seamless railway

seamless railway

How Much Do You Know About Seamless Railway Lines?

The seamless railway is a long rail line formed by the standard long rail, generally known as the welded long rail line.

On the ordinary line, the rail joint is one of the weak links of the track. Due to the existence of the rail joint, the import and vibration occur when the train passes accompanied by the striking noise, and the impact load generated can reach more the 3times of the non-joint area.

The biggest feature of seamless line is to eliminate a large number of rail joints, to ensure the smooth operation of the train, but also to improve the comfort of passengers riding the train. In addition, seamless lines eliminate rail joints, which in turn reduces the amount of railway maintenance.

How did seamless rail come into being?

First of all, the rail produced by the factory is transported to the welding rail base, and it is welded into the required long rail in the base. After welding, grinding, and testing the rail, the rail will be transported to the laying site, and then welded again with other tracks, and finally become a seamless railway hundreds of kilometers long.

(https://www.gloryrail.com/methods-of-welding-rails-and-their-advantages-and-disadvantages/ this article introduces the common methods of seamless railway welding, you can click the link to learn more.)

From the current point of view, seamless railway in the world has reached 1/3. For example, in Germany, seamless lines accounts for 96% of all lines; France accounts for 60% of all lines, and China’s seamless lines account for 50% of all lines. It can be seen that seamless line has become a development trend of railway.

How to solve the effect of thermal expansion and contraction in seamless lines

On the one hand, the rail of the seamless line will choose the steel with a relatively small range of thermal expansion and cold contraction; on the other hand, the rail is firmly fixed on the sleeper or ballastless track bed through the fasteners, increasing the complexity and firmness of the track structure, and resisting the internal force pf thermal expansion and cold contraction.

Of course, there are different types of seamless rail, because if the joints of the rail are eliminated, the rail will cause many problems when it is subjected to thermal expansion and contraction. Generally, according to the different temperature stress mode inside the rail, seamless railway can be divided into temperature stress type and release temperature stress type is divided into mobile release type and regular release type.

There are certain technical requirements when laying seamless lines, for temperature stress seamless lines, the rail temperature difference allowed when laying 100℃(212℉) and 140℃(284℉), the so-called rail temperature difference is the difference between the highest temperature of the rail in the natural environment in summer and the lowest temperature of the rail in the natural environment in summer and the lowest temperature in winter. However, in some areas where the temperature difference of the rail is relatively poor, it is necessary to lay the seamless with diffused temperature stress.

It is worth mentioning that when the seamless line is laid on the bridge, the bridge and the seamless line constitute a complex multi-layer structure system. Under the influence of the environment, the beam body and bridge pier will appear complex deformation such as expansion and deflection, which directly affects the stress deformation of the seamless line on the bridge, may lead to rail breakage and instability, and seriously affect the safety of high-speed driving.

Especially for long-span Bridges, the deformation is more complex, and the force transmitted to the rail by the bridge deformation is also larger and more unfavorable, so it is necessary to determine whether the safety and stability of the seamless line meet the requirements through calculation, which is also an essential part of the design process.