Procedure of distressing with rail tensor in LWR & CWR territory

Q - Describe in details procedure for Procedure of distressing with rail tensor in LWR & CWR territory. 

Ans - Distressing of LWR/ CWR shall be done whenever required as per condition and behavior of LWR/ CWR. But in any case it shall be done at least once in 5 years as per CE circular.

Distressing is to be done when – Abnormal behavior of LWR/ CWR whenever gets manifested in one or more of the following, distressing shall be undertaken as per procedure. 

i. When the gap observed at SEJ. 

a. Differs beyond limits. The gaps between the reference mark and tongue rail tip/stock rail corner at various tail temperatures shall not differ by more than +/-10 mm from the theoretical range. Where fish plated or SWP track is joined on one side of SEJ, the gap between the reference mark and tongue rail tip/stock rail corner on LWR/CWR side shall not differ by more than +/- 10 mm from the theoretical range. Exceeds the maximum designed gap of SEJ 

b. When stock/tongue rail crosses the mean position. After special maintenance operations such as:

• Through fittings renewal

• Deep screening/mechanized cleaning of ballast

• Lowering/lifting of track

• Major realignment of curves

• Sleeper renewal other than casual renewals

• Rehabilitation of bridges and formation causing disturbance to track 

ii. After restoration of track following an unusual occurrence. 

ii. If number of locations where temporary repairs have been done exceed three per km. Distressing of CWR shall be done by cutting it into LWRs of about 1 km length which shall be joined after distressing.

DESTRESSING OF LWR

General

I. The work of distressing shall be done during a traffic block under the personal supervision of a PWI.

II. It is preferable to impose a speed restriction of 30 km/h before actually obtaining the traffic block and to loosen/remove fastenings on alternate sleepers to reduce total duration of the traffic block. Sequence of operation The procedure to be adopted for distressing consists of the following steps:-

i. Remove impediments to free movement of rail such as rail anchors, guard rails, check rails etc. 

ii. Create gap of about 1 metre at the centre of LWR during a traffic block and insert a closure rail there at a restricted speed. 

iii. Mark anchor lengths at either end of the proposed LWR. 

iv. Erect marker pillars at the ends of anchor lengths on either side and at 100 metre intervals thereafter. 

v. Obtain a traffic bloc when tp is less than the desired installation temperature (tp ), remove the closure rail at the centre and unfasten the full length of rails leaving only the anchor lengths at either end. Mount the rails on the rollers. Side rollers shall also be used while undertaking distressing on curved track. Side supports on the inside of curve should be spaced at every nth sleeper, Where, n= Radius of curve (R) x No. of sleepers per rail length 50 x (to-tp ) Outside supports shall be used in addition at the rate of one for every three inside supports.

vi) Fix rail tensor across the gap at the centre ad apply tension so as to get the required amount of

extension.

vii) Re- fasten the rail starting from the anchor lengths at either end after removing the rollers progressively and adjusting tension at the rail tensor to make sure that the required extension has been achieved at each marker pilar. put paints marks on either side of the gap at the centre , spanning over the gap at a distance of 6.5 metre. 

vii. Inset a coosure rail of a length equal to (6.5 metre-2 gaps for welding + 1 mm for saw cut ends) and clamp.

ix) Release and remove the rail tensor.

x) During another traffic block, weld both the joints of the closure rail at the centre.

xi) Equalize stress at the centre and at the anchor lengths.

DESTRESSING OPERATION OF LWR WITH THE USE OF RAIL TENSORS

For distressing of LWR with the use of rail tensor, the following procedure shall be adopted:-

i. During the first traffic bloc, create a gap of 1 metre at location ‘B’ i.e. centres of LWR. Introduced rail closure as required and fasten with special fishplates and clamps. Allow traffic at restricted speed.

ii. Mark the anchor length A1 A2 and C1 C2 each equal to Ia at either end of the length A2 C2 to be distressed. 

iii. Erect marker pillers W1 W2 etc., on each of the length A2 B and C2 B. transfer the marks Wo onto the rail foot. The distance WoW1W1W2 etc. shall be marked at about 100 metre intervals, the distance from the previous pillars and the last pillar WB may be less than 100 metre. 

iv. During the second traffic block, when tp is less than the desired to, destressing operation shall be carried out for the lengths A2B and C2 B as described below:-

a) Remove the closure rail from location ‘B’ Unfasten and mount on rollers the portion from A2C2. 

b) Fix the rail tensor across the gap at ‘B’ and apply tension so as to contain some movement at Wo to remove any kinks or misalignment and to minimize the friction in the rollers etc. Release the tension and note the movement Yo at Wo. 

c) Transfer marks W1,W2 ........ onto the rail foot and note temperature tp. 

d) Calculate the required movement at W1 as under :- 

i) Movement at  W1 = Yo+ elongation of length WoW1 (L) due to temperature difference (to-tp)= Yo= Lα(to-tp) 

Calculate the required movement at W2 as under :- 

Movement W2 = movement at W1+ elongation of length W1W2(l) due to temperature difference (to-tp). 

Similarly calculate the required movements successively at each of the transferred marks referred at ©above on the rail foot on the side away from the tensor. Apply the tension by means of rail tensor till the mark of required extension comes opposite to the mark on the marker pillar W

1. Fasten down the segment WoW1. Then check at W2,bring the mark of required extension at this location opposite to the mark on the marker pillar W2, by adjusting the tensor either by reducing or increasing tension and fasten down the segment W1W

2. Similarly , check the remaining marks, adjust the tension as required and fasten down each segment before proceeding to the next. 

ii) Only one value of tp has to be taken at the time of marking W1,W2 etc. on the rail foot. The values of tp is not required to be taken thereafter. The variation of temperature, if any during the distressing operation shall automatically be taken care of by reducing or increasing the tensile force from the tensor, while coinciding the reference mark on rail with the corresponding mark on pillars. 

iii) if for any reason, both the length A2B and C2B cannot be fastened down simultaneously, the final adjustment in pull and fastening down of individual segments may be done in series, first from A2 to B and then, from C2 to B.

e) After the fastening down of the last length A2B and C2B is completed, make a paint mark near free end of one rail at a distance of (6.5 metre +2x25mm-1mm), measured from the end of the other rail across the gap spanned by the rail tensor.

f) Remove the tensor, close the 1 metre gap temporarily and allow traffic at restricted speed. 

v) During another traffic block, cut the rail at the paint mark, insert a rail closer of length exactly equal to 6.5 metre and weld one end thereof. If the gap at the other end is also 25mm, it can be welded in the same block. Otherwise fasten with special fishplates and clamps and allow traffic at restricted speed. In the latter case, during a subsequent block when tp is not greater than to, release rail fastening on either side to the required extent and pull the rails with rail tensor to get the desired gap of 25mm refasten the rail and weld the joint. Release the tensor after a lapse of a minimum of 20 minutes after pouring of the weld metal. 

vi) During a sun sequent traffic block, when tp is less than td, equalize the forces in the rail by releasing the fastenings over a length of 100metre on either side of location ‘B’ and rapping with wooden mallets etc. Fasten down the rail and allow traffic. 

vii) During another traffic block, when tp is within the range of temperature destress the end 100 metre from SEJ. Thereafter ,weld th closure rail next to SEJ duly ensuring setting of the SEJ.