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.