ABE 463 Electrohydraulic Systems

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ABE 463 Electrohydraulic Systems

• Energy Regulation Components

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The Problem
Moving-inducedpressure shock
Pressure
Stroke
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A Desirable Feature
Q
High-flow corner power
Low-pressureflow
Constant corner power line
Normal corner power
Pumpdisplacement
High-pressurecorner power
High-pressureflow
Intensifiedpressure
Relief valvesetting
Preset limiting pressure
High-flowpressure
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Common power regulating devices
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A Few Designs of Shock Absorbers
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Shock Absorbing Characteristics
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Special Absorbers Hydraulic Springs
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Accumulator
A type of power storage devices, functioning as a
temporal storage tank of fluid energy to
provide or absorbmomentary flow.

• An accumulator can serve as
• an auxiliary power source,
• a pulsation absorber,
• a shock damper,
• a leakage makeup source, and
• a thermal expansion compensator

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Functions of an Accumulator

• Energy storage
• Pulsation absorption
• Shock cushioning
• Supplementing pump flow
• Maintaining pressure
• Fluid dispensing

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Types Commonly used Accumulators
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Spring Loaded Accumulators
In a spring loaded accumulator, a change in
fluids volume is proportional to its pressure.
As the spring compression increases as fluid
enters the chamber and decreases as the
accumulator is discharged, the pressure is not
constant.
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Gas Charged Accumulators
In a closed chamber, a change in gas volume must
result in an identical fluids volume. It can
maintain a constant fluid pressure
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Six Stages of Operation
(a) empty - no gas charge (b) precharged with
dry nitrogen (c) system pressure exceeds
precharge pressure, and hydraulic fluid flows
into accumulator (d) system pressure peaks,
maximum fluid has entered accumulator, and system
relief opens (e) system pressure drops,
precharge pressure forces fluid from accumulator
and into system and (f) system pressure reaches
minimum needed to do work.
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Sizing Accumulators
Hydraulic accumulators are normally sized in
terms of specific applications. For example
For leakage compensation
For emergency power supply
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More on Sizing Accumulators
Some accumulator manufacturers provide some means
to help you in sizing an appropriate accumulator
for your specific applications. One example can
be found (http//www.wilkesandmclean.com/acc_20l
abeled_formulas.html)
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Applications of Accumulators (1)
Several gas bottles serving a single piston
accumulator through a gas manifold to provide a
large capacity of fluid storage.
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Applications of Accumulators (2)
Several piston accumulators through a fluid
manifold to provide a large capacity of fluid
storage.
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Power Regeneration Devices -- Pressure
Intensifier
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Power Regeneration Devices -- Two Speed Cylinder
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Power Regeneration Devices -- Stand-by Recharger
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Lecture Summary

• Discussed the basic principles of different types
  of hydraulic power regulation devices
• Hydraulic Shock absorber/hydraulic spring
• Hydraulic Accumulator
• Hydraulic power regenerators