Temperature monitoring of the axle boxes on the Liverpool Merseyrail

Railway specialist LÜTZE TRANSPORTATION supplies the programmable LCON Rail Infinity temperature threshold switches for one of the world's largest rail vehicle manufacturers, Stadler Rail AG. These are used to monitor the temperature of the axle boxes on the new Liverpool Merseyrail metro trains.
Anyone who wants to watch Klopp's Liverpool team at the Anfield Road should use the Merseyrail public network and get off at Kirkdale station. As of recently, passengers may even end up traveling on one of the new-generation EMUs (Electrical Multiple Unit) that are built by Stadler Rail AG. This Swiss train manufacturer will be supplying 52 four-part articulated carriages to the city on the banks of the River Mersey. The 40-year old vehicle fleet in Liverpool will be replaced gradually. The first three of the 52 metro trains were delivered in 2019. Stadler will also be assuming their maintenance for a period of 35 years. The new vehicles were specially developed to meet the requirements of Merseyrail and replace one of the oldest fleets in Great Britain. The new Metro trains can hold up to 60 percent more passengers, and they also have step-free accesses and offer more space for disabled persons, bicycles, children's prams and luggage. Travel times will be reduced by up to 10 percent. The operators of the Merseyrail proudly emphasize: "It will make Merseyrail the most accessible, traditional network in the country."

In addition to a number of safety features that have been integrated into the new Stadler vehicles, continuous monitoring of the temperature of the axles boxes is now also part of the basic safety concept. This is important because overheating of the axle boxes is always critical and must be avoided. Overheating can lead to broken axles and derailing; the heat that is generated can cause sparks and create fires in the train. This is the reason why many rail operators have installed stationary hot axle box detectors in the track beds to record the axle temperatures of passing trains. Stadler uses Pt100 sensors (platinum precision resistors) for precise and continuous measurement of the temperatures of the axle boxes; these measurements are sent directly to the LÜTZE LCON Rail Infinity temperature threshold switches. There are two Pt100-temperature sensors attached to the left and right of all ten axle boxes of a train. (See Figure 2)

All signals for monitoring the temperature of the 20 axle boxes on each Merseyrail train are collected in the driver's cab, and are indicated in the following forms:

• If the temperature of one of the 20 axle box temperature sensors is equal to or greater than 85 ºC, a signal is sent to the driver's HMI (icon on the driver‘s HMI illuminates yellow) indicating that there is excessive temperature in one of the axle casings. (See '1' in Figure 3b).
• If the temperature of one of the 20 axle box temperature sensors is at least 85 ºC, a message is shown on the maintenance screen indicating that the boxes need to be checked by the maintenance personnel. (See '1' in Figure 3a)
• If the temperature of one of the axle box temperature sensors is equal to or higher than 85 °C, an over-temperature red warning 'Hot axle box' signal lamp illuminates permanently below the screens. The redundant permanent signal below the HMI monitor indicates that the driver should switch to the main page of the HMI monitor to call up a more detailed error message, in case the train driver has just called up e.g. a timetable page. (See '10' in Figure 3a)
• After over-temperature in an axle box, the over-temperature signal is only reset after the axle box temperature has dropped below 80 ºC.

The technical base for precise monitoring and signaling critical axle temperatures is the programmable and potential-free LCON Rail Infinity temperature threshold switches by LÜTZE TRANSPORTATION. The LCON RAIL INFINITY threshold switches follow the 'all-in-one' principle trend of state-of-the-art equipment in the rail sector. For instance, LÜTZE TRANSPORTATION is the first company ever to supply combination units that integrate two potential-free threshold switches DC 110 V / 1.5 A as well as a very precise analog output in one casing. In addition to space savings in the control cabinet and the fact that much less wiring work is required, Stadler can now keep fewer components in production or spare parts in stock.

The LÜTZE temperature limit switch has measuring inputs for PT100/PT1000 with 2, 3 or 4-conductors, thermal elements, potentiometers and resistors. The threshold switch outputs are potential-free. This enables Stadler to connect the switching outputs of several devices in series and therefore implement a collective fault message.

Another benefit for Stadler is that the LCON temperature threshold switches each have a wide range power supply of DC 24V to 110V making them suitable for use in different rail onboard supplies across the globe.

The LCON temperature threshold switches by LÜTZE TRANSPORTATION can be configured using the free FDT/DTM software. The configuration is loaded onto the unit via a USB service cable. Stadler commissions LÜTZE to configure the temperature threshold switches to the required temperature values +85 °C to +75 °C. In light of the fact that a total of 20 LCON temperature threshold switches need to be configured for each train unit, this definitely saves time. The preconfigured units now only need to be installed in the Stadler production.

The LCON Rail Infinity temperature threshold switch can be used for other applications. For instance, it has an analog output, although this is not yet used in the Merseyrail project. Thanks to the permanent monitoring of the axle box temperature and analysis of the corresponding analog signal, it is possible to assume that a continuous increase of the temperature is an indication of expected damage or failure. The box can be serviced or replaced in good time during preventive maintenance.

In addition to the LCON Rail Infinity threshold switches, Stadler also uses a configured LCON analog/analog-converter with a measuring range of +/-500 mA in the space-saving 6.2 mm casing to analyze a current sensor in the Merseyrail project.

Stadler has been building trains for 75 years. The headquarters of the railway solutions system provider is located in the town of Bussnang in eastern Switzerland. More than 7000 employees work at several sites in Switzerland, Germany, Spain, Poland, Hungary, Czech Republic, Italy, Austria, The Netherlands, Belarus, Algeria and the USA. Stadler has an extensive product range for main-line trains and municipal vehicles: high-speed trains, intercity trains, regional and city trains, underground trains, trams and streetcars. Stadler also produces line locomotives, shunting locomotives and railway carriages. This also includes Europe's most powerful diesel-electric locomotive. Stadler is still the world's leading manufacturer of rack-and-pinion railway vehicles.

Author: Andreas Schindler | LÜTZE TRANSPORTATION Product Manager Interface
Title image: Stadler AG