كورس التدريب على الأنظمة النيوماتية من شركة هافنر - Pneumatic Training Course of HAFNER Pneumatik

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كورس التدريب على الأنظمة النيوماتية من شركة هافنر
Pneumatic Training Course of HAFNER Pneumatik

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Chapter 1 - Basic Concepts of Pneumatics
Chapter 2 - The general design of a pneumatic system and its components
Chapter 3 - Grouping and construction of control valves
Chapter 4 - Structure and function of directional valves
Chapter 5 - Schemes of directional control valves - ISO-symbols
Chapter 6 - Explanation of the Hafner type numbering system
Chapter 7 - The pneumatic cylinder - part 1
Chapter 8 - The pneumatic cylinder - part 2
Chapter 9 - The basics of air preparation
Chapter 10 - Air Preparation Units
Chapter 11 - Valves and Actuators with the NAMUR-Interface
Chapter 14 - Solutions for challenging environment - part 1
Chapter 15 - Solutions for challenging environment - part 2
Chapter 16 - Explosion protection
Chapter 1:
Basic Concepts of Pneumatics
Right of authorship: the content of the training (wording, drawings, pictures) are owned by the author. Any utilization except for
individual use is allowed only after permission of the author.
What is pneumatics?
Pneumatics is the utilization of compressed air in science and industry in order to perform mechanical
work and control. We can either talk about pneumatics or pneumatic systems.
In this course we define pneumatics as the control and transfer of power by using compressed air.
Advantages and Disadvantages of Compressed Air
Pneumatic systems have numerous advantages, the most important of which are:
 The medium, compressed air, can be easily extracted from our environment. There is no lack or
shortage of it.
 After usage the compressed air goes back to its original condition. It can be released into the
environment.
 Air can be compressed flexibly. Therefore it is ideal for absorbing shocks and vibrations.
 The distribution of compressed air can be easily handled with pipes and hoses.
 Compressed air can be used in fire- and explosion-hazardous environment.
 Both its pressure level and volume can be regulated quite easily. Therefore the energy brought to
the actuator can also be controlled quite easily and within broad parameters.
 The usage of pneumatic components is easy as well as their maintenance. Their functionality is
generally very reliable.
Besides these advantages there are some typical disadvantages:
 Compressed air – depending on its application – needs some preparation, especially filtration and
drying.
 Because of pricy electric energy and the limited efficiency of compressors, compressed air is a
relatively expensive means of energy.
 Because of air's compressibility, the precise and load-independent positioning of the actuator(s)
is not possible.Chapter 1:
Basic Concepts of Pneumatics
Physical Fundamentals and Units of Measurement (metric system)
The SI-system of units is based on numerous basic and derived units of measurement. We do not cover
that in detail. [International System of Units, short SI (french): Système international d’unités]
Units of measurement that are relevant in pneumatics:
 Meter – m (length / distance)
 Kilogram – kg (weight / mass)
 Second – s (time)
 Kelvin – K (temperature)
Derived units that are used:
 Newton – N (force)
 Pascal – Pa (pressure)
Force
Force is any interaction that, when unopposed, will change the motion of an object. In other words, a force
can cause an object with mass to change its velocity (acceleration, change of shape). Force can also be
described as a push or pull. It is a vector quantity consisting of magnitude and direction.
 Symbol: F
 Unit: Newton
 Unit symbol: N
 In SI-based units:Chapter 1:
Basic Concepts of Pneumatics
Pressure
Pressure is the force applied perpendicular to the surface of an object per unit area over which the force is
distributed.
 Symbol: P
 Unit: Pascal
 Unit symbol: Pa
 In SI-based units:
For measuring pressure, the following multipliers are common:
1 kPa (Kilopascal) = 1,000 Pa
1 MPa (megapascal) = 1,000,000 Pa
In pneumatics we normally use the unit bar.
1 bar = 100,000 Pa = 0.1 MPa = 0.1 N/mm2
1 mbar = 0.001 bar
1 nbar = 0.000000001 bar
In some countries such as the USA or Great Britain the unit psi (pounds per square inch) is also still in use.
1 psi = 0.07 bar (rounded)
Standard atmospheric pressure is the pressure of the air on sea-level, which equals 1 atm
(atmosphere).
1 atm = 101,325 Pa = 1013.25 mbar (Millibar) or hPa (Hektopascal)
This unit is normally used in meteorology. Rounded and precise enough for most applications:
1 atm = 1 barChapter 1:
Basic Concepts of Pneumatics
Excess pressure or gauge pressure is the value of pressure above standard atmospheric pressure. It is
also called relative pressure.
In case absolute pressure is measured, standard atmospheric pressure is included. The scale starts at 0
Pa = total vacuum.
Absolute pressure = standard atmospheric pressure + gauge pressure (relative pressure)
Expressions:
 P(a) : Absolute pressure
 P(t) : Excess/Gauge pressure
 -P(t) : Vacuum
Examples:
 6 bar excess pressure = 6 bar(t)
 7 bar absolute pressure = 7 bar(a)
 0.7 bar absolute pressure = 0.7 bar(a) or -0.3 bar(t)
The expressions „excess pressure“ and „vacuum“ refer to a value larger or smaller than standard
atmospheric pressure.
There are different levels of vacuum:
Standard atmospheric pressure 101325 Pa = 1.01325 bar = 1 bar
Low vacuum (rough vacuum) 100 kPa ... 3 kPa = 1 bar ... 0.03 bar
Medium vacuum 3 kPa ... 100 mPa = 0.03 bar ... 0.001 mbar
High vacuum 100 mPa ... 1 μPa = 0.001 mbar ... 0.01 nbar
Ultra-high vacuum 100 nPa ... 100 pPa
Extremely high vacuum < 100 pPa
Outer space 100 μPa ... < 3 fPa
Perfect vacuum 0 Pa
In pneumatics we use the unit bar for vacuum as well as for excess pressure.
Unless there is any further indication, we normally work with excess pressure = relative pressure.Chapter 1:
Basic Concepts of Pneumatics
In practice:
We will calculate the force of a cylinder with a defined diameter at a specific pressure.
According to Pascal's law:
 p: Pressure [Pascal]
 F: Force [N]
 A: Surface [m2]
How much force does a cylinder with a diameter of 40 mm apply at a pressure of 6 bar?
In order for us to use the correct units of measurement, we will use the unit Mpa for pressure. This
conforms to N/mm2. For the diameter we will use mm.
Diameter of the piston of the cylinder
d = 40 mm
The surface of the piston is to be calculated as a circular area:
In numbers:
At a (relative) working pressure p = 6 bar = 0.6
Thus:
In numbers:
This is the theoretical force. In practice we have to take losses due to friction into consideration
(approx. 5%).
Thus: A cylinder with a piston with the diameter of 40 mm at 6 bar pressure generates approx. 716 N
force. This translates into the ability to lift approx. 73 kg.Chapter 1:
Basic Concepts of Pneumatics
How much force does the same cylinder generate into the opposite direction
(pulling its rod back in)?
Due to the piston rod itself, the surface to push the rod out is larger than the surface to pull it
back in. The missing surface hast to be deducted.
D = diameter of piston (40 mm)
d = diameter of piston rod (16 mm)
After deducting 5% as loss for friction we find that the pulling force of the same cylinder is approx.
