Schematic Symbols

Hydraulic And Pneumatic Schematic Symbols

Photo of Wise Tech Wise Tech May 14, 2015
0 612 4 minutes read

To display fluid power components on schematic diagrams or drawings various schematic symbols has been developed over time. In America, ANSI (American National Standards Institute) is responsive for standardizing symbolic information. ISO (International-Standards-Organization) has same function over standarzing things internationally. Both systems iso and ansi has almost same format since ANSI updated its symbols to remove written information in 1966.

 

hydraulic and pneumatic schematic motor
Hydraulic and Pneumatic Schematic Motor

Most of the people even from different countries with different languages and origin but with the help of standard symbols and schematic diagram they knows how fluid flows and which components are being used. Standard used ANSI OR ISO in United States, however many companies uses ISO format for symbols which comply with foreign customers and suppliers.

The symbols are designed to make it easy to understand the most of hydraulic and pneumatic components. However,different parts’ schematic symbols are used to show whole component and how these work. First of one must look into the manual of supplied components, which symbols are being used. If there is no luck, other only option is design the component with standard method and procedures.

Lines:

 Connecting Pressure Lines (usually representing plastic tubing for pneumatic [air] lines with low pressures, metal piping for hydraulic [fluid] lines with high pressure)
continuous line for flow line (Schematic Symbol) -continuous line (for) flow line
dashed line for pilot, drain (Symbol/picture) -dashed line (for) pilot, drain
(Envelope) long and short dashes around two or more (Symbol/picture) -envelope (for) long and short dashes around two or more component symbols.

Circular:
large circle pump motor -large circle– pump, motor
small circle -small circle– Measuring devices
semi circle -semi-circle – rotary actuator

Square:
one square -one square– pressure control function-two or three adjacent squares – directional control

Diamond:
diamond fluid container -diamond – Fluid conditioner (filter, separator, lubricator, heat exchanger)

Miscellaneous Symbols:
Spring -Spring
Flow Restrictio -Flow Restriction

Triangle:
solid direction neumatic flow -solid – Direction of Hydraulic Fluid Flow
open direection pneumatic flow -open – Direction of Pneumatic flow

Pumps and Compressors
(turn rotary torque from an AC or DC electric motor into pressure in a hydraulic or pneumatic system)

Fixed Displacement hydraulic pump symbols:
Fixed Displacement hydraulic pump Schematic Symbol -unidirectional
Fixed Displacement hydraulic pump (Reversible flow) Schematic Symbol -bidirectional

Variable displacement hydraulic pump symbols:
Variable displacement hydraulic pump Schematic Symbol -unidirectional
Variable displacement hydraulic pump (Reversible flow) Schematic Symbol -bidirectional

Compressor symbol:
Compressor Schematic Symbol

Motors

Fixed displacement hydraulic motor symbol:
Fixed displacement hydraulic motor Schematic Symbol -unidirectional
Fixed displacement hydraulic motor (Reversible/bidirectional) Schematic Symbol -bidirectional

Variable displacement hydraulic motor symbol:
Variable displacement hydraulic motor Schematic Symbol -unidirectional
Variable displacement hydraulic motor (Reversible/bidirectional) Schematic Symbol -bidirectional

Pneumatic motor symbol:
Pneumatic motor Schematic Symbol -unidirectional
Pneumatic motor (Reversible/bidirectional) Schematic Symbol -bidirectional

Rotary Actuator symbol:
Rotary Actuator hydraulic Schematic Symbol – hydraulic
Rotary Actuator pneumatic Schematic Symbol – pneumatic

Cylinders

Single acting cylinder symbols:
Single acting cylinder symbol (pilot return) Schematic Symbol -returned by external force
Single acting cylinder symbol (spring Return) Schematic Symbol -returned by spring or extended by spring force

Double acting cylinder symbols:
Double acting cylinder symbol (single piston rod) Schematic Symbol -single piston rod (fluid required to extend and retract)
Double acting cylinder symbol (double ended piston rod) Schematic Symbol -double ended piston rod

Cylinders with cushions symbols:
Cylinders with a single fixed cushion Schematic Symbol – single fixed cushion
Cylinders with a double fixed cushion Schematic Symbol – double fixed cushion
Single Adjustable Cushion – single adjustable cushion
Cylinders with a double adjustable cushion Schematic Symbol – double adjustable cushion

Directional Control Valve symbols

Directional control valve (2 ports / 2 positions):
Normally closed, directional control valve with 2 ports and 2 finite positions (Schematic Symbol) -Normally closed directional control valve with 2 ports and 2 finite positions.
Normally open, directional control valve with 2 ports and 2 finite positions. (Schematic Symbol) -Normally open directional control valve with 2 ports and 2 finite positions.

