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A Brief Guide to Pneumatic and Compressed Air Components
Air Blow Guns
Compressed-air blow-off guns are used to clean hard-to-reach areas and corners. Blow-off guns should only be operated with condensate- and oil-free compressed air. The operating pressure should be set to a fixed value.
Sealing rings
Sealing rings are sealing elements. Depending on the application and requirements (such as resistance to oils, greases, acids, heat, and vacuum tightness), different materials are used, e.g., various types of rubber, perfluoroelastomer (FFKM or FFPM), polyethylene (PE), or polytetrafluoroethylene (PTFE).
Fittings
A fitting (plural: “fittings”) is a collective term for—typically standardized—accessories used in assembly technology.
Piping Fittings
Function
In the narrower sense, this term refers to pipe connectors that fulfill the following functions:
Application
In summary, a piping system consists of
Fittings serve to adapt the pipeline’s route to external conditions: obstacles must be bypassed, separation points for installation and maintenance must be provided for, and branches and changes in diameter must be implemented. In short, they allow the route of a pipeline to be adapted to design requirements. The connection type can be a threaded, flanged, brazed, welded, press-fit, or adhesive joint.
Functional Screw Connections
Pneumatic functional fittings serve many purposes in a very small space. They are used like standard fittings but perform additional functions, such as:
They are also commonly used in pneumatic cylinders.
Ball valves
Ball valves are valves with a hollow ball as the shutoff element and are also referred to as ball gate valves, especially for larger pipe diameters.[1] In most cases, they are used as shut-off valves. A characteristic feature of a ball valve is that it closes completely within a single rotation of exactly 90°, in contrast to other types of valves, for example.
Pressure Gauge
A pressure gauge is a measuring device used to measure and display the physical pressure of a medium such as liquids or gases. In most applications, relative pressure—that is, pressure relative to atmospheric pressure—is measured. Differential pressure gauges, like the others, measure a pressure difference, but between any two systems.
Bourdon tube pressure gauges are pressure measuring instruments whose sensing element consists of a Bourdon tube—also known as a Bourdon spring—wound in a circular, helical, or spiral pattern, depending on the pressure range to be measured. When pressure is applied, the Bourdon tube tends to uncoil. The displacement experienced by the end of the Bourdon tube is transmitted via a pull rod to a segmented gear and thus to the pointer axis
Silencers
Escaping compressed air causes noise. Silencers are designed to channel the exhaust air and release it into the ambient air. This reduces the noise level.
Typical applications for silencers include pneumatic valves and air motors.
Hoses
Hoses are flexible lines used to convey solids, liquids, and gases. As the wall thickness increases, the lines become sturdier but less flexible.
These are then referred to as pipes
Hose couplings
Hose couplings (also known as quick-connect couplings, single couplings, or multi-couplings) are needed to supply machines, systems, or blow-off guns with gaseous (compressed air) and liquid media. To ensure flexible and thus cost-effective use, many lines are not permanently connected to one another but are designed to be separable via quick-connect couplings. They enable efficient and reliable connection and replacement of systems, units, devices, etc. The design depends on the intended use, the medium conveyed through the hose (air, gas, water, oil), and the pressure conditions within the hose (vacuum or overpressure).
Hose Connections
The following are used to connect hoses to one another or from a hose to other fittings:
Cutting-ring fittings
A cutting ring fitting is a liquid-tight pipe connection technology developed for the highest pressures.
Application
Screw-on compression fittings are standardized according to EN ISO 8434 or DIN 2353 and are primarily used in hydraulics. The components of a screw-on compression fitting are: union nut, clamping cone, and cutting ring. They feature a 24° sealing cone, and the nut has a metric thread. The fittings are manufactured in three series: very light, light (up to approx. 350 bar), and heavy (up to approx. 600 bar).
Tightening the union nut, which tapers inward, compresses the cutting ring, causing the wedge-shaped inner surface of the ring to cut into the pipe wall and create a tight, form-fit seal.
