A breath of fresh air

A basic and indispensable pre-requisite for a well-functioning integrated rail system with over 37,000 trains a day running to tight schedules is having a high-tech, innovative rolling stock maintenance system. Thus a position of real importance falls to DB Fahrzeuginstandhaltung GmbH, which is assigned to the services division of Deutsche Bahn.

Currently, Deutsche Bahn AG, as the largest European mobility service provider, operates 12 works and three workshops for ‘heavy-duty maintenance’ in Germany. The works have accumulated a unique blend of specialist knowledge in heavy-duty rolling stock maintenance. They represent a combined system uniting competence and a broad range of specialist knowledge for providing rapid yet customer-oriented maintenance.

A broad range of work and services

Along with the technical infrastructure needed and highly qualified staff, DB Fahrzeuginstandhaltung GmbH, in particular, has acquired enough knowledge over the decades which makes its range of ‘heavy-duty rolling stock maintenance’ unique in Europe. DB Fahrzeuginstandhaltung GmbH works with approximately 6,600 employees who are specialists for overhauls, modernisation and conversions. Component regeneration, upkeep and repair of accident damage are also a part of what is on offer. At all the sites today, the works provide modern technology as well as simple, yet effective and efficient operating sequences. They are constantly optimised and adapted to tried-and-tested industrial standards. The quality and efficiency of the works are underpinned by international certifications.

Air-conditioners in double-decker commuter passenger carriages

There has been a constant rise over the past few years in the number of passengers using Deutsche Bahn commuter passenger services. This is down, in particular, to increasingly modern and comfortable mainline rail carriages being provided for commuter passenger services.

Air conditioning equipment, ensuring comfort and pleasant temperatures throughout the year in the passenger areas, has become part and parcel of modern comfort.

The modern double-decker rail carriages (from type series 1997) are fitted out as standard with air-conditioners.

For air-conditioning the passenger area, a compact air-conditioner is arranged in the roof at the end of Carriages 1 and 2. Each of these air-conditioners is an independent functional unit with all the equipment for heating, cooling and de-humidification.
The air-conditioners work with outer and re-circulated air which, depending on the operation, can be mixed in differing ratios. At each end of the carriage the air is drawn in transverse to the direction of travel through a grate and an air filter in the carriage side wall. The supply air ventilators in the air-conditioner press the air across the air cooler (evaporator of the refrigeration unit) or across the electrical heat accumulator and convey it via a duct node bolted to the appliance into the carriage supply air ducts. A separate section in the air-conditioner accommodates the condenser, related fans and the rotary screw compressor of the refrigeration unit. The condenser cooling air is also drawn in and expelled transverse to the direction of travel through the roof cap.

The air ducts run in the ceiling along the length of the carriage and along the floor on both sides. The supply air, under ventilation or cooling operations, is directed into the passenger area via a perforated ceiling in the upper and lower deck or via slots in the one-deck sections. In heating, the air supply flows out of the floor ducts parallel to the floor and side. Additional radiators are fitted in the floor ducts of the one-deck sections to cover the extra need for heating there.

The exhaust air escapes from the passenger area through grates at the carriage ends and through any non seal-tight points of the carriage. The exhaust air grate of Carriage 2 is larger than for Carriage 1. This is because the exhaust air grate surface there is also used for the exhaust air of the energy supply unit which obtains its cooling air from its own outer air intake device. When passengers are being transported, positive pressure is constantly maintained in the carriage. It practically stops any untreated outer air getting in even when the doors are opened.

The air-conditioner is designed so that it complies with the comfort requirements defined in the UIC 553 (No.: 5 dated 01.01.1990).

The ambient temperature is recorded by five or six temperature sensors in the passenger areas. The air-conditioner diagnosis computer processes the value from these sensors and by cooling, ventilating and heating regulates the ambient temperature. Given high outer temperatures, the ambient temperature designated value is raised so as to limit the system’s energy consumption and stop the passenger being subjected to any large temperature differences. Cooling is undertaken at the same time as the supply air is de-humified. The regulating system controls both carriage air-conditioners and the additional radiators in the floor ducts of the one-deck areas.

Compressor and condenser ventilators in the air-conditioners are energised from the frequency-variable air conditioning inverter. The supply air ventilators are supplied by frequency-variable small inverters of the energy supply unit – ‘General on-board power supplies’. The electrical heat accumulators in the air-conditioner are directly energised from the train busbar.
The compact air-conditioner can be delivered as a complete module. Four bolts connect the air-conditioner rigidly to the body. It is designed so that all components, with the exception of the heat exchangers, can be replaced as fitted.

Maintenance and upkeep

The air-conditioners of the modern double-decker rail carriages have stood the test of time in use and are highly reliable. There is little outlay needed on maintenance and upkeep.

During close-to-operation maintenance the systems are regularly inspected, upkeep is carried out and any faults during operations are read out from the fault memory. Every six months maintenance packages are involved, such as evaporator cleaning, filter pad replacement, safety chain examination (high and low pressure shutdown). These maintenance packages are designed so that they ensure the operational reliability of the air-conditioner in summer and winter.

There is not much difference between maintenance of the air-conditioner during an overhaul (examination of the rail vehicle after a maximum of eight years or 1.3 million kilometres) and close-to-operation maintenance. However, more extensive maintenance is envisaged during an overhaul.

