Appendix A. Standard Symbols for Hydraulic Components

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Geraldine Loraine Blair
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1 Table B.1 Flow lines Appendix A Standard Symbols for Components Continuous flow E Pilot connection L L>10E E Drain connection L L<5E Connected d L d 5E Not connected Flexible Plugged Restricted, affected by viscosity Restricted, not affected by viscosity

2 Table B.2 Basic Circuits Line, mech. connection (shaft, levers, piston rods) Line, enclosure (several components in a unit) Spring Miscellaneous E D D<5E Direction of rotation Electric motor Heat engine M M Filter or strainer Reservoir, with line above fluid level Reservoir, with line below fluid level Reservoir, as header Adjustable setting Reservoir switch Pressure switch Accumulator Sring Loaded Gas Loaded Cooler, without indicating flow line Cooler, indicating flow lines of coolant Heater Pressure gauge

3 Pumps and Fluid Motors With one direction of flow Fixed-capacity hydraulic pump With two directions of flow With one direction of flow Variable-capacity hydraulic pump With two directions of flow With one direction of flow Fixed-capacity hydraulic motor With two directions of flow With one direction of flow Variable-capacity hydraulic motor With two directions of flow

4 Cylinders Detailed Simplified Cylinder, single-acting Cylinder, returned by spring Cylinder, double-acting with single piston rod Cylinder, double-acting with double piston rod Cylinder, with single fixed cushion Cylinder, with double adjustable cushion Cylinder, telescopic single-acting Cylinder, telescopic double-acting

5 Control Methods Control, muscular With detents By lever By pedal By push button Control, Electrical By solenoid With 1 Winding With 2 Winding By electrical motor M Control, s ( Direct Acting) By application of pressure By release of pressure Control, s ( Indirect Control, Pilot-Operated) By application of pressure By release of pressure Control paths inside the unit Solenoid controlled and pilot operated Control, Electrohydraulic Solenoid operated or pilot operated

6 By plunger or tracer Control, Mechanical (Operating in One Direction Only) By roller By spring By roller Control, servo Pressure Control Valves Throttling orifice (normally closed) Throttling orifice (normally closed) Inlet pressure control Pressure relief valves Inlet pressure or remote pilot control Proportional pressure relief valves Inlet pressure limited to a value proportional to pilot pressure Sequence Without relief port Without relief port with remote control Pressure regulator or reducing valve With relief port With relief port with remote control

7 Differential pressure regulator (outlet pressure is reduced by a fixed amount with respect to the inlet pressure) Proportional pressure regulator (outlet pressure is reduced by a fixed ratio with respect to the inlet pressure) Shut-off valve Non-return valve (also called check valve) Non-return valve, spring-loaded Flow Control Valves Non-return valve, pilot-operated Non-return valve, with restriction Flow control valve, with fixed output Detailed Simple Flow control valve, with variable output Detailed Simple

8 Direction Control valves These squares indicate direction control valves, having as many distinct positions as there are squares. The pipe connections are represented as connected to the box, representing the unoperated condition. For operation, boxes are imagined to be displaced, so that pipe connections correspond with ports of the box in question. One-flow path Two closed ports Directional valve, with two extreme positions and an infinite number of intermediate conditions with varying degrees of throttling Detailed Directional valve single-solenoid-controlled, pilotoperated in both directions, spring return, four ports, two distinct position Simple

9 s Components Vacuum pump Detailed Symbol Filter with Auto Drain Lubricator with Drain Filter regulator lubricator Relieving Adjustable Regulator Simplified Symbol Filter with water trap with manual Air bleed Exhaust port Plain with no provision for connection Threaded for connection Air compressor

For system diagrams and component identification

Pneumatic Symbols For system diagrams and component identification Contents Standards Actuators Basic symbols Valve symbol structure t Functional elements Flowlines Connections Conditioners and plant Pressure