Quick-Connect Fittings / Push-On Fittings
Quick-connect screw fittings and couplings allow for lightning-fast manual assembly and disassembly without tools. They are available in a wide variety of designs, can be used in a wide range of operating temperatures and pressure ranges, and are compatible with a variety of media, such as compressed air, gases, and liquids. The hoses must be cut straight and externally calibrated for this purpose.
Quick-connect fittings
Quick-connect fittings are fittings in which the hose is attached to the fitting using a union nut.
Advantages:
Also suitable for liquid media
Valves
A valve is a component used to shut off or regulate the flow of fluids such as air, gas, and liquids. In valves, a closing element (e.g., a cone or a ball) is moved nearly parallel to the direction of fluid flow. The flow is reduced or interrupted by pressing the entire closing element against a suitably shaped opening.
Valves can be manufactured in such a way that, unlike other shut-off devices (e.g., gate valves, butterfly valves, ball valves), they maintain a uniform flow pattern across the entire flow cross-section throughout the entire operating range. For this reason, valves are well-suited not only for simply shutting off material flows but also for control tasks.
Valve Types
Classification by Valve Shape
Valves can be classified according to their geometric shape into:
Classification by Actuation Type
Valves can also be classified according to their actuation type as follows:
Classification by Valve Stages
A valve operates using a relatively small input energy and thereby influences fluid flow, which typically has greater energy. However, there are limits to the amplification in a single-stage valve. As the diameter increases in directly controlled valves, the static pressure force increases, requiring a correspondingly greater control force (e.g., magnetic force) to overcome it. If this force is insufficient, multiple valves are connected in series. These are referred to as multistage valves. Considered individually, the first valve is directly controlled, while the others are indirectly controlled or pilot-operated. Examples:
Classification by Function
Valves perform different functions in a pneumatic or hydraulic system. They act as a barrier to fluids (gases or liquids) depending on various factors. There are the following four cases:
Shut-off valves and flow control valves
Flow control valves reduce the flow cross-section or shut off the flow completely.
Examples:
Check Valves
Check valves prevent flow in only one direction. Special check valves:
Pressure valves
Pressure relief valves restrict the flow of fluid depending on the pressure. They normally become active only within a specific pressure range.
Examples:
Directional controlvalves
Three-way valves, four-way valves, or higher-order directional control valves restrict or allow flow in the same way as flow control valves—that is, regardless of pressure or direction. However, they simultaneously control multiple fluid flows, so they have at least three working line connections. They can be further classified based on their switching positions: discrete (directional control valve as a switching valve) and continuous (directional control valve as a continuous-action valve).
Examples:
Classification by Shut-off Body Design
Valves can also be classified based on the design of the shut-off body. Examples include:
Application
Valves allow flow rates in a pipeline to be precisely controlled and securely sealed off from the environment. Safety valves, on the other hand, are designed to allow large mass flows in order to quickly equalize impermissible pressure conditions (e.g., in a vessel). Valves always have a certain degree of flow resistance, which makes them unsuitable for some applications. Furthermore, it is very difficult to keep the actuator unit completely leak-tight.
Valves, particularly solenoid valves, are used frequently and in a wide variety of ways in industry: in automation for moving cylinders, gripping systems, or ejectors; in the chemical industry, the food industry, water treatment, and many other fields.
Maintenance Units
As a subassembly in pneumatic systems, the maintenance unit is responsible for treating the energy source—compressed air.
Proper compressed air treatment is essential for the operational reliability and service life of pneumatic components and control systems. The following functions are integrated into the maintenance unit:
Purification. The compressed air coming from the compressor contains dirt particles and moisture, which are removed by filters and special devices.
The air intended for the control lines and components achieves a particularly high degree of purity through additional fine filters.
