Building DMUs for extreme conditions
INTRO: Developed to provide a high quality passenger environment on very long journeys through harsh climates, DH4-1 diesel multiple-units are expected to enter service on the Tehran - Mashhad route in summer 2004
BYLINE: Dr Gerhard Schmidt
General Project Manager, Siemens Transportation Systems
Sales Manager, Commuter Trains,
Siemens Transportation Systems
Sales Manager, Mechanical Parts,
Siemens SGP Verkehrstechnik GmbH
THREE YEARS ago, Raja Passenger Trains, the passenger service arm of Iranian Islamic Republic Railways (RAI) placed an order with Siemens Austria for 20 inter-city DMUs. The result is the DH4-1, which uses proven technology to ensure high reliability and availability. The trainsets have underfloor traction packages, and up to three units can work in multiple.
A considerable amount of technology transfer is included in the project, to fulfil an RAI requirement for local involvement. The five initial units are being assembled at Siemens plants in Europe, and the remaining 15 will be supplied in kit form for local assembly by Wagon Pars. Dividing work between European and local production centres is favourable when exporting to countries which appreciate local added value.
In the longer term, Siemens Transportation Systems hopes to supply trains derived from the DH4-1 to railways in other countries where the environment is comparable with that in Iran.
Under the floor
The MAN D2842-LE602 engines in each vehicle of the four-car sets have a nominal rated power of 588 kW at the drive shaft and 2100rev/min at altitudes of up to 1800m above sea level. There is a high-pressure turbocharger with intercooler, and an electronic control system. Dry air filters are fitted to the inlets, and the elastic engine suspension is designed to avoid structure-borne noise transmission. At ambient temperatures below -25íC auxiliary heaters preheat the cooling circuits and fuel. Each car has a fuel tank, and the train will be able to travel the 926 km between Mashhad and Tehran without refuelling.
The Voith T312 BR hydrodynamic turbo transmission includes a torque converter and two fluid couplers for second and third gear, as well as a hydrodynamic retarder. Torque transmission to the wheels is by cardan shaft and axle-hung gearboxes, suspended on two bearings. The resulting torque is suspended by a torque support lever with elastic bearings on the bogie frame. The two gearboxes on each bogie are linked by a further cardan shaft.
The SF 5000 DD bogies were developed for DMU applications by Siemens TS in Graz, Austria. The welded compound box frames are fabricated from metal sheet, forgings and cast parts, and have one centre lateral beam and two longitudinal beams. The bogies comply with UIC 518 track wear behaviour standards, and include steel spring primary suspension and secondary air suspension. Longitudinal and lateral forces are transmitted between the bogie and bodyshell by pivot pin or traction rod. Unsprung mass is minimised, to give a high standard of ride and reduce rail and wheel wear.
There are three braking systems. Every powered bogie has a hydrodynamic brake, which dissipates energy as heat through the diesel engine cooling system. This will not be utilised during emergency brake applications. If the required retardation cannot be fully provided by the hydrodynamic brake, air disc brakes provide the remaining effort.
There are automatic high-performance electro-pneumatic wheel-mounted disc brakes, which incorporate wheel slip protection. These provide secondary braking, and will be fully applied only in emergencies or if the hydrodynamic brakes fail.
UIC standards require sufficient braking capabilities when parked with the power off, so the brake actuators are equipped with spring-loaded mechanisms which are automatically applied when the brake pipe air pressure is reduced.
Each vehicle has its own brushless generator, providing three-phase auxiliary power at 400V 50Hz. The 72 kVA capacity is designed for both summer air-conditioning and winter heating. There is a 24V lead acid battery and charger in each car, with a second to start the engine. In the event of a generator or charger failure the neighbouring car will take over the supply, providing around 50% of the normal power.
Hydrostatic circuits power all auxiliary components, including the generator, air compressor, and radiator fans for the cooling water and charge air. Each circuit has a variable displacement pump and a fixed or variable displacement motor. For optimum power availability the pumps are connected to a secondary diesel engine crankshaft coupling or to the auxiliary power outlet of the turbo transmission units. Starting the central train management computer automatically initiates preheating of the engine cooling water circuits in order to increase engine lifetime.
Above the floor
The bodies have lightweight fusion-welded steel structures (left) assembled from underframe, end, roof and two side sections. The underframes comprise a centre component and two end sections, with crumple zones in the side buffer axis. The roof structure is formed from two frame girders, with integral keys forming the exterior shape and a longitudinally corrugated steel sheet forming the external layer. The entire shell is acoustically de-tuned to avoid any significant local resonance.
Each vehicle has an independent heating and cooling system which uses waste heat from the diesel engine to warm the passenger compartments. There are roof-mounted heating, ventilation and air-conditioning units, coolant evaporators, compressors and air heating circuits at the end of each car, and individual HVAC units are installed under the driving consoles of each cab.
The trains will be exposed to high dust concentrations as well as heavy snow and rain, and so are dust-sealed. The air-conditioning operates automatically and can be manually switched to recirculate air when entering tunnels or during sand storms, keeping out exhaust fumes and preventing intake filters from becoming blocked. Automatic doors are fitted at the vestibules to reduce noise and temperature differences created when the external doors are opened.
The interiors include transparent overhead luggage racks, and these are used to mount reading lights, coat hooks and push buttons to call for a steward. Larger items of luggage can be stowed in compartments at the end of the saloons. At-seat five-channel passenger audio-visual entertainment systems and DVD/Video screens in each car are fully integrated into the on-board public address system.
Closed system vacuum water flush toilets are located at the inner ends of the A and B (driving) cars and both ends of the C (intermediate) cars. All toilets are equipped with baby-changing tables. Coach B has space for one folded and one open wheelchair at a table adjacent to a wheelchair-accessible European-style toilet, with easy and straight access through the cubicle's sliding door.
Galleys in the driving cars can provide hot and cold drinks, snacks and pre-prepared cold meals, and also have facilities to reheat food. An at-seat trolley service will be provided.
DH4-1 in Brief
Length m 107
Width m 3·1
Total seating capacity 252
Maximum speed km/h 160
TABLE: Table I. Vehicle design characteristics
Car A C B
Cab with seat for train manager Yes No Yes
Seats 55 70 57
Wheelchair space 0 0 2
Oriental-style toilet 1 2 0
European-style toilet 0 0 1
Luggage storage area Yes Yes Yes
Galley for on-board catering Yes No Yes
Fixed foldable tables No No Yes
Seat back tables Yes Yes No
TABLE: Table II. SF5000 DD bogies
Max speed km/h 160
Kinematic envelope UIC 505 1
Track gauge mm 1435
(1410 to 1465 possible)
Wheel profile UIC 510 2
DIN5573 E 1425 135
Min curve radius
ormal operation m 230
in workshops m 150
Max static axleload tonnes 18·5
CAPTION: Bodyshells for the first five units are being assembled by Siemens inEurope. The first trainset will enter service in summer 2004.
CAPTION: Artist's impression of the DH4-1, which is designed to provide comfortable air-conditioned services through the harsh environment of northeast Iran. Each four car DMU will be formed of two type-C cars between type A and B driving cars
CAPTION: The Siemens SF 5000 bogie series was designed for use on diesel multiple-units