Vossloh Kiepe UK was contracted by Bombardier Transportation (BT) to design, supply and install an automatic sanding system for the fleet of 20 off Virgin Trains’ Class 221 Super Voyager Diesel-Electric Multiple Units (DEMUs). The 20 off Class 221 DEMUs, numbered 221101 to 221118, 221142 and 221143, are operated by Virgin Trains (VT) and are maintained by BT at Central Rivers Depot where the installation took place in 2015.
The sanding system is a further development of Vossloh Kiepe’s automatic sanding product range that is compliant to Railway Group Standard GM/RT2461 (Sanding Equipment Fitted to Multiple Units and On-Track Machines) and includes a sand box level detection feed to the Train Monitoring System (TMS) and the facility for automated sand delivery via a lance.
Prior to the installation of the new automatic Vossloh Kiepe Sanding Systems, the Class 221 DEMUs were equipped with single shot sanding systems that discharged sand from pressurised sand bottles. The original systems were removed and replaced with Vossloh Kiepe Sanding Systems whilst the existing cables, components and bogie brackets were used in the new installation where possible. The new installations did not require the bogies to be lifted from the cars.
The sand boxes are underframe mounted behind the existing skirt panels on the non-drivers side of all driving motor vehicles and in front of the third axle from the leading (driving) end. Only the sander on the leading vehicle is operational on any train set.
Sanding is carried out automatically when the train is braking above 8 mph with wheel slide activity detected by the Wheel Slide Protection (WSP) system whilst the system negates the risk of losing track circuits. The system uses the existing signal to control the automatic sanding system and is also active when any wheel is sliding below 95% of the vehicle speed or at all times during emergency brake applications.
A feature is included which gives feedback to the driver that the sander is operating correctly with the sand button illuminated in the cab when the sand discharge electro-pneumatic valve is energised. A manual override is also fitted and controlled via the sander button and will be active at speeds above 8 mph whenever there is brake demand. Operation of the button will override the sander controls and lay sand as long as the button is depressed.
The Class 221 DEMUs are fitted with both blended pneumatic and dynamic braking systems and the signal for the automatic sanding is active with both systems. The Vossloh Kiepe equipment incorporates a device that either delays or inhibits sanding during WSP activity of less than one second’s duration in order to optimise sand usage and prevent false or unnecessary activation.
The new automatic sanding systems fitted to the Class 221 DEMUs have improved the operation in low-adhesion conditions during acceleration and braking thereby improving safety and reducing the likelihood of wheel flats and other wheel tread faults during braking.