2 years ago

MDA Technologies 5/2016

MDA Technologies 5/2016

01 The new generation of

01 The new generation of hydraulic check valves from Bucher Hydraulics offers 50 % higher flow rates for the same pressure differential 02 The new check valve is distinguished by its guided valve poppet with internal spring. The stroke was increased to optimise the valve’s Delta P values. The body and seat are press-fitted together and, like the poppet, are hardened. stroke and the design and manufacture of the valve poppet. In poppet check valves of this type, the valve poppet is pressed against the valve seat with help of a spring and thus prevents flow of the medium. To obtain a larger outflow area and thus a higher flow rate, the designers initially reduced the diameter of the valve poppet. At the same time the stroke was increased, which ensures optimum ‘Delta P’ values in the valve. The result of attacking the valve’s design gave rise to a new generation of hydraulic check valves that offer up to 50 % higher flow rates for the same pressure differential. The larger flow rate saves energy and in many cases allows a smaller valve to be used, which in turn has a positive effect on costs and installation space. Also under attack in the previous design were its specific safety features. A broken spring occurs only under extreme conditions, the consequent risk is now significantly reduced: the new series of check valves with spring-loaded valve poppets now features enclosed springs, so that even in the event of breakage the spring remains within the valve. Broader application range, lower manufacturing costs In modifying the designs, the designers also included the sealing technology. In the smaller check valves from nominal sizes 04 to 16, the valves have a screw-in design and a cutting edge for metal-tometal sealing. The soft seals previously used had to be carefully selected to suit the temperature and type of medium, and sometimes required special solutions, but soft seals have now been completely eliminated in the smaller sizes. This therefore widens the spectrum of possible applications, allowing users of the standard version of the new check valves to employ them at temperatures ranging from - 30 to + 120 °C. The inherent metal-to-metal sealing also minimises the risk of valve failure, as there is no possibility of selecting the wrong sealing material. Based on positive experience with the check valves in sizes 04 to 16 (12 to 120 l/min), Bucher Hydraulics is now complementing the range with valves in nominal sizes 25 to 40 with flow rates from 210 to 540 litres per minute. The new generation with thread sizes from G1/8” to G3/4” can be fitted in 118 ° cavities; with thread sizes from G1” to G1½”, the valves can be fitted in 180 ° cavities. All corresponding previous series can therefore be completely exchanged. By using the same installation cavity for valves that open in the screw-in direction (RKVG valve series) and, conversely, for valves that close in the screw-in direction, users need only one tool, which in turn reduces tool costs. Extensive tests increases system reliability During the development stage, Bucher Hydraulics places each series on the test stand and tests at maximum pressure, i.e. the valves are put through an endurance test with 1.5 times the flow rating at a pressure of 350 bar. They must withstand 2 million cycles with an in-circuit accumulator before they are released. In addition, Bucher Hydraulics carries out 100 % checks for leak-tightness before valves leave the factory. This new range of check valves, where thought has been given to every detail, is based on the company’s extensive product and application knowledge. Although this small component is only a tiny proportion of a control block, it is continuously and highly stressed. The availability of the hydraulic system or equipment is therefore directly dependent on the reliability of the check valve that is used. In this context, a high quality standard ensures long life and minimises expensive and time-consumingrepairs in points in the system that are usually difficult to access. In terms of ‘Total Cost of Ownership’, high-quality check valves pay dividends for block manufacturers and end users alike. Photographs: Bucher Hydraulics GmbH About Bucher Hydraulics The company Bucher Hydraulics located in Klettgau- Griessen, Germany is an international manufacturer of advanced hydraulic systems and products including pumps, motors, valves, power units, elevator drives and control systems with integrated electronics. The company has manufacturing facilities and distribution companies in Europe, Asia, the USA and Brazil. The Dachau location is part of a Bucher Hydraulics global competence centre with its own design and production facilities. Built on extensive technological know-how, Bucher’s product spectrum covers check valves in cartridge design as well as flange-mounting check valves. MDA Technologies 5/2016

Machines should not pose risks A number of different standards and guidelines regulate the assessment of machine related hazards and how they should be dealt with by manufacturers and operators. SMC products can be used to support the objective of reducing risks and ensuring machine safety with a range of intelligent products. Machines should not pose any significant risks to people. Functions that are commonly used by machine builders to reduce risk in pneumatics are “Safe venting”, “safe stop”, “two-hand actuation” and “protection against unintentional start-up”. SMC has products which can be used to help fulfil these principles. About SMC The company SMC is a manufacturer of pneumatic and electrical automation technology and also a partner for individual solutions. The more than 12,000 product groups include air treatment, valves and throttles, actuators (pneumatic and electrical), screw fittings and hoses as well as vacuum and instrumentation components. Headquartered in Tokyo, SMC has a total of 400 sales offices in 82 countries and offers automation solutions on all five continents. In Europe, Machinery Directive 2006/42/EC in conjunction with EN ISO 13849 standard requires that, for example, pneumatic drives must be in a safe state when opening protective enclosures. As a second example, when manually removing parts from a conveyor belt, safety precautions must be taken to ensure that all the drives in the hazardous area are in a safe state. Often a light barrier will be used which issues a signal to the control system which is responsible for performing the stop and ensuring that no unintentional machine startup may occur within the danger area while personnel are present. Secured position The SMC solenoid valve series VQC2000-X27, VQC4000-X17 as well as the SY3000/5000/7000 series are compatible with the “secured position” safety principle. The valves satisfy the requirements of EN ISO 13849 for use in safety related control systems. Both series have a soft-sealing, bistable valve with detent option (VQC-X77 and SY-X25). Systems that rely purely on friction do not satisfy the requirements of the standard. Important practical considerations for ensuring safe application are that the pneumatic valves and the pressure switch is assembled close to the valve to detect the pressure in the circuit. For diagnostics SMC has a range of different pressure sensors and in addition a range of position switches to detect the cylinder piston position. Safe venting If the guard doors are opened while a system is in operation, or a person accesses a defined hazardous area in which, for example, a robot arm is in operation, the pneumatic system and the robot must be safely stopped. In this case venting of the pneumatic system is advisable. Furthermore, no unintentional machine or robot startup may occur within the hazardous area during maintenance MEASUREMENT AND CONTROL MDA Technologies 5/2016


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