601 N, in comparison to the 716 N pushing force.
Chapter 2:
The General Design of a Pneumatic System
and its Components
Right of authorship: the content of the training (wording, drawings, pictures) are owned by the author. Any utilization except for
individual use is allowed only after permission of the author.
The route of compressed air from its generation to the consumer
In pneumatics compressed air is utilized for performing mechanical work and for control. In order
to do so we need different equipment to generate, treat and handle compressed air.
The graph displays the route of the environmental air from the compressor to the consumer of
compressed air:
When designing a pneumatic system, typically the individual elements are distributed spatially depending
on their task. Although they are spatially separated, they are still connected systematically.
Particles (solid)
Air filter
Compressor
Air dryer
Tank for compressed air
Including safety-valve and
condensate drain
Compressed air network
Air preparation
Filter, regulator, lubricator,
starter valve
Pneumatic tubes
and fittings
Valves
Control valves
Air
W Engine E
Thermal energy
Generation of
compressed air
Actuators W
Cylinders ConsumerChapter 2:
The General Design of a Pneumatic System
and its Components
Generation and transportation of compressed air
We will have a brief look at the following elements of pneumatic systems.
Air filter
The air filter is integrated into the intake of the compressor. It prevents large, polluting particles on the
outside from entering the air system. Through filtration, a major portion of unwanted particles can be kept
out of the system.
Compressor
The task of the compressor is to compress the air to the required pressure and in the required volume.
The engine consumes energy. The compressor transforms this energy and stores it as compressed air.
Unfortunately losses are severe. The screw compressor is the most common type. Piston compressors
are used as well.
Air Dryer and Pre-Filters
When air is compressed it loses its ability to hold water. Therefore water remains when air is compressed.
As this water, the condensate, would be disturbing the following processes, it needs to be removed from
the pneumatic system. In a so called refrigeration dryer the water condensates and can be removed.
There are also absorption dryers in which the water is absorbed by special materials.
The compressed air is also regularly polluted by oil from the compressor or particles that have not been
caught by its intake filter. Those can cause problems in the pneumatic system, e.g. in the valves. Often
times they are separated from the compressed air by using a central filter unit.
We will cover air preparation in a later chapter of the course in detail.
Tanks
Tanks are used for storing compressed air temporarily. The storage guarantees that the demand can be
covered securely. Often times you can find a condensate drain at the tank. The condensate can then drain
off through a valve. The drain is actuated manually or automatically.
Compressed Air Network
The task of the network is to distribute the compressed air from the compressor to the user(s). The size of
its tubes is important because it has a significant influence on the security of supply.
In general:
 The longer the tubes the bigger the loss of pressure due to friction.
 The more users are connected the bigger the orifice of the tubes needs to be.Chapter 2:
The General Design of a Pneumatic System
and its Components
The Quality of Compressed Air
The operational safety of an air system is directly linked to the quality of the compressed air.
In general:
‐ A „better“ = cleaner air increases the operational safety of the system as the risk of blockage and
wear is reduced.
‐ Please take into consideration that the manufacturers of the components and devices
communicate the quality requirements for the air in use. Air quality is standardized by
ISO 8573-1:2010.
Contaminants and purity classes – the standard ISO 8573-1
Particles, oil and water are the most important contaminants in compressed air. For each of these three
there are purity classes in the standard.
ISO 8573-1:2010
Class
Particles Water Oil
Maximum number of particles of
the following size [µm] / m³ of
compressed air
Concentration
Pressure dew
point
°C
Content of
liquid
[g/m3]
Total content
(liquid, aerosol,
gas)
[mg/m3]
0,1 ... 0,5
µm
0,5 ...1 µm 1 ... 5 µm [mg/m3]
0. By definition of the user, less contamination than class 1
1. ≤ 20 000 ≤ 400 ≤ 10 - ≤ -70 - ≤ 0,01
2. ≤ 400 000 ≤ 6000 ≤ 100 - ≤ -40 - ≤ 0,1
3. - ≤ 90 000 ≤ 1000 - ≤ -20 - ≤ 1
4. - - ≤ 10 000 - ≤ +3 - ≤ 5
5. - - ≤ 100 000 - ≤ +7 - -
6. - - - ≤ 5 ≤ +10 - -
7. - - - 5 ... 10 - ≤ 0,5 -
8. - - - - - 0,5 ... 5 -
9. - - - - - 5 ... 10 -
X - - - > 10 - > 10 > 5
Purity classes in accordance to standard ISO 8573-1
For example: ISO 8573-1:2010 [4:3:3]
Particles = class 4, water = class 3, oil = class 3Chapter 2:
The General Design of a Pneumatic System
and its Components
High quality compressed air is (by definition) 100% oil free = class 0. Air of this quality is required in
medical applications, the food-industry and electronic industry.
Let's not forget air pollution!
When designing a compressed air system take environmental factors into consideration! Air pollution is
concentrated when the air is compressed. Industries with high emissions in the neighbourhood can be of
severe impact. Other factors such as a high concentration of ozone can influence your system and
eventually harm seal materials as well. Never ignore climatic conditions. The dryer has to be more capable
in a hot and humid environment.
Therefore it is important that…
 we know what kind of air is sucked into our compressor
 we make sure that after compressing the air is dried, cleaned and potential oil is separated from it
 we consider the influence of the environmental factors (climate and pollution)
 components with very high loads are lubricated where necessary
.. in order to guarantee a safe operation.
The most important elements at the machine-level
The sketch exemplifies a pneumatic system at the machine-level:
The individual elements are represented by ISO-symbols, which are connected with lines. They display
the route of the compressed air. In order to get a better overview we position the air preparation on the
bottom and the actuators on the top of the drawing.
Cylinder
Flow regulators
Control valve
Air preparation units, short-form: FRLChapter 2:
The General Design of a Pneumatic System
and its Components
We can form logic groups of the elements – as you can see in the drawing above:
 Air preparation
o Filter
o Pressure regulator
o Lubricator
o Switch-on valve
o Soft start
o …
Control valves
o Directional control valves
o Other types of control valves
o Logic elements
o …
Flow control valves, check-valves
o Flow control valves, uni- or bidirectional
o Exhaust flow-regulators
o Non-return valves = check valves
o Function fittings
o …
 Actuators, cylinders
o Cylinders
o Rodless cylinders
o Rotary actuators
o …
 Tubes and fittings
o To distribute compressed air and to connect different componentsChapter 2:
The General Design of a Pneumatic System
and its Components
Hafner-Pneumatik distributes its products under the following groups and categories:
 HAFNER Valves
 Cylinders
 Process Valves
 Air Preparation Units
 Fittings
 Tubes
We will study the function of all these groups in later chapters.Chapter 3:
Grouping and construction of control valves
Right of authorship: the content of the training (wording, drawings, pictures) are owned by the author. Any utilization except for
individual use is allowed only after permission of the author.
Pneumatic valves control pneumatic actuators such as cylinders, rotary actuators
etc. The valves control the direction, speed (by flow) and force (by pressure) of the
actuator.
We can form the following groups of valves by distinguishing between their functions:
The ISO-symbol tells you a valve's function. By “reading” the symbol correctly you get hints of how to use
it.
