What weights and kinds of rails does IR use?

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What weights and kinds of rails does IR use?

July 1, 2019, 11:44 AM

The IRS standard for most mainline tracks is 52kg/m (really 51.89kg/m, 105lb/yd), and it allows 25-ton axle loads. Until about 1970, most sections had RBS standard rails of 44.7kg/m (90lb/yd). The RBS standard had been adopted in 1914, and allowed 22.5-ton axle loads at 100km/h. It is still found in many places. For sections with heavy traffic, the newer IRS standard rails are 60kg/m (really 60.34kg/m, 130.4lb/yd). A 62kg/m standard has been mooted. For BG branch lines, the commonly used rail weights are 37.2kg/m (75lb/yd), 42.2kg/m (85lb/yd), and 44.7kg/m (90lb/yd) (these are also being replaced now by the standard 52kg/m weight). See table below.

Although rails allowing 22.5t or 25t loads are in place, as a matter of operating procedure goods wagons are currently [5/05] restricted to 20.3t axle load. There are proposals to raise this to 23t.

The standard 52kg/m and heavy 60kg/m rails mentioned above are made of a steel of strength 90ksi ultimate tensile strength (90UTS steel). Some sections with heavy mineral freight traffic use steel rails of 110UTS. The move to 90UTS steel was necessitated because of the heavier loads and also to minimize wear from the harder steel used for the cast wheels manufactured by the Wheel and Axle Plant (now Rail Wheel Factory) especially for the newer BOXN wagons. The steel used is a medium manganese type with some chromium and vanadium as well. Rails are often head-hardened (heat treated to harden the top surface) as well (‘HH’ rails).

About 85% of the 52kg rails and about 95% of the 60kg rails are used for track renewals, track doubling, or gauge conversion, only about 15% of all rail production being needed for single-length rail repair, points, and crossings. The total service life of 52kg / 90UTS medium manganese rails is specified in terms of a traffic limit of 525GMT (gross million tonnes); for 60kg/90UTS rails the service life is 800GMT. Head hardening of the rails increases the service life considerably, often by a factor of 2 or 3.

The older rails (until about 1993) of 90lb/yd, etc., were of 72UTS medium manganese steel which were suitable for use with the older forged wheels. The 90UTS steel now used routinely, and especially the 110UTS steel used in some places, require extra care in the production of the rails as well in their transport and maintenance since they tend to be less resistant to brittle fracture on encountering bending or impact stresses.

The metallurgical quality of the steel was of some concern especially after a derailment at Khanna in Punjab in 1999 was blamed on rails snapping due to excessive hydrogen left behind in the rails during manufacture. The older 72UTS steel rails expanded up to about 14% under thermal and mechanical stresses, whereas the 90UTS and higher tensile strength rails expand much less (10% for 90UTS). This allows the 90UTS rails to be welded together for longer lengths with the provision of expansion joints less frequently than for the 72UTS rails.

The Steel Authority of India Ltd. (SAIL) is the main supplier of all kinds of rails for IR, although some initial consignments of 110UTS steel rails were also imported in the mid-1990s. (See below for suppliers.)

Rail Dimensions and Other Specifications: Cross-sectional area for BG rails ranges from 7686mm2 for 60kg UIC rails to 6615mm2 for 52kg IRS rails. Rail height is 156mm for 52kg rails, and 172mm for 60kg rails. Flange width is 136mm (52kg rails). The 90UTS rails have a hardness of 260BHN, while the 72UTS rails have a hardness of 230BHN.

Chemical Composition: Manganese in 72UTS rails: 0.95%-1.4%. Silicon: 0.05% to 0.30%. Sulphur (sulfur): 0.035% max. in HH rails, 0.04%-0.05% in 710 grade rails. Carbon: 0.72%-0.82% in HH rails, 0.45-0.6% in 710 grade rails, 0.6%-0.8% in 880 grade rails. Phosphorus: 0.035% max. in HH rails, 0.05% max. in 710/880 grade rails.

Meter Gauge MG rail weights are usually 37.2kg/m (75lb/yd) for busier sections. This is an IRS standard adopted in the early 1970s and allows 17.5-ton axle load. Much MG trackage still uses the older RBS standard adopted in 1914, which specifies 27.6kg/m (60lb/yd) (allowing 13-ton axle loads and 75km/h speeds).

Narrow Gauge There is a large variety of rails used for NG lines. Common rail weights are 14.9kg/m (30lb/yd), 19.8kg/m (40lb/yd), 20.5kg/m (41.3lb/yd), 24.8kg/m (50lb/yd), and 37.2kg/m (75lb/yd) (this last kind is essentially the same rails for MG being re-used on NG sections). The Darjeeling Himalayan Railway originally had 30lb or lighter rail, which was replaced quite early on with 41-1/4lb rail. After Independence much of it was replaced with 50lb rails and in more recent times, much relaying has been done with 60lb rails obtained from MG gauge conversions. Most NG lines have flat-bottomed rails, although a few had bull-headed rails.

History

GIPR’s first BG tracks used 65lb/yd double-headed rails made of wrought iron. Rails of 80lb/yd were common (e.g., Indian Midland Railway). Both flat-bottomed and bull-headed rails were commonly used. MG railways started off with 40lb/yd rails, although 30lb/yd rails were also used. The Barsi Light Rly. used 30lb/yd rails. The Rajputana Malwa Rly. used 50lb rails.

Source – IFRCA.org

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