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Using the Thermit Welding technique

Using the Thermit Welding Technique on the Rail Infrastructure

Thermit welding is a widely used method of welding rails together on the UK rail infrastructure. The Thermit Welding technique involves heating a specially formulated compound called Thermit, which then reacts with a metal oxide to produce a high-temperature reaction that fuses the two rail ends. This article will discuss the advantages of using thermit welding techniques over other welding methods, such as flash butt rail welding, gas pressure welding, and electric arc welding.

Advantages of the Thermit Welding Technique

High-quality welds

Thermit welding produces high-quality welds with excellent tensile and fatigue strength. The strength of the weld is crucial in the rail infrastructure, where trains travel at high speeds, and any defects in the weld can cause significant damage. The weld is highly resistant to wear and tear, ensuring longevity and durability.

Quick and Efficient

Thermit welding is a fast and efficient process that can be completed in minutes. This efficiency reduces the time that the rail has to be out of service, reducing disruption to the rail network. In contrast, electric arc welding can take several hours to complete a single weld, leading to more extended downtime.

Low Maintenance

Thermit welding produces a seamless joint, which requires less maintenance than other welding techniques. The seamless joint is highly resistant to fatigue and wear, reducing the need for regular inspections and repairs. This results in cost savings for rail managers and a more reliable rail network.

High Precision

Thermit welding produces highly precise and accurate welds with minimal distortion or warping of the rails. This process ensures the rails remain straight and true, reducing the risk of derailments and other accidents.

Minimal Environmental Impact

Thermit welding produces very little waste, making it an environmentally friendly option. The only by-products of the process are slag and metal shavings, which can be easily collected and recycled.

Comparison with Other Welding Methods

Flash butt rail welding, gas pressure welding, and electric arc welding are other welding methods used on the rail infrastructure. However, they have several disadvantages when compared to thermit welding.

Flash butt rail welding, while producing high-quality welds, is a slow process that requires the rail to be out of service for a long time. Gas pressure welding requires specialised equipment and is limited to specific rail profiles, making it less versatile than thermit welding. Electric arc welding is also slow; the resulting welds are weaker than thermit welding.

Thermit Welding for Rail Maintenance and Repair

In addition to its advantages over other welding methods, the thermit welding technique suits specific rail maintenance and repair tasks. One of the main areas where thermit welding is used regularly is to repair broken steel rails. When a rail is damaged, it is often more cost-effective to repair it rather than replace the entire rail. Thermit welding can repair the broken section, creating a seamless joint as strong as the original rail.

Thermit welding is also ideal for on-site joint welding on railway frog sections. These are the areas where two or more tracks converge, and the rails must be joined to form a continuous track. The joint can be made quickly and efficiently using thermit welding, ensuring the rail network is up and running as soon as possible.

Finally, thermit welding is often used for heavy transportation tasks, such as large machinery or heavy goods. The resulting weld is extremely strong and durable, ideal for supporting heavy loads.


Thermit welding is a fast, efficient, cost-effective method of welding rails together on the UK rail infrastructure. It produces high-quality welds that are highly resistant to wear and tear, require minimal maintenance, and have a minimal environmental impact. The thermit welding technique offers numerous advantages over other welding techniques and is well-suited for specific rail maintenance and repair tasks. Its speed, precision, and durability make it a popular choice for ensuring a reliable and efficient rail network for years to come. Speak to our Welding experts about your next project.

About Us

RSS Infrastructure (RSSI), based in Birmingham, Cwmbran, and Doncaster, provides infrastructure services for the rail, civil, and utilities sectors. They serve clients like Network Rail, WMCA, HS2 and Tier 1 & 2 contractors. Their services include Arboriculture, Civils and Construction, Geofencing, Industrial Rope Access (IRATA), Magnetic Track Safety, Rail Operations including Possession Management and P/Way, Rail Welding, Signalling, and Track Warning Services.

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