HYDRAULICS AND
PNEUMATICS
SYMBOLS
Presented By: Shashank Jain(A-24)Vipul Jain (A-25)Samar Jain (A-40)
INTRODUCTION
A study of operation of hydraulic & pneumatic system is more convenient if a diagram of the system or circuit is available.
A schematic diagram indicates the function of various parts.
A set of fluid power symbols approved by the AMERICAN STANDARDS INSTITUTE, Inc. is as shown
RULES FOR SYMBOL1. Symbols are used to show connections , flow paths
and functions of the components represented.
2. Conditions occurring during transition from one flow-path arrangement to another can be indicated by symbols.
3. Symbols are not used to indicate construction , and they are not used to indicate values , such as pressure , flow rate , and other component setting.
4. The locations of ports , direction of shifting of spools and the positions of the control elements on the actual component are not indicated by symbols.
GENERAL SYMBOLS
-----------------
A working line or pipe line carrying either oil or air under pressureA pilot line , usually running from a pilot valve to a master valve
Flexible line , usually a rubber hose , such as used to connect a pivot-mounted cylinder
Connector , as used in piping layout
Indicates the flow direction of oil
Indicates the flow direction of the air
Indicates that a line passes another line ,but is not connected to it
A pressure line and a connector , representing a T-connectionA junction of four pressure lines
Elbow . These are usually not shown on a schematic diagram
A plug or a plugged connection
A pressure line with a plugged connection
LINES FOR HYDRAULIC EQUIPMENT
-------------- Drain line
A line to the reservoir , entering the reservoir above the fluid level in reservoir or tank
Line with fixed restriction
LINES FOR PNEUMATIC EQUIPMENT
-------------- Exhaust lines used to pipe the exhaust in from a control valve
A restricted pressure line . Can be accomplished either by reducing the pipe size or by adding a restriction to the line
HYDRAULIC PUMPS
A fixed-displacement pump has a fixed number of gallons of oil per minute leaving the pump
A variable-displacement pump is one in which rate of oil flow leaving the pump may be varied
AIR COMPRESSORS
An air compressor with a fixed displacement . A fixed number of cubic feet of air per minute can enter the compressor
MOTOR AND CYLINDERS ( HYDRAULIC AND PNEUMATIC )
Rotary motor with a fixed displacement . The output shaft from the motor rotates , and the volume rate of flow through the motor is fixed.
oil air
airoil
Rotary motor with a variable displacement . The output shaft from the motor rotates at various speed when the volume rate of flow varies.
Single-acting cylinder . The oil or compressed air acts only on one side of the piston.
Double-acting cylinder, single-end rod . The oil or air acts on either side of piston . The rod passes through one end of cylinder.Double-acting cylinder , double-end rod . The fluid acts on either side of piston . The rod extends through each end of the cylinder.
M
MISCELLANEOUS UNITS ( HAYDRAULIC AND PNEUMATIC )
Electric motor used to drive either an air compressor or a hydraulic pumpIntensifier or booster contains a piston having a different area on each of its two ends. Low pressure acts on the larger piston face to develop a high pressure on the smaller piston faceAccumulator , which is essentially a pressure storage reservoir
Filter . Removes dirt and foreign matter from the system , thus protecting it
Pressure gauge for indicating either oil or air pressure
Spring used to return a piston or other part
Heat exchanger , used to cool the oil in a system . The radiator on an automobile is an example of a heat exchanger for cooling the circulating water
Separator . A device for removing water from a compressed-air system
Exhaust muffler . A device for reducing noise , as on an automobile
VALVES ( HYDRAULIC AND PNEUMATIC )
Check valve , which allows fluid to flow in only one direction Variable-restriction valve . The faucet in the home is an example of valve that offers variable restriction to the flow of fluidBasic symbol for valve
An arrow inside the box indicates internal flow
EXAMPLES OF HYDRAULIC AND PNEUMATIC VALVES
Manual shutoff valve operated by either hand or foot
Directional valve with two positions and four connections
REFRENCE BOOK
Hydraulics & Pneumatics by H. L. Stewart. Page no. 59-68.