Rail Joints in Railways: Types, Applications, and Importance

Introduction

Rail Joints in Railways: Types, Applications, and Importance, Rail joints are frequently used to unite two tracks and guarantee that trains go through space safely.

A rail joint that has the same rigidity and strength as the parent rail is desirable.
Here is a brief summary of the qualities of an excellent rail joint.

• Holding the rail ends: To provide maximum track continuity, the ideal rail joint should maintain the rail ends in their exact positions in both the horizontal and vertical planes.
• This helps in avoiding wheel jumping or the deviation of the wheel from its normal path of movement.
• Power The strength and stiffness of the ideal rail joint should match those of the parent rails.
• Cost An optimal rail joint should have low initial and ongoing maintenance expenses.
• Gap in expansion For the rails to freely expand and contract due to temperature variations, the joint should have a sufficient expansion gap.
• Adaptability When necessary, a perfect rail joint should be flexible enough to make rail replacement simple.
• Elasticity To provide a trouble-free track, the perfect rail joint should have sufficient flexibility and resistance to longitudinal forces.
• Rail junctions can be divided into three categories based on the sleeper’s position:
• Supported joints,
• Suspended joints and
• Bridge joints.

Types of Rail Joints: The following types of joints are commonly used on Indian and foreign railways:

(1) Supported Rail Joints

When the rail ends rest on a single sleeper called a “joint sleeper” it is termed a “supported joint”. The duplex joint sleeper with other sleepers is an ample of the supported joint. Three sleeper supports (as shown in Fig. 1.) with long fish plates, i.e., combined supported and suspended joints are most objectionable. In this case,e when the packing under the outer sleeper gets loose, undue load comes on the central sleeper and in turn the loose central sleeper converts this joint into a weak suspended joint.

(2) Suspended Rail Joint

When rail ends are projected beyond sleepers called “shoulder sleepers” it is termed as suspended joint (as shown in Fig). This type of joint is generally used with timber and steel trough sleepers on Indian and foreign railways.

(3) Bridge Joint

When the rail ends are projected beyond sleepers as in the case of a suspended joint and they are connected by a flat or corrugated plate called a “bridge plate”, it is termed as a bridge joint. This type of joint is not used on Indian Railways (Fig).

(4) Base Joint

This is similar to the bridge joint, with the difference that the inner fish plates are of bar type and outer fish plates are of the special angle type, in which the horizontal leg is further extended over the sleepers to be bolted to both bridge plate and sleeper. Due to complicated design, this is not generally used.

(5) Welded Rail Joints

Since they meet almost every condition for an ideal or flawless joint, they are the best joints.

In railway tracks, welded rail joints are utilized to create a continuous, seamless rail that enhances durability, safety, and comfort. Unlike conventional fish-plated joints, welded joints close the spaces between rail sections, lowering impact loads and maintenance needs.

(6) Staggered or Broken Joint

In this, the position of joints on the railway tracks is the basis of its nomenclature. In this type of joint, the joints of one rail track are not directly opposite to the joints of the other rail track (Fig). These joints are generally provided on curves, where the length of the outer curved track is greater than the length of the inner curved track.

(7) Square or Even Joint

In this also, the position of the rail joint is the basis of its nomenclature, the joints of one rail track are directly opposite to the joints of another rail track.
This type is generally used on straight tracks (Fig).

(8) Compromise Joint

Where two different rail sections are required to be joined together. it is done by means of fishplates which fit both rails and this joint is termed as compromise joint (Fig. 6).

(9) Insulated Joint

When an insulating medium is inserted in a rail joint to stop the flow of current beyond the track-circuited part, it is called an insulated joint.

(10) Expansion Joint

An insulated joint is created by inserting an insulating material into a rail joint to prevent current flow past the track-circuited portion. This gap is 2.2 cm in the case of the “mitred” joint and 7.2 cm for the “Halved Joint”.
Experiments carried out in India have revealed that comparatively, in view of stresses produced in rails and fish plates, the wooden sleepers are best for joints. They produce less stress in rails and fish plates, and their performance, from the viewpoint of deflection, and maintenance of gauge and cross levels, is found to be the best. Duplex sleepers, however, produce minimum deflection. However, such joints should be avoided at the following places:

1. At rail level crossings (where railway track crosses the road)
2. On short bridge spans of any type.
3. On approaches of bridges.
4. On the ends or centre of the span of long bridges. If at all, the use of a joint on bridges is warranted, it should be at a point which is 1/3rd of the span length.

The number of joints can be reduced by the process of welding of rails. Welded joints are considered as the most perfect and strongest type of joints.