Global competition and increasing cost pressures have raised expectations for every aspect of hydraulic systems. According to officials at Bucher Hydraulics, that’s why it pays to review even the smallest elements of a circuit, such as non-return valves. These valves must work continuously and reliably with long lives, combine a compact design with high performance and, ultimately, make a positive contribution to the cost, uptime and energy efficiency of an entire machine.
With that in mind, engineers at Bucher Hydraulics have developed a new series of non-return valves, designated RKVE-VD, with the same footprint as previous versions but offering 50% higher flow.
Non-return valves, more commonly known as check valves, permit flow in only one direction and prevent return flow in the opposite direction. While that sounds simple, the underlying design is actually quite sophisticated.
Check valves are usually incorporated into hydraulic control blocks in both industrial and mobile applications. Today’s machines, ranging from excavators to injection-molding machines, are tending toward smaller components running at higher pressures. As a result, engineers sought to increase performance of the screw-in check valves without changing the pressure differential or raising costs. Equally important was energy efficiency, a key tenet of Bucher Hydraulics’ corporate philosophy of “ECOdraulics.”
One goal was to increase flow capacity of the new check valves while maintaining the same dimensions as previous versions. To that end, Bucher engineers redesigned the poppet valve’s flow cross-section and stroke. In this type of check valve, a spring presses the valve poppet against a seat to prevent flow. To permit higher flow when the valve opens, designers reduced the poppet’s diameter while increasing its stroke, which reportedly optimized ΔP values across the valve.
Compared with previous versions, the new-generation RKVE-VD valves offer up to 50% higher flow rates for the same pressure differential. More flow capacity saves energy and, in many cases, permits a smaller size valve—which, in turn, reduces costs and installation space.
Safety was also a key consideration. While springs generally only break under extreme application conditions, the new valve’s enclosed spring reduces that risk. Now, even if a spring fails it remains inside the valve.
Engineers also improved sealing capabilities. Previous versions relied on elastomeric seals, which had to be carefully selected to suit the application temperature and type of fluid. The RKVE-VD units instead feature metal-to-metal sealing. Thus, the new valves face no fluid compatibility issues and can operate at temperatures from –30 to 120° C. The metal-sealing technology is used in smaller versions with nominal sizes 04 to 16 (12 to 120 lpm), and is being extended to valves in nominal sizes 25 to 40 with flow rates from 210 to 540 lpm.
Engineers also understand that although this component is only a small part of a control block, it is continuously and highly stressed. Thus, the new check valve also has a rugged design that is reliable and insensitive to contamination. According to company officials, it is built for durability and minimizes expensive and time-consuming repairs at locations in systems that are usually difficult to access. To prove the point, during development the valves were subjected to endurance tests with 1.5× rated flow at 350-bar pressure. The units withstood 2 million cycles without problems. And as an added layer of protection, company technicians check every valve for leak-tightness before it leaves the factory.
The new-generation valves with thread sizes from G1/8 to G3/4 fit 118° cavities; valves with thread sizes from G1 to G1½ fit in 180° cavities. All the valves are interchangeable with the company’s previous series.