Destressing is the process of securing stress-free conditions in long welded rails (LWR) at a specified rail temperature. It is needed during initial laying of LWR, maintenance like gap adjustments at rail joints, and after special track work. There are two methods - without using a rail tensor, which is the conventional practice but can only be used within certain temperature ranges, and with a tensor, which requires more skilled supervision and block time but can be used at lower temperatures. The procedure without a tensor involves loosening fastenings, cutting the rail, and refastening from the center outwards while placing rollers between sleepers to allow free movement.

1. Destressing of LWR

2. Definition
• Destressing is the operation undertaken with or without rail
tensor to secure stress free conditions in the LWR/CWR at the
desired/specified rail temperature.
• Destressing Temperature (td) is the average rail temperature
during the period of fastening the rails to the sleepers after
destressing LWR without the use of rail tensor.
• Range of td :-
o Temperature zone I,II,III
i) All sections tm to tm + 5C
o Temperature zone IV
i) 52kg & heavier tm+5C to tm+10C
ii) Others tm to tm+5 C

3. Need for destressing?
1) On initial laying of LWR
2) During maintenance of LWR
i) Gaps at SEJ
a) Gap between the reference mark and tongue rail
tip/stock rail corner at various rail temperatures
shall not differ by more than +/- 10 mm from
the theoretical range as shown in Annexure-V
b) Gap exceeds maximum designed gap of SEJ
c) Tongue/Stock rail crosses mean position

4. Need for destressing?
ii) After special track maintenance operations
namely TFR, D/S, Lifting of track, major
reliagnment of curves, TSR etc.
iii) After restoration of track following an
unusual occurance namely rail fracture,
buckling, accidents, breaches etc
iv) If number of repairs where temporary repairs
have been done exeed 3 per km

5. Need for destressing?
3) If rail temp is likely to fall outside td+10 & td-
20 C during special maintenance activities like
D/S, TSR, lifting etc then 1 round of temporary
destressing is essential

6. Practice
• Once in 3 years, all LWRs shall preferably with
destressed.

7. LWR destressing operation
• Under supervision of JE/SSE Pway during traffic
block of adequate duration at appropriate rail
temperature
• SR of 30 kmph before traffic block shall be availed
to loosen rail fastenings on alternate sleepers
• Impediments to free movement of rail shall be
removed such as rail anchor, guard rail, check rail
etc
• During destressing operation, rail is required to
be lifted and placed on rollers at every 15th
sleeper to permit free movement of rail

8. LWR destressing operation
• During destressing following activities shall
also be done:-
a) Fitting renewal namely damaged rubber pad,
ERC, liners.
b) Shifting of liner biting zone shall be done,
wherever required
c) Greasing on leg of pandrol clip ,inside of
inserts, below liners & liner sealing
d) LC overhauling

9. Destressing methods
• Without tensor
o Conventional practice
o Do not require skilled supervision
o Can be used only tp is within range
• With tensor
o Used when prevailing temperature tp is below to
o Require skilled supervision, more number of supervisors
o More block time is required

10. Procedure (without tensor)
• Approximately 1 km patch of LWR is
destressed in single block of 2/2.5 hrs which
involves 2-3 welds. Minimum 30-40 nos
labour, 2 supervisors required during block
• Pre block activities:-
o SR of 30 kmph is imposed
o ERCs are removed every alternate sleeper
o LC check rail is removed if any LC is coming in
destressed portion

11. Procedure (without tensor)
• Cut is made in central portion and rails made out of
alignment to permit free expansion/contraction.
• Fittings are unfastened from centre cut towards LWR
on either side with placing of rollers on every 15th
sleeper & tapping with wooden hammer to facilitate
free movement of rail
• Fastening is then started from either side of LWR
portion towards central cut.
• If less than 2.5 hours block is permitted then welds are
not done during this block & caution persists till next
block is granted.

12. Procedure (with tensor)
• Para 5.7.3 of LWR manual

13. THANKS