Deep screening in single rail section, SWR & LWR,

Question - Describe procedure of Deep screening in single rail section, SWR & LWR, pre caution to be observed at site also to be mentioned.

Ans. Due to presence of bad formation abrasion and attrition of ballast, impact loads excessive rainfall, ballast gets chocked up and track drainage is impaired. At this stage entire ballast under sleeper and crib right up to formation level/sub ballast level is removed to improve drainage and running quality of tack, the process is called Deep screening. It can be carried out at following locations:

1. Deep screening shall be done after 500 GMT or 10 years whichever is earlier. However Deep screening can be carried out when clean cushion ballast is less than 150mm to ensure dropper machine temping.

2. Prior to CTR

3. Prior to TSR

4. Due to caking of Ballast resulting into unsatisfactory riding.

5. Need of intermediate Deep screening is to be decided by C.T.E. Process of Deep screening in track other than LWR is as below.

i. Longitudinal section of the track shall be prepared indicating the rail level at every 30 m. including changes of grades obligatory points like culverts, Bridges, Tunnels, Level crossing points & Crossing etc.

ii. In station yards on run through lines x-section at every 50 m. shall be plotted indicating

platforms levels, Rail Levels etc.

iii. On the bases of L-section and x-section the Final level shell be decided keeping in view the

a. Depth of Ballast cushion to be provided

b. Lifting and lowering track

c. Possibility of elimination humps, sags and unevenness in the existing longitudinal

section.

Screening operation:-

1. The work of Deep Screening shall be done under the supervision of authorized supervision having

compliancy certificate.

2. The rail direction of Deep screening should be in opposite direction of traffic. 

a. Remove ballast from ‘A’, B on either side sleeper ‘I’ down to final formation level and provide wooden block to support the rail level for passing Train.

b. Remove ballast from Under ‘1’ down to final track level sub ballast level, screen ballast put back under sleeper ‘1’ and pack.

c. Remove wooden block from space “A”.

d. Remove ballast from space ‘c’ down to formation level, screen it and place in space support the rail in space ‘C’ with wooden blocks. 

e. Remove ballast from under sleeper ‘2’ down to formation level. 

f. Provide screened ballast under sleeper ‘2’ and pack. 

g. Remove ballast from space ‘D’ down to formation level, screen it and place in space ‘B’ up to bottom of sleeper. Take ballast from quantity outside and screen the 

h. Remove ballast from under sleeper’3’ and so on till the entire length is provided with screened ballast up to bottom of sleepers. 

i. Lift the track to provide additional cushion where required. Pack the track in final passion and box. 

Precautions during the work Following precaution should be observed strictly to avoid any undesirable situation during the deep screening work-

i. No unscreened length is left in between the screened portion as it may lead to uneven settlement.

ii. When ballast is being removed from any sleeper, invariably there will be at least 4 fully supported sleepers In between and next sleeper tackled. 

iii. Lifting shall be limited to 50mm at a time .

iv. Working tools such as beater, crow bar and ballast etc. is removed before the passage of traffic.

v. Rail is supported properly on wooden blocks before any traffic is allowed to passes. During manual deep screening the S/R will be as under:-

Deep screening operation in LWR track:-

Precautions during Deep Screening:-

i. Ballast cleaning machine, Tamping machine and dynamic Track stabilizes shall as for as possible, be deployed in one consist.

ii. Temperature records of the section when deep screening is to be undertaken, shall be studies for the previous and the current year. The maximum and minimum rail temperature attainable during the period of deep screening ad during the period of consolidation shall be estimated.

a. If range of rail temperature falls within Td + 10 degree to Td- 20 degree, deep screening may be done without cutting or temporary distressing.

b. If range of rail temperature fall outside (a) above Temporary deep screening shall be carried out 10 degree below the maximum rail temperature likely to be attained during the period of work.

c. Wherever rail renewals are being carried out, LWR/CWR may be converted into three rail panels and deep screening done.

iii. Constant monitoring of rail temperature shall be done during the progress of work should the temperature rise more than 10 degree above Td/temporary distressing temperature, adequate precaution shall be taken including another round of temporary distressing .

iv If min. rail temp. falls TD=30 degree, cold weather patrolling is to be introduced to detect/guard against rail fractures.

v. Deep screening of LWR may done from one end of LWR to another end.

vi . The Deep screening in LWR is to be carried preferably by ballast.

The Speed Restriction schedule be as under:-

The period mentioned in the schedules shown above is the minimum and can be suitably increased to suit local condition of the track consolidation. 

Precaution during BCM working at site --- Precaution to be taken during deep screening of track by BCM followed by TTM and DTS machines; (The section can be opened at a speed of 45 kmph subject to fulfilling of conditions as stipulate

(d). i. All precautions laid down in LWR manual shall be strictly followed.

ii.Hard sal wood blocks of size 600 x 300 x 300mm (six numbers) duly end bounded shall be arranged for supporting ends of three adjoining sleepers where cutter bar is left in the track and remains untamed.

iii. Sleepers of cutter bar area shall be manually packed and ballast under cutter bar location sleeper shall be removed only half an hour before the expected traffic block. Adequate care shall be taken to ensure that wooden blocks are not dislodged before arrival of BCM at site.

iv. Fish plated joint shall not be located in cutter bar location.

v. Ramp shall not be located in locations like level crossing, girder bridge, transition portion of curve etc. It shall be kept minimum two rail length away. 

vi. In case of fracture or cut in CWR/ LWR, a speed restriction of 20 Km/h shall be imposed till it is repaired.

vii. In case of malfunctioning of TTM and /or DTS, deep screening shall be stopped and track which has not been tamped and stabilized shall be attended manually by ballast ramming.

viii. In case of non- availability of traffic block on subsequent days of deep screening by BCM, speed restrictions shall be Imposed and relaxed as per procedure. 

ix. When BRM is not deployed, adequate track men shall be deputed to recoup ballast, particularly in shoulder and maintain ballast profile after machine working.

x. Lifting of track shall be resorted after ensuring adequate availability of ballast for maintaining ballast profile for planned lifting.

xi. Adequate arrangements for supply and training out of ballast prior to deep screening should e made.

Special care shall be taken by deploying watchman on stretches overdue for rail renewal.