SHALLOW SCREENING OF BALLAST

SHALLOW SCREENING OF TRACK BALLAST 


Objective:
It is a process, Which demonstrate the procedure for cleaning of contaminated ballast on track/in-situ. If the contaminated ballast is dumped by hoppers for top ballasting and tamping of track was not done, so we can adopt Shallow Screening method to remove the contaminated ballast from new construction track or in maintenance track also.  

Principle:
In the case of manual maintenance, the crib ballast between sleepers is opened out to a depth of 50 to 75 mm. below the bottom of sleepers, sloping from the centre towards sleeper end. For machine maintained section, the crib ballast in the shoulders should be opened out to a depth of 75 to 100mm. below the bottom of sleepers, sloping from the centre towards sleeper end. The ballast in the shoulders opposite to the crib as well as the sleepers is removed to the full depth.

Equipment:
Manual cleaning (Conventional method):
  1. 20mm sieve with inclined support (At least 1 no for every 30m),
  2. Measuring scale/tape, and
  3. Ballast handling tools.
Machine Maintenance (3-tier system of track maintenance):
  1. Ballast cleaning machine.
    BCM
Procedure (Conventional method):
  • The chosen non-conformity area should be protected by restricting traffic by mounting Red Flag on the both ends of the track an the information is passed on to traffic controller for proceeding authority.
  • As per the Indian Railway Permanent way manual, Para 227. In the case of manual maintenance, the crib ballast between sleepers is opened out to a depth of 50 to 75 mm. below the bottom of sleepers, sloping from the centre towards sleeper end. For machine maintained section, the crib ballast in the shoulders should be opened out to a depth of 75 to 100mm. below the bottom of sleepers, sloping from the centre towards sleeper end. The ballast in the shoulders opposite to the crib as well as the sleepers is removed to the full depth.   
  • A slope is given at the bottom sloping away from the sleeper end. The ballast is then screened and put back. Care should be taken to see that the packing under the sleepers is not disturbed and the muck removed is not allowed to raise the cess above the correct level.
  • Two contiguous spaces between sleepers should not be worked at the same time.
  • Screening should be progressed in alternate panels of one rail length. In no circumstances should several rail lengths of track be stripped of ballast.
  • Where drains across the track exist, they should be cleaned and filled with boulders or ballast to prevent packing from working out and forming slacks.
  • After screening, fresh ballast should be poured back, extra ballast being run out previously for the purpose. Work should be commenced after making sure that the ballast will not be seriously deficient. Deficiency, if any, should be shown in the central portion of sleeper and this also should be made up soon.
Precautions:
    1. Traffic controller must aware of the working area and should restrict the traffic.
    2. The execution team must mount the red flag on either side of the track.
    3. Under sized (passe through 20mm sieve) should not poured back on track and they throw from the working area after completion.
    4. Sleepers top surface should also be cleaned if any mud lumps are there.
    5. Sleeper packing (Bellow the sleeper) must not disturb. 
    Reference:

    1. Indian Railway P-Way manual.

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