Valves Non-return valves Flow control valves Pressure control valves Directional control valves Non-return valves Flow control valves Pressure control valves Shut-off valves

Directional control valves Directional control valves are devices which influence the path taken by an air stream. Normally this involves one or all of the following: opening the passage of air and directing it to particular air lines, cancelling air signals as required by blocking their passage and/or relieving the air to atmosphere via an exhaust port.

Directional control valves The valve is described by: Number of ports or openings (ways): 2-way, 3-way, 4-way, etc. Number of positions: 2 positions, 3 positions, etc. Methods of actuation of the valve: manually actuated, mechanically actuated, pneumatically actuated, electrically actuated. Methods of return actuation: Spring return, air return, etc.

Directional control valves: symbol development

numbering system used to designate directional control valves

Actuation of valves

Actuation of valves

3/2-way valve,normally closed,ball seat

3/2-way valve: disc seat normally closed,

3/2-way valve: disc seat normally open,

3/2-way valve single pilot, normally closed, with spring return,

Pilot valve: left unactuated, right actuated

3/2-way roller lever valve, internal pilot, Normally closed Normally open

4/2-way valve, disc seat, unactuated actuated

4/3-way plate slide valve, mid-position closed

5/2-way valve: longitudinal slide principle

5/2-way double pilot valve, suspended disc seat, flow from 1 to 2 flow from 1 to 4

5/3-way valve, neutral position variations

Non-return valve and its derivatives Check valve Shuttle valve Dual-pressure valve Quick exhaust valve

Non-return valve

Dual pressure valve: logic AND function

Shuttle valve: logic OR function

Quick exhaust valve: flow from 1 to 2 Quick-exhaust valves are used to increase the piston speed of cylinders by reducing the resistance to flow, the air is expelled to atmosphere close to the cylinder via a large orifice opening

Flow control valves

Throttle valve Flow control valves influence the volumetric flow of the compressed air in both directions normally adjustable used for speed control of cylinders

One-way flow control valve air flow is throttled in one direction only A check valve blocks the flow of air in the bypass

Fundamentally, there are two types of throttling circuits for double-acting cylinders: Supply air throttling Exhaust air throttling

Mechanically adjustable one-way flow control valve

Pressure valves They are divided into the three groups: Pressure regulating valve Pressure sequence valve Pressure limiting valve

Pressure regulating valve

Adjustable pressure sequence valve

Pressure relief valves Pressure limiting valve Pressure relief valves protect the compressor and components by setting the maximum sys tem pressure within safe working limits.

Combinational valves Components of different control groups can be combined into the body of one unit with the features, characteristics and construction of a combination of valves, such as:. Time delay valves: for the delay of signals Two-hand start unit Pulse generator Stepper modules Memory modules

Time delay valve: normally closed

Time delay valve: normally open

Time response of circuits with time delay valves

Time response of circuits with time delay valves

Time response of circuits with time delay valves

Pulse generator, Stepper modules Memory modules which incorporate directional control valve functions and logic elements to perform a combined processing task. This reduces size, cost and complexity of the system