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Table B.2 Basic Hydraulic Circuits 

Miscellaneous

Line, mech. connection (shaft, levers, piston

rods)

D

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Pumps and Fluid Motors

Fixed-capacity hydraulic pump

With one direction of flow

With two directions of flow

Variable-capacity hydraulic pump

With one direction of flow

With two directions of flow

Fixed-capacity hydraulic motor

With one direction of flow

With two directions of flow

Variable-capacity hydraulic motor

With one direction of flow

With two directions of flow

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Cylinders

Detailed Simplified

Cylinder, single-acting

Cylinder, returned by spring

Cylinder, double-acting with single

 piston rod

Cylinder, double-acting with double

 piston rod

Cylinder, with single fixed cushion

Cylinder, with double adjustable

cushion

Cylinder, telescopic single-acting

Cylinder, telescopic double-acting

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Control Methods

Control, muscular By lever

With detents By pedal

By push button

Control, Electrical

By solenoid

With 1 Winding 

With 2 Winding 

By electrical motor M

 Control, Hydraulics ( Direct Acting)

By application of pressure

PneumaticHydraulic

 

By release of pressure

Hydraulic Pneumatic

 

Control, Hydraulics ( Indirect Control, Pilot-Operated)

By application of pressure

PneumaticHydraulic

 

By release of pressure

HydraulicPneumatic

 

Control paths inside the unit

Control, Electrohydraulic

Solenoid –  controlled

and pilot – 

 operated

Solenoid –  operated

or pilot – 

 operated

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Control, Mechanical (Operating in One Direction Only) 

By plunger or tracer By roller

By spring By roller

Control, servo

Pressure Control Valves

Throttling orifice

(normally closed)

Throttling orifice

(normally closed)

Pressure relief valves

Inlet pressure control

Inlet pressure or remote pilot

control

Proportional pressure

relief valves

Inlet pressure limited to a value

 proportional to pilot pressure

Sequence

Pressure regulator or

reducing valve

Without relief port Without relief port with remote

control

With relief port With relief port with remote

control

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Differential pressure regulator (outlet pressure is reduced

 by a fixed amount with respect to the inlet pressure)

Proportional pressure regulator (outlet pressure is reduced

 by a fixed ratio with respect to the inlet pressure)

Flow Control Valves

Shut-off valve

 Non-return valve (also called checkvalve)

 Non-return valve, spring-loaded

 Non-return valve, pilot-operated

 Non-return valve, with restriction

Flow control valve, with fixed output

Detailed  

Simple  

Flow control valve, with variable

output

Detailed   Simple  

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Direction Control valves

These squares indicate direction control valves, having

as many distinct positions as there are squares. The

 pipe connections are represented as connected to the box, representing the unoperated condition. For

operation, boxes are imagined to be displaced, so that

 pipe connections correspond with ports of the box in

question.

One-flow path

Two closed ports

Directional valve, with two extreme positions and an

infinite number of intermediate conditions with varying

degrees of throttling

Directional valve single-solenoid-controlled, pilot-

operated in both directions, spring return, four ports,

two distinct position

Simple

Detailed

 

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Pneumatics Components

Vacuum pump

Filter  – regulator  – lubricator

Detailed Symbol

Relieving Adjustable

Regulator

Lubricator with

DrainFilter with Auto

Drain

 

Simplified Symbol

 

Filter with water trap with manual

Air bleed

Exhaust port

Plain with no provision

for connection  

Threaded for connection 

Air compressor