Fluid Power Devices Circuits 683e66

HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

FLUID POWER – DEVICES & CIRCUITS

RANA SAHA DEPARTMENT OF MECHANICAL ENGINEERING JADAVPUR UNIVERSITY KOLKATA – 700 032 [email protected]

FLUID POWER DEVICES & CIRCUITS

THE SYSTEM ACCESSORIES Voltage EHP

ELECTRIC MOTOR

Current

rpm

lpm

IHP

HHP PUMP

Torque

CONTROL DEVICES

Pressure

RESERVOIR

rpm or m/s

lpm

HHP

OHP ACTUATOR

• Power Supply Pressure • Controller • Sensors • DAS • PC Interface

LOAD

Torque/ Force

AUTOMATIC CONTROL

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Hydraulic fluids

FLUID POWER DEVICES & CIRCUITS

Reservoir In addition to holding the supply of fluid needed to ensure that all lines and components are completely filled with fluid at all times, the reservoir has four other functions: 1. It separates entrained air. Dwell time in the reservoir provides opportunity for air bubbles in the fluid to rise to the top and burst on the surface. 2. It dissipates pressure pulses. Circuits with several actuators and random actuation of these actuators can have significant pressure pulses in the return line. Off-line filtration eliminates the influence of these pulses on the filter, because they are dissipated by the reservoir. 3. It provides cooling. 4. It traps contaminant. If the reservoir has to trap contaminant, the filtration is not working correctly. The reservoir does trap contaminant when the filter byes.

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Pumps

Positive Displacement

Non Positive Displacement Centrifugal

Variable

Fixed

Axial Propeller

Vane

Mixed Flow

Gear

Internal Internal External (Crescent) (Gerotor)

Piston

Vane

Screw

Balanced

Radial

Unbalanced

Axial

Piston

Swash Plate Radial

Bent Axis

Axial Rotating Cylinder Block

Bent Axis

Swash Plate Rotating Swash Plate

Classification of Pumps

FLUID POWER DEVICES & CIRCUITS

GEAR PUMP

• For relatively low level of pressure (about 140 to 180 bar or 14 to 18 MPa) • Very simple, reliable, relatively cheap and less dirt sensitive • In order to prevent cavitation, the pressure at the suction side of the pump should not exceed 0.1 to 0.2 bar (10 to 20 kPa) below atmospheric pressure (minimim absolute pressure: 0.8 bar or 80 kPa).

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

GEAR PUMP – DETAILS

FLUID POWER DEVICES & CIRCUITS

VANE PUMP

Variable

Fixed

•Maximum pressure: about 200 bar. •Pulse free delivery and low level of noise. •The amount of eccentricity determines the displacement of the pump. •In order to prevent cavitation, the pressure at the suction side of the pump should not exceed 0.1 to 0.2 bar (10 to 20 kPa) below atmospheric pressure (minimim absolute pressure: 0.8 bar or 80 kPa).

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

AXIAL PISTON PUMP Fixed • Workingpressure above aprox. 250 bar. • This type of pump can be driven in both directions. Rotating Swash Plate • Can operate without valves because the rotating barrel has a determined suck and pressure zone. • Normally this pump has 5, 7, 9 or 11 pistons.

Rotating Barrel

FLUID POWER DEVICES & CIRCUITS

AXIAL PISTON PUMP – CYLINDER VALVE PLATE DETAILS

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Variable •The angle of the swashplate determines the stroke of the pistons and therefore the amount of displacement of the pump. •Normally the swashplate is adjusted by a hydraulic cilinder built inside the pumphousing.

FLUID POWER DEVICES & CIRCUITS

Valves Pressure Control

Flow Control

Direction Control Check Valve

Pressure Relief

Fixed Shuttle

Pressure Reducing

Variable Two Way

Sequence Unloading

Pressure Compensated Deceleration

Three Way Four Way

Counterbalance

Valve Functions Classification

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

PRESSURE RELIEF VALVE Single Stage

FLUID POWER DEVICES & CIRCUITS

PRESSURE RELIEF VALVE Pilot Operated (2 Stage)

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

PRESSURE RELIEF VALVE AS AN UNLOADING VALVE • •

•

The pilot operated pressure relief valve is applied in systems with a considerable amount of flow. It's task is to limit the pressure in the system on an acceptable value. The pilot valve is adjusted at 150 bar. The pressure below the main valve is equal to the pressure above the main valve, for example 100 bar (determined by the load on the hydraulic motor). The spring on the main valve (about 1 to 5 bar) keeps the valve in the closed position. As long as the pressure in the system does not increase the adjusted pressure, the pump flow goes to the hydraulic motor. When the hydraulic motor is overloaded, the pressure will increase and the pilot valve will open. From that moment on the pressure above the main valve is limited on 150 bar. However, the pump flow cannot be drained by the small throttle in the by- canal, so the pressure below the main valve will increase with the spring pressure of about 1 to 5 bar (the pressure below the main valve will increase to 151...155 bar). Then the main valve opens and the majority of the pump flow will be drained by the main valve.

