Reliable pressure measurement is essential in railway vehicles – especially in the various brake systems. However, the monitoring of pressure is also relevant for other transportation applications such as pantographs, cooling systems of power units, air conditions or dampers. Due to the vibrations during the operation, the pressure measuring devices have to be extremely robust. Baumer offers a wide range of measuring instruments which meet the standards for railway applications and have been homologated by numerous railway vehicles manufacturers.
Challenges for Measuring Instruments in Railway Applications
In order to be approved for the use in railway vehicles, measurement devices have to fulfil all important standards for railway applications: DIN EN 50155 (for electronic equipment used on rolling stock), DIN EN 61373 (tests regarding shocks and vibrations), DIN EN 50121-3-2 (electromagnetic compatibility) as well as the fire and smoke preventions specifications NF F 16-101 and NF F 16-102. All of Baumer’s measuring instruments for railway applications are developed according to those standards. If developed especially for a certain manufacturer, the product design also considers customers’ specifications. The creation of a compliance matrix guarantees that the customers’ requirements are fulfilled during the product development. At the end of the first production run, the customer’s quality management carries out a First Article Inspection (FAI), which has to be successful in order to continue with the production. This type test includes a series of tests ensuring that the products meet the usual standards for railway applications as well as the customer-specific requirements. The test series include a voltage analysis, several pressure load cycles, the operation at high temperatures and tests with shocks and vibrations. The accuracy respectively the total error band is checked within a defined temperature range. During long-term tests, a certain number of sensors have to be operated at a high temperature for 10.000 hours.
With the EF6, Baumer has developed a pressure transmitter suitable especially for the severe conditions in transport applications. In order to achieve the homologation of different manufacturers of railway vehicles and suppliers, the sensor had to pass through numerous test series, for example for accuracy. In order to meet the standard EN 60770-1, the total error band must not be be higher than 0.5% in a temperature range between -20°C and 60°C, and 1% in a range between -40°C and 80°C. Other tests – some of them taking up to twelve months time – exam the robustness, long-term stability and thermal resistance, the degree of self-heating, overpressure stability, burst pressure and leak tightness.
Application Examples
The EF6 controls the brake system pressure of several high speed trains. It is especially suitable for railway applications in which the pressure sensors are submitted to many pressure cycles. This happens in hydraulic and pneumatic brake controls or in cooling circuits. The transmitter is also used in high voltage areas. In several types of locomotives, the EF6 controls the pressure of the pantograph (a device collecting electric current with up to 2.500 Ampere from overhead lines) on the power supply line. The output signal is transmitted to a microcontroller for the pressure regulation.
The EF6, protected by a stainless steel case, is available with a piezoresisitive or a capacitive ceramic sensor. The measuring range can be chosen individually according to customer needs between -1…100 mbar and 0…200 bar. The response time is less than 15ms. With a MTTF (mean time to failures) of 10 million hours, the EF6 has en excellent long-term stability. Due to its high reliability, the device can also be used in harsh transportation applications like tank and fire trucks or underground construction vehicles.
The pressure control in pantographs can also be carried out by the pressure gauge MEX3 with a Bourdon tube. It measures a pressure range between 0 and 250 bar with an accuracy class of 1.6. For heavy duty applications, Baumer offers the MEX3 in a particularly robust version, where the device made of stainless steel is mounted in an aluminium housing equipped with a polycarbonate window. In that reinforced version, the MEX3 controls the pressure in hydraulic parking brakes in trains.
The MFE series was also developed especially for railway applications. The pressure gauge is mainly used for on-board applications. Offered as simple or duplex gauge, each measuring channel can measure from 0…6 bar gauge up to 0…16 bar gauge. The measuring device is mounted in an aluminium case and available with 80, 100 or 150 mm diameter. Due to the dial illumination (internal or external), the visibility in the cab is excellent. The internal backlight works with a power supply from 24V to 130V (AC or DC). The MFE3 version with a two-coloured dial is used to control the brake or suspension systems of the bogies.
The pressure switch CPX was developed for a temperature range from
-40 °C up to 150 °C. The compact, cost-effective device is applied particularly in the cooling system of power control systems (thyristors) as well as in tramway braking systems. Its pressure range lies between 0 and 160 bar. The measuring instrument can be adapted to customers’ specifications, as it happened in a version for an increased operating voltage of up to 130V.
Leave a Reply
You must be logged in to post a comment.