 Control of the effective direction of actuators – Directional control valves
These valves control the actuators directly or they control other control valves.
Application example: Control of a double acting cylinder by a 5/2-way hand-lever valve:
 Control of the amount of compressed air into / out of the actuator – Flow regulators
These valves limit the amount of air flowing through them.
Application example: We can add two uni-directional flow regulators to the example above.
They control the speed of the cylinder by limiting the amount of air that is exhausted from it.
Limiting the exhaust air is generally the better way in comparison to limiting the air-supply, since it
results in a smoother movement of the piston.Chapter 3:
Grouping and construction of control valves
 Pressure regulation – Pressure regulators
These products keep the secondary pressure at a distinct level when the incoming pressure is
volatile. As you know from Chapter 1, pressure determines the force of an actuator.
Please note: The secondary pressure can only go as high as the entry pressure.
Application example: We can add a pressure regulator to the example above. That way we can
control the maximum force of the cylinder by regulating the maximum pressure of the system
behind the pressure regulator. A pressure gauge indicates the secondary pressure.
 Quick exhaust – Quick exhaust valves
These valves are designed to exhaust the air from an actuator quickly, which increases the speed
of the piston.
Application example: We can replace one of the flow-regulators with a quick exhaust valve in the
example above. By doing so, the air in the chamber of the cylinder exhausts directly into the
environment and the air does not flow back through the control valve. This maximizes the pushspeed of the piston.Chapter 3:
Grouping and construction of control valves
 Logic elements
These valves are not used for directly controlling actuators but to set up pneumatic control
systems. Typical elements are: AND, OR, YES, NO. With these functions taken from the Boolean
algebra, most (mathematical) problems can be solved.
Application example: A single acting cylinder has to be controlled by either one OR the other of
two 3/2-way valves. In case you want to make sure that the cylinder only moves if BOTH 3/2-way
valves are actuated, replace the OR-gate by an AND-gate.
 Non-return valves = Check valves
Check valves provide a free flow into only one direction. If compressed air comes from the
opposite side, it is blocked.
Application example: In order to save compressed air on a double acting cylinder that is „doing
work“ in only one direction, the air-pressure that is needed to return the piston can be reduced
significantly. A second pressure regulator is required for that. This regulator has to have a by-pass
when the air exhausts from the relevant cylinder-side. The “one-way” by-pass is realized by using
a check-valve.
A typical application of a check-valve is the combination with a flow-regulator (see above
example). This product is called Uni-directional flow regulator. In one direction the air can by-pass
the regulator, whereas in the other direction the free flow is blocked and the air is forced to go
through the regulator.Chapter 3:
Grouping and construction of control valves
General information on directional control valves
Directional control valves are the most important elements of a pneumatic control system.
In any fluid application they are utilized to define the route of the medium. They are used to control
cylinders or other actuators. They can also control the movement and the direction of pneumatic motors
or control other control valves.
Directional control valves are not designed for regulating pressure or flow.
We can form categories of directional control valves as follows:
 By basic design
o Spool valves
o Poppet valves
 By actuation
o Mechanically actuated
o Manually actuated
o Pneumatically actuated
o Electrically actuated (solenoid valves)
 By the number of (stable) positions
o One stable position: single solenoid / single pilot valve or spring return valve.
o Two stable positions: double solenoid / pilot valve, lever valve indexed.
o 3-positions valves.
 Flow in basic position
o For 2/2-way and 3/2-way valves with spring return
 Normally open
 Normally closed
o For 3/3-, 4/3- and 5/3-way valves
 Centre closed
 Centre exhausted
 Centre pressurizedChapter 3:
Grouping and construction of control valves
 By the number of ports / positions
o 2/2-way (2 ports, 2 positions)
o 3/2-way (3 ports, 2 positions)
o 3/3-way (3 ports, 3 positions)
o 4/2-way (4 ports, 2 positions – only one exhaust port)
o 5/2-way (5 ports, 2 positions)
o 4/3-way (4 ports, 3 positions – only one exhaust port)
o 5/3-way (5 ports, 3 positions)
The most common types are in bold. Besides the ones mentioned above there are more possibilities for
special applications (e.g. 5/4-way valves, 7/3-way valves, ...)Chapter 3:
Grouping and construction of control valves
Basic design of directional control valves
Let's have a look at the basic difference between spool and poppet valves.
One of the basic elements of any directional control valve is the valve body. The body holds the parts of
the valve together. The second important element is the moving part(s), which blocks and opens ports, or
connects two or more of them with each other.
The closing element can either be a spool or a valve disk. Therefore we distinguish between:
 Spool valves and
 Poppet valves.
Spool valves
In spool-valves the different ports are connected by axially moving a cylindrical spool.
The drawings below display the closed and open position of a spool valve.
Poppet valves
In a poppet valve a valve-disc is pushed onto the valve-seat. When the disc is released again, the valve
opens.
The drawings below display the closed and open position of a poppet valve.Chapter 3:
Grouping and construction of control valves
Grouping directional control valves by modes of actuation
Actuation means the source of energy which moves the closing element (disc or spool):
 mechanically a part of a machine pushes onto a stem or a roller-lever of the
valve
 manually a human being operates a knob or a lever
 pneumatically a pressure signal moves the spool or the disc
 electrically / solenoid the plunger of a solenoid opens a poppet valve (lifts the disc
on the seat)
 solenoid pilot the plunger of a solenoid opens a poppet valve, the moves a spool
or a second (larger) disc.
Solenoid valves can be distinguished as:
 Direct acting valves
The (poppet) valve is directly opened by electric energy.
 Piloted valves (solenoid pilot spool valves)
The main valve is generally a spool valve. The spool is driven by compressed air. This pilot air is
controlled by a poppet valve. Part of the energy used to control the valve is supplied by the
medium.
The method of using the energy of the medium is not only used in spool valves. Poppet valves or
diaphragm valves can be designed like that, too.
 Solenoid valves with external pilot feed
This function is very similar to the solenoid pilot valves. The difference is that it's not the energy of
the medium of the main valve which is used to move the spool, but instead there is an additional
port for compressed air. The solenoid system is separately supplied through that.Chapter 3:
Grouping and construction of control valves
Valves are available with different numbers of (stable) positions:
 One stable position
As soon as the actuation is gone (i.e. the pneumatic signal or electric energy is cut, the button is
released) the spool or the disc is forced back into its basic position. This movement can be
powered either by a mechanical spring or by the energy of the medium (“air spring”).
 Two stable positions
Whenever the actuation stops, the spool or disc stays in its current position until there is an
actuation into the opposite direction.
 3 positions valves
The spool / disc can generate 3 different kinds of connections of the ports (very rarely more).
Manually actuated valves can be designed with 3 stable positions or in a way that the spool is
driven into centre position by mechanical springs. Valves that are actuated in other ways are
normally only available with a basic position.
Description number of ports and number of positions:
The following will only offer a first glance at this topic. You will receive more information in a later chapter.
The valve is called X/Y-way valve, where X represents the number of ports in the main valve and Y the
number of positons.
Example:
3/2-way valve
The valve has 3 ports and
2 positions.
