Quality products for demanding use BRAKING SYSTEMS SOLUTIONS SINCE 1946

Transcription

1 Quality products for demanding use BRAKING SYSTEMS SOLUTIONS SINCE 1946

2 APPLICATIONS BRAKING SYSTEMS In many mechanical drives, vehicles and machines, brakes are a crucial safety element. Their reliability and longevity are decisive for the security and quality of the complete system. BRANCHES REQUIREMENTS Brake systems have to ensure a fast, reliable and controlled braking action. In order to fulfil these requirements, the designer has to take into account a number of guidelines. A decisive prerequisite for a sensitive control is that the action of the hydraulic cylinder on the braking system itself is exerted as linearly as possible and exhibits only a minimal hysteresis. Braking systems ensure the controlled deceleration and secure standstill of a complete plant respectively of its moving components. As security-relevant elements, they have to meet very high requirements. These depend on the particular range of applications. Braking systems thus have to be designed specifically for the intended service surroundings. Hydraulically actuated brakes are particularly suited when high yet sensitively controlled braking forces have to be exerted within tight spatial limits. For applications with especially high security requirements, e.g. for vehicles or aerial cableways, additional features such as redundant valves and switching position monitoring equipment are deployed. For wind power plants, hydraulically actuated braking systems are used to adjust and secure the horizontal orientation of the rotor. Especially in the case of high wind speeds, the system must feature the ability to be turned out of the wind in a controlled way in order to avoid damage to the gearbox and the generator. Also in the case of stationary machines such as e.g. plants for the manufacturing of textiles, braking systems play a decisive role. In such applications, fast-turning drums have to be brought to a standstill within milliseconds in order to avoid that textile fibres become entangled or even get ripped apart. Typical application areas for hydraulically actuated braking systems are, among others: Rail cars Self-propelled work machines Winches Wind power generators Material lifts Textile plants Cableways Cranes Decisive features of braking systems: CONTROL In order to achieve a controllable braking action, the braking force has to be altered as steadily as possible. SPEED The response time of the hydraulic valve used as controlling element has to be short in order to achieve minimal time lags before braking starts. RELIABILITY In order to secure an all-time reliable functioning of the system, its components have to meet stringent requirements. EFFICIENCY The amount of energy released has to be minimized in order to avoid overheating of the hydraulic system. LONGEVITY Hydraulic braking systems are made of modern high performance materials, a prerequisite for high durability and low maintenance expenditures. COMPACTNESS Hydraulic brakes excel by their good power density. This makes it possible to achieve compact dimensions and minimum space requirements. Modern hydraulic braking systems are actuated using proportioning valves. These are equipped with solenoids exactly controlling piston position and thus hydraulic pressure, resulting in a linear increase of braking forces. Such systems are often fitted with proportioning pressure valves. Increasingly, designers switch to closed pressure control circuits using proportioning throttles and the assorted electronic control systems. In order to ensure good controllability, these valves exhibit small hystereses and their linearity can be precisely adjusted. Their frequent use in pressure reservoir circuits makes small leakage and control oil volumes mandatory. In spring-loaded brake systems, a pressure release down to nearly zero is of prime importance in order to avoid dragging of the brake liners. PAGE 1 BRAKING SYSTEMS BRANCHES APPLICATIONS BRAKING SYSTEMS BRANCHES REQUIREMENTS PAGE 2

