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world of industries 8/2016 (EN)

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world of industries 8/2016 (EN)

Non return valves with

Non return valves with advanced design and higher performance As Aristotle in his writing on metaphysics said “The whole is greater than the sum of its parts.” In the context of machine and their individual components, this is all the more true in today’s world of globalised competition and high cost pressures. Today components are no longer viewed as just individual parts of the system that only have to meet the technical requirements. Instead, their impact on the cost effectiveness, availability and energy efficiency of the entire system comes into play. To optimize the total cost of ownership, even the smallest elements of the system such as non-return valves need to work reliably over a long period with high performance. Non-return valves, also known as check valves, allow flow in only one direction and prevent return flow in the opposite direction. What looks quite simplistic – a “one-way flow principle” – is actually a sophisticated technology that has been refined over time. In developing the new series of these valves, the specialists at Bucher Hydraulics had clear objectives: to increase the performance without changing the pressure differential, and to optimize the cost. Bucher’s expertise was crucial for creating a new design of screw-in non-return valve. Focussing on customer requirements, the company undertook an in-depth exploration of the technical possibilities in the non-return valve technology for producing improved performance, increased availability of the complete machine and energy efficiency. Usually incorporated into hydraulic control blocks, check valves are used in both industrial and mobile applications. From excavators to injection moulding machines – all application requirements today are characterised by comparatives such as smaller, more economical, and more powerful. For this reason, it is a distinct advantage for system integrators and end-users if they can incorporate smaller valves with a higher performance. Small design modifications deliver big impact The developers at Bucher Hydraulics put the previous series of check valves on the test stand and questioned its cross-sections, its MDA INDIA Tiny yet vital: Non-return valves which are tiny compared to large machines like mobile cranes and harvesters are vitally important for these giant machines to perform to their maximum ability 34 World of Industries 8/2016

MACHINE ELEMENTS 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. World of Industries 8/2016 35