Number of positions
Ports
In Europe you will find mostly 2/2-, 3/2-, 5/2- and 5/3-way valves. In the USA 4/2 and 4/3-way valves
are common.Chapter 3:
Grouping and construction of control valves
Application examples, distinguishing between solenoid valves:
Direct acting solenoid valve (e.g.: MH 311 015)
Basic design: poppet valve
Control: solenoid - direct acting
Number of ports / positions: 3/2-way
Stable position(s): one, single solenoid
Basic position: normally closed
The electric energy consumed by the coil is directly used to open the
valve disc.
Solenoid-pilot valve (e.g.: MH 310 701)
Although there are basically 2 valves inside this product - the
main valve and the pilot valve -, the characteristics of the
main valve define the product.
Basic design: Main valve = spool valve
Pilot valve = poppet valve
Control: solenoid-pilot
Number of ports / positions: 3/2-way
Stable position(s): one, single solenoid
Basic position: normally closed
The electric energy consumed by the coil is used to operate the
plunger in the pilot valve. The energy for the main valve is given by
the medium.
Solenoid valve with external pilot feed (e.g.: MEH 311 701)
There are 2 valves inside this product as well.
Once again the characteristics of the main valve define the product:
Basic design: Main valve = spool valve
Pilot valve = poppet valve
Control: solenoid-pilot
Number of ports / positions: 3/2-way
Stable position(s): one, single solenoid
Basic position: normally closed
The electric energy consumed by the coil is used to operate the
plunger in the pilot valve. The energy for the main valve is fed into the
valve through an additional port in its head. Therefore the operation
of the spool is independent from the medium's pressure applied to
the main valve.
In the next chapter we will have a more detailed look at the function of directional control valves.
External pilot feed portChapter 4:
Structure and function of directional valves
Right of authorship: the content of the training (wording, drawings, pictures) are owned by the author. Any utilization except for
individual use is allowed only after permission of the author.
Structure and function of directional valves
1. Structure of direct acting solenoid valves
Direct acting solenoid valves are typically poppet valves. The movement of the valve disk opens and
closes the route of the medium.
The graphic below shows the cross section of an electrically actuated direct acting 3/2-way valve.
Actuation: electrically (solenoid valve)
The electric current generates a magnetic field which is used to lift
the plunger in the operator tube. Without current the plunger is
pushed down by a mechanic spring. In a 3-way valve the plunger
has two seals = valve discs, one on the bottom and one on the top.
They are marked in green.
Control type: direct acting
The force of the magnetic field is used to open the valve. There is
no other source of energy, including the medium.
Stable positions: one
The valve has one stable position defined by the mechanic spring
holding the plunger. When the electric signal is applied the valve
switches. Once it is absent, the valve switches back.
Basic position: normally closed
Without electric energy the media is blocked at port 1, thus the
valve is closed.
Number of ports and positions: 3/2-way
The valve has 3 ports and 2 positions.
Typical features of direct acting valves:
 Orifice size: DN 1,2 … 3 mm
 Operating pressure: PN up to 10 bar
 Nominal flow: QN 10 … 210 l/min
 Port sizes: M5, G1/8“ and G1/4“
 Power consumption: 3W / 5VA and more
This type of valve offers a small orifice size at 10 bar. Therefore the flow is relatively low. If a larger orifice
size is required, the power consumption increases at the same rate.Chapter 4:
Structure and function of directional valves
Function:
Pressure supply is connected to port 1. The force of the spring pushes the valve disk onto the seat and
closes port 1. This force has to be larger than the force of the medium. In basic position the valve is open
from port 2 to 3. (This is the normal basic position of a 3/2 way normally closed valve.)
As soon as sufficient electric current is applied to the coil the valve disc is lifted from the valve seat of
port 1. Simultaneously a second valve disc closes the seat between ports 2 and 3. Therefore the medium
is free to flow between 1 and 2. The route between 2 and 3 is blocked.
As soon as the electric current is absent, the valve switches back into basic position (1 closed, open from
2 to 3).
Important! Direct acting solenoid valves only use the electric energy provided to lift the plunger against
the force of the mechanic spring. Therefore this type is mainly used for valves with smaller orifice size. The
force of the spring has to be larger than the force of the medium below the seat and the generated force
of the coil larger than the one of the spring.
How are direct acting valves with larger orifice sizes designed?
The graph below shows the cross section of an electrically actuated direct acting 2/2-way valve.
The technical characteristics of this valve with large orifice
size are:
 Operating pressure (max): PN 2,5 bar
 Nominal flow: QN 1.670 l/min
 Port size: G3/8“ and G1/2“
 Power consumption: 16W / 20VA
 Orifice size: DN 10 mm
The power consumption of this valve is 16W/20VA, which is
relatively high. The heat emission will be significant so the coil
needs to be large.
In order to overcome the mechanics explained above:
“The larger the orifice (DN) or the required pressure range, the
stronger the spring needs to be in order to close the seat” the
design here is different:
Pressure is not applied below the plunger but at the top. Therefore
the valve can work with a softer (weaker) spring supported by the
force of the medium. The applied electric force needs to overcome
these 2 forces (spring plus medium) in order to open the valve. As
mentioned above the required amount of electric energy is
significant.
We learn from this example that if valves with a large orifice used at
high pressure are required, we need to use a second source of
energy. This energy is typically coming from the medium.Chapter 4:
Structure and function of directional valves
2. Structure of pilot operated spool valves
Pilot operated valves (spool valves) consist of 2 parts. The graphic below shows the cross section of a 5/2-
way single solenoid valve.
The pilot valve is a 3/2-way poppet valve. The main valve is a 5/2-way spool valve.
The characteristics of the main valve are:
Basic design: spool valve
The axial movement of the spool opens and closes the route between distinct ports in the valve. This
movement is provided by the energy of the compressed air.
Actuation: electrically (solenoid valve)
The pilot valve is electrically actuated. For its function see the explanation above.
Control: piloted
The pilot valve controls the pilot air which is taken from port 1 of the main valve and internally supplied to
the pilot valve. Port 2 of the pilot valve is connected to the top of the spool, triggering its movement.
Number of stable positions: one
The valve has one stable position. As soon as the electric signal is absent, the pilot valve exhausts and the
spool is pushed into basic position by either a mechanic spring or the force of the medium feed from port
1 of the main valve to the back-end of the spool (called air spring). Sometimes a combination of both
types of springs is used.
Basic position: Typically a 5/2-way valve is open from 1 to 2 and from 4 to 5. There is no such thing as
“normally closed” or “normally open” for 5-way valves.
Number of ports and positions:
5/2, the valve has 5 ports and 2 positions.Chapter 4:
Structure and function of directional valves
The typical features of Hafner spool valves are:
 Orifice: DN 3 … 18 mm
 Operating pressure: PN 10 bar
 Nominal flow: QN 200 … 6.000 l/min
 Port size: M5 … G3/4“
 Medium: Compressed air
 Power consumption: 3W / 5VA
Spool valves can combine a high flow (large orifice size) at a significant maximum pressure (the standard
is around 10 bar, can be larger on request) with a low power consumption.
In order to function correctly, the valves require a minimum pressure. If there is less pressure applied to
the valve, the spool might not move. In this case the friction is too high.
