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Suresh Pal Singh
Sr.Section Engineer(P.Way)

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PostPosted: Fri Jul 08, 2011 10:53 pm Back to top

As per IRPWM para 238(b)it is clear that the Deep Screening of ballast should be repeated at-least once in ten years but it is not clear that what is the minimum period for repeating the Deep Screening on account of other criteria given. And it is also to be cleared that what amount of clear cushion must be ensured for satisfactory riding. As per the annexure-2/11 para 263 the reccomended minimum required clean cushion is 250mm or 200mm over 150mm sub-ballast. With above annexure we understand that the deep screening should be conducted to create minimum required cushion. It is learnt that keeping in view the above, speed of train on route and machine maintenance the deep screening has to be repeated more frequently if lifting is not allowed during this period to create required cushion. Pl clarify if any other criteria of deep screening to be followed.
            
            
            
- Suresh Pal Singh Sr.Section Engineer(P.Way) ... 08-07-11

V Natarajan
AEN(TP)CCG

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PostPosted: Sat Jul 09, 2011 8:27 am Back to top

Other criteria for deepscreening (other than minimum cycle of 10 years) laid down in the manual are (a) prior to carring out TSR/CTR, (b) while conversion to LWR or introducing machine maintainance if the track was previously not deepscreened in the recent past, (c) riding is poor due to caked ballast and during formation treatment. For (a), (b), (c) & (d) deepscreeing can be done even if time since last deepscreening is less than 10 years. The need for intermediate deepscreening can be decided by CE based on local conditions.

But there was a TSC item proposed by RDSO themselves, to lay down the criteria for deepscreening on the basis of fouling index which is fixed after sample analysis.

If shallow screening is done as per the laid down cycles, it can increase the cycle of duration of deepscreening (except at locations of weak formation where the ballast is puncturing the formation) by reducing the rate of fouling.

As per para 238 (d) of IRPWM. at the time of deepscreening standard cushion is to be provided (which is as per the route classification and type of sleepers as per dimension `A' in annexure to para 263 of P.way manual) and not to create the minimum cushion. The remarks in table in annexure 2/11 to para 263 are not in context of deepscreening but minimum cushion required.
            
            
            
- V. Natarajan AEN(TP)CCG ... 09-07-11

Dharampal Bhartiya
J.E (P.Way) BUNDI

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PostPosted: Sat Jul 09, 2011 9:21 am Back to top

Respected @Sh Natarajan Sir,
Revised minimum criteria for ballast cushion
http://iricen.indianrailways.gov.in/IRICEN1/documents/Shared/B2098521/IRPWM%20CS%20126.pdf
            
            
            
- Dharampal Bhartiya J.E(P.Way) ... 09-07-11

MOHAMMAD BAKHSH
Rtd. Dy Chief Engineer

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PostPosted: Sat Jul 09, 2011 10:00 am Back to top

The fundamental to Deep screening is to restore main tasks of the ballast bed.These tasks are uniform distribution of the wheel set forces on the sub-grade,reduction of dynamic stress,caused by dynamic axle loading,maintain and hold vertical position achieved during maintenance,lateral resistance to displacement.It therefore suggests that good drainage and lateral strength.I do not think period of 10 years now holds good.With increasing axle load,the track is under tremendous stress.So IR should devise a methodology to check the quality of ballast as in other world railways. The ballast cleaning must be necessary if 30% of fins of less than 22mm or 40% pollution is detected.
            
            
            
- MOHAMMAD BAKHSH  Rtd. Dy Chief Engineer ... 09-07-11

V Natarajan
AEN(TP)CCG

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PostPosted: Sat Jul 09, 2011 11:37 am Back to top

Thanks Shri.Dharampal for bringing the latest CS of IRPWM to my notice.
Standard of cushion laid down is required to be maintained while deepscreening and not the minimum prescribed for the speed certificates
            
            
            
- V. Natarajan AEN(TP)CCG ... 09-07-11

Dharampal Bhartiya
J.E (P.Way) BUNDI

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PostPosted: Sat Jul 09, 2011 12:45 pm Back to top

The criteria for Deep screening of ballast based on Fouling Index
Another
Ballast Fouling Index

Concept of Fouling Index for fouling of Ballast
Formula suggested by RDSO:
FI : 0.3(P40-50)+(0.3P20)+(0.3P10)+(0.4P4.75)

P40 , P20 , P10 , P4.75 are % passing on 40mm, 20mm, 10mm, 4.75mm sieve.

Underline factor can not be negative . Omit underline factor if negative.

Where FI = % Contamination Fouling Index.
P40 = % Undersize 40mm sieve.
P20 = % Undersize 20mm sieve.
P10 = % Undersize 10mm sieve.
P4.75 = % Undersize 4.75mm sieve.

Proposed values for Fouling Index for Deep Screening Criteria are as under :--
Speed Annual GMT Contamination Fouling

> 120KMPH 30 >30 %
> 100KMPH 15 >35 %
> 90KMPH 10 >40 %
Others ~~ >50 %




Letters:
1)RDSO:- CE/GEN/11/CE conference dated 3.2.2010.

2)RB letter no. 2008/CE-II/MT/TS/1/2 dated 16.7.2009 (sr. no 444)
The analysis was carried out with 10 samples of core ballast up to a depth of 300mm from sleeper bottom and details were sent in the compliance of an order from divisional office.
            
            
            
- Dharampal Bhartiya J.E(P.Way) ... 09-07-11

MOHAMMAD BAKHSH
Rtd. Dy Chief Engineer

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PostPosted: Sat Jul 09, 2011 3:59 pm Back to top

Sh Dharmpal has latest updates. However, It is not indicated whether fouling index have been mandated.
            
            
            
- MOHAMMAD BAKHSH  Rtd. Dy Chief Engineer ... 09-07-11

V Natarajan
AEN(TP)CCG

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PostPosted: Sun Jul 10, 2011 8:12 am Back to top

Criteria for deepscreening based on fouling index was first initiated in the 80th TSC meeting during Dec'2009 at IRICEN vide item no.1166 which fortunately i could attend while accompanying the CTE..

Shri.Dharampal is requested to advise what was the fouling index and when was the track last deepscreened in the stretch where sampling was done.

From the discussions in the TSC, it is learnt that with improvements in specifications of ballast (machine crushed instead of hand crushed, increase in nominal size from 40/50 to 65mm, improvement in the grading, higher abrasive values, breakage of ballast reduced by machine maintainance etc..), the revised criteria may prolong the duration of deepscreening. Weak formation, Higher axle loads & higher speeds are impending factors which can reduce the duration of deepscreening.

We should keep doing the sample analysis at regular intervals on various sections and plot the graphs with fouling index on X axis and the month & year on the Y axis to see the rate of fouling of ballast. We should also mark on the graph the year & month when shallow screening is done and also the year & month of machine packing and any other relavant details. The formula for fouling index is likely to be modified and improved further with experience gained and data generated.
            
            
            
- V. Natarajan AEN(TP)CCG ... 10-07-11

Dharampal Bhartiya
J.E (P.Way) BUNDI

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PostPosted: Thu Jul 14, 2011 2:27 pm Back to top

Respected @ Sh. Natarajan Sir,
The value of Ballast Fouling Index was 52% and last deep screening was done in 1989 at initial laying followed by a round of lifting(approximately 100mm) in 2006 during TSR with ST sleepers.
This is a Group "D" route and at present the stretch under consideration is on PRC sleepers wef May 2010 with deep screening.
            
            
            
- Dharampal Bhartiya J.E(P.Way) ... 14-07-11
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