Railway Sleepers: Strong Load Bearing To Support For Train Safety

Sleepers must support the rails, maintain their position, and transfer the huge pressure from the rails to the ballast. They must have a certain degree of flexibility and elasticity; being too hard or too soft is not acceptable. When a train passes by, they can deform appropriately to buffer the pressure, but they should return to their original shape as much as possible after the train has passed. Sleepers include wooden sleepers and concrete sleepers.

1. Wooden sleepers (wood sleepers) are sleepers made of wood. Also known as crossties, preservative-treated wooden sleepers, or oil-impregnated crossties. To make wooden sleepers, tough and elastic wood must be selected. Wooden sleepers can be classified into common wooden sleepers, switch sleepers, and bridge sleepers based on their uses. The standard length of common wooden sleepers is 2.5 meters, and their cross-sectional shapes are divided into types I and II, used on different grades of tracks. Switch sleepers, used on turnouts, have a wider cross-section than common wooden sleepers, with lengths ranging from 2600mm to 4800mm, divided into 12 types, each differing by 20mm. They are selected in groups based on the actual width of the turnout. Bridge sleepers, used on bridges, have cross-sectional dimensions that vary depending on the distance between the main beams (or longitudinal beams). Wooden sleepers have the advantages of good elasticity, ease of processing, and convenience of use. Since the advent of railways, wooden sleepers have been the main type of sleepers. However, due to the source of materials, the elasticity, strength, and durability of wooden sleepers are not uniform enough, which can increase the dynamic interaction between the wheel and the rail, and a large amount of high-quality wood is required. The service life of wooden sleepers is short, and their failure reasons are numerous, mainly including decay, mechanical wear, and cracking. Due to their susceptibility to decay, wooden sleepers need to undergo preservative treatment before being laid on the track. Wooden sleepers that have not undergone preservative treatment are called plain sleepers. China has a relatively scarce wood resource and high prices, so wooden sleepers have gradually been replaced by concrete sleepers on major trunk lines.

2. Concrete sleepers, including the structure of threaded rail spikes, reinforcement, fasteners, and track gauge adjustment and height adjustment, are characterized by: the shoulder concrete is raised, the track gauge spacer is thickened, the rubber pad is thickened, and the spiral ribbed steel bars are arranged in a staggered manner in the vertical direction inside the concrete sleeper. Shear reinforcement is provided at the end of the shoulder, and the spacer seat fits the grooves at both ends of the concrete sleeper shoulder. The track gauge spacer is in close contact with the spacer seat.

3. Concrete sleepers for railway accessories, also known as concrete ties, have been widely used since World War II. The advantages of concrete sleepers are good stability, long service life, and low maintenance costs. The disadvantages are their heavy weight, poor elasticity, and poor insulation performance. Buffer insulation pads must be installed at the bottom of the rail.

The reason why sleepers can undertake such important tasks lies in their series of meticulously designed excellent performances:

Strong load-bearing and compressive performance: This is the lifeline of sleepers. Whether it is the firmness and straightness of concrete sleepers, the flexibility and toughness of wooden sleepers, or the innovative breakthroughs of composite material sleepers, they all must have the ability to withstand huge vertical loads (train weight, load) and dynamic impact forces. They evenly distribute the huge pressure transmitted from the rails to a wider area of ballast and subgrade, preventing local subsidence and deformation of the track. Imagine that when a high-speed heavy-load train passes by, each sleeper bears tens of tons or even hundreds of tons of impact in an instant, demonstrating its strong load-bearing capacity.

Outstanding elasticity and shock absorption performance: The track is by no means a rigid entity. Excellent sleepers must have a moderate degree of elasticity, functioning like precise shock absorbers to effectively absorb the vibrations and noise generated by the high-speed impact of train wheels. This not only significantly enhances passenger comfort but also significantly reduces the “clattering” noise’s impact on the surrounding environment. Moreover, it protects vehicle components, rail joints, and the underlying foundation (ballast, subgrade) from long-term severe impacts, thereby extending the service life of the entire track system. The internal structure or material characteristics (such as the natural fibers of wooden sleepers, the layout of prestressed steel bars in concrete sleepers, and the special formula of synthetic sleepers) are key to achieving effective shock absorption.

Durable longevity and stability: Sleepers are constantly exposed to harsh conditions such as wind, sun, rain, freeze-thaw cycles, and ballast friction. Therefore, they must possess excellent resistance to decay (wooden sleepers are treated with preservatives), weathering, biological erosion, chemical corrosion (such as de-icing salts), and temperature stress deformation. Concrete sleepers are renowned for their high strength and durability, while modern synthetic sleepers excel in corrosion resistance, pest resistance, and UV resistance. Additionally, sleepers themselves must maintain geometric stability, avoiding dimensional changes due to shrinkage, expansion, or creep that could lead to track gauge misalignment or deterioration of track geometry.

Reliable insulation performance (for electrified railways): In electrified sections, sleepers are an integral part of the track circuit. Concrete sleepers and synthetic sleepers inherently have good insulation properties, effectively isolating the current between the two rails and ensuring the normal operation of the track circuit. This is a core guarantee for precise train position detection, signal interlocking control, and automated train safety. Although wooden sleepers are naturally insulating, their resistance values fluctuate with humidity, requiring special attention to maintenance.

Stable grip and anchoring performance: Sleepers must firmly “hold” the rails and fasteners. The embedded sleeves or rail seats in concrete sleepers, the spike holes in wooden sleepers, and the dedicated anchoring structures in synthetic sleepers must ensure that fasteners (such as elastic bars, bolts, and plates) can generate and maintain sufficient and lasting clamping force to securely “lock” the rails onto the sleepers, preventing rail creep (longitudinal movement) and ensuring track gauge stability. This is the most direct defense for train safety.

Supplier

Luoyang Fonyo Heavy Industries Co., Ltd, founded in 1998,is a manufacturer in railway casting parts.Our factory covers an area of 72,600㎡, with more than 300 employees, 32 technicians, including 5 senior engineers, 11 assistant engineers, and 16 technicians. Our production capacity is 30,000 tons per year. Currently, we mainly produce casting, machining, and assembly for locomotive, railcar, high-speed trains, mining equipment, wind power, etc.
We are the railway parts supply to CRRC(including more than 20 branch companies and subsidiaries of CRRC), Gemac Engineering Machinery, Sanygroup, Citic Heavy Industries, etc. Our products have been exported to Russia, the United States, Germany, Argentina, Japan, France, South Africa, Italy and other countries all over the world.
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