For instance, certain air-conditioner components (evaporator, filter, intake zones, duct system parts) are thoroughly cleaned. Certain components, such as supply air and condenser ventilators, are replaced to schedule and a regeneration (renewing the bearings) is carried out.

The heating accumulators are also replaced as planned. They are thoroughly cleaned during regeneration and gauged; heating elements are renewed, if needed and a check is made on the safety equipment. The faults or trouble read from the diagnosis system are examined and irregularities put right. Finally the air-conditioner is tested as to complete functioning and documented.

Air-conditioning retrofit

In view of the expiry of the transportation contracts with the German federal states, applicants for new route network tenders are being forced to comply with the requirements of the transportation authorities. This means either purchasing new rail vehicles with the appropriate equipment or modernising existing ones.

The Deutsche Bahn AG regional divisions have embarked on modernising their mainline and commuter passenger vehicle stock. This means subjecting the double-decker rail vehicles to a re-design and, as the case may be, to retrofitting an air-conditioner.

Only with these kinds of vehicles meeting customer demands will the routes tendered for of the federal states be acquired!
Particularly involved here is the project ‘Air-conditioner retrofit of double-decker vehicles built between 1994 and 1997’, by Bombardier, Görlitz Works. The 751 – DBz, 756 – DABz and 761 – DBbzf vehicles (292 in total) made during this period only have an air-heating unit for ventilation and heating. The following equipment configurations are involved:

• Central energy supply: from the ZS 1,000 V, 16 2/3 Hz and 50 Hz using high-voltage converter R 15 KVA Pintsch-Bamag company, including charger
• Rotary inverter: DR / WR 8.5 KVA company GEZ for frequency-variable power supply of the supply air motors of the two air heater sets
• two air heater sets: LHA S 80 C company HFG-Faiveley whose heating accumulators (each of 2 x 15 KW) are energised directly from the ZS
• BGT air-conditioning computer: 11 HA 18 from Bombardier Mannheim with diagnosis Form two and central ZAG 4 indicator

Vehicles with this equipment cannot compete today with other suppliers. This means that there is an enormous potential here for DB Fahrzeuginstandhaltung GmbH.

The project ‘Air-conditioning retrofit Dosto 1994 year of construction’ is concerned with satisfying the ideas and wishes of the vehicle owner as regards enhancing interior air conditions and improvement and stabilisation of the energy supply.

The vehicle owner is especially interested in following up on a solution that has proved to be reliable and is low on maintenance. Other aspects are:

• Using the ventilating ducts in the ceilings of the upper and lower deck for the cooling air
• Using a roof-type air-conditioner where the present air heater set is
• Minimum number of openings for inspection work
• No alteration in the appearance of the passenger areas
• Retaining the number and arrangement of seats
• Extending the energy supply under minimal outlay

The objective has been to construct a cost-optimised air-conditioner, including the additionally needed energy supply components, whilst retaining most of the available electrical and heating/ventilation equipment. In its design, the air-conditioner had to be state-of-the-art especially in terms of:

• Reliability
• Efficiency
• Operating economy
• Environmental compatibility
• Low upkeep and maintenance
• Weight optimisation

Under a European-wide tender, DB Fahrzeuginstandhaltung GmbH put in a bid for this order. Following a bid and selection procedure involving several potential suppliers of air-conditioners, we submitted a bid in coordination with the Liebherr company (previously Bombardier Mannheim) which was accepted in May 2006.

The approach envisages the use of a new energy supply unit based on Dosto 2003 production status and compact air-conditioning units based on the 1997 production status. As a result, this completes adaptation of this vehicle series to those that are fully air-conditioned today and also brings about optimisation of the maintenance and supply inventory costs. The high degree of reliability and the little maintenance required for these units was a further factor which positively affected the decision. Other benefits of the solution are:

• All supporting records for EBA (Federal German Rail Office) approval are available including impact and jolting test
• Most-favourable cost and optimised solution
• Use of components tested under operating conditions over many years
• Fulfilment of the EMV (electro-magnetic compatibility) requirements including shunting radio communication system
• Unreserved diesel locomotive performance capability
• Reduction of expenditure in electrical installation work
• Integrated temperature-dependent battery charging

The air-conditioning retrofit project is currently in the model carriage production stage followed by being placed into service. The conversion/upgrading work concentrates on the following:

• Dismantling the air heater sets, duct nodes, cold air duct guideways, ceiling elements in the upper, intermediate and lower decks
• Removing the energy supply system and the battery box and adaptation work from the steel construction side for fitting the new energy supply unit
• Opening the roof above the boarding points, welding both the support structures for the compact air-conditioners and upgrading three exhaust air grates at Carriage ends 1 and 2
• Installing a new duct node and upgrading the cooling air guideways
• Laying the cabling in the roof and adjustment of the S 1, S 3 and H 3 control cabinet support structures to the control and diagnosis technology of the Dosto 2003 series
• Upgrading the entire ceilings in the upper, lower and intermediate decks

The objective is to obtain production clearance in January 2007 with the model vehicle following tests in the thermal and air-conditioning chamber in Görlitz and Vienna-Arsenal, start-up trials and the electro-magnetic compatibility inspection. Then, a further 27 vehicles are to be upgraded in a 1st phase. Options for a further air-conditioning retrofit of this series are already on hand. This will level the path for a uniform state-of-the-art and ensure modular component change-over in all the regions.