FLUID POWER DEVICES & CIRCUITS

SEQUENCE VALVE

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

COUNTER BALANCE VALVE

FLUID POWER DEVICES & CIRCUITS

FLOW CONTROL Fixed

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

PRESSURE COMPENSATED FLOW CONTROL VALVE

FLUID POWER DEVICES & CIRCUITS

CHECK VALVES

Pilot – operated check valve

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

SHUTTLE VALVE

FLUID POWER DEVICES & CIRCUITS

DIRECTION CONTROL VALVE

Method of actuation: • Manual • Electrical - Solenoid - Force/Torque Motor

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Actuators Rotary

Linear Symmetric

Limited rotation

Continuous rotation Gear

Vane

Asymmetric

Vane

Piston Single Acting

Piston Fixed Unidirectional

Double Acting

Bidirectional

Variable

Classification of Actuators and their Symbols

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

A typical linear actuator details

FLUID POWER DEVICES & CIRCUITS

ACCUMULATORS

An accumulator is a container in which fluid is stored under pressure as a source of power. Functions: 1.Auxiliary power source to supplement the pump 2.Emergency power source in case of power failure to operate critical circuit functions 3.Hydraulic shock absorber for circuits where sudden impact loads, quick stops, or reversals with heavy loads are a characteristic of the system

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

INTENSIFIERS

• Converts low-pressure fluid power into higher-pressure fluid power. • Intensifiers (also called boosters) are used to multiply forces when a great force is needed through a relatively short distance. • Hydraulic presses, riveting machines, and spot welders are typical applications.

FLUID POWER DEVICES & CIRCUITS

Some Basic Hydraulic Circuits • Basic Hydraulic Circuit - Linear - Rotary • Regenerative Circuit • Counterbalance Circuit • Hydraulic Circuit with Speed Control - Meter-In - Meter-Out • Sequence Circuit • Accumulator Circuit • Intensifier Circuit

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS RETRACT EXTEND

Linear Actuator (Hydraulic Cylinder)

Directional Control Valve A P

B T

Pressure Relief Valve

Pressure Gauge

Pump

Suction Strainer

BASIC HYDRAULIC CIRCUIT-1 Reservoir

FLUID POWER DEVICES & CIRCUITS

Rotary Actuator (Hydraulic Motor)

A P

B T

BASIC HYDRAULIC CIRCUIT-2

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS RETRACT EXTEND

A P

B T

REGENERATIVE CIRCUIT (Extension stroke)

FLUID POWER DEVICES & CIRCUITS

Counter balance Valve

COUNTERBALANCE CIRCUIT

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Pressure Compensated Flow Control Valve

SPEED CONTROL CIRCUIT (METER-IN)

FLUID POWER DEVICES & CIRCUITS

Pressure Compensated Flow Control Valve

SPEED CONTROL CIRCUIT (METER-OUT)

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Sequence Valve

SEQUENCING CIRCUIT

FLUID POWER DEVICES & CIRCUITS Accumulator 2 way, Solenoid operated DCV

4 way, Solenoid operated DCV

ACCUMULATOR CIRCUIT (AUXILIARY POWER SOURCE)

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Intensifier (Booster Cylinder)

INTENSIFIER CIRCUIT (High speed, low pressure approach followed by low speed high pressure piercing operation)

FLUID POWER DEVICES & CIRCUITS

A TYPICAL ELECTROHYDRAULIC CONTROL SYSTEM

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HYDRAULIC CONTROL DEVICES & CIRCUITS

FLUID POWER DEVICES & CIRCUITS

Suggested Reading: • Pease, D.A. Basic Fluid Power. Prentice Hall. • Merritt, H. E. (1967), Hydraulic Control Systems. Wiley, New York. • Esposito, A.; Fluid Power (with Application). 2003 • Sullivan, James A., 1998, Fluid Power Theory and Applications, Fourth Edition, Prentice-Hall International • Yeaple, Frank, 1996, Fluid Power Design Handbook, Third Edition, Marcel Dekker, Inc., N.Y.

Thank You…

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