2008 463 LECT09 Accumulators

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ABE 463 Electrohydraulic ABE 463 Electrohydraulic SystemsSystems

Energy Regulation Energy Regulation ComponentsComponents

ABE 463, Lect 09ABE 463, Lect 09

The ProblemThe Problem

Stroke

Pres

sure

Moving-induced

pressure shock

Hydraulic capacitorabsorbing

3


Pumpdisplacement

Q

Normal corner power

Relief valve

setting

Preset limiting pressure

Intensifiedpressure

High-flow corner power

High-pressurecorner power

P

High-flowpressure

High-pressureflow

Low-pressureflow Constant corner power line

A Desirable FeatureA Desirable Feature


Common power regulating Common power regulating devicesdevices

hydraulic shock absorber

Hydraulic accumulators

Pressure intensifier


A Few Designs ofA Few Designs of Shock Shock AbsorbersAbsorbers


Shock Absorbing Shock Absorbing CharacteristicCharacteristicss


SpecialSpecial Absorbers – Hydraulic Absorbers – Hydraulic SpringsSprings

Stroke

Pres

sure

Moving-induced

pressure shock

Hydraulic spring


AccumulatorAccumulator

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

A type of power storage devices,functioning as a temporal storage tank of fluid energy to provide or absorbmomentary flow.

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Functions of an AccumulatorFunctions of an Accumulator

o Energy storageo Pulsation absorption o Shock cushioning o Supplementing pump flow o Maintaining pressure o Fluid dispensing


Types Commonly used Types Commonly used AccumulatorsAccumulators

Weight-loaded Spring-loaded Pressure gas-loaded


Spring Loaded AccumulatorsSpring 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.

dtPPd

kQ loadpre


Gas Charged AccumulatorsGas Charged Accumulators

In a closed chamber, a In a closed chamber, a changechangein gas volume must result in in gas volume must result in an identical fluids volume. It an identical fluids volume. It can maintain a constant fluid can maintain a constant fluid pressure pressure

2

22

1

11

TVP

TVP

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Six Stages of OperationSix 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 AccumulatorsSizing AccumulatorsHydraulic accumulators are normally sized in terms of specific applications. For example:

For leakage compensation

SVpppppV

120

210

For emergency power supply SV

ppp

V

21

2

21

1

21

0

0

11

1

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More on Sizing AccumulatorsMore 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_%20labeled_formulas.html)

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Applications of Accumulators Applications of Accumulators (1)(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 Applications of Accumulators (2)(2)

Several piston accumulators through a fluid manifold to provide a large capacity of fluid storage.

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Power Regeneration DevicesPower Regeneration Devices -- Pressure Intensifier

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Power Regeneration DevicesPower Regeneration Devices -- Two Speed Cylinder

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Power Regeneration DevicesPower Regeneration Devices -- Stand-by Recharger

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Lecture SummaryLecture Summary

Discussed the basic principles of different types of hydraulic power regulation devices:

Hydraulic Shock absorber/hydraulic springHydraulic AccumulatorHydraulic power regenerators

Documents

2008 463 LECT09 Accumulators