Pressure regulation. A pressure-regulating valve ensures that the outlet pressure (pressure in the compressed air network) remains constant, even with fluctuating inlet pressure or air consumption.
Pressure Gauge. A pressure gauge displays the pressure in the system.
Lubrication. If the pneumatic components require lubrication, an oiler ensures an adequate supply of lubricant.
Cylinder
A pneumatic cylinder is a working cylinder operated by compressed air. Pneumatic cylinders are used in many pneumatic applications, such as in injection molding tools, in conveying, drive, or handling technology.
A basic distinction is made between cylinders that can be pressurized from one side and those that can be pressurized from both sides, also known as single-acting and double-acting cylinders, respectively.
The schematic symbols for pneumatic cylinders are standardized according to ISO 1219.
Compressed-air blow-off guns are used to clean hard-to-reach areas and corners. Blow-off guns should only be operated with condensate- and oil-free compressed air. The operating pressure should be set to a fixed value.
Sealing rings
Sealing rings are sealing elements. Depending on the application and requirements (such as resistance to oils, greases, acids, heat, and vacuum tightness), different materials are used, e.g., various types of rubber, perfluoroelastomer (FFKM or FFPM), polyethylene (PE), or polytetrafluoroethylene (PTFE).
Fittings
A fitting (plural: “fittings”) is a collective term for—typically standardized—accessories used in assembly technology.
Piping Fittings
Function
In the narrower sense, this term refers to pipe connectors that fulfill the following functions:
- Straight connections between pipe sections, such as sockets and couplings
- Changes in direction using pipe elbows (not pipe bends, which are formed by bending straight pipe!)
- Diameter changes (reducers)
- Branches, such as T-fittings (3-way) and cross fittings (4-way)
- Connections to fittings, such as flanges or threaded connections (nipples)
- Connecting different pipe materials. Corrosion-prone elements should be avoided when connecting dissimilar metals; for example, a brass fitting is used to connect a steel pipe to a copper pipe.
Application
In summary, a piping system consists of
- Straight pipe sections and, if necessary, pipe bends
- Fittings or shaped parts
- Piping accessories (such as valves, gaskets, thermometers, and pressure gauges)
Fittings serve to adapt the pipeline’s route to external conditions: obstacles must be bypassed, separation points for installation and maintenance must be provided for, and branches and changes in diameter must be implemented. In short, they allow the route of a pipeline to be adapted to design requirements. The connection type can be a threaded, flanged, brazed, welded, press-fit, or adhesive joint.
Functional Screw Connections
Pneumatic functional fittings serve many purposes in a very small space. They are used like standard fittings but perform additional functions, such as:
- Throttle check valves
- Throttle valves
- Air-saving valves
- Shut-off valves.
They are also commonly used in pneumatic cylinders.
Ball valves
Ball valves are valves with a hollow ball as the shutoff element and are also referred to as ball gate valves, especially for larger pipe diameters.[1] In most cases, they are used as shut-off valves. A characteristic feature of a ball valve is that it closes completely within a single rotation of exactly 90°, in contrast to other types of valves, for example.
Pressure Gauge
A pressure gauge is a measuring device used to measure and display the physical pressure of a medium such as liquids or gases. In most applications, relative pressure—that is, pressure relative to atmospheric pressure—is measured. Differential pressure gauges, like the others, measure a pressure difference, but between any two systems.
Bourdon tube pressure gauges are pressure measuring instruments whose sensing element consists of a Bourdon tube—also known as a Bourdon spring—wound in a circular, helical, or spiral pattern, depending on the pressure range to be measured. When pressure is applied, the Bourdon tube tends to uncoil. The displacement experienced by the end of the Bourdon tube is transmitted via a pull rod to a segmented gear and thus to the pointer axis
Silencers
Escaping compressed air causes noise. Silencers are designed to channel the exhaust air and release it into the ambient air. This reduces the noise level.
Typical applications for silencers include pneumatic valves and air motors.
