RE_Develops Proportional Valve

ROSS Europa Develops Proportional Valve ROSS directional control valves, for more than eight decades, have been known the world over to be top-quality and highly reliable pneumatic devices, which provide fully open or fully closed operating positions. Of course, these traditional valve characteristics continue to be perfectly adequate for the majority of industrial processes both today and in the future. Yet, there are certain applications, which call for more subtle functions. Applying proportional valve technology, which combines conventional valve know-how with electronics and sensors, makes it possible to introduce intermediate operating positions, in steps, within a range of 0 to 100%, with full adjustability and repeatable performance. Certain machine control specifications can be met precisely in this way. Compare this new technology with traditional type valves, which are so common in the pneumatic industry. The “classic” valve delivers virtually the same outlet pressure as is supplied to the valve inlet - less a small amount of pressure drop due to flow. The new ROSS proportional valve, however, is designed to pinpoint the required outlet pressure even though the required pressure may be considerably lower than the inlet pressure, thus ensuring that the operating pressure requirements of the machine are met precisely. The output pressure can also be changed to any pressure in the output range nearly as quickly as the input signal can be changed. Bearing in mind this new capability, the use of proportional valves should be recommended wherever precisely controlled and regulated air pressure is crucial. Sparked by a recent inquiry from a glass industry customer, this latest ROSS product is based on a valve concept presented by ROSS Europa (RE) in late 1994, which was decorated with an innovation award at the time. The original concept was a vapor recovery valve, master-minded by RE’s product marketing manager, Wilfried Stroh, designed for use in gas pumps at filling stations to capture potentially harmful vapors and return them to the fuel storage reservoir. The patented valve system was acknowledged as a truly innovative achievement and has been optimized to become a standard product offering. The “proportional valve for proportional pressurizing and exhausting”, as the new valve is officially referred, is a poppet design with force-balanced valve elements. A special feature of this design is that exhausting of the system is done via a second proportional type valve. The system was specifically developed for applications, which must be pressurized and exhausted proportionally and where the system pressure must be kept constant over a fairly long period of time. Aslong as the pressure downstream system remains unchanged, there is no need for the valve to add or release any pressure. Both valve elements remain closed except when the valve is reacting to downstream pressure changes. Other proportional valves utilize a constant flow of pilot air and continually adjust the pilot orifice to maintain the correct output pressure from the valve. This constant flow from the pilot can be viewed as a leak as the valve consumes pneumatic energy constantly. Whereas the valve developed by RE will shut off the flow of pilot air once a steady downstream pressure is achieved and, thus, not leak constantly. RE’s valve was designed to have a very small hysteresis in order to achieve an optimal degree of efficiency. This small hysteresis was realized by using special bearings in the solenoid. The design of the valve internals combines the benefits of a balanced spool with the advantages of a poppet valve so that this valve can be used as a shut-off with very good sealing properties. The electronic circuitry of the proportional valve is designed to control both the pressurizing and exhausting solenoids in relation to an indicated electrical set value (0 - 10 volt or 4 - 20 mA), thereby increasing or decreasing control (pilot) pressure to achieve and maintain the desired valve output pressure. All analog input values are digitalized and used in the regulator algorithm for calculating the set values. Due to the fact that this is an all-digital electronic device, no additional adjustment is required. The product’s application scope is further enhanced by electrical plug options developed for various environments. Also, the valve system’s rapid response characteristics and high operating safety level stands out among the competition. Virtually no maintenance is required, despite the complex structure of the system. The rugged design, featuring stainless-steel internals and special seals, forms the foundation for a long working life, so it is safe to say that the product has a remarkable price-performance ratio. ROSS’ Global Glass Industry Team will be glad to provide further information about this generation of products, which is considered to be yet another important step in providing state-of-the-art controls to the system designers of the world.

For information or technical assistance please call ROSS Technical Services in the U.S.A. at 1-888-TEK-ROSS(835-7677) www.rosscontrols.com