Pneumatic Schematics and Basic Circuit Design 352

2/2 valve

A type of two-way directional control valve with two ways and two positions. 2/2 valves most frequently are used to only block or allow fluid flow.

3/2 valve

A directional control valve with three ways and two positions. A 3/2 valve can be either mixing valve or a diverting valve.

5/3 valve

A directional control valve with four ways, five ports, and three positions. In a 5/3 valve, the three positions are normal, straight, and cross way.

actuator

A device that converts pneumatic energy into mechanical energy. Actuators can be linear, rotary, or motor devices.

air preparation

The process of treating air for a pneumatic system. Air preparation usually involves filtering for contaminants, regulating for pressure, and lubricating for ease of component movement.

air receiver

A component that stores compressed air. In an air receiver, as the air is used, the pressure will drop unless the compressor can pump enough air to maintain the pressure in the receiver.

American National Standards Institute

ANSI. A private, nonprofit membership organization that administers and coordinates voluntary standards and systems in the U.S. private sector. The American National Standards Institute is one of the groups that sets the standards for symbols used in pneumatic schematics.

bidirectional

Moving in two directions. Bidirectional actuators have an output shaft that can move in two directions.

cam-operated

A method of mechanical valve actuation. Cam-operated directional control valves are able to stop or start at precise cylinder piston locations.

check valve

A pneumatic control valve that ensures air flow in one direction. Check valves prevent backflow.

compressor

A component that pressurizes ambient air and directs it into a pneumatic system. Compressors are powered by prime movers.

computer-aided design

CAD. A computer software program that aids in the automated design and technical precision drawing of a part, product, process, or building. Computer-aided design programs allow designers to access standard part and component drawings to evaluate how they can be used in a particular system.

condensation

The liquid that has been converted from a vapor or gas. Condensation collects on cold surfaces when the air is humid.

conductors

A component such as a pipe, tube or hose that conveys fluid throughout a fluid system. Conductors are represented by solid lines in a schematic.

connector

A symbol in a fluid schematic that represents a fitting. Connectors are indicated by a solid dot.

contaminants

Any foreign substance in a pneumatic fluid that causes a loss of efficiency or a breakdown in a fluid system. Contaminants include solids, liquids, gases, and forms of energy.

cross

A fitting that allows air to change directions. A cross joins pipe runs to anothers that run perpendicular and through the main run.

cycle

One complete revolution or rotation of a rotary component. A cycle may also be one complete extension and retraction of a linear component.

cylinder

A type of linear actuator that uses a piston to produce motion in a straight line. Cylinders physically contact a valving element to change its position during mechanical actuation.

diesel engine

An internal combustion engine fueled by a petroleum-based liquid. A diesel engine uses high temperatures caused by compression for ignition.

directional control valve

A fluid system component that determines the path air takes in a pneumatic system. Directional control valves are used to move actuators into various positions.

directional control valves

A fluid component that determines the path air takes in a pneumatic system. Directional control valves are used to move actuators into various positions.

directional control valves

DCV. A fluid component that determines the path air takes in a pneumatic system. Directional control valves are used to move actuators into various positions.

double shutoff quick disconnect fittings

A quick disconnect fitting with one valve located in the stud connected to the hose and another valve located inside the fitting component that attaches closest to the air supply. A double shuttoff quick disconnect fitting allows a conductor to be disconnected without losing system pressure.

double-acting cylinder

A cylinder with a port at each end supplied with compressed air for both the retraction and extension of the piston. A double-acting cylinder is used where high force is required in both directions of fluid travel.

drain line

A line that leads to a drain in a pneumatic system. A drain line is represented by a broken line with several breaks.

efficiency

A measure of the work output of a system versus the total energy input. An efficient system is able to convert a greater amount of the supplied energy into the intended useful work.

electric motor

A component that converts electricity into rotary mechanical energy. An electric motor is a type of prime mover for a pneumatic system.

energy triangle

An open triangle used in a pneumatic schematic diagram that indicates whether a device consumes or produces pneumatic energy. An energy triangle shows the direction of fluid flow in a device.

