GB2388437A

GB2388437A - Calibration of apparatus used in determining forces on railway track

Info

Publication number: GB2388437A
Application number: GB0210712A
Authority: GB
Inventors: Roger West
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-10
Filing date: 2002-05-10
Publication date: 2003-11-12
Anticipated expiration: 2022-05-10
Also published as: GB0210712D0; GB2388437B

Abstract

The invention consists of a calibration process for a system of electronic apparatus which is attached to a railway line/track to determine the longitudinal stress set up in the line/track. This information is important to know in order to detect cracks and breakages in the line/track as well as the tension/compression changes caused by temperature changes, particularly in continuously welded track/line. The calibration process is based on providing two discrete points corresponding to two different forces and their respective electronically measured stress levels. It being known that there is a straight line graphical relationship between the two points. The readings are taken from a sensor S before and after tensioning of the track by "tensor" TR. These two force levels are set up by <SL> <LI>a) cutting the line/track to give zero stress/tension. <LI>b) using a tensor jack to tension the line/track prior to clipping it down to give the tensioned line/track force. Alternatively <LI>c) using temperature variation between day and night which will cause a change in stress/tension level at the rate of 1.73T per degree centigrade. </SL> A means of cross checking using 'one shot' devices for method c) above, when the force levels are not known, is proposed to easily determine rail tension.

Description

-1- 2388437

A calibration process for apparatus designed to measoreldetect railway lioe/track cracks and breaks and measure strew and tension Even monitoring these levels as the ambient temperature changes.

Background

There has been a problem virtually worldwide, of railway lines/tracks cracking and breaking. With the advent of continuously welded trackiline this problem has increased.

The causes of this are many and various and depend on the quality of the line/track, the quality of the installation and monitoring, the damage caused by train wheel flats and train overloading etc. This invention consists of a calibration process for a system of electronic apparatus which is attached to a railway line/track to determine the longitudinal stress set up in the linettrack. This information is important to know in order to detect cracks and breaks in the line/track as well as the tension/compression changes caused by temperature changes.

Desenption The calibration process is based on providing two discrete points corresponding to two different forces and their respective electronically measured stress levels. It being known that there is a straight line graphical relationship between the two points.

These two force levels are set up by a) cutting the line/track to give zero stress/tension.

-2 ( b) using a tensor jack attached to the adjacent clipped down section of track/line to tension the line/track prior to clipping it down fully.

Alternatively c) using temperature variation between day and night times which will cause a change in stress/tension level at the rate of 1.73T per degree centigrade.

or alternatively d) using an unclipped section of newly laid beck prior to clipping to give zero tension then tensioning and clipping, see FIG 1.

As shown in FIG 1, the first stage involves the noting of the output of sensor (S).

This output will be due to an initial offset caused by installation and residual voltage of the strain gauge within the sensor. In the example this is l SO millivolts.

Stage 2 involves clamping a tensor to the adjacent section. A tensor is a device for pulling on newly laid sections of railway line/track from a section already pinned or clipped down, in order to tension the new section. This tension overcomes the problem of the line/track buckling when the temperature rises and the section goes into compression.

The new section is tensioned and the new output of the sensor (S) is noted, in the example 500 millivolts.

The tension (T) is noted which is in the example 20 tonnes.

Stage 3 involves calculating the sensitivity of the sensor (S).

This is done by subtracting the initial sensor offiet voltage, 150 millivolts, from the setter output under tension,500 millivolts, to give 350 millivolts. This is then divided by 20 tonnes to give a sensitivity of 17.5 millivolts/tonne.

-3 Stage 4 gives the means by which the tension is calculated. An equation of sensor output in millivolts balanced by the sensitivity multiplied by the unknown tension (T) added to the initial offset voltage, is derived. The only unknown, tension (T) can then be calculated, 37.14 tomes in this example.

