Directed Track Maintenance

As the name suggests, directed track maintenance (DTM) is a method of maintaining the track on the basis of directions that are given in this regard every day, and not as a prescribed routine. Directed track maintenance essentially consists of need-based maintenance rather than routine maintenance. In the case of DTM, track maintenance is done by proper identifying any defects in track geometry and rectifying these defects by attending to the track at the affected locations under close supervision, thereby maintaining the track at predetermined standards.

20.6.1 Objectives

The two main objectives of DTM are as follows.

(a) To maintain high standards of track maintenance as per predetermined tolerances.

(b) Reduction in the cost of maintenance mainly by the avoidance of unnecessary work.

In order to achieve the desired objectives, the following special features are incorporated in DTM vis-a-vis the conventional system of maintenance.

(a) The level of supervision is improved by hiring a well-trained and qualified permanent way mistry.

(b) A thorough record of the track defects identified before and after the completion of work is maintained to assess the inputs and also to help devise remedial measures of a more permanent nature by carrying out a scientific study based on the assimilated facts.

(c) Increasing the length of the unit especially on single lines increases the number of the gangmen available, resulting in an improvement in the productivity of the gang as well as the quality of work.

(d) The track is aimed to be brought to a predetermined level of service tolerances.

20.6.2 Work Done Under DTM

The maintenance operations to be carried out in a section where DTM has been introduced can be placed into the following four categories.

(a) Systematic overhauling In DTM, while the emphasis is on need-based maintenance, the intention is not to completely dispense with routine maintenance works such as systematic overhauling. Instead, the frequency of systematic overhauling is suitably increased, say by three to four years or as decided by the chief engineer, depending on local factors such as the condition of the track and

the formation, traffic density, permissible speed, and rainfall. A certain number of working days in the appropriate months of the year are earmarked for this work so as to cover one-third or one-fourth of the gang length by systematic overhauling, depending on the site conditions.

(b) Periodic maintenance work This includes works such as the lubrication of joints, cleaning of side drains, catch water drains, and repairs of the formation and cess. In the annual program, an adequate number of working days should be set aside during the appropriate months for periodic maintenance work.

(c) Occasional maintenance work This includes other works such as scattered renewal of rails, sleepers, and other track components, adjusting creep, restoring correct spacing between sleepers, building damaged rail ends, realigning curves, overhauling level crossings as well as points and crossings, and properly removing any deficiencies in the ballast section. The permanent way inspector assesses the quantum of such works that are to be carried out periodically in the order of their priority and draws up a programme in consultation with engineers after taking into consideration the availability of track material, ballast, welding parties, etc.

(d) Need-based maintenance The remaining working days in the annual programme are devoted to need-based maintenance, which is a new concept and forms the main distinguishing feature of DTM as compared to the conventional system of maintenance. The operations involved in need-based maintenance are as follows.

(a) Location of defects by analysing the results of the track recording car/ oscillograph car/hallade recorder and by foot plate/rear vehicle/trolley/foot inspection.

(b) Identification of defects by means of systematic inspection and by ground measurements taken by trained supervisors using precision instruments.

(c) Recording of the observations.

(d) Rectifying track defects by attending only to the defective portion followed by a post check of the same portion conducted by the supervisor to check its quality and output.

20.6.3 Annual Program for DTM

Table 20.4 depicts a typical chart showing the annual program of track maintenance under DTM.

The following points need to be mentioned with respect to the data given in Table 20.4.

(a) The chart is only for guidance, and the chief engineers of zonal railways can make variations to suit the local conditions.

(b) The chart is for that section of the track where manual methods of maintenance are adopted. Whenever maintenance involves the use of machines, the DTM unit will assist in the same by taking care of the work of pre-tamping and post-tamping and other operations not covered by machines.

Table 20.4 Annual program of DTM

Month

Work to be done

No. of days per week

January

(a) Lubrication of fish-plated joints

4

(b) Need-based maintenance

2

Feb. to

(a) Occasional maintenance work

As programmed by

April

AEN/PWI

(b) Need-based maintenance

Rest of the days

May

(a) Pre-monsoon work such as cleaning of side drains, catch water drains, and waterways

4

(b) Need-based maintenance

2

June to

(a) Periodic maintenance works incidental

As required

Aug.

of the monsoon season, such as attention to drainage, patrolling

(b) Need-based maintenance

Rest of the days

Sept to

(a) Systematic overhauling

4

Nov.

(b) Need-based maintenance

2

December

(a) Occasional maintenance works

As programmed by AEN/PWI

(b) Need-based maintenance

Rest of the days

Summary

Manual methods of track maintenance are not suitable for modem tracks consisting of long welded rails and heavy concrete sleepers. Mechanized maintenance has many advantages over manual maintenance. Measured shovel packing (MSP) and directed track maintenance (DTM) are two modern methods of track maintenance that have been found suitable for high-speed tracks in India. They are cost effective, time effective, and efficient. Indian Railways is slowly switching over to these methods of track maintenance.

Review Questions

1. Explain the following methods of packing of tracks that are a part of the periodic correction of track geometry.

(a) Beater packing

(b) Measured shovel packing

(c) Packing by track tamping machines

2. What is directed track maintenance (DTM)? In what way does it differ from through packing?

3. List the methods used for the maintenance of high-speed tracks and discuss the suitability of each method under Indian conditions.

4. What do you understand by modern methods of track maintenance? Why are modern methods of track maintenance required?

5. What is an on-track tamper? What kind of work is it used for? Describe the principles behind the working of a on-track tamper. What is the difference between an on-track and an off-track tamper?

6. What do you understand by measured shovel packing (MSP)? What are its advantages with respect to other methods of track maintenance? Briefly describe the main equipment used for MSP.

7. Briefly describe the procedure adopted for the MSP of a wooden sleeper track. How is the dehogging of rail ends achieved through MSP?

8. What are the various track components that are attended to under directed track maintenance? Name the equipment required to be kept with each unit of DTM.

9. Write short notes on

(a) MSP of turnout

(b) Viseur and mire

(c) Dehogging of rail ends

(d) Non-infringing track jack

CHAPTER

21

Measured Shovel Packing | RAILWAY ENGINEERING | Rehabilitation and Renewal of Track