Overview of advantages and disadvantages:
Directly actuated
valve
Small orifice
Directly actuated
valve
Big orifice
Piloted valve
Big orifice
Orifice / Flow small high high
Max. Operating
pressure
high low high
Min. Operating pressure 0 0 > 0
Power consumption small high smallChapter 4:
Structure and function of directional valves
We will now introduce you to the function of 5-way solenoid spool valves which are pilot
operated and explain the advantages of the Hafner design.
The graph below shows the cross section of a 5/2-way single solenoid pilot valve.
Function of a Hafner 5/2-way single solenoid valve (type: MH 510 / MD 510 / MMD 510)
Pressure is connected to port 1. Through an axial hole in the spool compressed air is fed towards one end
of the spool into the end-cap (right side in the drawing), there the air spring is built up. The spool is pushed
into basic position. (Generally the valve can also be equipped with a mechanic spring). Simultaneously the
pilot valve is supplied with compressed air through the pilot air duct (indicated in blue).
The different sections inside the body of the main valve are separated by seals pressing onto the spool
(green).
In basic position air is allowed to flow from 1 to 2. Besides that ports 4 and 5 (exhaust port) are connected.
Port 3 is closed.
The main valve is piloted by a direct acting 3/2-way normally closed poppet valve that is supplied with air
from the main valve. As the coil sitting on the operator tube is supplied with sufficient electric current the
plunger is lifted. This opens the valve seat in the pilot valve and pilot air is fed to the “left side” of the spool.
As the surface of the spool on that side is larger (approximately double) than on the spring side (right) the
spool is moving towards the end cap.
Result: The main valve switches. Air connected to port 1 is now free to flow to port 4. Ports 2 and 3 are
connected, 5 is closed.
When the current is taken away from the coil, the plunger drops and closing the seat in the pilot valve. Pilot
air exhausts through the operator tube. The air spring becomes stronger than the opposite side of the
spool and switches the main valve back into basic position.Chapter 4:
Structure and function of directional valves
Special features of Hafner valves with the “swimming O-ring”.
By using high quality materials and modern means of manufacturing we can offer a range of products at
high quality and with high reliability.
Materials in use – standard valves:
 Body: anodized aluminum
 Spool: Stainless steel
 Operator system: brass, stainless steel, FKM
 Inner parts: brass, POM, NBR
 Seals: NBR, FPM (FKM)
HAFNER also offers valves made from other materials or for specific applications such as:
 Stainless steel valves
 Brass-free products
 Low temperature valves (to -50°C)
 Poppet valves made from polyamide
 Valves for explosion hazardous environments (ATEX- approved)
Features of the sealing system with the „swimming O-ring“:
There is no deformation of the seal during assemblage of the valve - they are allowed to move
independently within the brass cage. Without air pressure there is no contact pressure and, therefore, no
friction. This construction also has consequences for the seals of the valves in use. When switching a 5/2-
way valve only three of the five seals are exposed to pressure and applying friction to the spool.
 Becasue of the low friction, there is very
little wear on the seals.
 As friction is low when pressure is low and
friction as well as sealing effect increases
with pressure the valves switch safely at
low as well as at high pressure.
 Our customers benefit from high durability
and extended lifetime, high flow combined
with compact design as well as high
reliability.Chapter 4:
Structure and function of directional valves
Communication of flow rates
The Hafner catalogue contains information about the flow-rates of the valves l/min (liter per minute).
The nominal flow is measured according to standard as follows:
Supply pressure p1=6 bar, back pressure 5 bar
The flow of the air at Δp=1 bar is indicated after expanding the air from 5 to 0 bar in l/min.
Therefore the amount of „expanded“ compressed air is 5 times the volume of the air that is actually
flowing.
Important notice!
Some manufacturers communicate the „maximum flow“ at „maximum operating pressure“. This value
might be significantly higher. In case you design your pneumatic system for significantly lower pressure
than 6 bar you might want to use components with a bigger orifice.
HAFNER Pneumatik offers a very wide range of direct acting poppet valves and pilot operated
spool valves with port size M5 to G 3/4” and a nominal flow of up to 6.000 l/min!
In a later chapter we will introduce you to diaphragm valves and other poppet valve designs. Those are
mainly used in process industry. In these industries, the medium is often times not compressed air.Chapter 5:
ISO Schemes of directional control valves
Schemes of directional valves
The description of directional valves is standardized by DIN ISO 121.
IMPORTANT! The ISO symbols display only the function of the valves. They do not give any further information
about the design, flow, orifice size, etc.
Basics of the ISO symbols:
 Each position the valve can take is represented by a square.
 The number of squares tells you the number of positions the valve can take.
 The air pathways are represented by lines.
 The direction of the airflow is represented by an arrow.
 In case air flows in both directions there is a double arrow.
 Closed ports are displayed as a T.
 The ports carry numbers. The numbers are only shown in the square with the basic position of the valve.
 The type of actuation is also symbolized.
 The ISO-symbol contains information concerning the stability of the positions and the reset.
Directional valves – number of ports and positions
The directional valves are described by the numbers of ports in the main valve (excluding pilot ports) and the
number of positions the valve can take, [number of ports] / [number of positons]
for example:
2 squares = 2 positons
3 ports
Number of positions
Number of ports
In this case we speak of a 3/2 way valve (spoken: three two way valve). Each position of the valve is displayed in
a square. The basic position is symbolized by the numbers of the ports.Chapter 5:
ISO Schemes of directional control valves
On the right hand side you can see the basic position of a normally closed 3/2-
way valve.
 Port 1 = pressure supply is closed (blue).
 Port 2 = working, in basic position connected to port 3 = exhaust (red).
 Basic position or normal position drawn in green.
The second square displays the actuated position of the valve.
 Valve has been actuated (actuation elements not shown here).
 Port 1 is connected to working port 2 (blue).
 Exhaust port 3 is closed (black).
 Actuated positon drawn in green.
Symbols of the most common valves
2/2-way valve
Normally closed
Normally open
3/2-way valve
Normally closed
Normally openChapter 5:
ISO Schemes of directional control valves
4/2-way valve
5/2-way valve
4/3-way valve Center closed
5/3-way valve Center closed
Symbols of actuation elements and resets
Apart from the squares showing the valve's function, the symbols for its actuation elements and elements to
reset/return it are shown on the left, respectively right side of them.
Mechanically actuated,
Actuation by stem
With spring reset
Mechanically actuated,
Actuation by roller lever
With air spring reset
Mechanically actuated,
Actuation by roller lever with idle
return
With combined (mechanical)
spring and air spring resetChapter 5:
ISO Schemes of directional control valves
Manually actuated,
Actuation with a push-button
Manually actuated,
Actuation by a lever
Manually actuated,
Actuation by a lever, indexed, 2
positions
Actuated by foot / foot valve
Pneumatically actuated
Electrically actuated,
Direct actuated valve
Electrically actuated,
Solenoid pilot valve
Manual override
Pneumatically actuated,
Differential piston, dominating side
Pneumatically actuated,
Differential piston.Chapter 5:
ISO Schemes of directional control valves
Numbering of ports
All the ports in the valve are counted through. The numbers indicate the function of the port. The numbers
always appear on the square for the valve's basic/normal position. In case we talk about a valve with 2 stable
positions, the numbers are shown for the „implicit standard position“.
Basic position = normal position is the position the valve is in without actuation.
