Schaltbau Transportation UK are a mechanical and electrical engineering company that provide a full overhaul package to bring rolling stock HVAC systems and products back to day one condition. Their dedicated HVAC team are available to support all maintenance requirements at their facility in Milton Keynes or via their mobile service team at customers’ sites. They will provide analysis of the systems, make recommendations for improved performance and reliability and will handle obsolescence issues.
Schaltbau approached Axair looking for costs to replace the bearings on three different fan references for a HVAC rolling stock refurbishment project for their end customer. Axair offers solutions to a wide range of rail and rolling stock applications including cab and passenger compartment cooling, component cooling of the drive and braking system and switch cabinet ventilation. In this case, passenger compartment ventilation was the focus.
After a period of consultation in conjunction with Axair’s supplier partner Rosenberg GmbH, Schaltbau were presented with two distinct options; replacement of the bearings as originally requested or the complete replacement of the old units with brand new units built in Germany. In the end, the preferred solution was to go ahead with brand new stock.
One of the issues that was solved with opting for a new unit, rather than rebearing the old unit, was the relatively high failure rate of the motor during the operation of replacing the old bearings. Secondly, lead times could be handled much better as fans did not have to travel twice across Europe before being refitted to the HVAC units they came from.
The fan specified was the DKHR 500 which manages the necessary operating points reliably and with minimum space requirements. The impeller is made of aluminium (AlMg3) with 7 backward curved blades and efficiency optimised circumferential diffusor with pressure orientated behaviour. The motorised impeller is statically and dynamically balanced according to DIN ISO 1940 G6.3 maintenance-free ball bearings, closed on both sides with long-term lubrication. The motor is protected via thermal contacts, which are inlaid into the motor windings. These contacts protect the motor from being overloaded through phase failure, too high medium temperature or locked rotor.