filter

A device used for limiting contamination by trapping very fine and fine particulate matter and separating this matter from air. A filter is a component of a filter, rugulator, lubricator unit.

filters

A device used for limiting contamination by trapping very fine and fine particulate matter and separating this matter from air. A filter is a component of a filter, regulator, lubricator unit .

fittings

A fluid component that connects, redirects, extends or terminates the run of a fluid conductor. A fitting can be a piece such as a coupling or an elbow.

fixed-displacement compressors

Having a fluid capacity that is not changeable. The symbol for a fixed displacement compressor is a circle with an open triangle at the top of the circle.

flexible line

Any working line that is designed to bend or flex. A flexible line is represented in a schematic by a U-shaped solid line.

flow control valves

Fluid component that controls the rate of air flow. Flow control valves make it possible to control other system variables like the speed of an actuator.

four-way, three-position valve

4/3 valve. A directional control valve with four passages and three positions. A four-way, three-position valve is used to control double-acting cylinder actuators.

gas engine

An internal combustion engine fueled by a petroleum-based liquid. Gas engines use spark plugs for ignition.

hoses

A type of pneumatic fluid conductor that joins other components usually in a non-linear fashion. Hose bends and flexes and is the most versatile pneumatic conductor.

inlet port

An opening on the side of a fluid system through which fluid enters the system. Multiple inlet ports can be included in one system.

internal combustion engine

A type of engine in which heat energy and mechanical energy is produced inside the engine. Internal combustion engines include gas turbines and types of diesel motors.

International Organization for Standardization

ISO. A nongovernmental organization based in Switzerland that establishes standards and guidelines for various products and processes. The International Organization for Standardization is one of the groups that sets the standards for symbols used in pneumatic schematics.

linear actuator

An actuator that directs force in a straight line. Linear actuators include double- and single-acting cylinders.

lines

A component that conveys fluid throughout a fluid system. Lines include pipe, tubes, and hoses.

load

The resitance to actuator movement. The load exerted on a cylinder actuator results in cylinder extension.

lubricant

A substance to reduce friction between two surfaces in relative motion. Common lubricants are oil and grease.

lubricator

A component that releases oil into certain portions of a pneumatic system to lubricate moving parts. A lubricator is a component of an FRL.

meter-in circuit

A speed control circuit that uses a flow control valve at the actuator inlet. A meter-in circuit controls actuator extension speed.

meter-out circuit

A speed control circuit that uses a flow control valve at the actuator outlet. A meter-out circuit controls actuator retraction speed.

needle valve

A valve that adjusts the flow of fluid in a range from fully on to fully off. The needle valve consists of a sharp conical obstruction that is extended or retracted to block or allow flow.

normally not passing

A valve position in which the valving element is unactuated and covering a port. A normally closed valve opens when it actuates.

normally passing

A valve position in which the valving element is unactuated and not covering a port. A normally open valve closes when it actuates.

passing lines

A line that is not connected to another at the point at which they cross. To indicate that the two lines are not connected, one line has a U-shape at the crossing point.

pilot line

A passage that transmits fluid pressure to control another device. Pilot lines are represented in a schematic by a wide dashed line.

pilot signal

The auxiliary fluid pressure used to actuate or control a component. Pilot signals actuate the pilot portion of a pilot-operated check valve.

pilot-operated directional control valve

A type of check valve that has an additional port for a pressure signal. Pilot-operated directional control valves allow operators to override normal check valve operation.

pipes

A type of fluid conductor that joins other components, usually in a straight line and on a permanent basis. Pipe can be made of metal or plastic.

piston rod

The movable part of a cylinder actuator that is attached to the piston. A piston rod is represented in a cylinder symbol as a straight line through the middle of the rectangle.

plug

A fitting that terminates a run by closing an end. A plug has OD threads and is represented in a schematic symbol by an X.

pneumatic circuit

A series of connected components that move compressed air through a system in order to perform work. Pneumatic circuits are designed using schematics.