3 HYDRAULIC BRAKING SYSTEMS Braking systems are either active or passive. Operational brakes are often designed as active systems, while security brakes are always passive systems whose braking action is activated by spring forces. For both types, designers can opt for a number of different hydraulic control designs. Steered hydraulic solutions are realized using pressure limiting or pressure control valves. In the case of closed hydraulic pressure control systems, either pressure control valves or pressure limiting throttles are used. For both designs, an electronic control circuitry optimized for the valves is a crucial factor. VALVE TECHNOLOGY In order to meet the requirements for a braking system, the designer can select between different sizes of proportioning valves. Compact directly controlled valves are available for confined space applications. For large systems, pilot-controlled valves are preferred. In order to meet the different requirements, one may choose between more than 20 variants of valves. The available bandwidth ranges from valves with low max. pressure to models featuring a max. output pressure of 450 bar. Likewise, throughput flows can vary between some 100 ml/min up to 40 l/min. WITH PRESSURE LIMITATION For such systems, the pressure within the cylinder is adjusted to the required braking force. Additionally, the pressure in the braking system is monitored using a pressure sensor. Usually, these are directly controlled valves with compact dimensions and short response times. In the case of passive systems, one has to resort to reverse-action hydraulic valves. Such valves are held open by springs and will deliver their max. pressure when power to the solenoid is turned off. The max. pressure value can be adjusted using a setscrew. WITH PRESSURE CONTROL VALVES In systems of this type, the pressure in the cylinder is adjusted to the required braking force by means of a proportioning pressure control valve. The output pressure of the control valves is decoupled from the input pressure, thus eliminating any influence from higher system input pressures onto the braking action. Such solutions are often selected for accumulator-backed systems in order to achieve long standstill intervals of the motor pump. Proportioning control valves for such applications thus have to feature low leakage rates. For passive systems, reverse-action valves are required. WITH ELECTRONIC PRESSURE CONTROL For some designs, proportioning pressure relief valves are selected as controlling element. A sensor monitors the braking pressure, which is fed back into the electronic control system where actual and scheduled value are compared. In other cases, the control can be realized using two proportioning throttles positioned in the pressure line and in the tank line. Proportioning throttles excel by their short response times as well as by an enhanced flexibility with respect to the optimized adjustment of the controller. PRESSURE CONTROL VALVES MDPPM16 P max.: 40 bar Q max.: 6 l/min Size: M16 cavity MGPPM16 The compact solution for higher braking pressures P max.: 100 bar Q max.: 6 l/min Size: M16 cavity MPPPU10 The solution for larger brake cylinders Q max.: 20 l/min Size: UNF 7/8-14 cavity PRESSURE LIMITING VALVES BDPPM18 P max.: 315 bar Q max.: 8 l/min Size: M18 cavity BDPPM22 The solution for large brake cylinders Q max.: 25 l/min BSPPM22 For high braking pressures, leak-proof P max.: up to 450 bar Q max.: 2 l/min THROTTLE VALVES DNPPM18 P max.: 250 bar Q max.: 12 l/min Size: M18 cavity DNPPM22 For fast movements of large brake cylinders P max.: 350 bar Q max.: 25 l/min MQPPM22 For fast movements of large brake cylinders Q max.: 40 l/min BDPPM22_W D_PPM22_ME Control system Pressure limiting Pressure control Electronic control Pressure accuracy Space conditions Costs Leakage protection MDPPM16 Response times and hysteresis PAGE 3 BRAKING SYSTEMS PRODUCTS HYDRAULIC BRAKING SYSTEMS BRAKING SYSTEMS PRODUCTS VALVE TECHNOLOGY PAGE 4

