Sauer-Danfoss Inc. (www.sauer-danfoss.com) has rolled out two new directional valves for off-road equipment that reportedly offer less pressure drop and lower prices than that of competitors.
The new valves could enable hydraulic power systems to provide greater force at key moments, while also reducing fuel consumption and heat generation. Sauer-Danfoss engineers say the new valves can be applied in construction and agricultural equipment, including backhoe loaders, truck-mounted cranes, farm implements, drilling equipment, and pavers, as well as tractors, garbage trucks, and dump trucks.
The company's engineers note that the key difference between the new design and its predecessors is the ability to reduce pressure drops. "When you have a pressure drop, you ultimately have less force available to lift or move a load," notes Rob Arndt, product portfolio manager for spool valves at Sauer-Danfoss. "You also consume more engine horsepower, which translates to higher fuel consumption."
Known as the CDS 60 and CDS 100, the new valves offer inlet flow capacities of 60 l/min and 100 l/min, respectively, with maximum working pressures of about 3,000 psi. The company's engineers say that the pressure drop for its new valves is around 60 psi. In contrast, pressure 5 drops for conventional directional control valves for such applications range between 80 and 140 psi, depending on the valve model and flow rate, they say.
Sauer-Danfoss engineers note they achieved the lower pressure drop by designing larger port galleries into the valves. They did that, in part, through a willingness to make a slightly larger valve, and also by employing a casting process, instead of a machining process, to make the holes. "The coring of the inlet valves is larger, and that drives the inlets and outlets themselves to be larger," Arndt says. The result is a valve with fewer flow restrictions and less fluid drag, he adds.
A side benefit of the larger, thicker port galleries is that the CDS valves are said to be less prone to deflection and, therefore, leakage, in a stack configuration. That's important for demanding applications, the company says, because such applications can place mechanical stresses on valves that can result in hydraulic fluid leakage between sections. "If you have larger inlet or outlet sections, you have less deflection," Arndt says. "That way, you can eliminate spool binding and ensure that you don't have leaking between the sections."
Sauer-Danfoss reports that the valve also offers other advantages, such as modular construction and a priority flow-control system. Modularity allows for control of various work functions from a single valve stack, thereby simplifying machine design, plumbing, and pump applications, the company says. The priority flow-control system, meanwhile, ensures that the most important flow circuit gets its flow first, with excess flows being diverted to other functions, where possible. As a result, the system always provides flow to critical functions, such as steering or brakes.