Three-in-one filter simplifies plumbing, eases maintenance, and improves filtration over systems using individual filters.However, in systems with shared oil management for the hydraulics and the gearbox, protecting the pumps and downstream components is critical because a large portion of solid contaminants is generated by the gearbox. This leads to an obvious conclusion: as in the classical return-suction filter, the ultra-fine-filtered oil from the return flow of the working hydraulics should be made directly available to both pumps. On average, then, only the quantity for the steering pump needs to be drawn from the tank through a suction filter.
System benefits
Oil in the return line flows through the return filter element and is directed to the suction port o f t h e pumps for steering, lubrication, and the hydraulic system. When cylinders extend and retract, the oil quantity varies depending on the differential piston area ratio. If the quantity of oil in the return flow is less than the quantity supplied by the working pump (due to difference in volume between the two ends of the cylinder), both pumps draw oil directly from the tank through a suction filter and the second suction port. If any surplus exists when the cylinders retract, fluid flows back to the tank through the suction filter element. An integrated bypass valve protects the return filter element against overload during cold starts. The downstream valve protection strainer prevents coarse particles from entering the system when the bypass is open.
Benefits of the new return-suction filter include:
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excellent cold-start properties compared to conventional systems. The fluid drawn directly from the reservoir is considerably less than that with conventional systems, leading to much better cold-start properties and much lower risk of cavitation damage.
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downstream components are protected. The valve protection strainer in the bypass line protects downstream components from coarse particles during a cold start.
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all functions are integrated into one filter housing made of high-strength plastic, so only one filter is needed for the entire hydraulic system. The innovative connection concept makes it easy and inexpensive to fit the return and suction lines with plug-in connectors and O-ring seals.
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maintenance costs are cut. Just one combined filter element (re-turn filter element with bypass valve, protective strainer, and suction filter element) is used for the entire hydraulic system. This simplifies maintenance by making the filter easily accessible, and the filter element can be changed in seconds. Plus, intervals between services can be twice as long as with a conventional system.
Summary
This discussion illustrates how products can be created on the basis of existing technical solutions, with appropriate application know-how and intelligent concepts. Technical improvements are even more welcome when user benefits are significantly increased thanks to reduced system and maintenance costs.
Larry Gerken is general manager at Argo-Hytos, Bowling Green, Ohio. For more information call (877) 377-2746 or visit www.argo-hytos.com.