Track Recording and Oscillograph Car

HISTORY OF TRACK RECORDING CARS ON INDIAN RAILWAYS

1. 1963 -- Amselar T R C

2. 1975 -- Electronic T R C

3. 1978 -- Track Reco. Cum Research Car (TRRC)

4. 1985 -- Microprocessor Based T R C

5. 1989 -- Phase I T R C μ-P Based + Limited Data storing

6. 1992 -- Phase II T R C (TGMS)

7. 1997 -- Phase III T R C Contactless Sensor

Track Recording by Mechanical / Electronic Equipment –

The following track recording equipments are in use in Indian Railways at present :–

(1) Track recording cars.

(2) Hallade track recorder.

(3) Oscillograph car.

(4) Portable accelerometers.

Track Recording Car – There are two types of track recording cars currently in use in Indian Railways, one mechanical and the other electronic. With these track recording cars, it is possible to have a continuous record of the track geometry under loaded conditions, by running the cars at nominated intervals.

Mechanical Track Recording Car (B.G.)–

(1) It has two bogies one of two axles and the other of three axles. The measuring

bogie has a base of 3.6 metres, and is three axled with an axle load of 7.0 tons. It

gives a continuous record of –

(a) Unevenness - Left rail. Short Chord 3.6 m & Long Chord 9.6 m

(b) Unevenness - Right rail. Short Chord 3.6 m & Long Chord 9.6 m

(c) Gauge – Variation over 1676 (B.G)

(d) Twist – At lower base of 3.6 m & higher base of 4.8 m.

(e) Alignment – Left rail. Short Chord 7.2m & Long chord 9.6m.

(f) Alignment - Right rail. Short Chord 7.2m & Long chord 9.6m.

(g) Speed

Frequency of Track Recording -

Track geometry monitoring of Metre Gauge routes is not to be done by track recording car. The Broad Gauge routes should be monitored by TRC as per the following frequencies (except for the routes where track recording is to be dispensed with):-

Track categories for various Parameters – The track charts record - Imperfections in the form of peaks and the magnitude of the peaks is an indication of the extent of the defect. For each track parameter, track should be classified kilometre-wise based on the number of peaks and their magnitude occurring in that kilometre. The specified values for different categories for various parameters are given below

Note : -

(i) 10 points exceeding the outer limit of an irregularity under each category is allowed in 1 Km. length of track. If more than 10 peaks in one Km. cross the outer limits of ‘A’ category the kilometer is classified ‘B’ and so on. Based on the number of peaks and extent of irregularity the track is classified into ‘A’, ‘B’, ‘C’, and ‘D’ categories separately for each parameter-gauge twist, unevenness and alignment.

(ii) The number of peaks in each kilometer exceeding the outer limit for the ‘B’

category isindicated as a suffix.

(2)The following limits of track tolerances are prescribed for the guidance of the Engineering officials on the suitability* of standard of maintenance of track for sanctioned speeds above 100 Km/hr. and upto 140 km/hr on BG track.

(i) Alignment defects - (versine measured on a chord of 7.5 metres under floating

conditions)

a) On Straight Track - 5mm; values upto 10mm could be tolerated at few isolated

locations**.

b) On Curves- + 5mm over the average versine, Values up to +7mm could be

tolerated at few isolated locations**. Total change of versine from chord to chord

should not exceed 10mm.

(ii) Cross Level Defects - No special tolerance limits. As regards cross levels, the

track should be maintained, to standards generally superior to that at present

available on main line track on which unrestricted speeds upto 100 Km/hr. are

permitted.

(iii) Twist- (to be measured on a base of 3.5 m)

(a) On straight and curve track, other than on transitions - 2mm/metre except that

at isolated locations**, this may go upto 3.5mm/metre.

(b) On transitions of curves - Local defects should not exceed 1mm/metres, except that at isolated locations** this may go upto 2.1 mm per metre.

(iv) Unevenness rail joint depressions (versine measured on a chord of 3.5m) - 10mm in general and 15mm for isolated locations**.

(v) Gauge variations - No special specifications. The maximum limits for tight and slack gauge should be within limit

(*) Suitability - Suitability refers to good riding quality for passenger comfort and not from stability point of view.

(**)In above `few isolated locations' has been taken as not exceeding 10 per km

(As per CS.no 96) 

The stability of trains against derailment depends upon several factors such as track geometry vehicle characteristics and state of their maintenance and speed of the particular vehicle at relevant point of time etc. rail wheel interaction is thus a complex phenomena and therefore safety tolerances for track alone cannot be prescribed in isolation. With in this view safety tolerances maintenance of track have not been prescribed on Indian railways. Each derailments faced therefore needs careful examinations of all available evidence in respect of track rolling stock, speed anc other factors considered relevant to arrive at cause.

The provision and tolerances mentioned in above para and elsewhere are with

a view to maintain track geometry for good riding comfort.

Oscillograph Car: -

(1) Brief description of the car :– The main equipment in this car is an Accelerometer, which consists essentially of a mass attached to one end of thin flexible plate, the other end of the plate being fixed firmly to the casing of the accelerometer. The space within the accelerometer casing is filled with a damping fluid (usually silicon liquid). The cantilever plate is strain gauged so that the deflection of the mass ‘m’ is sensed. This is calibrated to indicate the acceleration to which the mass is subjected. This acceleration is recorded in the form of an accelerogram. Thus the vertical and lateral acceleration on any part of the vehicle where the accelerometer is installed can be recorded. In track monitoring runs the accelerations at the loco cab floor are recorded by keeping the accelerometer as close to bogie pivot as possible.