Pressure supply 1 P
Working port(s) 2, 4, (6) A, B, C
Exhaust(s) 3, 5, 7 R, S, T
Pilot ports(s) 10, 12, 14 X, Y, Z
Examples:
The following lever- and pneumatically actuated valves allow airflow in both directions (double arrows).
 Actuation : manually (by a lever)
 2 positions, both stable, indexed
 Number of pneumatic ports: 5
 Thus: 5 ports, 2 positions = 5/2-way valve
Manually actuated, 5/2-way valve, indexed
Type e.g.: HVR 520 701Chapter 5:
ISO Schemes of directional control valves
 Actuation : pneumatically (with air)
 2 positions, one stable (with spring reset)
 Number of pneumatic ports: 5
 plus pilot port 14
 Thus: 5 ports, 2 positions = 5/2-way
valve
Pneumatically actuated 5/2-way valve, single
pilot, mechanical spring reset
Type e.g.: P 511 701
 Actuation : electrically (solenoid-pilot)
including manual override.
 3 positions, one stable (spring centered)
 Number of pneumatic ports: 5
 Thus: 5 ports, 3 positions = 5/3-way valve
Solenoid-pilot 5/3-way valve, 2 springs center
the spool. Center position closed.
Type e.g.: MH 531 701Chapter 5:
ISO Schemes of directional control valves
General information on circuits
Looking at the following circuits you can see potential ways for using different types of directional valves.
2/2-way valves
2/2-way valves are for opening and closing. They block the medium or let it pass. 2/2-way valves can be either
normally closed or normally open.
In the scheme below two 2/2-way solenoid valves (S1 and S2) are used to control a cylinder with spring return
(single acting) C1. Without actuation both solenoid valves are closed. In order to move the piston rod to the outer
position (right) S2 has to be actuated. Compressed air is flowing from the source through S2 into the cylinder. In
order to move the piston rod to the opposite position S2 needs to be de-energized and S1 has to be actuated. In
case none of the valves are actuated, the piston rod stays in last position.
(The symbol at the bottom displays an FRL-unit (filter, regulator, lubricator). The functions of cylinders as well as
of air-preparation units will be discussed in a later chapter.)Chapter 5:
ISO Schemes of directional control valves
3/2-way valves
3/2-way valves are mostly used to control single acting actuators. They can be normally closed or normally
open. In the scheme below you can see two applications.
1. An electrically actuated 3/2-way valve (S1) controls the single acting cylinder (C1).
When the valve is actuated, air flows from 1 to 2; the piston rod of the cylinder is moving to outer position.
When the valve is de-energized, it switches back to normal position and the mechanic spring in the cylinder
drives the piston rod back.
2. The double acting cylinder (C2) is controlled by a 5/2-way valve (Y1). Valve Y1 is controlled by an electrically
actuated, normally closed 3/2-way valve (S2).
Valve S2 is actuated (air flows from port 1 to port 2). The air actuates valve Y1. It switches and air flows from
port 1 to port 4; the piston rod of cylinder C2 moves to the outer position.
As soon as valve S2 is de-energized, air exhausts from port 2 to 3. Valve Y1 switches back into normal
position because of the built-in mechanic spring. Compressed air in valve Y1 flows from 1 to 2 and the
cylinder's exhaust from 4 to 5 as the piston rod moves back in.Chapter 5:
ISO Schemes of directional control valves
4/2-way and 5/2-way valves
4/2-way and 5/2-way, as well as 4/3-way and 5/3-way valves are usually used to control double acting
actuators.
In the example below a manually actuated valve (S1 or S2) controls a double acting cylinder (C1 or C2).
Additionally, in order to control the speed of the cylinder, flow control silencers are in use.
The major difference between the 4-way and the 5-way valve is that the 4-way valve offers only one exhaust port.
Therefore the speed of the piston rod moving in or out cannot be controlled independently as the two chambers
of cylinder C1 are exhausted through the same exhaust port 3 of valve S1.
As for the 5/2-way valve (S2), the two chambers on cylinder (C2) are exhausted through separate exhaust
ports (5 and 3). This offers the possibility to regulate the speed of the piston rod independently.Chapter 6:
Explanation of the Hafner type numbering
system
Review of previous chapters
In the earlier chapters we introduced you to the most important characteristics of directional valves.
We have summarized them below:
Categorizing control valves by the following criteria (chapter 3):
 Basic design
(spool valve, poppet valve)
 Actuation
(mechanically, manually, pneumatically or electrically actuated valves)
 Number of positions
(2-, 3-, 4-, 5-way)
 Number of ports (in combination with positions)
(2/2-way, 3/2-way, 5/2-way, 5/3-way, …)
 Normal position
(for 2/2-and 3/2-way valves: normally closed or open, for 5/3-way valves: center closed, exhausted,
pressurized)
By design (chapter 4) we have to distinguish between poppet and spool valves. It is important to understand
the difference in order to select the right valve for any application.
 2/2- or 3/2-way electrically and directly actuated poppet valves: directly controlled by the plunger of
the solenoid system.
 3- or 5-way electrically actuated spool valves: controlled by an additional pilot-valve
Introduction to directional valves (chapter 5):
 ISO symbols and their meaning when it comes to function and positions
 Numbering of their portsChapter 6:
Explanation of the Hafner type numbering
system
Explanation of the Hafner type numbering system
The HAFNER type numbers are a combination of letters and numbers, which carry further meaning. The most
important characteristics of the valves are to be found in the type number.
The type number contains 3 major blocks (1-3)
M H 5 1 0 7 0 1
1 2 3 4
… the fourth block indicates a special variation.
M H 5 1 0 7 0 1 G
1 2 3 4
To explain the system we use the valve
type MH 510 701 G. This number has 3
main parts plus a suffix (block 4, variable).
The valve is defined by the 3 main blocks.
The fourth block is there to indicate extra
features, special materials etc.
Although there are some exceptions, this
standard covers most of the products.
Block 1 - actuation
The first letter defines the mode of actuation of the valve
Type
M H 5 1 0 7 0 1
1 2 3
 B = Mechanically or manually actuated
 H = Hand lever valve
 P = Pneumatically actuated
 M = Solenoid valveChapter 6:
Explanation of the Hafner type numbering
system
Type
The next letter(s) give further information
M H 5 1 0 7 0 1
1 2 3
This list is not limited to the types mentioned
above, but only gives an overview about the
most common products. There are many
more.
 B = Mechanically or manually actuated
o BV = stem actuated valve
o BR = roller lever valve
o BL = roller lever valve with idle return
o BA = stem valve with coupling for knob
o BH = push-pull valve
 H = Hand lever valve
o HV = with spring return (one stable position)
o HVR = indexed
o HV(R)N = valve-body with interface following
NAMUR-standard
 P = Pneumatically actuated - no further information for
standard products
o PN = valve-body with NAMUR-interface
 M = Solenoid valve
o MH = with manual override to turn, normally closed
o MD = momentary manual override to push, normally
closed
o MOH = normally open MH valve (2/2 and 3/2-way)
o MOD = normally open MD valve (2/2 and 3/2-way)
o MEH / MED = with external pilot feed
o MEOH = n.o. and with external pilot feed
o MK = modified MH-valve, with solenoid MA16 (low
power consumption 1.8W and for valve terminals)
o MNH / MND = valve-body with NAMUR-interface
o MNOH = valve-body with NAMUR-interface, normally
openChapter 6:
Explanation of the Hafner type numbering
system
Block 2
The second block contains information about the number of ports, the number of stable positions and the type
of spring.
