As multi-tasking becomes more prevalent in today’s day and age -- texting your mother while picking up groceries and simultaneously catching up on your latest podcast after taking your kids to practice -- it is no different with mobile machinery. In the name of increased productivity and output, operators are pushing machines to their limits by using all the oil in the system to support multi-function control.
Modern hydraulic systems are being developed with an increased awareness for optimizing efficiency and productivity. Depending on the function demands, many systems engineers are choosing a pre-compensated hydraulic load sense valve as it can provide an array of benefits for your hydraulic system including:
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Consistent flow regardless of load pressure:
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Compensator spools maintain a constant pressure drop across the main spool regardless of the change in work port pressure creating load-independent metering of the main spool.
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Example: A 10 GPM spool will give your actuator 10 GPM no matter work port pressure fluctuation.
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Multi-function capability:
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Pressure compensators combined with the load sense shuttle network within the valve allow operators to perform multiple work functions at once, increasing productivity and work output.
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Example: Clamping an object while simultaneously performing swing, boom down and travel functions. *Limited to the amount of pump flow available*
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Work port pressure limitation:
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Pressure limiters in a pre-compensated valve allow the work port pressure to be adjusted to a value that is less than the overall system pressure.
- Example: The system pressure of your refuse truck is 3000 PSI but your clamp function needs to be 2000 psi to not crush the can. You can limit the clamp function work port pressure to 2000 PSI using a pressure limiter.
An unpractical solution may be to use a 2000 PSI work port relief to achieve this same pressure limitation, but work port reliefs send large amounts of oil and heat to the tank. This lessens the efficiency of your system by increasing heat and lessening the amount of available oil to perform work. Pressure limiters send minimal amounts of oil to the tank (.5GPM) and are far more effective from an efficiency standpoint.
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The challenge with pre-compensation
While pre-compensated valves are an excellent choice for increasing the efficiency and multi-function capability of your hydraulic system, a challenge can arise with the pump capacity. Machine operators who perform multiple functions at once are limited by the amount of oil available in the hydraulic system. Once all the oil is utilized, the pump has become saturated. Any request for oil past the saturation point will result in the highest loaded function losing oil and satisfying the lowest loaded function as the oil will always go to the path of least resistance. See the figure below of a typical pre-compensated system.
Figure 1: Functions 1, 2, and 3 are satisfied and the pump is saturated. The introduction of function 4 moves oil from function 3 (highest loaded) to satisfy function 4. The operator will start to lose functionality of function 3.
Parker’s solution to combatting pump saturation
To fix the issues that arise when saturating the pump, Parker L90 and K220 valves can flow share using anti-saturation technology. Anti-saturation utilizes a unique inlet and compensators to share the flow amongst all active machine functions. Instead of the highest loaded function losing oil, all active functions will have the same priority and slow to satisfy the need of the newly introduced function-- sharing the flow. See figure below:
Figure 2: Utilizing Parker Anti Saturation Compensators, all functions have the same priority and share the flow to satisfy function 4. Functions will slow but the operator will not lose functionality of the highest loaded function
The value of the Parker L90 and K220
The ability to flow share can save your system hundreds, even thousands of dollars by not having to upsize your pump for more capacity, saving on space claim while simultaneously boosting end-user productivity by allowing multi-functioning without the threat of saturating the system.
Combining anti-saturation compensators with the ability to pressure limit work functions and systems will also see an added boost in efficiency and cost savings on their cooler by mitigating the heat associated with using port reliefs to achieve the same pressure limiting functionality.
Mixing standard compensators with flow share compensators allow designers to designate flow priority for the standard compensated functions without having to design priority through external manifolds or options.
Example: Priority to steering. Any remaining flow is shared amongst other active functions. See figure below:
In an era of life hacks and multi-tasking to maximize efficiency, the Parker L90 and K220 are there to answer the call. Interested in cost savings while boosting efficiency? Contact your local Parker representative or contact us to see how we can optimize your hydraulic system.
This article was contributed by Brian Baranek, product sales manager, Parker's Hydraulic Valve Division.
Related articles:
The Fundamentals of Applying Electrohydraulic Valves
Load Sensing Valve Improves Heavy Duty Machine Productivity and Fuel Savings
Tandem Circuitry and the Prevention of Function Drift
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