Pneumatic Valves
For precision and control
Introduction
The range of pneumatic valves is vast
To help select a valve they are placed in a variety of categories:
style
type
design principle
type of operator
function
size
application
For all of them, their basic function is to switch air flow
From the simplest function of switching a single flow path on and off, to the exacting proportional control of pressure and flow
Style
Style reflects the look of a valve range as well as the underlying design principle. Examples are XF, ISO Star and Super X
Type
Type refers to the valves installation arrangement for example sub-base, manifold, in line, and valve island
Operators
An operator is the mechanism that causes a valve to change state
They are classified as manual, mechanical and electrical
Shrouded
Button
Mushroom
Button
VALVE FUNCTION

Valve Function
Function is the switching complexity of a valve
Shown by two figures 2/2, 3/2, 4/2, 5/2, 3/3, 4/3 & 5/3
First figure is the number of main ports. Inlets, outlets, and exhausts excluding signal and external pilot supplies
Second figure is the number of states
A 3/2 valve has 3 ports, and 2 states, normal and operated.
Valve Function
Combination of valve function determines complexity of control circuit logic
Design
Design refers to the principle of operation around which the valve has been designed, for example, spool valve, poppet valve and plate valve
Valve Size
Size refers to a valve’s port thread.
For similarly designed valves the amount of air flow through the valve usually increases with the port size.
Port size alone however cannot be relied upon to give a standard value of flow as this is dependent on the design of the valve internals.
The port size progression M5, R1/8 , R1/4, R3/8 , R1/2, R3/4, R1.
M5
R1/8
R1/4
R3/8
R1/2
R3/4
R1
Application
Application is a category for valves described by their function or task
Examples of specialist valves are quick exhaust valve, soft start valve and monitored dump valve
Examples of standard valves are power valves, logic valves, signal processing valves and fail safe valves
A standard valve could be in any category depending on the function it has been selected for in a system

2/2 VALVE
2/2 POPPET VALVE
2 ports 2 positions

A 2/2 valve is usually used as a simple on/off function

Here the valve is in essence a plunger or poppet with a seal acting against a spring
1
2
12

3/2 VALVE
3/2 VALVE
3 ports 2 positions
A 3/2 valve is the next step up from the 2/2
The valve is not only just on or off it also allows another path through it to enable air to exhaust
It is available in both poppet and spool designs
The best way to show its function is in the operation of a single acting or spring return cylinder
3/2 VALVE PRINCIPLE
3/2 VALVE PRINCIPLE
Actuator Control (3/2 valve)
A 3 port valve provides the inlet, outlet and exhaust path and is the normal choice for control of a single acting cylinder
In the normal position produced by the spring, the valve is closed
In the operated position produced by the push button the valve is open
The push button must be held down for as long as the cylinder is outstroked
1
2
3
12
10
Actuator Control (3/2 valve)
A 3 port valve provides the inlet, outlet and exhaust path and is the normal choice for control of a single acting cylinder
In the normal position produced by the spring, the valve is closed
In the operated position produced by the push button the valve is open
The push button must be held down for as long as the cylinder is outstroked
1
2
3
5/2 VALVE
5/2 VALVE
5 ports 2 positions

A 5/2 valve is the next step up from the 3/2

The valve enables air passage to be swapped between two ports each with a corresponding exhaust path

The best way to show its function is in the operation of a double acting cylinder
Actuator Control (5/2 valve)
A five port valve provides an inlet port 1 that is switched between two outlet ports 2 and 4 each with an exhaust port 3 & 5
In the normal position produced by the spring 1 is connected to 2 with 4 to exhaust 5
In the operated position produced by pushing the button port 1 is connected to 4 with 2 to exhaust 3
Actuator Control (5/2 valve)
A five port valve provides an inlet port 1 that is switched between two outlet ports 2 and 4 each with an exhaust port 3 & 5
In the normal position produced by the spring 1 is connected to 2 with 4 to exhaust 5
In the operated position produced by pushing the button port 1 is connected to 4 with 2 to exhaust 3
12
14
1
5
3
4
2

