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Common Problems and the Causes Concerning Rail Joints

2019-10-29 13:58


Common Problems and the Causes Concerning Rail Joints


As the vulnerable part in railway lines, the defects of rail joints may cause serious impact on the quality of railway lines and thus lead to grave damage to the rail joints due to the force applied during the passing of trains. In order to guarantee the smooth and safe operation of railway lines, necessary maintenance and repair work are imperative.

Common rail joint defects

1. Forms of commonly observed problems

Deformation may occur to the rail joints, the key part for the continuous operation of railway lines, due to overpressure imposed during the passing of the trains, for which constant maintenance of rail joints are called upon. And various defects may appear if poorly maintained, thus causing severe impact on the train operation. The defects may come in the following forms:

(1) Saddle type abrasion at the end of rail joint (2) depressed joint which mostly occurs in poorly tamped section and on curved lines in particular. (3) Rail damage that features rail surface scaling, chipping and bolt hole cracking. (4) Bending or breakage of clamping plates, mainly in the form of tiny flaws in the middle of top part that penetrate later. (5) Concrete sleeper rupture caused by damage that mainly occurs under the rail.

railway maintenance

2. Causes for defects

As there are various causes that contribute to rail joint defects and a number of factors concerned, we should have certain understanding to them to facilitate better routine maintenance of rail joints. Through years of experience we conclude that there are two main causes as below: Firstly, those rail joints manufactured with poor quality material or unqualified quenching technique are subject to defects. Secondly, the vibration and pressure imposed on the rail joint during the normal operation of trains is another key factor that attribute to the defect. Special attention should be paid to the above two points in daily rail joint maintenance.

There are three factors that contribute to the deformation of rail joint after force loading: (1) rail gap, the part that is prone to deformation due to force carrying during the train passing. (2) the ends of two adjacent rail are not aligned with each other, thus the incoming end stays higher than the exiting end. (3) bevel that forms due to subsidence of rail joint. The above three cases may overlap sometimes under force employment and cause severe concussions to the rail joints. Subsidence of rail joint may occur under long term force applied, which may lead to vicious circle and pose threat to the safe operation of trains. There are mainly four factors that lead to the progressive deformation of rail joints: (1) The rail joint falls into deformation due to the force imposed upon it, which is called plastic deformation, a normal phenomenon. (2) Bending coming out at the juncture of rail and clamping plates, which is called hard bending and also a common phenomenon. (3) The loosening screw fixed on the rail causes deformation to the elastic layer below and vast damage occurs to the rail and clamping plates, which also leads to damage to the rail joint. (4) The rail bed becomes loose or subsidence with force applied to the rail joint and causes hanging hollow at the rail joint, which pose grave threat to the normal operation of the rail.