The eight-year project includes completely upgrading the company’s compressed air and air treatment systems on its F74, F76 and F79 series rail cars to meet the requirements for clean, dry, oil-free air that supplies their brake and auxiliary (doors, sanding, wheel flange greasing) systems.
The original compressed air systems on BVG Berlin’s railcars were very compact, but were oil-lubricated and non-cooled piston compressors with separate service-intensive desiccant dryers, as big as the piston compressors themselves. When BVG Berlin requested proposals to overhaul the compressed air systems in their railcars, they presented strict requirements and a big challenge to bidders: replace each of the old units with a 100-percent oil-free unit with minimal noise and vibration levels, forced cooling and with a fully integrated air treatment system.
The new units had to be supplied with power from the original power attachment points, and accommodated in the existing under-floor space with 1:1 exchangeability to the previous piston compressors. Finally, the entire system had to be able to be mounted longitudinally or crosswise, depending on the series of the railcar, and, of course, run reliably and as expected.
Atlas Copco’s Railway Solutions Department gathered the necessary company information, as well as the critical equipment and technical data, required by BVG Berlin. The proposal a completely customized compressed air solution with fully integrated maintenance-free membrane dryer and proven railway core components won Atlas Copco the public tender for 100 of the units to be delivered between December 2011 and March 2019. As of today, 44 units have been delivered and, for the most part, installed.
For the basic air supply unit, Atlas Copco chose a 100 percent oil-free 3.7 kW SFR 4 scroll compressor driven by a 750 VDC electric motor protected by a pre-resistor. The SFR 4 is a simple, highly reliable compressor package design. It incorporates a minimum of moving parts, a shaft-driven cooling fan, corrosion-resistant materials, such as stainless steel and aluminum, and a sturdy construction to withstand external vibrations, shock loads and projectiles.
The compressor performs in temperatures from -25°C to +50°C, optional up to +75°C, and is designed to withstand the most extreme weather conditions.The compressed air is cooled down to a maximum of 15 °C above ambient temperature. The rated air flow is 450 l/min at 7 bar end pressure, with real FAD of 372 l/min at 7 bar at outlet after the dryer. The oil-free compressor operates between 6 bar cut-in and 7 bar cut-off pressure, and it is rated at a 100 percent duty cycle. The air treatment is carried out by a fully integrated water separator, fine pre-filter and a maintenance-free membrane dryer that supplies clean, dry, oil-free compressed air with a quality class of at least 2.2.0 acc. to ISO 8573-1. The new SFR 4 units even with the integrated maintenance-free membrane dryer take up less space and weigh less than the previous units, creating space for other purposes.
With dimensions of 1130 L x 785 W x 445 mm H, the compact air supply unit is mounted under the floor with easy access to its two air filters, hour counter and electric connectors. The membrane dryer is placed in a horizontal position along the inside of the unit since no further access space is required to maintain it. With a minimum of moving parts, the new oil-free units operate at a low vibration level and a low noise level of 72 dB(A), which increases passenger comfort.
BVG Berlin’s new compressed air systems are cost-effective and require minimal maintenance. The SFR 4 features long service intervals, which further reduces its overall life cycle costs. Backed by Atlas Copco’s service network in Berlin, BVG Berlin can be certain that its 100 new compressed air and treatment systems will provide a sustainable compressed-air solution for their railcars.
Contact: Andre de Backer, Railway Solutions Manager
Atlas Copco (atlascopco.com) is an industrial group with world-leading positions in compressors, expanders and air treatment systems, construction and mining equipment, power tools and assembly systems. With innovative products and services, Atlas Copco delivers solutions for sustainable productivity. The company was founded in 1873, is based in Stockholm, Sweden, and has a global reach spanning more than 170 countries. In 2012, Atlas Copco had 39 800 employees and revenues of BSEK 90.5 (BEUR 10.5).
Industrial Air is a division within Atlas Copco's Compressor Technique business area. It develops, manufactures and markets oil-injected and oil-free air compressors, vacuum pumps, gas generators, air treatment solutions and compressor controls and monitoring under several brands. In addition to serving a wide variety of industries, dedicated solutions are also available for marine, railway and oil and gas customers. The division's focus and main drive is to further improve its customers' productivity. The divisional headquarters and main production center are located in Antwerp, Belgium.