1. For system diagrams and component identification
Hydraulic Symbols
Basic Hydraulics
HYDR 1305
For system diagrams and component identification 1

2. Flow Lines and Connections
Main line
Single
Pilot line
Four way junction
Hydraulic components in box or cabinet
Enclosure
Hose usually connecting
parts with relative movement
Flexible
line
Reservoir
Junction
Single
Junction
Four way junction
not connected
Crossing 17

3. Functional Elements Triangle Spring Tee Arrow Arrows
Direction of fluid flow
Spring
Tee
Closed path or port
Long sloping arrow that crosses another line indicates adjustability
Arrow
Straight or sloping
path and flow direction
Arrows 15

4. Equipment Accumulator Filter Operator Pressure Gauge
Solenoid Operator Shown
Pressure Gauge 15

5. Equipment
Electric Motor M
Pump
Hydraulic motor
Isolating valve

6. Equipment Check valve One way flow control valve Flow control valve
Flow in one direction
Check valve
FLOW
One way flow control valve
RESTRICTED FLOW
FREE FLOW
Flow control
valve
Adjustable
Non-adjustable

7. Actuators Single acting spring return cylinder
Rotary actuator
Single acting spring return cylinder
Single acting load return cylinder
Double acting cylinder

8. Pressure Regulators
A pressure regulator symbol represents a normal state with the spring holding the regulator valve open.
The dotted line represents the feedback, that opposes the spring and can vary the flow through the valve from full flow through shut off.
Non-Adjustable regulator
Adjustable regulator

9. Pressure Relief Valves
A pressure relief valve symbol represents a normal state with the spring holding the valve closed
The dotted line represents feed-forward, this opposes the spring and can lift the valve to allow flow.
Non-adjustable relief valve
Adjustable relief valve

10. Control Valve Symbols - Structure
Boxes are used to indicate the number of valve positions.
The number of adjacent boxes indicate whether a valve is a two position or three position valve.
The boxes are two states of the same valve
TWO
POSITION
VALVE
THREE 1 2 1 2 3
Arrows are used to indicate the direction of flow.
A tee indicates that a port is blocked (no flow).
NO FLOW POSITION
FLOW POSITION

11. Control Valve Symbols - Structure
The function of a valve may be given by a pair of numerals separated by a stroke.
Examples: 2/2, 3/2, 5/2, etc.
The first numeral indicates the number of main ports.
These are inlets and outlets.
The second numeral indicates the number of physical positions the valve can be placed in.
Such as left or right, pushed in or pulled out for two positions, and left / center / right for three position.
A 3/2 valve therefore has 3 ports (normally these are inlet, outlet, and exhaust) and 2 states (the normal state and the operated state.
2/2
2 PORTS
2 POSITIONS
3/2
3 PORTS

12. Control Valve Symbols - Structure
The port connections are shown on only one of the boxes to indicate the shelf state.
The shelf state is the state that the valve would be in if it were setting on the shelf with no fluid flow, not being operated, not powered, etc.
Below, shown in the shelf state; flow is from port 1 to port 2 and port 3 is blocked.
If the control valve is made to change state, the blocks are swapped.
Flow is now from port 3 to 1 and now 2 is blocked. 2 3 1
OPERATED STATE
FLOW P TO 1
E IS BLOCKED
SHELF STATE
FLOW 1 TO E
P IS BLOCKED

13. Control Valve Symbols - Structure
The control valve operator is shown against the box that the valve will change state to when operated.
This is a push button symbol:
The "shelf state" (in this case caused by a spring) is shown on the opposite box.
If there is no spring than the control valve is operated by pushing the button in and pulling the button out. 2 3 1 2 3 1
SHOWN IN SHELF STATE (WITH SPRING)
PUSH BUTTON IN GOES TO LEFT BLOCK STATE
PUSH BUTTON RELEASED GOES BACK TO SHELF STATE AS SHOWN
THERE IS NO SHELF STATE (NO SPRING)
PUSH BUTTON PULLED AND PUSHED IN CHANGES STATES RESPECTIVELY
NOTE ON DIAGRAM INDICATES IF PUSHED IN OR OUT FOR POSITION SHOWN.

14. Control Valve Symbols - Structure
The valve symbol can be visualised as moving from one state to another state with the port connections not moving.
The 3/2 control valve shown is frequently used for a single acting cylinder. 2 3
3/2 CONTROL VALVE
SHOWN IN ITS
TWO POSITIONS 2 3

15. E P 1 2 3

16. E P 1 2 3

17. E P 1 2 3

18. E P 1 2 3

19. E P 1 2 3

20. Control Valve Symbols - Structure
A 4/2 valve symbol is shown below.
This valve could be used to operate two different pieces of equipment at the same time from the same control valve. 1 2 3 4

21. Control Valve Symbols - Structure
A 5/2 valve symbol is shown below.
The most frequent application is controlling a double acting cylinder. 1 2
SHELF STATE 3 4 5 1 2
OPERATED STATE 3 4 5

22. Control Valve Symbols - Structure
5/3 control valves have a normal central position that is set by springs or with a manual control such as a lever.
The flow pattern in the center position varies with the type.
Depending on the application, there are three types that may be used.
5/3 VALVE 1 2 3 4 5
LEVER OPERATED - SHOWN IN CENTER POSITION, ROCKS BACK AND FORTH
SOLENOID OPERATED – IF THE LEFT SOLENOID IS ENERGIZED, THE BOX NEXT TO IT WILL BE THE POSITION OF THE VALVE

23. Control Valve Symbols - Structure
All valves types shown in the Shelf State Position
Type 1.
Type 2.
Type 3.
Control Valve Symbols - Structure

24. Control Valve Symbols - Structure
All valves types shown in the Left State Position
Type 1.
Type 2.
Type 3.

25. Control Valve Symbols - Structure
All valves types shown in the Shelf State Position
Type 1.
Type 2.
Type 3.

26. Control Valve Symbols - Structure
All valves types shown in the Right State Position
Type 1.
Type 2.
Type 3.

27. Valve Operators Manual General manual Lever Push button Pedal
Pull button
Treadle
Push/pull button
Rotary knob 27

28. Control Valve Symbols - Operators
Mechanical
Plunger
Pressure
Spring normally as a return
Pilot pressure
Roller
Differential pressure
Uni-direction or one way trip
Detent in 3 positions
Electrical
Solenoid direct
Solenoid pilot 27