Hoses
Hoses are flexible lines used to convey solids, liquids, and gases. As the wall thickness increases, the lines become sturdier but less flexible.
These are then referred to as pipes
Hose couplings
Hose couplings (also known as quick-connect couplings, single couplings, or multi-couplings) are needed to supply machines, systems, or blow-off guns with gaseous (compressed air) and liquid media. To ensure flexible and thus cost-effective use, many lines are not permanently connected to one another but are designed to be separable via quick-connect couplings. They enable efficient and reliable connection and replacement of systems, units, devices, etc. The design depends on the intended use, the medium conveyed through the hose (air, gas, water, oil), and the pressure conditions within the hose (vacuum or overpressure).
Hose Connections
The following are used to connect hoses to one another or from a hose to other fittings:
- Hose connectors, short pipe sections for connecting hoses
- Claw coupling (hose connection)—featuring 2 claws per coupling half (4 in total, resulting in a kink-resistant connection) and closing with a clockwise rotation, approximately 90...120° closing angle that locks into place via cams, but can only be closed by hand when depressurized
- Hose connection—faucet connection for garden hose or washing machine, 3/4 inch
- Compressed air quick-connect coupling—NW 7.2, 5, or 2.7 mm, each rated for 0–35 bar [1]
- Safety coupling with vent
- Quick-connect hose fitting [3]
- Quick-connect coupling—for PU hoses
- Cutting-ring fitting (for pipe) with insert sleeve, also for hose [4] 4...18 (42) mm outer diameter, 180...50 bar
- Hydraulic hose—crimped with fitting, sealed push-to-connect fitting, optionally with screw lock
Cutting-ring fittings
A cutting ring fitting is a liquid-tight pipe connection technology developed for the highest pressures.
Application
Screw-on compression fittings are standardized according to EN ISO 8434 or DIN 2353 and are primarily used in hydraulics. The components of a screw-on compression fitting are: union nut, clamping cone, and cutting ring. They feature a 24° sealing cone, and the nut has a metric thread. The fittings are manufactured in three series: very light, light (up to approx. 350 bar), and heavy (up to approx. 600 bar).
Tightening the union nut, which tapers inward, compresses the cutting ring, causing the wedge-shaped inner surface of the ring to cut into the pipe wall and create a tight, form-fit seal.
Quick-Connect Fittings / Push-On Fittings
Quick-connect screw fittings and couplings allow for lightning-fast manual assembly and disassembly without tools. They are available in a wide variety of designs, can be used in a wide range of operating temperatures and pressure ranges, and are compatible with a variety of media, such as compressed air, gases, and liquids. The hoses must be cut straight and externally calibrated for this purpose.
Quick-connect fittings
Quick-connect fittings are fittings in which the hose is attached to the fitting using a union nut.
Advantages:
- Secure connection
- A wide variety of hoses and hose types can be used
- Hoses do not need to be calibrated
- High installation reliability
Also suitable for liquid media
Valves
A valve is a component used to shut off or regulate the flow of fluids such as air, gas, and liquids. In valves, a closing element (e.g., a cone or a ball) is moved nearly parallel to the direction of fluid flow. The flow is reduced or interrupted by pressing the entire closing element against a suitably shaped opening.
Valves can be manufactured in such a way that, unlike other shut-off devices (e.g., gate valves, butterfly valves, ball valves), they maintain a uniform flow pattern across the entire flow cross-section throughout the entire operating range. For this reason, valves are well-suited not only for simply shutting off material flows but also for control tasks.
Valve Types
Classification by Valve Shape
Valves can be classified according to their geometric shape into:
- Straight-through valve (inlet and outlet are in the same direction), where the passage can be “reduced” (with a reduction in cross-sectional area) or “unchanged” (without a reduction in cross-sectional area).
- Angle-seat valve (the shut-off element is (usually) inclined at a 45° angle to the flow direction)
- Three-way valves for the controlled mixing of fluid flows.