ports

An interface that links one device with another. Ports, also called ways, are openings on a valve through which fluid can flow.

positions

The number of physical settings on a directional control valve. Valves can have two or more positions.

pressure control valves

A mechanism that controls the intensity of the flow of compressed air in a pneumatic power system. Pressure control valves regulate the amount of pressure in a pneumatic system.

prime mover

The component of a pneumatic system that powers the compressor. Common prime movers for pneumatic systems include electric or diesel-powered motors.

pushbutton directional control valves

A manual control device that actuates when pressed. Pushbutton directional control valves can be noramlly closed or normally opened.

quick disconnect fittings

A fitting that is designed to attach to a line quickly and efficiently. A quick connect fitting is often a one-piece fitting that is forced onto the end of a hose and locked into place.

receiver tank

A component that stores compressed air. Receiver tanks are also called air receivers.

reciprocating

To move back and forth repeatedly. The reciprocating movement of a piston rod in a cylinder actuator produces linear motion or force.

reducing valve

A pneumatic power device that maintains a reduced pressure in the system. Reducing valves are sometimes called air regulating or regulator valves.

regulator

A pneumatic device that monitors the pressure level of the air sent to downstream components. A regulator is a component of an FRL and is also called a separator.

regulator valve

A pneumatic power device that maintains a reduced pressure in the system. Regulator valves are sometimes called air regulating or reducing valves.

relief valve

An adjustable control valve that regulates pressure in a fluid system. The relief valve can shut off fluid flow when a desirable pressure is reached.

resistance

The opposition to a force, such as the weight of a load. Fluid takes the path of least resistance.

rotary actuator

An actuator that directs force in a circular motion. Rotary actuators are used in fluid systems to produce rotary mechanical force.

schematic

A document containing all the instructions necessary for building and maintaining a fluid circuit. A schematic with instructions for fluid systems contains a series of print symbols.

sequence valve

A normally closed pressure control valve that diverts fluid from a primary branch of the circuit into a secondary branch of the circuit after a critical pressure is reached. Sequence valves are typically used in circuits containing multiple actuators.

sequence valve

A pneumatic valve that actuates and allows air into a secondary system after a critical pressure is reached. Sequence valves, relief valves, and pressure reducing valves have symbols that have similar appearance.

shut-off valve

A valve that controls the on-and-off supply of fluid to or within a fluid system. A shut-off valve is represented in a schematic with two facing arrows.

single-acting cylinder

A pneumatic actuator that directs energy in one direction. In a single-acting cylinder, the working fluid acts on one side of the piston only.

straight through quick disconnect fittings

A quick disconnect fitting with no valves. Straight through quick disconnect fittings cannot be added or removed without first shutting off the air supply.

stroke

The action a piston takes when it moves in or out of a cylinder. The stroke of a piston is its length of travel.

tee

A fitting that allows air to change directions. A tee joins three runs.

tubes

A type of pneumatic fluid conductor that joins other components usually in a non-linear fashion. Tubing is made of thin wall steal or flexible plastic and is easily bent.

unidirectional

Moving in only one direction. Unidirectional actuators have an outlet shaft that can only move in one direction.

valves

A device that controls air in a pneumatic system. Valves are responsible primarily for controlling the direction, flow, and pressure of air as it moves through the system.

variable

Not fixed. A variable component can change its function based on the needs of the system.

variable feed circuit

A speed control circuit with a two-way directional control valve and a meter-out flow control valve located in parallel. A variable feed circuit results in varying speeds at different parts of the circuit.

variable-displacement compressors

Compressors having a fluid capacity that is changeable. Variable displacement compressors are indicated by a slanted arrow passing through the middle of the symbol.

ways

An opening on a valve through which fluid can flow; can also be called ports. Ways, also called ports, allow air into and out of a pneumatic system.

wear

The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

working line

An active line in a fluid system. A working line is represented in a schematic by a solid line.

wye

A fitting that allows fluid to change directions. Wye fittings run in one direction at 45° to the main run.