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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