Modern bogie solutions

The bogies of railway vehicles have become a high-tech component nowadays. At Siemens, they are developed and manufactured for the whole company in a World Centre of Competence for bogies (CoC) in Graz/Austria, where the most modern technical methods are used in development and production.

With totally new bogie concepts and a system for onboard-condition maintenance (as opposed to widely practiced mileage-based maintenance) Siemens is positioning itself in the vanguard of technical development.

The requirements placed on the bogies of railway vehicles have changed tremendously in the past 10 years. Originally, bogies represented a design and production technology which, from today’s perspective, is considered to be outdated.

Service-proven types were constantly improved on the basis of field experience and new knowledge. Then they were manufactured in a more or less manual process. The necessary mechanical safety of the bogies was essentially guaranteed by oversizing and their operational reliability by fixed inspection intervals.

Modern bogies, however, are designed on the computer – in keeping with the current state-of-the-art. Bogie-Frames are calculated using the finite element method and their running characteristics is optimised in computer simulations. Then they are manufactured with maximum precision in an extensively automated process.

The result is: Modern bogies are high tech components responsible for main characteristics of railway vehicles.

Siemens designs modern bogies which differ tremendously from conventional ones. One example of a completely new bogie concept is the Syntegra. This bogie-concept is a highly-integrated solution that makes optimum use of all synergies of the bogies, drive and brake technology. Important advantages are low weight and less space needed for mounting as well as reduced cost of bogie operation.

It is also already possible today to perform on-condition maintenance, i.e. maintenance depending on the actual condition of the bogies and that of their components instead of according to a specific number of kilometers. The required hard and software is available, validated and tested and ready to be used.

These above mentioned changes are also reflected in a new industrial structure and culture. At Siemens, the entire bogie development and production have been concentrated in a Centre of Competence in Graz, Austria. This move made the Siemens TS plant (formerly Simmering-Graz-Pauker) not only the most optimised of its kind in the world, but also the focal point of the corresponding know-how.

Today, nearly 800 highly qualified employees work there, 170 of whom are engineers. They develop all the bogies for all rail vehicles produced by Siemens and, in the meantime, for those of external customers as well.

On average, 2,500 bogies are manufactured and delivered worldwide every year; in peak years, more than 3,000. In fiscal 2006, 42 contracts were executed for 21 countries. To guarantee the highest quality, the facility in Graz is not only ISO 9001 and ISO 14001 certified, it is also the only location in the world to be certified according to the new IRIS system specially created for the rail industry.

This specialisation in bogies makes it possible to maintain an extremely high standard of quality. The principle consists in being able to satisfy all customer requirements efficiently and cost-effectively by using a few, basic modular bogie platforms as well as by combining and adapting bogie components and modules. In each case, the result is a combination of familiar features (basic designs) and new aspects (customer-specific changes) and a customised but nonetheless proven – and that means, above all, a reliable and easy-to-maintain – individual solution. As it is exactly developed to customer requirements, bogies are, by definition, also the most cost-effective components. This is an important point because the bogies are a key expense factor: while they make up only 10 to 15 per cent of the value of the vehicle, their intensive maintenance accounts for around 40 per cent of the lifecycle costs!

The secret for success lies in the integrated, system-oriented working methodology practiced at Siemens TS BG. Accordingly, a bogie is regarded as a complete, integral part of the overall system and therefore part of the vehicle and the infrastructure as well. Like the vehicle, the bogie is tuned as a whole product as far as possible to the operator’s requirements, his railway network and his operating structure. All processes from development to design, from design to certification and service are performed according to this perspective.

The first step in every order is the acquisition of the technical and physical data of the overall system and including the drive system. At the same time, all key design criteria such as the intended speeds and loads as well as the physical properties of the rail network, i.e. curve radii, track geometry and so on, are collected and entered into the system. This results in complex requirement matrices as well as the necessary load assumptions which, in turn, form the basis for the complete computer-aided engineering work. The findings are verified by means of complex computer simulations. This process stretches up to the complete combination of the bogie and car body. In the end phase, the computer screens show virtual vehicles running at the specified speeds over their future rail network, while the forces, elongations, vibrations, etc. that occur are recorded in real-time and compared with the target values.