Classification by Actuation Type
Valves can also be classified according to their actuation type as follows:
- Manually operated valves. A handwheel is usually provided for this purpose. There are versions with rising or non-rising stems. For large nominal diameters, a gearbox is interposed. Likewise, manual operation may be provided solely as an emergency operation in case the normal motorized drive is unavailable.
- Electric motor-operated valves with valve actuators
- Electromagnetically operated valves
- Fluid-operated valves, which are pneumatically or hydraulically controlled, such as pinch valves. Fluid-operated valves can be further classified into self-operated and externally operated valves.
- Self-medium-operated valves, such as check valves
- External-medium-operated valves, such as all indirectly controlled valves. Because they can also be part of a multistage valve, external-medium-operated or indirectly controlled valves should be treated separately.
Classification by Valve Stages
A valve operates using a relatively small input energy and thereby influences fluid flow, which typically has greater energy. However, there are limits to the amplification in a single-stage valve. As the diameter increases in directly controlled valves, the static pressure force increases, requiring a correspondingly greater control force (e.g., magnetic force) to overcome it. If this force is insufficient, multiple valves are connected in series. These are referred to as multistage valves. Considered individually, the first valve is directly controlled, while the others are indirectly controlled or pilot-operated. Examples:
- Forced-actuated valves: A diaphragm or piston coupled to the magnetic core serves to seal the actual valve seat. When the electrical current is turned on, the core is attracted and opens the auxiliary valve seat in the diaphragm or piston. The medium resting on the diaphragm or piston can then flow out. This creates balanced pressure conditions within the valve, and the main valve seat is opened via the core/diaphragm or core/piston coupling. In this design, no differential pressure is required. The nominal pressure range starts at zero pressure.
- Pilot-operated valves: Pilot-operated valves feature a 3/2-way pilot solenoid valve. A diaphragm or piston is used to seal the actual valve seat. When the pilot valve is closed, the prevailing fluid pressure can build up on both sides of the diaphragm via a throttle orifice. As long as there is a pressure difference between the inlet and outlet, a closing force acts on the diaphragm due to the larger surface area on its upper side. When the pilot valve opens, the pressure above the diaphragm decreases. The resulting increase in force on the underside of the diaphragm lifts it upward, opening the valve. Pilot-operated valves require a minimum pressure differential to ensure proper opening and closing.
Classification by Function
Valves perform different functions in a pneumatic or hydraulic system. They act as a barrier to fluids (gases or liquids) depending on various factors. There are the following four cases:
- The fluid’s flow can simply be restricted in both directions (flow control valves),
- or restricted depending on the direction of flow (check valves),
- it can be restricted depending on the pressure (pressure valves),
- or flow can be controlled simultaneously across multiple lines (directional control valves, 3/2 or higher)
Shut-off valves and flow control valves
Flow control valves reduce the flow cross-section or shut off the flow completely.
Examples:
- Throttle valve
- Delay valve
- Changeover valve (OR)
- Dual-pressure valve (AND)
- Quick-closing valve: A quick-closing valve allows for the sudden interruption of flow in a pipe. For example, in the event of a sudden mechanical unloading of a generator (load shedding), the steam supply can be abruptly interrupted. This prevents the turbine from “running away.”
- In the chemical industry, quick-closing valves are used to isolate pipelines as quickly as possible in the event of a fault.
- Straight-through valve, flow control valve, or 2/2-way valve: Shut-off valves with one inlet and one outlet. In the closed position, the main spring—assisted by the medium pressure—presses the seal against the valve seat, closing the passage. When the valve is energized, the spool with the seal is pulled by the solenoid coil all the way to the pole face, opening the valve. The electromagnetic force is greater than the sum of the spring force and the static and dynamic pressure forces.
