We think so, because OEMs can reduce the cost of underground construction machines by using Parker's Overcenter Intelligent Flow Control (IFC) architecture.
Closed-loop hydraulic systems are commonly utilized for rotary functions. They provide a simple solution without additional valving but can be very expensive when compared to open-loop hydraulics. In certain applications, closed-loop systems are used, but may be over-specified for the application. In these applications, a partial overcenter solution may be worth considering.
In looking at drills and trencher machines there is an opportunity for OEMs to reduce the costs of small and medium-duty machines using the Parker's Overcenter IFC architecture. The applications where this system could be applied include:
• Trenchers – trencher chain drive
• Directional drill – drill rotate
To see why these machines are an attractive application, think about the typical duty cycles. Reversing applications are rare and typically do not require full flow. The reversals are typically only required when breaking or making pipe, or in the case of trenchers, cleaning out a trench.
During these reversals, other pumps may be available to provide reverse flow such as a mud pump or front implement. This architecture is based on applications where during a reversal, another system on the machine is idle or has capacity to provide flow for reversing the drill rotate or trencher mode.
Parker's Overcenter IFC architecture uses our uniquely designed overcenter open-loop pump in conjunction with a reversing valve and one additional flow source. This architecture better optimizes the use of pumps on a machine and helps to reduce the need for expensive closed-loop components.
When applied to a drill, for example, the hydraulic flow from a mud pump function can be diverted to the drill rotate function to provide reversal. During pipe break, the mud function should not be required. This diverter functionality can be added to an existing manifold valve for packaging.
The diagrams below compare a traditional system to Parker's Overcenter IFC system. First, we explore the drilling duty cycle. A traditional system may consist of a closed-loop pump that operates the drill in both directions. When adding a pipe to the drill string, wrenches hold the pipe while the pump reverses direction to unscrew from the pipe allowing a new pipe to be added.
Using the Overcenter IFC system, the duty cycle is the same, however, instead of reversing the drill by changing the direction of a closed-loop pump, flow is diverted from the mud pump function that then reversed the drill motor. The flow then drives the drill pump overcenter returning the flow back to tank.
Traditional System Overcenter IFC System
Because proportional control is provided by the pump, valves are needed simply to provide direction change, assuming directional control is needed. When designing these systems, pressure drop through a directional valve must be considered. High-pressure drop can lead to excess heat and may reduce system performance. Parker has designed custom low-pressure drop manifolds that can be integrated into existing manifolds or mounted as a standalone component. These directional cartridges and manifolds are designed for high flow while maintaining pressure drop. Our target is to be no more parasitic than a charge system.
The R08E3 cartridge provides simple reliable directional flow control at 300 LPM while maintaining pressure drop at or below 3 bar. The R08E3 is also pressure rated to 420 Bar for high-pressure systems.
There are three main reasons why the Overcenter IFC is superior. The first is cost, the closed-loop systems tend to be more expensive than open-loop systems. The second is that the system reduces complexity. There is no longer a need for a charge filter, and there is no need for a flushing valve in the system. And, finally, the system may provide superior efficiency, it eliminates charge losses, although valve pressure drop should be considered and minimized.
In many applications, we see cost and system simplification advantages to utilizing the Parker Overcenter IFC concept. While not all systems are applicable, it is probably time to consider the Parker Overcenter IFC system during your next machine architecture redesign.
The Parker Global Mobile Systems engineering team and Hydraulic Pump and Power Systems Division's application engineering experts are available to assist our customers in designing and implementing new systems to meet your application needs.
This article was contributed by David Schulte, P.E., senior systems engineer, Parker Hannifin Corporation.