Concurrently with the technical definition of the bogie, the characteristics relating to safety and the design features determining future maintenance and, if need be, repair procedures are monitored and optimised. As regards safety, there is a kind of checklist with 500 to 800 items for each type of bogie. Each item describes a possible failure pattern, places it in one of four effect classes (from severe = ‘Derailment’ to light = ‘Train at standstill’) and defines corresponding preventive and remedial measures. Comprehensive manuals are compiled for the maintenance staff, which should enable the rail operator to carry out efficient servicing of the bogies.

In view of the high share of the overall maintenance costs incurred in connection with the bogies, Siemens engineers are attempting to gradually move away from the fixed maintenance intervals customary today. According to requirements laid down by the buyers, Siemens’ bogies are today usually designed for a 30-year lifespan and for a general overhaul period of 1.2 million kilometers. In this case, the fixed interval for the general overhaul is an anachronism since modern bogies are usually a long way from reaching the wear and tear limits when they are overhauled. This means that maintenance is now of a purely preventative nature and, from a safety perspective, is not really necessary. This is why, in the civil aviation field, these fixed intervals are no longer adhered to, particularly for jet engines. Instead, the engines are continuously monitored during operation and only then overhauled when analysis of the data recorded indicates the early stages of wear (on-condition maintenance). Where jet engines used to be overhauled after every 8,000 to 12,000 hours of operation, it is possible today to increase that interval for individual types and particularly for ‘healthy’ engines to over 30,000 hours without jeopardizing operating safety. Siemens has developed a procedure which similarly enables a permanent bogie diagnosis based on the continual analysis of vibrations. Just how precisely this system functions was proven in a test run using a specially prepared German ICE train, in which a wheel had been replaced by a worn wheel. According to test bench measurements, the deviation from the ideal dimension was 0.432mm. The vibration analysis produced a value of 0.456mm. By using this system, bogie maintenance costs could be reduced by 15 to 30 per cent. Economic considerations alone mean that this type of system will find its way into the maintenance practice for rail vehicles relatively quickly – and Siemens bogies will be leading the way!

If, from a technical development point of view, the bogie has an optimal concept and design, a highly automated Siemens manufacturing process stands ready in the Graz Centre of Competence (CoC) for efficient production. The welded construction method is employed for the frames here. Since 2001, a new type of production line has been implemented in the frame shop. The production cells are loaded automatically and the frame components are welded by robots. Currently, this is taking place to a great degree in tandem welding processes, in which two welding wires and an arc achieve a melt-off rating of over 10kg/hour. Every year, around 7,000 tons of steel plate and 12,000-18.000 kilometers of welding wire go into the production of 2,500 to 3,000 bogie-frames. The total length of all welding seams amounts to over 1,450 kilometers, of which approximately 50 per cent are produced by welding robots. The goal is to increase the share of robot-welded seams to over 75 per cent. In addition, one of the most modern laser hybrid welding systems is to be put into operation here.

The finished frames are then machined on the most modern NC machines and in dry condition, too, which means that no coolant is used. Then they pass through a fully automated painting process complying with the highest ecological standards, in which they are first shot-blasted and then, depending on the customers’ requirements, are coated with conventional or water-soluble paints. The Graz plant currently uses 161.5 tons of paint a year (a little over 60kg per bogie), of which approximately 70 per cent are water-based – a trend which is constantly increasing.

The final assembly is now carried out by strictly organised, component-oriented teams. In terms of added value, only about 30 percent of a bogie is made up of parts produced at CoC Graz. Other components like wheelsets, brakes, springs and drives are bought in from third parties, in which case the CoC strives to establish supplier partnerships for key components to ensure an optimal exchange of know-how. Since between 40 and 50 different orders are being processed at any given time, the component logistics plays a major role. A SAP system ensures that, firstly, the correct components are used for the individual bogies and that, secondly, each safety-critical component can be seamlessly traced back to the loading of the raw materials.

The above-mentioned process ensures, on the one hand, that all bogies fully meet customer requirements and quality standards and, on the other, that they can still be produced cost-effectively.

After undergoing tests and necessary adjustments, the bogies are delivered to the customer in a fully operational state –‘Plug and Go’, so to speak…

Customers therefore benefit from bogies from Siemens CoC Graz. These are truly high-tech products and represent the latest state-of-the-art worldwide.