Check Valves
Check valves prevent flow in only one direction. Special check valves:
- Throttle check valve
- Quick-release vent valve
Pressure valves
Pressure relief valves restrict the flow of fluid depending on the pressure. They normally become active only within a specific pressure range.
Examples:
- Pressure relief valve and pilot-operated valve
- Differential pressure valve
- Pressure-reducing valve
- Pressure control valve
Directional controlvalves
Three-way valves, four-way valves, or higher-order directional control valves restrict or allow flow in the same way as flow control valves—that is, regardless of pressure or direction. However, they simultaneously control multiple fluid flows, so they have at least three working line connections. They can be further classified based on their switching positions: discrete (directional control valve as a switching valve) and continuous (directional control valve as a continuous-action valve).
Examples:
- Proportional valve (directional control valve as a continuous valve)
- Control valve (directional valve as a continuous valve)
- Servo valve (directional valve as a continuous-action valve)
- Directly Actuated 3/2-Way Valve (directional control valve as a switching valve): 3/2-way valves have three ports and two valve seats. At any given time, only one valve seat remains open or closed. Different functions result depending on how the working fluid is connected to the various working ports. Pressure is applied to the valve seat. When de-energized, a spring presses the lower spool seal against the valve seat, closing the valve. The line at port A is vented via R. When the electrical current is turned on, the spool is energized and seals the valve seat at port R via a spring-loaded seal. The medium flows from P to A.
Classification by Shut-off Body Design
Valves can also be classified based on the design of the shut-off body. Examples include:
- Disc valve, also known as a seat valve: The shutoff element is disc-shaped; a typical example is a standard faucet.
- Tube valve or double-seat valve: The shut-off element is a tube section and has two annular sealing surfaces; this enables pressure-relieved actuation.
- Piston valve: The valve body is a piston
- Rolling diaphragm valve: The closing element consists of a diaphragm that more or less opens the valve cross-sectional area as it rolls; this design is used, for example, in venting and bleeding valves.
- Pinch valve: The shutoff element is tubular.
- Needle valves: The conical tip of the shutoff element presses against an annular inlet/outlet opening
- Ball valve: The closing element is a ball.
Application
Valves allow flow rates in a pipeline to be precisely controlled and securely sealed off from the environment. Safety valves, on the other hand, are designed to allow large mass flows in order to quickly equalize impermissible pressure conditions (e.g., in a vessel). Valves always have a certain degree of flow resistance, which makes them unsuitable for some applications. Furthermore, it is very difficult to keep the actuator unit completely leak-tight.
Valves, particularly solenoid valves, are used frequently and in a wide variety of ways in industry: in automation for moving cylinders, gripping systems, or ejectors; in the chemical industry, the food industry, water treatment, and many other fields.
Maintenance Units
As a subassembly in pneumatic systems, the maintenance unit is responsible for treating the energy source—compressed air.
Proper compressed air treatment is essential for the operational reliability and service life of pneumatic components and control systems. The following functions are integrated into the maintenance unit:
Purification. The compressed air coming from the compressor contains dirt particles and moisture, which are removed by filters and special devices.
The air intended for the control lines and components achieves a particularly high degree of purity through additional fine filters.
Pressure regulation. A pressure-regulating valve ensures that the outlet pressure (pressure in the compressed air network) remains constant, even with fluctuating inlet pressure or air consumption.
Pressure Gauge. A pressure gauge displays the pressure in the system.
Lubrication. If the pneumatic components require lubrication, an oiler ensures an adequate supply of lubricant.
Cylinder
A pneumatic cylinder is a working cylinder operated by compressed air. Pneumatic cylinders are used in many pneumatic applications, such as in injection molding tools, in conveying, drive, or handling technology.
A basic distinction is made between cylinders that can be pressurized from one side and those that can be pressurized from both sides, also known as single-acting and double-acting cylinders, respectively.
The schematic symbols for pneumatic cylinders are standardized according to ISO 1219.