As a check on this value a discrete strain gauge, initially bonded to the line/track, can be used to checlc on the tension level. The output level is measured whilst bonded to the track and then cut from the line/track trepan drill. The new output, unstressed by the tension of the lineltrack, is subtracted from the initial reading to give the change due to the tension in the line/track.

The level of tension can be gleaned from this information and the sensitivity of the strain gauge. Alternative a system using a loadcell can be used to check on tension levels. In this the triangle of forces, created by jacking up a partially unclipped track/line' can be used by measuring the force through the jack and accurately measuring the distance jacked. The tension in the jack can be worked out by a combination of trigonometry and the triangle of forces. The strain gauge checking method and/or the loadcell method can be used in nwr the forces/tensions in the line/track when the zero reference Cannot be used as one of the forces, as in c) above.

A simple electronic system involving hardware and bespoke software could carry out 'in situ' calculation and indication of tension (T) for several lines/tracks/sensors simultaneously replacing the longhand vasion used for purposes of example above and in FIG 1. A software programme giving an alarm condition for cracked or broken line/track and Stress Free Temperature SET indication is proposed.

It has been paramount in desigrung this calibration process and the system itself that madly existing equipment for rail installation is used. The only additions involve very small and unobtrusive electronic equipment and components.

The possession of the track, normally at a premium for frequently used track, will be kept to a rnin1mum Once installed the electronic equipment should require no routine maintenance and infonnation from it can be either routinely downloaded via on line computer or transmitted via a telemetry line to a strategic controVmonitoring position.

As the calibrating process provides for a permanent indication and monitoring system there is the probability of use of such a system generally throughout the rail networks of the world to provide information on alarm/unsafe conditions.

Thus providing an early warning system of cracks and breaks in tracks and buckled tracks.

HEY TO FIGURE 1& CALIBRATION PROCEDURE STEPS

Key NR - New Rail ER - Existing Rail S - Sensor SL - Sleeper T - Tension TR - Tensor CALIBRATION STEPS

Take Reading from S e.g., 1 50mV.

Apply force to tension. Fasten down and take reading from S (there could be an in-line loadeell to measure it whilst pulling).

e.g. 500 mV with T = 20 tonnes.

3. Calculate sensitivity of S e.g. 500 - 150 = 17. SmV/Tonne 4. Now the tension equation for this section of rail is: sensor output = 17.5 x T + 150 mV i.e. 800 mV = 17.5xT + 150 mV 17.5 T = 650

T = 37.14 Tonnes Note: As a checking arrangement a strain gauge could be bonded to the web of the rail to cross check the tension against the calculated value of T.

Claims

1. An invention is proposed whereby simple techniques to create two quite different forces in a railway line/track give a means of calibrating an electronic equips nt system which measures forces and cracks/breaks in the line/track.

2. An invention is proposed which will provide for 'in situ' use and calibration of such a system as in Claim I using predonunatety equipment already available when the

line/track is laid or nod,

3. A means is proposed for send automatically calibrating such a system as in Claim I and 2.using bespoke hardware and software to read tension (T) directly.

4. A means is proposed by which the calibrated system as in Claim 1, 2 arid 3 can be used to indicate alann states due to cracking or breaking ofthe track. This alarm indication is part of a permanent monitoring system.

S. A means by which the calibrated system as in Claim 1, 2, 3 and 4 can be used to indicate Stress Free Temperature, SET.

6. A means by which for calibration and installation/maintenance of the electronic equipment as in Claim 1, 2, 3, 4 and 5, possession of the track, normally at a premium for frequenter used track, will be kept to a mrnurn.

7. A means by which the calibration process as in Claim 1, 2, 3, 4, 5 and 6 can use generally available stress measuring means to check on the levels of tension in the li'/track. These stress measurements are by simple 'one shot' devices.

8. A means by which the calibration process as in Claim 1, 2, 3, 4, 5, 6 and 7can use generally available stress measuring means to indicate tension levels in the line/track as part of the calibration process.