Directional control valve (3 ports / 2 positions):
Normally closed, directional control valve with 3 ports and 2 finite positions. (Schematic Symbol) -Normally closed directional control valve with 3 ports and 2 finite positions.
Normally open, directional control valve with 3 ports and 2 finite positions. (Schematic Symbol) -Normally open directional control valve with 3 ports and 2 finite positions.

Directional control valve (4 ports / 2 positions):
directional control valve with 4 ports and 2 finite positions. (Schematic Symbol) -directional control valve with 4 ports and 2 finite positions.

Directional control valve (4 ports / 3 positions):
directional control valve with 4 ports and 3 finite positions. (Schematic Symbol) -directional control valve with 4 ports and 3 finite positions
*-(center position can have various flow paths)

Directional control valve (5 ports / 2 positions) Normally a pneumatic valve:
directional control valve with 5 ports and 2 finite positions. (Schematic Symbol) -directional control valve with 5 ports and 2 finite positions

Directional control valve (5 ports / 3 positions) Normally a pneumatic valve:
directional control valve with 5 ports and 3 finite positions. (Schematic Symbol) -directional control valve with 5 ports and 3 finite positions

Proportional directional control valve:

Electro-hydraulic servo valve:

-The spool positions on these valves is variable allowing for variable flow conditions.
single-stage Electro-hydraulic servo valve, direct operation unit which accepts an analog signal and provides a similar analog fluid power output (Schematic Symbol) -single-stage direct operation unit which accepts an analog signal and provides a similar analog fluid power output
two-stage Electro-hydraulic servo valve with mechanical feedback indirect pilot operation unit which accepts an analog signal and provides a similar analog fluid power output (Schematic Symbol) -two-stage with mechanical feedback indirect pilot operation unit which accepts an analog signal and provides a similar analog fluid power output

Control Method
Operator symbols for valves

Manual Control:
general symbol of a Valve's Manual Operator (without showing the control type) (Schematic Symbol) -general symbol of a valve’s manual operator (without showing the control type)
symbol for a pushbutton Valve's Operator (Schematic Symbol) -pushbutton
symbol for a lever Valve's Operator (Schematic Symbol) -lever
symbol for a foot pedal Valve's Operator (Schematic Symbol) -foot pedal

Mechanical Valve Control:
symbol for a plunger Valve's Operator (Schematic Symbol) -plunger or tracer
symbol for a Valve with spring return on one side (Schematic Symbol) -spring (used on one side of a valve to hold it in the normally open or normally closed state)
symbol for a roller Valve's Operator (Schematic Symbol) -roller
symbol for a roller Valve's (one direction only) type Operator (Schematic Symbol) -roller (one direction only)

Electrical/Solenoid Valve Control:
symbol for a Solenoid Valve's Operator (Schematic Symbol) -Solenoid (the one side’s winding shown)

Pilot Operation
(uses pressure to actuate valve):
symbol for a pneumatically actuated pilot Valve's Operator (Schematic Symbol) -pneumatic actuated pilot
symbol for a hydraulically actuated pilot Valve's Operator (Schematic Symbol) -hydraulic actuated pilot

Pilot operated two-stage valve
(uses a second lesser force to actuate the pilot actuation of the valve):
symbol for a two-stage piloted (Pneumatic: Solenoid first stage) Valve's Operator (Schematic Symbol) -Pneumatic: Solenoid first stage
symbol for a two-stage piloted (Pneumatic: Air pilot second stage) Valve's Operator (Schematic Symbol) -Pneumatic: Air pilot second stage
symbol for a two-stage piloted (Hydraulic: Solenoid first stage) Valve's Operator (Schematic Symbol) -Hydraulic: Solenoid first stage
symbol for a two-stage piloted (Hydraulic: Hydaulic pilot second stage) Valve's Operator (Schematic Symbol) -Hydraulic: Hydaulic pilot second stage

Check valves, Shuttle valves, Rapid Exhaust valves
symbol for a Check Valve (Schematic Symbol) -check valve symbol-free flow one direction, blocked flow in other direction
symbol for a pilot operated check valve, pilot to close (Schematic Symbol) -pilot operated check valve symbol, pilot to close
symbol for a pilot operated check valve symbol, pilot to open (Schematic Symbol) -pilot operated check valve symbol, pilot to open

Shuttle valve:
symbol for a shuttle valve (Schematic Symbol) -to isolate one part of a system from an alternate part of circuit.