(2) Details of recording: – the following parameters are recorded in the oscillograph car runs:–

(a) Vertical acceleration of loco cab.

(b) Lateral acceleration of loco cab.

In addition to the above, timing marks-one for every second-telegraph and km.

marks and even marks such as station buildings, bridges etc., are also recorded on the chart. The primary spring deflections left and right are also recorded.

(3) Frequency of recording –On B.G. routes oscillograph cars are used to monitor all group A routes. These cars are run once in six months to assess the riding quality of track as distinct from actual track geometry recorded by the track recording cars. The recording is done at the maximum sanctioned speed of the section.

Analysis of oscillograms and interpretation of results –

(1) The Oscillograms obtained from the oscillograph car are analysed for the vertical and lateral acceleration.

(2) The analysis of records is done on the following lines :–

(a) All peaks are to be measured from the base zero line i.e.,no allowance is to be

given when the trace shifts because of cant deficiency on curves. However, for the purpose of “ride index” calculations, lateral acceleration peaks are to be measured from the shifted base line on curves.

(b) The vertical and lateral accelerations above the threshold values are separately counted: Threshold value of acceleration may be taken follows :–

(i) In Loco Cab floor – The threshold value of acceleration in vertical mode is taken as 0.20 g. for locos (Diesel and Eletric). The threshold value of acceleration in lateral mode is taken as 0.20g. for diesel and electric locos with double stage suspension (i.e., for WDM-3, WDM-4, WDM-1, WDM-2/3 and WAG-2) with the exception of WDM-2 modified with single stage suspension. In case of other locos, with single stage suspension (i.e.,WDM-2 std., WAM-1, WAM-4, WAG-1, WAG-3,WAG-4,WCG-2, WCAM, WCM,WCM-2, WCM-4 and WCM-5) the threshold value may be taken as 0.30g.

(ii) On Passenger Coach Floor :– The threshold value of acceleration for both vertical and lateral modes shall be taken as 0.15g.

(iii)The analysis is done kilometer-wise and results are given, after counting the

peaks above threshold value for the particular locomotive –Station Yards, Other than Station Yards(Isolated locations), Active continuous stretches, Speed grouping table is also prepared.

Use of Oscillograph Car recordings :–

(1) Threshold values of acceleration are given. For ensuring good riding, track should be attended to at such locations where peaks above threshold values are noticed.

(2) Efforts should be made not only to check the extent of defect but also to find out whether it is occurring in an active patch; as such condition may lead to excessive oscillations.

FACTORS AFFECTING VEHICLE RESPONSE

• Frequency of track irregularity

• Spacing of the track defects

• Speed of the vehicle

• Direction of movement

• Natural frequency of vehicle

Portable Accelerometers-

(1) General- OMS-2000 equipment’s are portable accelerometers used for Oscillation monitoring using a portable accelerometer and transducers converting the oscillations to electrical signals which can be recorded electronically and

processed on PC.

(2) Operation- The OMS Accelerometer is kept in the cabin of locomotive or on the coach floor, as close to the bogie pivots as possible. It is preferable that same

coach and the same vehicular position are used in successive runs. The accelerations recorded are transferred to electronic recorder and are readable on

the LCD display on real time basis. The stored data can be downloaded on TMS

Computer for maintenance planning. This equipment measures the Track Performance by measurement of vehicle response in terms of vertical and lateral accelerations. The real time output of the equipment is in the form of value of peaks exceeding the limiting value, their location and Ride Index. These values

are available for both vertical and lateral accelerations.

(3) Frequency of Recording:

(A) Broad Gauge: Speed above 100 Kmph Once every month.

Others Once in two months

(B) Meter Gauge: Speed above 75 Kmph Once every month

Others Once in two months

The above schedule is only a guideline. Chief Engineers may vary it, depending

upon the availability of instrument and its use. For the time being A, B and C

routes are to be covered once a month and other routes can be covered as per

capacity and need.

(4) Recording of Defects: To assess the track quality, vertical and lateral acceleration peaks exceeding the values as below are to be considered:

Broad Gauge:

High Speed Routes above greater than 0.15g.

110 Kmph On A & B routes

Other Routes upto greater than 0.20g

110 Kmph

Meter Gauge : greater than 0.20g

(5) Classification of Track Quality - To classify a continuous section's (PWI's

jurisdiction/sub-division/ division) track quality, the following criteria is to be

used (average total number of peaks per km.):

The above criteria are for judging the quality of track. However, if the average

number of peaks of vertical and lateral accelerations exceeding 0.30g is more than 0.25 per km or more than one in any particular kilometer, the track will need

attention : At locations where peaks of lateral and vertical accelerations exceed

0.35g, the track will have to be attended to urgently.

Monitoring of the riding quality of track– While the track recording cars can

record the track geometry, the Hallade track recorders, the Oscillograph car and

the portable accelerometers record vertical and lateral accelerations, on which

depends, the riding quality.

Hallade track recorder –

(1) General– The Hallade track recorder is an instrument which produces a graphic record of defects in alignment and surface of the track over which it is carried.

The main parts of the instrument are –

(a) a drum rotated at a fixed speed by a clock work mechanism which carries a strip of paper 100 mm. wide covered over a carbon on which the chart is plotted,

(b) four sets of pendulums sensitive to movement in different directions which

records the oscillations in those directions of the vehicle and track.

(2) Frequency of testing with Hallade – On routes where Hallade track recorder is exclusively used for the track monitoring the following frequencies may be adopted:-