Over 28,000 people use the train network in Greater London during the morning rush hour to avoid impenetrable traffic.
To allow even more people to fall back on the train, transport operator Thameslink has placed an order for 1,140 regional cars from the Desiro City series, developed specifically for this purpose, with train manufacturer Siemens Mobility in Germany.
At the start: a tailored electronic leveling valve from AVENTICS.
In its advanced Desiro City vehicle family, Siemens relies on modern electrification of the air suspension function. The new generation enables quicker boarding and exiting at every station. With electronically controlled air suspension, the vehicle boarding height is adapted to every platform height. Furthermore, energy savings of up to 50% of the air consumption are possible. This decreases the burden on the environment and lowers operating costs significantly. Instead of train suspension based purely on mechanical control, the engineers integrated an electronic leveling valve to control the air suspension. It consists of one proportional and two switching valves, as well as control electronics with sensors. For the Desiro City, AVENTICS engineers in Austria and Germany developed a customer-specific product. It communicates with the train’s control system via the PROFINET fieldbus protocol. The assembly was delivered to the Siemens plant in Graz readyto-install, and is mounted directly to the vehicle body. Compared with the previously used, purely mechanical solutions, electropneumatics offers a range of advantages over the entire life cycle.
They simplify commissioning after assembly and demand-based operation substantially. Via web services, technicians set the parameters with a laptop and read out diagnostic messages.
With its integrated pressure sensor, the assembly is also capable of precisely measuring the transport load. The train control forwards these values to a platform information system, which shows passengers which wagons are already completely full and which still have space. If passengers change their wagon during the journey, changing the load, the electronics request air pressure based on the demand in order to keep the distance between the bogie at an optimal level.
A special feature: Unlike in the mechanically controlled pneumatic suspension systems that were standard up to now, practically no compressed air is required during travel – except in the event of load changes. This results in a significant decrease in train power consumption and lowers operating costs. According to internal calculations of AVENTICS, the operator saves €100-€150 on compressed air per year and valve.
It is planned to further reduce maintenance requirements with an option to change parameters. Wheelsets are regularly twisted off to remove minor damage. As a result, and due to wear, the wheel diameter changes. With other systems, the air suspension has to be readjusted mechanically in an elaborate process. With the AVENTICS assembly, the new diameter simply will only have to be entered via the fieldbus. This reduces both the required time and expenses.
The entire assembly corresponds to protection class IP66 and is designed for an operating temperature range of -40 to +50 degrees celsius. In rail technology, reliability and availability are extremely important. Even in the event of valve power failure, the trains can continue their journeys. Siemens gave special attention to the validation of the software functions and the interaction of the train control as the master with the air suspension control as the slave.
The first new Desiro City has been in test operation since summer 2015 and has proven successful. This year, delivery of the series will begin. Good news for the commuters in Greater London.