Short Welded Rails
A short welded rail (SWR) is a
welded rail that undergoes thermal expansion throughout its length. These rails
are composed of 3, 5, or 10 rails welded together.
It has been experienced on Indian
Railways that short welded panels of more than three rail lengths produce
excessive thermal forces and it is felt that the extra effort required for
their proper maintenance cannot be economically and technically justified.
Short welded rails of three rail lengths (3 × 13 m for BG and 3 × 12 m for MG)
have, therefore, been standardized on Indian Railways.
1 Track Specifications for Short Welded
Indian Railways enumerates the
following specifications for a track to be laid with SWRs.
Foundation and alignment An SWR
should be laid on a stable and efficiently drained formation. It should
not be laid on a track curved sharper than 3 o on metal or concrete sleepers and
2 o on wooden sleepers in the case of BG tracks. In the case of MG tracks it
should not be laid on curves sharper than 5 o on metal or concrete sleepers and
3 o on wooden sleepers.
Rails Only new
rails or good-quality second-hand rails must be used for SWRs. The
minimum rail section specified for three rail panels is 90 R for BG tracks and
60 R for MG tracks for all temperature zones. However, 60-kg rails should,
however, be laid as 3 × 13 m SWR panels only in temperature zones I, II, and
Sleepers and sleeper density Only the
following type of sleepers should be used for SWRs.
sleepers with anticreep or elastic fastenings
(b) Cast iron
sleepers with key-type or elastic fastenings
trough sleepers with key-type or elastic fastenings
sleepers with elastic fastenings
Wooden sleepers should preferably
be used at all fish-plated joints when SWRs are to be laid on metal sleepers
and these may preferably be provided with MS bearing plates with non-anticreep
The minimum sleeper density
specified for BG and MG tracks is M + 4, except in the case of 60-kg
rails on BG tracks, where it should be M + 7.
stone ballast should be used with SWRs. The minimum ballast cushion below
the sleeper should measure 200 mm both on BG and MG tracks. An extra 100 mm
width of shoulder ballast over and above the standard ballast section on a
straight track should be provided on the outer edges of the curves.
2 Regular Maintenance Operations of SWRs
Regular track maintenance work
including all operations involving packing, lifting, aligning, local
adjustments of curves, screening of ballast other than deep screening, and
scattered renewal of sleepers may be carried out without restriction when the
rail temperature is below tm + 25 o C.
All major lifting, major
realignment of track, deep screening, and renewal of sleepers in continuous
lengths should normally be done when the rail temperature is below tm
+ 15 o C after suitable precautions have been taken. If it becomes necessary to
undertake such work at rail temperatures exceeding tm + 15 o C,
adequate speed restrictions should be imposed.