Rod Holroyd discusses the role of antivibration and suspension solutions in maintaining reliable and safe rail services, and how Crossrail is striving to achieve that
With passenger numbers and rail fares continuing to rise in the UK, the demand on operators to provide improved efficiency and reliability around the clock has never been higher. To help avoid unnecessary operational delays and improve the customer experience, operators are now turning to train manufacturers and OEMs to guarantee that components are not only long-lasting but will satisfy the demand for 24/7 rail transportation.
The New York Subway has long operated a 24 hour service thanks to rigorous train and track maintenance, with many urban and surburban rail operators across the world following suit – either introducing new, longer running services or announcing plans to increase demand. Operators in Seoul, Korea, have already outlined plans for an overnight service, with Transport for London recently announcing overnight services will begin this summer.
Questions about 24/7 operation
While the introduction of the overnight tube service has largely been met with positive feedback from passengers and stakeholders, there are queries from operators about the impact longer-running services may have on maintenance patterns and whether those responsible for repair and overhaul will be able to undertake the work in smaller time frames. This comes at a time when the industry is looking to increase maintenance intervals and utilise other methods and strategies to identify component failure.
Typically, passenger trains operate up to 20 hours a day but the extended service will see an extra four hours added to their running period, increasing the amount of miles each train travels every day. While daily maintenance and routine inspections are a necessity, the additional pressure on maintenance operators could be removed if longer-lasting, reliable components are installed and specified during the design and build stage. This in turn could help lengthen time frames for regular preventative maintenance, and ensure parts are only replaced during the heavy overhaul stage.
When it comes to integral compenents, such as antivibration and suspension solutions, a number of environmental factors can influence the longevity of their performance, including heat, light, chemicals, track conditions and load bearing. Commuter trains operating in the morning and the evening will inevitably have higher loads during these periods as more people travel by train, and by comparison early morning or late evening services will transport fewer passengers. Nonetheless, the longer running period will have an impact on the service life of rolling stock, so the key focus is to ensure the trains are safe and reliable whenever they are in operation.
Not just a matter of comfort and safety
Suspension and antivibration components are recognised for the role they play in ensuring customer safety and comfort, but they are also vital in decreasing the overall maintenance costs by reducing the force of the vibrations on surrounding components and improving their longevity. Passenger trains are exposed to a range of forces and vibrations during service as a result of track conditions, which can cause noise and discomfort for those on board. Antivibration products are an essential consideration in maintaining passenger comfort at varying loads and speeds, and to counteract track irregularities while optimising vehicle movement, allowing vertical and lateral forces to be transmitted safely.
With safety the number one concern for the industry, antivibration products play an important role in protecting those on board. Although many components are currently fit for purpose for the present operating conditions, Original Equipment Manufacturers (OEMs) need to ensure their products are robust enough to meet the demands of future performance requirements, such as longer operating times and increased passenger levels.
Applying this to Crossrail
This challenge was recognised by Bombardier Transportation who awarded Trelleborg a contract to supply a suite of suspension and antivibration components for their Class 345 Aventra EMU fleet currently being constructed to supply Crossrail in London. The new service will run up to 24 trains per hour and once fully operational in 2019, it will increase London’s rail transport use by 10 per cent, reinforcing the need for durable and reliable rolling stock, which requires little or no heavy maintenance.
The components which have been supplied to Bombardier include primary suspension, anti-roll bar bushing and lateral buffers. The springs are produced from a rubber formulation which provides low creep performance and a high damping factor, ensuring longevity and minimum maintenance. The lateral buffers have a strong compression stiffness characteristic, combined with low-friction padding to prevent shearing movement damage, with the anti-roll bushings benefiting from optimised high radial and low torsional stiffness. These solutions deliver long service life, reduced maintenance, increased passenger comfort and reliability.
In addition, the primary conical springs fully comply with the updated EN45545 fire safety standard, thanks to the application of a unique fire protective coating, DragonCoat. The flexible coating is flame and fire retardant, helping to delay the effects of fire on rubber products while ensuring the spring component retains all performance characteristics. It also adheres to Bombardier’s specification of selecting partners who follow safety standards and develop products which protect passenger safety.
The products supplied to Bombardier have been designed and developed to accommodate longer and more frequent service periods, undergoing extensive element analysis and rigorous lab testing prior to final delivery to ensure they can provide longer periods between maintenance windows, and help reduce unplanned downtime. As a result of this approach, the suspension products can last up to 15 years, which is considerably longer than was possible in the past.
In the future, while sourcing and installing parts that avoid unnecessary downtime and maintenance is a key priority for train manufacturers, condition-based monitoring is a concept which will help to improve the performance of fleets. This strategy helps to utilise the maximum lifespan of each component on the basis that its remaining working life can be predicted. Using accurate and up to date information about rolling stock fleets, maintenance operators can recognise and monitor faults before they occur based on external factors such as vibration, noise or heat. The process helps ensure rolling stock is only taken out of service for maintenance when it is actually necessary.
With train service life increasing and passengers travelling via rail on the rise, it has never been more important for OEMs to harness ongoing innovation and development to ensure the products they supply meet the safety requirements of the industry. At a time when services are being extended and rolling stock will be required to operate for longer periods of time, operators are looking to decrease maintenance intervals and strategies such as condition-based monitoring are providing a popular way to achieve this.
Ultimately, whatever methods are used, the onus will be placed on OEMs to ensure their components are reliable, long-lasting and above all, fit for purpose to guarantee reliability and user safety.
Rod Holroyd is global rail market manager of Trelleborg’s Industrial Antivibration Solutions operation