried by an arm which is pivotally mounted on the trolley.

6. A method as claimed in Claim 5, in which the probes are arranged in pairs, one pair of probes being carried by the arm by means of a spring mounting in a location such that they engage the facing layer at a position generally centrally of the conductor rail and the other pair of probes being carried by the arm, again by means of a spring mounting, in a location such that they engage a preselected part of the main body.

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7. A method as claimed in Claim 1, in which, when a reading is obtained as a result of a measurement taken at the end of the rail. that reading is compared with one set of data whereas, when a reading is obtained as a result of a measurement taken within the main length of the rail, that reading is compared with another set of data.

8. A method for the non-destructive testing of a conductor rail substantially as hereinbefore described.

9. Equipment for use in the carrying out of the method claimed in Claim 1, said equipment comprising a first probe or probe assembly movable into engagement with a selected part of the facing layer. a second probe or probe assembly movable into engagement with a selected part of the main body of the rail, said probes or probe assemblies engaging the rail in substantially the same plane longitudinally of the rail, and processor means for providing a reading related to the electrical resistance of the conductor rail at the position at which it is engaged by the probes or probe assemblies.

Equipment as claimed in Claim 99 in which the probes or probe assemblies and the processor means are mounted on a wheeled trolley.

11. Equipment as claimed in Claim 10, in which the probes or probe assemblies are carried by an arm pivotally mounted on the trolley.

12. Equipment as claimed in Claim 10, in which the wheels of the trolley are such that the trolley can run on the rail being tested.

13. Equipment for use in the non-destructive testing of a conductor rail substantially as hereinbefore described.