INSIGHTS & RESOURCES

This article was published in the Fluid Power Journal in March 2025. View the digital article here. View the case study here. The railroad industry has long relied on innovative technologies to ensure the safety, efficiency, and durability of its infrastructure. One such critical innovation designed for use in service or repair of rail, is the mobile hydraulics and controls system used in rail car heating equipment. These systems are designed to heat continuous welded railroad rails to 400-500 degrees Fahrenheit, enabling them to enlarge and be secured in place while in a hot, expanded state. Once cooled, the rails contract, creating the tension and stability necessary to support the immense loads of locomotives and rail cars. This article explores the technical aspects, challenges, and innovations behind these systems incorporated into rail service cars, highlighting their importance to the railroad industry. The Role of Mobile Hydraulics in Rail Heating Systems To achieve the precise range of speeds and torque required for heating rails, a combination of hydrostatic drive and mechanical linkage systems was deployed. This setup ensures sufficient power to move the system across the rails at controlled speeds, even on inclines. Additionally, an auxiliary pressure-compensated, load-sensing circuit operates ancillary equipment, such as burner assemblies, blower fans, and vibratory mechanisms. The system’s hydraulic components include a hydrostatic pump with PWM (Pulse Width Modulation) control, radial piston motors for the main drive system or vehicle propel function. Pressure-compensated piston pumps are used to supply hydraulic power to the auxiliary functions, while directional control valves, both cartridge-style and sectional-style, manage the hydraulic flow. These components, paired with a robust mobile control module, create a hydraulic and control system capable of thriving in harsh outdoor environments. Control System Operation and Design The control system is built around a durable mobile PLC control module programmed with software developed using the CoDeSys environment. This module interfaces with the directional control valves through wired communication and with the diesel engine via the J1939 CAN bus protocol. Sensors, both analog and digital, provide real-time data for monitoring system performance. This design ensures reliable operation, even in extreme conditions. Challenges in the Field One of the primary challenges faced by rail heating systems is operating in severe outdoor environments with minimal downtime. These machines often function in remote areas across North America, where resources for repairs and troubleshooting are limited. Downtime can halt an entire segment of the railroad system, making simplicity and reliability paramount. The system’s design prioritizes ease of maintenance, allowing field technicians to quickly identify and address issues. Heating System Configurations The rail heating system comes in two configurations: propane-powered and diesel-powered. The propane system requires controlled propane flow, while the diesel system uses a fan/blower assembly with a closed-loop control system to maintain consistent airflow. Both systems feature independent burner banks to heat each side of the rail, ensuring uniform temperature distribution. Innovative Features The rail heating system incorporates several innovative features, including a cruise control function that enables precise speed control. In work mode, the rail car system operates at speeds as low as 1/8 MPH, a capability unique to the industry. This slow, steady speed is critical for effective rail heating. Additionally, transport mode allows speeds of up to 20 MPH for relocating the equipment. Operator controls include an electronic joystick for speed and directional adjustments, along with comprehensive system monitoring and fault indicators for troubleshooting. Safety Measures Safety is a key consideration in the system’s design. Real-time monitoring ensures optimal fluid levels and temperatures, while built-in shutdown mechanisms protect against low or overheated conditions. The system also includes "driver presence" technology, preventing the machine from operating in an unmanned state. Ease of Maintenance Maintenance is facilitated by detailed operator manuals, on-site training, and diagnostic tools such as test points and fault indicators. These features enable railroad industry technicians to efficiently service the equipment and minimize downtime. The system’s simplicity and robustness are essential for reliable operation in remote and challenging environments. Historical Context and Evolution The concept of rail heating systems dates to the 1950s, when mechanical technology was used to perform the task. Since the early 2000s, advancements in hydraulics and electronic controls have revolutionized these systems, providing greater efficiency, reliability, and precision. Modern designs, operational for over 15 years, continue to set the standard in the industry. Energy Efficiency and Environmental Considerations The closed-loop hydrostatic drive system improves fuel efficiency by reducing waste, allowing longer operating durations before refueling. In the diesel-powered configuration, the shared fuel system between the engine and burners further enhances efficiency. These features contribute to a more sustainable approach to rail heating. Conclusion Mobile hydraulics and control systems have transformed rail heating in the railroad industry. By combining advanced hydraulic technology, innovative control features, and robust safety measures, these systems ensure reliable operation in even the harshest environments. Their efficiency, simplicity, and adaptability make them indispensable tools for maintaining the stability and safety of railroad infrastructure. As the industry continues to evolve, these systems will remain at the forefront of technological advancements, meeting the demands of modern rail operations. Written by Kevin Smith, Vice President of Sales, SCOTT Industrial Systems