Hydraulic symbols
Energy transfer
Energy conversion
line, supply line, return line, component framing
and symbol boxed in
hydraulic pump with constant delivery rate
internal and external pilot line, leakage oil line,
purging line, exhaust line
frames for several components
hydraulic variable displacement pump with alternating
direction of delivery at constant direction of rotation
Actuation
Manual actuation
Valves
Directional control valves
Valves
Basic symbols
A
by
pushing
by
pulling
by pulling
and pushing
by
turning
by
lever
by
rocker
Function unit for valves with main ports.
The number of ports corresponds to the number
of lines shown above and below a square.
tubing line
line
connection
hydraulic motor with
constant displacement/
absorption capacity and
two directions of rotation
rotary drive/semi-rotary
drive with limited angle
of rotation and two
directions of flow
crossing
line
pressure supply port,
closed
hydraulic
energy source
closed exhaust
port
plug within a fluid line
X1
by
plunger
by
roller
by roller lever, actuation
in one direction of travel
only
paths and directions of flow through a valve
reservoir open to
atmosphere
hydraulically
actuated
function: leak-tight locking, hydraulic seat
directional control valve with intermediate
positions – dynamic control valve
by solenoid coil with one winding
– active direction
– active direction
towards the
away from the
valving element
valving element
by solenoid coil with two windings, active direction
to and from the valving element
quick decoupler with
two non-return valves,
coupled
by electric motor with
by stepper motor
continuous rotary motion
Combined actuation
filter
filter with bypass valve with optical contamination
indicator and switch
p2
B
P
T
1M2
X
cooler without flow lines
for the direction of flow
of coolant
by solenoid coil
and pilot valve
by solenoid coil or
manual override and
pilot valve
by solenoid coil
or manual override
by solenoid coil or
manual override with
detent
5
heating
G
B
Y
examples for connection
identification:
A = port
B = port
T
L
P = pump
T = reservoir
X = control oil supply
Y = control oil relief
1M1
L = leakage oil
M = solenoid coil
Connections must be marked on the circuit diagram
using the identification marked on the component,
sub-base or block (ISO 1219-2).
A
T
P
3/2-way poppet valve with solenoid coil and
limit switch
gas pressure accumulator, separation of
media through:
diaphragm
bladder
piston
(diaphragm
(bladder
(piston
accumulator)
accumulator)
accumulator)
1
2
3
1
2
3
three-way rotary connection
053032 en © Festo Didactic GmbH & Co. KG
www.festo-didactic.com
A2
A1
dual-pressure valve
(AND function)
Flow control valves
A
B
flow control
valve, adjustable
B1
B
A
one-way flow control
valve, adjustable
orifice, fixed
B2
A
flow distributor
T
B
A
A
3-way flow control
valve, adjustable
2-way flow control
valve, non-adjustable
Accessories
Measurement and display devices
Pressure control valves
A
P
2/2-way valve with 2 ports, 2 switching positions
for 2 flow directions.
– normally closed
– normally open
position
position
directly actuated
pressure relief valve,
adjustable
A
P
3/2-way valve with
3 ports and
2 switching positions,
normally closed position
4/2-way valve with
4 ports and
2 switching positions
Detents are to be symmetrically matched with the
mechanical connection.
With more than three detent positions the number
of positions can be displayed above the detent
element.
L
P
sequence valve,
self-actuating, with
bypass valve
A
L
pressure gauge
temperature gauge
(thermometer)
flow rate display
flow meter
fluid level display
(sight glass)
tachometer
pressure switch, electromechanical, adjustable
pressure sensor,
analogue output signal
L
P
P
piloted 2-way pressure
directly actuated
2-way pressure regulator regulator with external
control oil relief
with external control
oil relief
P
A
A
P T
T
pressure switch, electronically adjustable,
output signal switching
3-way pressure regulator accumulator charging valve
P
double-acting cylinder
double-acting cylinder
with displacement
with integrated
encoder on the piston rod displacement encoder
A1
B1
double non-return valve,
piloted
T
Mechanical components
G
A
1M1
B2
B
A2
flow control
valve, fixed
T
P
4/3-way servo valve, piloted, solenoid coil with two
windings, with mechanical feedback of the valve slide
position to the pilot stage
tank – ventilation filter
single-acting cylinder, plunger cylinder
pressure booster, single-acting, which
converts a pneumatic pressure p1 into a
higher hydraulic pressure p2
B
G
X
Y
T
P
4/3-way servo valve piloted by a control solenoid,
with closed-loop position control of main and pilot
stage, with integrated electronics, external pilot
supply and drain
A
hydraulic pump and hydraulic motor with shaft
coupling
quick decoupler with
two non-return valves,
decoupled;
i.e. line closed
A1
B
pump shaft points to
the left (preferably)
or to the right
compact gear unit (simplified representation)
telescope cylinder,
double-acting
A
A
A2
shuttle valve
(OR function)
Pressure actuation
reservoir closed
with cover
B
B
B
G
3-way stop-cock
non-return valve with spring
X2
T
P
4/3-way proportional valve, directly actuated
tank connection, ending
below and above the oil level
motor shaft points to
the right (preferably)
or to the left
telescope cylinder,
single-acting
T
shut-off valve
non-return valve
A X
piloted non-return
valve with spring
A
Electrical actuation
p1
P
A
basic elements with 2, 3, 4 switching positions
P
T
actuated in initial position
pneumatically
actuated
double-acting cylinder with through piston rod of
different diameters, with adjustable cushioning
at both ends
B
4/3-way valve, hydraulically actuated, spring-centred
electric motor
single-acting cylinder
double-acting cylinder
with piston rod at one end, with piston rod at one end
spring chamber with
leakage oil connection
A
B
T
P
4/2-way valve with two
solenoid coils, directly
actuated, with detent
(double solenoid valve)
T
P
3/2-way valve with
solenoid coil, directly
actuated, reset by
spring and manual
override with detent
Mechanical actuation
reversible hydraulic pump/hydraulic motor unit with
two directions of flow and variable displacement
volume, external leakage oil line and two directions
of rotation.
A
Valves
Stop valves
T
G
G
displacement encoder
with analogue output
signal
displacement encoder
with digital output signal
optical indicator
digital display
G
X
reset by spring
spring-centred
4/3-way valve with 4 ports and 3 switching
positions – various mid-position variants
T
shut-off/
counterbalancing valve
P
proportional pressure
relief valve, directly
actuated with closed-loop
position control of
solenoid coil and with
integrated electronics
4
fluid level switch with
4 normally closed
contacts
L
electrical fluid level
monitoring with analogue
output signal and
digital display