Continuous Welded Rails

On Indian Railways, the length of long welded rails has been limited to only 1 km taking into consideration the convenience of laying, destressing, and maintenance. Welded panels longer than 1 km have also been tried and are known as continuous welded rails. Such rails have been laid from station to station, but the conventional insulation joints and turnouts have been left out and isolated by switch expansion joints. Trials for LWR/CWR passing through points and crossings are also in progress.

The theory behind continuous welded rails is the same as for long welded rails. Once the concept of locking up of longitudinal thermal forces is accepted, there is no reason why the length of LWR should be limited to only 1 km. However, the switch expansion joints or buffer joints that are provided after every 1 km of LWR. have been a source of weakness in the track, requiring heavy maintenance. It was to avoid this effort that continuous welded rails were laid from station to station. In fact, on European Railways, particularly on German and British Railways, LWR or continuous welded rails have been laid for several miles together, without the inclusion of any SEJ, which pass through stations, yards, etc. The important features of SWR, LWR, and CWR are presented in Table 17.4.

Table 17.4 Comparison of SWR, LWR, and CWR

Item

SWR

LWR

CWR

Definition

A welded rail, which expands and contracts through out its length

A welded rail, the central portion of which does not undergo any thermal expansion

A welded rail like the LWR, which has to be destressed in stages

Length

3-5 rail lengths

0.5-1 km

Above 1 km

Expansion

arrangement

Expansion gap

Switch expansion Joint

Switch expansion joint

Relevant theory and occurrence of stresses

Normal expansion/ contraction theory

Theory of locked up stresses in the rail with no stresses

Same as LWR

Destressing of rails

Not required

Can be done in one stage

Has to be done in stages

Maintenance

precautions

Can be maintained any time in any way

Regulated maintenance in specified

temperature ranges

Same as LWR

Cost of laying

Minimum

More than SWR

Almost the same as LWR

Comfort in travelling

Minimum due to a large number of joints

Better than SWR

Best

Type of maintenance

Manual

Both manual and mechanized

Same as LWR

Short Welded Rails | RAILWAY ENGINEERING | Buckling of Track