A 3rd rail transit system is an electrified railway configuration in which the power to operate trains is supplied through a conductor rail. This additional banister is positioned parallel to and at a lower level than the running rails, typically between the tracks. It carries the electric current necessary to power the trains and is in continuous contact with the vehicle’s power collection mechanism.The train’s power collection device then establishes direct contact with the top surface of the 3rd rail to extract electrical power. Typically, the power supply in this configuration is provided as direct current (DC).
Selco Manufacturing Corp provides 3rd rail products such as steel brackets, fiberglass brackets, fiberglass insulators, protection boards, F-anchors, end approaches, copper terminals, connectors, pothead assemblies, direct fixation material, signal platforms and signal cages. Selco Manufacturing Corp also provides DC Disconnect switches, snow melters, wayside power, stinger systems and substation equipment. Selco Manufacturing Corp., also receives awards annually from the MTA for electrified transit maintenance.
Types of 3rd Rail Systems and How They Work
Third rail transit systems offer a viable and cost-effective solution for electrifying railway networks by delivering consistent power to trains. They also reduce the visual impact and space requirements of overhead cables.
The train’s power collection device then establishes direct contact with the top surface of the 3rd rail to extract electrical power. Typically, the power supply in this configuration is provided as direct current (DC). Selco Manufacturing Corp provides all 3rd rail products as brackets, insulators, protection boards, F-anchors, rail covers, end approaches, copper terminals and connectors.
The conductor rail is positioned at the bottom and between the running rails in the bottom contact system. The power collection device then contacts the underside of the third rail to extract electrical power. This design is commonly used in metropolitan metro systems, providing a safer alternative by keeping the rail out of pedestrian reach.
Side contact rail systems offer a distinctive configuration in which the conductor rail is positioned on the side of the running rails. The train’s power collection mechanism establishes contact with the side surface of the 3rd rail to draw electrical power. While less commonly used than other configurations, side contact systems enhanced safety and reduced electrical interference.
Materials Used in 3rd Rail Construction
The construction of third rails involves the utilization of various materials, with each one selected based on its distinct properties and suitability. The choice usually depends on different factors, including budget considerations, specific requirements of the system, and environmental impact. Nonetheless, the ultimate objective is to ensure optimal performance, durability, safety, and minimal maintenance requirements.
Discussed below are common materials used in the construction of these transit configurations:
Copper is known for its high corrosion resistance, making it suitable for exposed environments where it can withstand harsh weather conditions. Its superior conductivity also allows efficient transmission from the power source to the trains, ensuring reliable and effective operation. Moreover, it can be easily formed into the required profile for third rail applications.
Steel is a strong material that can handle the loads and impacts passing trains impose. This makes it well-suited for high-traffic and heavy-duty rail applications. Steel third rails can also endure constant contact and friction with the train’s power collection mechanism without wear or damage. Lastly, coatings and treatments can be applied to prevent corrosion and extend its lifespan.
Aluminum is occasionally used as an alternative material in constructing third rails, offering specific advantages in certain applications. One of its major advantages is its lightweight nature, resulting in lower energy consumption and reduced structural requirements. Its corrosion resistance can also contribute to its durability and longevity.
Composite materials are gaining recognition and being explored for their potential applications in third rail construction. They offer a combination of unique properties that can be advantageous in certain scenarios. They also exhibit exceptional mechanical strength while significantly lighter than traditional materials like copper or steel. Examples of composite materials include fiberglass-reinforced plastic (FRP) or carbon fiber-reinforced polymer (CFRP).
Importance of Insulation Materials
Third rail systems rely on insulation materials to ensure the safety of both operators and the general public. They reduce the risk of electrical shocks by preventing accidental electrical contact. They also serve as a barrier, prohibiting unwanted access to the electrical current flowing through the third rail. This protection is especially important in urban areas where third rails are close to pedestrians.
In addition, they prevent unwanted electrical coupling between the third rail and nearby structures or equipment. This interference reduction maintains the integrity of signaling systems, communications devices, and other sensitive electronics near the third rail. Moreover, insulation materials with specific electrical properties can effectively control and mitigate electromagnetic fields.
Here is a list of commonly used insulation materials:
- Cross-linked polyethylene (XLPE)
- Polyethylene (PE)
- Polypropylene (PP)
- Polyurethane (PU)
- Polyvinyl chloride (PVC)
- Silicone rubber
Essential Considerations for Selecting 3rd Rail Transit Materials
When selecting materials for rail transit systems, the following key considerations should be taken into account to ensure optimal performance, safety, and durability:
Materials with high electrical conductivity, such as copper or aluminum, are preferred for rail transit configurations. They allow for efficient transmission, ensuring minimal energy loss during the transfer of electrical current from the power source to the trains. Higher conductivity materials also result in less resistance and improved efficiency in power delivery.
Mechanical Strength and Durability
Rail transit systems experience substantial mechanical stresses and loads due to the weight of trains, vibrations, and dynamic forces. Materials with sufficient mechanical strength are required to withstand these loads without deformation or failure. Choosing those with high durability and low susceptibility to degradation also helps reduce the need for frequent inspections, repairs, and replacements.
Weight and Structural Considerations
The weight of the materials can impact the ease of installation and handling during construction or maintenance activities. For example, heavy materials may require specialized equipment, additional workforce, or more complex installation processes. Conversely, choosing lighter materials can simplify installation, reduce logistical challenges, and lower labor and equipment costs.
The materials must also have sufficient structural integrity to support the loads and stresses of trains and environmental factors. They should maintain their shape and stability over time, ensuring the safe operation of the infrastructure. For example, strong and structurally sound metals prevent failures, deformations, or premature deterioration that could compromise the integrity of the rail system.
Choosing environmentally sustainable materials is becoming increasingly critical in rail transit systems. Sustainable materials have minimal negative environmental impacts throughout their lifecycle, from extraction or production to disposal or recycling. Additionally, materials with eco-friendly attributes help reduce resource consumption, waste generation, and greenhouse gas emissions.
It is essential to consider the materials’ upfront cost and availability in the market. Comparing the expenditures of different materials allows for informed decision-making and selecting options that align with the project’s financial constraints. Conducting a life cycle cost analysis (LCCA) also comprehensively evaluates the costs associated with materials over their entire life cycle.
Compatibility With Existing Infrastructure
When upgrading an existing rail transit system, it is crucial to consider the compatibility of the new materials with the existing infrastructure. Therefore, the selected materials should seamlessly integrate with the current configuration, ensuring compatibility with power collection devices, track components, and other relevant infrastructure elements.
Selco Manufacturing for High-Quality Infrastructure Solutions
Selco Manufacturing Corp. is a trusted custom niche manufacturer specializing in products essential for constructing and sustaining critical infrastructure. We deliver top-quality solutions to the construction, rail transit, electrical, highway, industrial, and utility industries. We are also proud to be an AISC-certified company for structural and miscellaneous steel fabrication and assembly.