Identification of the component parts of a typical 5/2 solenoid valve with spring return
(Sub-base not shown)
(1) Solenoid (15mm)
(2) Piston
(3) Spool with disc seals
(4) Valve body
(5) Return spring
(6) Alternative ports 2, 4
(7) Pressure indicator
(8) Manual override
(9) Electric connectors
3
4
5
6
7
8
2
1
9
Typical Valve
Poppet Valves
Poppet Valve 2/2
The Poppet valve is a simple and effective design used mainly in 2/2 and 3/2 functions
It has good sealing characteristics and can often be the choice for a supply shut off valve
A poppet seal has a butt action against a raised edged aperture
Illustrated is a 2/2 air operated poppet valve
Poppet Valve 3/2
Miniature 3/2 valve used for generating signals
The poppet seal will give long life (not subjected to sliding friction)
Supply to port 1 assists the spring to hold the poppet shut
Outlet port 2 is connected through the plunger to a plain exhaust port
When operated exhaust path sealed and poppet opened (flow 1 to 2)
1
2
3
Poppet Valve 3/2
Miniature 3/2 valve used for generating signals
The poppet seal will give long life (not subjected to sliding friction)
Supply to port 1 assists the spring to hold the poppet shut
Outlet port 2 is connected through the plunger to a plain exhaust port
When operated exhaust path sealed and poppet opened (flow 1 to 2)
1
2
3
Poppet Valve 3/2
Miniature 3/2 valve used for generating signals
The poppet seal will give long life (not subjected to sliding friction)
Supply to port 1 assists the spring to hold the poppet shut
Outlet port 2 is connected through the plunger to a plain exhaust port
When operated exhaust path sealed and poppet opened (flow 1 to 2)
1
2
3
Spool Valves
A long standing popular versatile design
Available in most functions 3/2, 3/3, 5/2, 5/3, etc.
Fully force balanced
Wide range of styles, sizes, operators and mounting arrangements
Suit a multiple range of applications
Spool Types
A spool has a number of major and minor diameters called lands and valleys
The lands seal with the valve bore and the valleys connect valve ports to control flow direction
Dynamic seal type has the seals on the spool
Glandless type have no sliding seals
Static seal type has the seals fixed in the valve bore
Disc Seals
A disc seal is a loose fit in the groove, with the outer diameter just in contact with the valve bore.
Under differential pressure the disc seal is pushed sideways and outwards to seal the clearance between the outer diameter of the piston and the valve bore
The slim profile gives low radial force therefore reducing friction
Spool Valve (dynamic seals)
This 5/2 valve has a spool fitted with disc seals
The seals move with the spool therefore they are called dynamic
Normal position: port 1 is joined to 4 and 2 is joined to 3
Operated position: port 1 is joined to 2 and 4 is joined to 5
Spool Valve (glandless)
This 5/2 valve has a matched spool and sleeve. The fit is so precise that seals between them are unnecessary
The tiny amount of air crossing the spool lands provides an air bearing
The result is low friction and long life
Spool Valve (static seals)
This 3/2 valve has a plain spool sliding within static seals
The O Ring seals are held in carriers fixed in the valve bore and positioned by spacers (not shown)
The larger O Rings seal the valve bore with the carriers
The smaller O Rings seal the carriers with the spool
Spool Valve (static seals)
This 5/2 valve has a plain spool sliding within static seals
The O Ring seals are held in carriers fixed in the valve bore and positioned by spacers (not shown)
The larger O Rings seal the valve bore with the carriers
The smaller O Rings seal the carriers with the spool
Balanced Spool
The pressure acting at any port will not cause the spool to move
The areas to the left and right are equal and will produce equal and opposite forces
Balanced spool valves have a wide range of application as any selection of pressures can be applied to the 5 ports. Single pressure and twin pressure supply versions shown
14
12
14
12
Overlap
Most spool valves are designed with a positive overlap
When the spool is in transit from the normal to the operated state port 2 will be closed before port 4 is opened (or 4 before 2)
If the spool is being moved slowly a negative overlap will cause pressure loss during the spool changeover and may even stall
14
12
14
12
Positive
overlap
Negative
overlap
Three Position Spool Valves
This type of valve has a normal state where the spool is in a mid position
The characteristic in the centre position is determined by the land spacings on the spool
The three types are:
All ports blocked
Open exhausts
Open pressure
2
4
Other Valve Designs
Plate Valves
Have no sliding synthetic rubber seals
The rotary slide (red) is ground flat with the base
Pressure supplied at port 1 pushes the plate down to seal, also supplies outlet port 2
The cavity in the plate connects outlet port 4 to exhaust port 3
When operated the plate swings to connect port 2 to exhaust 3 and 1 to 4
Versions 4/2 and 4/3 with detented centre position
Part movement of lever will give flow control
Pressure Switches (electrical)
This fixed value example uses a built in single acting cylinder to operate a standard changeover microswitch
The operating pressure is about 3 bar this needs to overcome the combined force of the cylinder and microswitch springs
Adjustable pressure switches are also available
Fixed
Adjustable
Pressure Switches (electrical) - Range
Logic “OR” Shuttle Valve
An air signal given to either the left hand port 1 or the right hand port 1 will result in an output at port 2
The sealing disc moves across to seal the exhaust signal line to prevent loss of signal pressure