Number of ports in main valve
M H 5 1 0 7 0 1
1 2 3
The first digit displays the number of ports.
 2 = 2-way = 2 ports (2/2)
 3 = 3-way = 3 ports (3/2 or 3/3)
 5 = 5-way = 5 ports (5/2 or 5/3)
Positions
M H 5 1 0 7 0 1
1 2 3
The second digit displays the number of positions
and whether the valve has one or two stable
positions.
 1 = one stable position (single sol. / pilot)
 2 = two stable positions (double sol. / pilot)
 3 = 3-postions ( _/3-way valves)
Return
M H 5 1 0 7 0 1
1 2 3
In combination with the second digit (in this case
“1”), the third digit informs about the type of spring:
 10 = air spring (no mechanic spring)
 11 = mechanic spring inside, can also be
executed as a combination of an air- with a
mechanic spring. At double solenoid valves
the third number is always a “0” as they don’t
have any spring return.
Center position
for 3-position valves (e.g. MH 531 701)
M H 5 3 1 7 0 1
1 2 3
In case we are talking about a 3-position valve, the
third number defines the center position:
 31 = Center closed
 32 = Center exhausted
 33 = Center pressurizedChapter 6:
Explanation of the Hafner type numbering
system
Block 3
Block 3 contains information about orifice size and ports.
Orifice size
M H 5 1 0 7 0 1
1 2 3
The first digit(s) represent the orifice and thread size.
 20 = DN 2 mm, port: M5
 30 = DN 3 mm, port: M5 or G1/8"
 34 = DN 3 mm, 4 mm push-in fitting
 40 = DN 4 mm, port: G1/8"
 46 = DN 4 mm, 6 mm push-in fitting
 50 = DN 5 mm, port: G1/8"
 70 = DN 7 mm, port: G1/4"
 80 = DN 8 mm, port: G1/4"
 10 = DN 10 mm, port: G3/8"
 12 = DN 12 mm, port: G1/2"
 18 = DN 18 mm, port: G3/4"
The orifice size also lets us know about the flow:
 20 = DN 2 mm, flow: 115 ... 125 l/min
 30 = DN 3 mm, flow: 280 l/min
 40 = DN 4 mm, flow: 450 l/min
 50 = DN 5 mm, flow: 650 l/min
 70 = DN 7 mm, flow: 1250 l/min
 80 = DN 8 mm, flow 1450 l/min
 10 = DN 10 mm, flow: 2250 l/min
 12 = DN 12 mm, flow: 3000 l/min
 18 = DN 18 mm, flow: 6000 l/min
You can get more information about flow from the
catalogue.
Ports are BSP threaded by default.
NPT threads are to be indicated by a “NPT” suffix
in block 4.
The second digit in block 3 defines the type of
connection:
 0 = tapped working ports 2 and 4
 4 = 4 mm push-in fitting(s) in port(s) 2
and 4
 6 = 6 mm push-in fitting(s) in port(s) 2
and 4Chapter 6:
Explanation of the Hafner type numbering
system
Position of ports
M H 5 1 0 7 0 1
1 2 3
The last digit in block 3 defines the position of the ports within
the body:
 1 = Standard, ports on both sides of the valve
 2 = All the ports on one side
 3 = For manifold-plates only, supply and exhaust on
one side, working ports on opposite side in the valve
 4 = For manifold-plates only, all the ports are in the
plate.
Standard (e.g. MH 510 701, MH 510 703)
All the ports on one side (e.g. MH 510 502, MH 510 704)Chapter 6:
Explanation of the Hafner type numbering
system
On the following four pages we explain some exemplary type numbers based on
catalogue items:
BV 311 201 Block 1
Actuation: BV
 B = Mechanically actuated
 V = Stem
Block 2
 First digit: number of ports = 3
 Second digit: number of (stable) positions = 1
 Third digit: return = 1 = mechanic spring
 3/2-way valve
 Mechanic spring return
Block 3
First and second digit: orifice size = 20 = orifice size 2 mm
Third digit: position of the ports = 1 = standard
 M5 tapped ports (belongs to orifice size 2 mm)
 Port 1 and 3 on one side, working port 2 on the
opposite side.
Therefore the valve BV 311 201 is a:
 Stem actuated valve
 3/2-way with mechanic spring return
 M5-ports on both sides of the valve, orifice size 2 mmChapter 6:
Explanation of the Hafner type numbering
system
HVR 520 701 Block 1
Actuation: HVR
 H = Hand lever valve
 VR = Indexed (without spring return)
Block 2
 First digit: number of ports = 5
 Second digit: number of (stable) positions = 2
 Third digit: return 0 = non = 2 stable positions
 5/2-way valve
 2 stable positions
Block 3
First and second digit: orifice size = 70 = orifice size 7 mm
Third digit: position of the ports = 1 = standard
 G 1/4” tapped ports (belongs to orifice size 7 mm)
 Ports 1, 3, 5 on one side, working ports 2, 4 on the
opposite side.
Therefore the valve HVR 520 701 is a:
 Hand-lever valve
 5/2-way indexed
 G 1/4” ports on both sides of the valve, orifice size 7 mmChapter 6:
Explanation of the Hafner type numbering
system
MD 531 401 24 DC Block 1
Actuation: MD
 M = Solenoid valve
 D = Manual override to push, momentary
Block 2
 First digit: number of ports = 5
 Second digit: number of positions = 3
 Third digit (if second one is a 3): center 1 = closed
 5/3-way valve
 Center closed
Block 3
First and second digit: orifice size = 40 = orifice size 4 mm
Third digit: position of the ports = 1 = standard
 G 1/8” tapped ports (belongs to orifice size 4 mm)
 Ports 1, 3, 5 on one side, working ports 2, 4 on the
opposite side.
Block 4
(Misc.) 24DC for MD and MK valves only: voltage
Therefore the valve MD 531 401 24 DC is a:
 Solenoid valve with manual override to push
 5/3-way center closed
 G 1/8” ports on both sides of the valve, orifice size 4 mm
 Integrated solenoid 24V DCChapter 6:
Explanation of the Hafner type numbering
system
MNH 311 701 Block 1
Actuation: MNH
 M = Solenoid valve
 N = NAMUR-interface
 H = Manual override to turn
Block 2
 First digit: number of ports = 3
 Second digit: number of (stable) positions = 1
 Third digit: return = 1 = mechanic spring inside
(in this case a combined spring).
 3/2-way valve
 Normally closed
 With combined mech.-pneum. spring
Block 3
First and second digit: orifice size = 70 = orifice size 7
Third digit: position of the ports = 1 = standard, in combination with
the N in Block 1 with NAMUR-interface.
 G 1/4” tapped ports (belongs to orifice size 7 mm)
 Ports 1, 3, 5 on one side, working ports in
accordance to NAMUR-standard (VDI/VDE 3845)
Therefore the valve MNH 311 701 is a:
 Solenoid valve with manual override to turn
 3/2-way n.c.