4 ELECTRONIC DEVICES The control of proportioning valves is performed using electronic control systems. These determine respectively control the electric current through the solenoid. Overlaying a pulse width modulation with a dithering signal results in a very sensitive control of the valve with a small hysteresis. Our control systems are equipped with microprocessors. This enhances their functionality as well as their flexibility for use in different control systems. Our electronic systems feature a range of amplifying and control functionalities as well as an optional fieldbus interface for easy connection to superordinate control systems. INDIVIDUAL SOLUTIONS Wandfluh is offering its customers a plethora of individual solutions based on improvements of its existing components. In a first step, the specific requirements are defined in cooperation with the customer prior to the design of a product exactly matching these prerequisites. Thanks to the profound experience of our engineers and the flexibility of our manufacturing organisation, we achieve optimized solutions for your specific needs. EXPLOSION PREVENTION For equipment used in ambient conditions where explosive gases or liquids are present, special features preventing explosions are mandatory. This particularly applies to sectors such as the extraction or processing of oil and gas, but also in mines where dangerous dusts or gases may occur. In all such cases, explosion preventing valve technology is required. Decisive prerequisites for an optimized electronic control of the pressure are high-end capabilities with respect to signal processing and control of the solenoids. Designers can choose between three different electronic control variants. A user-friendly parameterizing and diagnosis software facilitates the task of adjusting settings for valves and PID control systems. SNAP-IN MOUNTING MODULE SD7 Digital electronic control system for the control of max. 2 solenoids designed for easy integration in control cabinets. The input and output ports can be freely assigned, allowing for an optimized utilization of existing hardware to the given application even without programming skills. Parameter adjustments are stored in a non-volatile memory and are thus immediately available after restoring power to the control system. Instead of an analogue interface, all control system types can also be fitted with a fieldbus interface (Profibus DP, CANopen, J1939 oder HART). The device is available in 24 VDC and 12 VDC versions. ON-BOARD ELECTRONIC DSV This digital control module for the control of max. 2 solenoids is mounted directly onto the electromagnet. The digital smart valve features digital electronic control circuitry in an extremely confined space, making it the most compact design currently available on the market. The solution has been designed especially for high end block assembly solutions for stationary as well as mobile systems. The plug-and-play valves excel by the simplicity of their configuration during commissioning. The easy replacement facilitates fast repairs and thus short downtimes. Control can be exerted either by analogue signals or by a CAN fieldbus. MOBILE ELECTRONIC MD2 The digital amplification and control module MD2 for max. 8 solenoids was especially designed for the control of hydraulic valves under extreme ambient conditions. It is the right choice for all service conditions where moisture, vibrations, higher temperatures or fluctuating voltage supplies might occur. Thanks to its large voltage supply tolerance range (8 32VDC), the MD2 can be flexibly integrated into various different systems. The module features digital input and output interfaces as well as high-powered pulse-width modulated (PWM) output interfaces for the control of solenoids. Its digital input ports can easily process FM or PWM signals. Instead of an analogous interface, the MD2 can also be fitted with a CAN fieldbus interface. The MD2 is the ideal solution when several braking systems have to be controlled by a single electronic circuit board. CORROSION RESISTANCE For valves operating in continuous contact with salt water, a salty atmosphere or adverse weather conditions, an enhanced corrosion protection is required in order to enhance their service life. For such applications, we offer the choice between valves with a protective zinc/nickel coating (> 800 h salt spray test) or in stainless steel design (AISI 3162). MQBPM22_M248 MDIPM16 LOW TEMPERATURE APPLICATIONS For use in extremely cold conditions, we offer valves in two suited designs. Z604 (-40 C): Suited sealings, partly adapted fitting tolerances Z591 (-60 C): Special materials, special sealings, augmented fitting tolerances SD7 DSV MD2-60 Z Z PAGE 5 BRAKING SYSTEMS PRODUCTS ELECTRONIC DEVICES BRAKING SYSTEMS PRODUCTS INDIVIDUAL SOLUTIONS PAGE 6

5 SWITZERLAND CHINA Wandfluh AG Hydraulik + Elektronik Wandfluh (Shanghai) Hydraulic System Co. Ltd. Helkenstrasse 13 CH-3714 Frutigen Tel Fax sales@wandfluh.com Block B, 8th Plant No. 450 Beihengshahe Road Minhang District PRC-Shanghai Tel Fax sales@wandfluh.com.cn.cn AMERICA Wandfluh of America, Inc. Hydraulics + Electronics 909 High Street Mundelein, IL Tel Fax sales@wandfluh-us.com FRANCE Wandfluh SARL Hydraulique + Electronique Parc Technologique Immeuble le Pôle 333, Cours du Troisième Millénaire F Saint-Priest Cedex Tél Fax contact@wandfluh.fr GERMANY Wandfluh GmbH Hydraulik + Elektronik Wandfluh Friedrich-Wöhler-Strasse 12 D Emmingen Tel Fax info@wandfluh.de GREAT BRITAIN Wandfluh UK Ltd Hydraulics + Electronics Northfield Road GB-Southam CV47 0FG Tel Fax sales@wandfluh.co.uk More information on our products, services and branches can be found on our website. ID1617E