1
2
1
1
2
1
1
1
2
Logic “AND” Shuttle Valve
A single air signal at either of the ports 1 will cause the shuttle to move and block the signal
If a signals are applied at both the left hand AND right hand ports 1 only one of them will be blocked the other will be given as an output at port 2
If the pressures are not equal the one with the lowest pressure is switched
Flow Regulation
By the use of flow regulators the outstroke speed and instroke speed of a piston rod can be independently adjusted
Speed is regulated by controlling the flow of air to exhaust
The front port regulator controls the outstroke speed and the rear port regulator controls the instroke speed
Flow Regulator
Uni-directional, line mounted adjustable flow regulator
Free flow in one direction
Adjustable restricted flow in the other direction
Flow Regulator
Uni-directional, line mounted adjustable flow regulator
Free flow in one direction
Adjustable restricted flow in the other direction
Banjo Flow Regulator
Designed to fit directly in to cylinder ports, so placing adjustment at the appropriate cylinder end
Two types:
One to give conventional flow restriction out of the cylinder and free flow in (as illustrated)
The other type to give restricted flow in to the cylinder and free flow out (not illustrated)
Flow Regulator - Core Range
T1000 Series Uni-Directional Flow Regulator
10TA Series Banjo Flow Regulator
Quick Exhaust Valve
In some applications cylinder speed can be increased by 50% when using a quick exhaust valve
When operated, air from the front of the cylinder exhausts directly through the quick exhaust valve
The faster exhaust gives a lower back pressure in the cylinder therefore a higher pressure differential to drive out the piston rod
T70 Series
Quick Exhaust Valve
1
2
Port 2 is connected directly to the end cover of a cylinder
Port 1 receives air from the control valve
Air flows past the lips of the seal to drive the cylinder
When the control valve is exhausted, the seal flips to the right opening the large direct flow path
Air is exhausted very rapidly from the cylinder for increased speed
1
2
Quick Exhaust Valve
1
2
Port 2 is connected directly to the end cover of a cylinder
Port 1 receives air from the control valve
Air flows past the lips of the seal to drive the cylinder
When the control valve is exhausted, the seal flips to the right opening the large direct flow path
Air is exhausted very rapidly from the cylinder for increased speed
1
2
Filtration and Lubrication
Valves should be supplied with clean dry air with or without lubrication
Water droplets and solid particle removal using a standard 40µ filter will normally be sufficient
Valves are greased when manufactured, this alone will give a long lifetime to the seals and valve bore
If the air carries additional lubrication from a micro-fog lubricator the normal life of the valve will be extended
If air is process dried to a very low dewpoint lubrication is necessary
For extreme high or low operating temperatures lubrication is necessary
Solenoid Valves
Solenoid valves are electro-pneumatic relays
The state of an electrical input controls the state of a pneumatic output
Solenoid valves are the interface between electronic control systems and pneumatic power
Types are:
Direct acting
Pilot operated
Proportional
Principle of operation
The double poppet armature is held by a spring against the inlet orifice sealing the supply at port 1
Outlet port 2 is connected to exhaust port 3
When the coil is energised the armature is pulled up closing the exhaust orifice and connecting the supply port 1 to the outlet port 2
1
2
3
1
2
3
Principle of operation
The double poppet armature is held by a spring against the inlet orifice sealing the supply at port 1
Outlet port 2 is connected to exhaust port 3
When the coil is energised the armature is pulled up closing the exhaust orifice and connecting the supply port 1 to the outlet port 2
1
1
2
3
Manual Override
To test during set up or maintenance without energising the coil
In position 0 the armature is in the normal closed position
Turning the cam with a screwdriver to position 1 lifts the armature to operate the valve
Important to return to position 0 before the machine is restarted
1
2
0
1
3
1
2
3
Manual Override
To test during set up or maintenance without energising the coil
In position 0 the armature is in the normal closed position
Turning the cam with a screwdriver to position 1 lifts the armature to operate the valve
Important to return to position 0 before the machine is restarted
0
1
1
2
3
1
2
3
Direct Acting Solenoid Valves
The design is a balance between quantity of air flow (orifice diameter) and electrical power consumed
The higher the air flow, the larger the inlet orifice
The larger the orifice, the stronger the spring
The stronger the spring, the greater the power of the magnetic field
The greater the field, the higher the electrical power consumption
The desire for low electrical power for direct interface with PLC’s and other electronic devices makes this design of valve ideal
The range offers a variety of orifice sizes and electrical power ratings
This design is used alone and as an integrated pilot to operate larger valves