Rapid exhaust valve/Pneumatic:
symbol for a (Pneumatic) Rapid exhaust valve (Schematic Symbol) -installed close to an actuator for rapid movement of the actuator.

Pressure Control Valves

Pressure Relief Valve(safety valve) normally closed:
symbol for a Pressure Relief Valve(safety valve) normally closed (Schematic Symbol) – line pressure is limited to the setting of the valve, secondary part is directed to tank.

Proportional Pressure Relief Valve:
symbol for a Proportional Pressure Relief Valve (Schematic Symbol) – line pressure is limited to and proportional to an electronic signal

Sequence Valve:
symbol for a Sequence Valve (Schematic Symbol) – when the line pressure reaches the setting of the valve, valve opens permitting flow to the secondary port. The pilot must be externally drained to tank.

Pressure Reducing valve (Hydraulic Pressure Regulator):
symbol for a Pressure Reducing valve (Pressure Regulator) (Schematic Symbol) – pressure downstream of valve is limited to the setting of the valve

Flow Control Valves

Throttle valve:
symbol for a Throttle valve (Schematic Symbol) -adjustable output flow

Flow Control valves:
symbol for a Flow Control valve(variable inlet pressure) (Schematic Symbol) -Flow control valve with fixed output (variations in inlet pressure do not affect rate of flow)
symbol for a Flow Control valve(with fixed output and relief port to reservoir with relief for excess flow [variations in inlet pressure do not affect rate of flow] ) (Schematic Symbol) -Flow control valve with fixed output and relief port to reservoir with relief for excess flow (variations in inlet pressure do not affect rate of flow)
symbol for a Flow Control valve(with variable output) (Schematic Symbol) -Flow control valve with variable output
symbol for a Flow Control valve(fixed orifice) (Schematic Symbol) -Flow control valve with fixed orifice
symbol for a Flow Control valve(metered flow toward right free flow to left) (Schematic Symbol) -Flow control valve with metered flow toward right free flow to left
symbol for a Flow Control valve(pressure compensated flow control fixed output flow regardless of load) (Schematic Symbol) -Flow control valve with pressure compensated flow control fixed output flow regardless of load
symbol for a Flow Control valve(pressure and temperature compensated) (Schematic Symbol) -Flow control valve with pressure and temperature compensated
symbol for a Flow Control valve(variable output and relief port to reservoir) (Schematic Symbol) -Flow control valve with variable output and relief port to reservoir

Flow dividing valve:
symbol for a Flow divider (Schematic Symbol) -flow is divided equally to two outputs.

Shut-Off Valve
symbol for a Shut-Off Valve (Schematic Symbol) -Shut-Off Valve Simplified symbol

Accumulators
symbol for an Accumulator (Schematic Symbol) -Accumulator symbol (Stores Pressure)

Reservoir (Tank)
symbol for your tank or resorvoir (Schematic Symbol) -Reservoir symbol (Holds Fluid medium of your system)

Filters, Water Traps, Lubricators and Miscellaneous Apparatus

Filter or Strainer:
symbol for a Filter or Strainer (Schematic Symbol)

Water Trap:
symbol for a Water Trap (with manual drain) (Schematic Symbol) -with manual drain
symbol for a Water Trap (with automatic drained) (Schematic Symbol) -with automatic drained

Filter with water trap:
symbol for a Filter with water trap (with manual drain) (Schematic Symbol) -with manual drain
symbol for a Filter with water trap (with automatic drained) (Schematic Symbol) -automatic drain

Air Dryer:
symbol for an Air Dryer (refrigerant, or chemical removal of water from compressed air line) (Schematic Symbol) refrigerant, or chemical removal of water from compressed air line

Lubricator:
symbol for a Lubricator (oil vapor is injected into air line) (Schematic Symbol) -oil vapor is injected into air line

Conditioning unit (FRL, Pressure Regulator):
symbol for a Conditioning unit (Pneumatic Pressure Regulator) (FRL compound symbol of filter, regulator, lubricator unit) (Schematic Symbol) -compound symbol of filter, regulator, lubricator unit(FRL symbol)
symbol for a Conditioning unit (Pneumatic Pressure Regulator) (FRL compound symbol of filter, regulator, lubricator unit) (Simplified Schematic Symbol) -Simplified Symbol

Heat Exchangers
symbol for a Heat Exchanger (Schematic Symbol) -air or water cooled unit designed to remove heat from oil returning to reservoir
Read Also>>Plumbing pipe and fitting symbols

 

 
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