 NAMUR-interface and ports 1, 3, 5 G 1/4, orifice size 7 mmChapter 6:
Explanation of the Hafner type numbering
system
As you can see the HAFNER type numbering system is following a standard that allows you to understand what
type of valve is in use or required whenever those numbers are mentioned.
An overview about the structure of the Hafner type numbers can also be found on page 16 and 17 in the
valve catalogue 2016:Chapter 7:
The pneumatic cylinder – part 1
Right of authorship: the content of the training (wording, drawings, pictures) are owned by the author. Any utilization except for
individual use is allowed only after permission of the author.
In the earlier chapters we looked at the basic design of a pneumatic system and its most important elements:
 Air preparation
 Control valves
 Flow-regulators
 Actuators / cylinders
 Tubes and fittings
In this chapter we will be looking at pneumatic cylinders. Cylinders are the most important means of
actuation in pneumatics. The cylinder transfers the energy that is stored in the compressed air into
movement.
They can be classified by:
 Design
o Cylinders with piston rods
o Rodless cylinders
o Diaphragm cylinders
o Rotary cylinders
 Movement
o Linear
o Rotary = turning
 Function
o Single-acting
o Double-acting
o 3- or 4-positions
 Cushioning
o Adjustable, pneumatic cushioning
o Flexible cushioning
o Without cushioning
There is a very wide variety of pneumatic cylinders. In this training we will only focus the most common ones.Chapter 7:
The pneumatic cylinder – part 1
Cylinders with piston rods
Cylinders are available in different types and follow different international standards. Besides the ones that follow
standards there are also “non-standardized cylinders”. Especially before the standardization into
DIN/ ISO norms 6431 and 6432, there were numerous cylinder-types offered by different manufacturers.
Common standard cylinders are:
 Mini cartridge cylinders
 Round cylinders | DIN ISO 6432
 Profile cylinders | ISO 15552 | VDMA 24562 | (old norm: DIN ISO 6431)
 Compact cylinders | ISO 21287 | UNITOP
 Short stroke cylinders
 Tie rod cylinders | ISO 15552Chapter 7:
The pneumatic cylinder – part 1
We will look at the following characteristics:
1. Design
2. Diameter and stroke
3. Movement
4. Number of positions
5. ISO symbols
6. Cushioning  chapter 8
7. Detection of cylinder position (magnetic)  chapter 8
8. Speed control  chapter 8
1. Design of a cylinder
Most of the cylinders with a piston rod contain the following parts: a tube that is closed on both ends with a
cap and head. Inside the tube seen below a piston rod moves with a drive piston.
The movement of the piston is triggered by compressed air, controlled by a directional valve. The direction is
defined by the chamber into which compressed air is allowed to flow inside the cylinder.
The force is transferred by the piston rod.
Components of a piston rod cylinder:Chapter 7:
The pneumatic cylinder – part 1
2. Diameter and stroke
Diameter and stroke are the most important attributes of a cylinder.
e.g. HAFNER Cylinder DIP: DIP 40/320
Type numbering system:
 DIP – type of cylinder / design
(DIP = ISO 15552 standard – double-acting cylinder – adjustable cushioning – magnetic piston)
 40 – diameter of the piston [mm]
 320 – stroke of the cylinder [mm]
The diameter is actually the diameter of the piston. The diameter of the cylinder defines its force relative to the
air-pressure.
The stroke tells us how many millimetres the piston and therefore the piston rod can travel.Chapter 7:
The pneumatic cylinder – part 1
If the stroke is long, the forces on the bearing between head and piston rod are high. In order to avoid a defect
we recommend to select a larger diameter (cylinders with larger piston diameters also offer larger piston rod
diameters).
In case of very long strokes or radial forces we recommend the use of a guide unit.
Pictures: DIP cylinder with assembled guide unit
Diameters and strokes are standardized, the most common values are:
Piston diameters [mm]:
| ø8 | ø10 | ø12 | ø16 | ø20 | ø25 | ø32 | ø40 | ø50 | ø63 | ø80 | ø100 | ø125 | ø160 | ø200 | ø250 | ø320 |
Stroke lengths [mm]:
| 5 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 | 80 | 100 | 125 | 160 | 200 | 250 | 320 | 400 | 500 | ...
The available diameters depend on, and are limited by, the type / standard. The availability of strokes on the
other hand is less limited.
The maximum force generated by a cylinder depends on:
 Operating pressure
 Diameter of the piston
 Friction of the inner parts
As an example we calculate the force of a cylinder DIL 40/320 at 6 bar.Chapter 7:
The pneumatic cylinder – part 1
Piston diameter:
Surface of drive piston:
Operating pressure:
Calculation of the force:
Thus we have a theoretical force of 753,6 N.
As a rule of thumb we can deduct 5% for friction. Therefore a cylinder with a piston diameter of 40 mm, and an
operating pressure of 6 bar, can exert a force of approx. 716 N.
If we divide the force by gravity (9,81 m/s2), we find - in practice - that our cylinder can hold a mass of
about 73 kg.
CAUTION! We can only hold the weight with this force, we cannot move it yet!
If we want to move a weight we have to (again) take gravity into consideration. Only then our cylinder is not only
able to hold a weight but to perform work.Chapter 7:
The pneumatic cylinder – part 1
3. The Movement of a cylinder
We call the two end-positions of a cylinder positive / plus and negative / minus positions.
Therefore we also call the two chambers inside the cylinder the plus and the minus chamber.
Positive movement Negative movement
The position where the piston rod is out of the cylinder the furthest possible is called the plus end-position. In
order to reach it, the plus chamber needs to be inflated.
The minus end-position is positioned on the opposite side; the minus chamber needs to be inflated.
The cylinder cannot reach an end-position if the opposite chamber is not fully exhausted!
4. Stable positions of a cylinder
We distinguish between single-acting and double-acting cylinders.
In single-acting cylinders only one chamber is inflated with compressed air. Therefore work is performed only
in one direction by compressed air. For the movement into the opposite direction a mechanic spring is the
source of energy. The stroke is limited by the length of the spring. In general single-acting cylinders offer a
relatively short stroke.
Two different types of single-acting cylinders are available:
Single-acting cylinder with base position minus Single-acting cylinder with base position plus
(spring between head and piston) (spring between cap and piston)Chapter 7:
The pneumatic cylinder – part 1
Double-acting cylinders are driven in both directions by compressed air. They are always used when work has to
be performed in both directions or when the required stroke is longer than the available springs.
There are different designs for different applications:
 Double-acting cylinder
(standard design)
 Double-acting cylinder with through piston rod
(Cylinder has a piston rod on both ends)Chapter 7:
The pneumatic cylinder – part 1
 Double-acting cylinder, guided / non-rotating rod
(integrated guide unit for higher radial forces)
 Cylinders with non-rotating piston rods
(If the application does not allow a rotation of the piston rod, either a rod that does not have circular
cross section or a double piston-rod is in use)
 Multi-position cylinders
(Two cylinders are assembled back to back. Thus 4 different strokes with different lengths are possible.)
 Tandem cylinder
(Target: Higher force of the cylinder without increasing its diameter. In order to achieve this, two or more
cylinders are connected to each other so that their piston rods are connected as well and working in
line. In other words several pistons use the same piston rod. Thus the force adds up.

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