<p>Plain atmospheric air is the most commonly used for compression; there's plenty of it, and in itself, it costs nothing. Pneumatic systems are generally preferred in industry and manufacturing over hydraulic systems, because they're quieter, cheaper to run and easy to use.</p><h1>What Is Pneumatics?</h1><p>Pneumatics is the blanket term for the physical science of compressing air, and for the branch of mechanical engineering that deals with the use of <strong>compressed air or gas</strong>. Pneumatics was originally as simple as compressing the air in your lungs by taking a deep breath, and then blowing it out forcefully to do something like igniting sparks for a fire or shooting a sharpened dart out of a tube.</p><h2>Common Parts Of A Pneumatic System</h2><p>The most common parts of a pneumatic system are:</p><ul><li>Drives</li><li>Valves</li><li>Fittings</li><li>Tubing &amp; Hoses</li><li>Vacuum Technology</li><li>Air Preparation (Filters, Regulators &amp; Lubricators)</li><li>Silencers</li></ul><hr><h3>DRIVES/CYLINDERS</h3><p>Pneumatic systems work by converting force into potential energy, which then drives an actuator or <a href="https://www.rowse-pneumatics.co.uk/help-advice/how-to-choose-a-pneumatic-cylinder/" target="_blank" title="Pneumatic Cylinders">cylinder</a> with kinetic energy. This is usually in a linear motion by means of a piston rod, or using other forms of actuation commonly called 'rodless'. The piston rod produces a simple up-and-down or back-and-forth motion, and the rod can be pushed either via a single action or a double-action stroke.</p><p>In single-acting pneumatic cylinders the compressed air drives the linear motion of the piston rod in one direction only. At the end of the stroke, a vacuum is created by expelling the compressed air, so the piston rod can make the return stroke via a mechanical spring. Double-acting cylinders allow the load to work in a push-pull motion, manipulating the compressed air with valves to drive the piston rod out and back. This can increase the length of stroke achievable, as well as enabling constant force to be maintained on alternating movements.</p><p>Rodless cylinders work in several different ways, including linear slide, magnetic coupling, inflatable bellows and rotary vane pump. The load is usually situated on a carriage alongside the piston, and they are often chosen for applications requiring a long stroke action or having high moment loads.</p><hr><h3>VALVES</h3><p><strong>Valves are used in pneumatics to control and direct the airflow</strong>, and have many different functions. When you start up the system, you might use a soft start or a simple on-off valve, and you can control the rate of the airflow with flow control valves. For controlling flow direction, there are ball valves and angle seat valves, and you can use pilot valves to control a separate, secondary system.</p><p>When you need to vent the system you'll use an exhaust valve. To close it down requires a shut-off valve, and to initiate an emergency stop you'll need a safety dump valve. All these types of valve release the air pressure from the system at specified times.</p><p>Simple air valves control the inward and outward flow of air into the pneumatic system, requiring some motivating force to direct or position the flow. If this force is applied directly to the operating medium, it's a direct-operated valve rather than a pilot or secondary valve. Other simple valves are the two-position flow control valves, which are either on or off.</p><p>Flow and directional control valves are self-explanatory, but there are also versions which allow three-way directional control from the inlet to either of two outlet ports, and the more complex four-way valve. This can direct flow from the inlet to a choice of three outlet ports. Proportional valves are electronically actuated using solenoids, and can alter the flow rate or pressure of the output in accordance with those of the inlet. This type of valve is used for more complex operations with one or more outputs, where fluid pressures and flow need to be distributed in varying ratios.</p><p>It's also increasingly common in modern pneumatics to use solenoid valves, and today's complex systems have given rise to universal valve terminals which enable modular valve configurations. The use and <a href="https://www.rowse-pneumatics.co.uk/pneumatics/valves" target="_blank" title="Pneumatic Valves">choice of valves</a> has therefore become quite a complicated undertaking, so as to provide simultaneous control of many advanced and specific situations.</p><hr><h3>FITTINGS</h3><p>Pneumatic systems comprise many components, and they all need to be joined together with fittings. <a href="https://www.rowse-pneumatics.co.uk/help-advice/choosing-pneumatic-fittings/" target="_blank" title="Pneumatic Fittings">Pneumatic fittings</a> join together the major system components with their requisite hoses, pipes and tubes, conducting the compressed air to the active parts of the application. The whole system is operating under the pressure of compressed gas or air, so all its component parts require tight, leak-proof seals and must fit together compatibly.</p><p>Fittings come in all shapes, types and sizes, are made of various materials, and have different ways of joining together. Fittings that use metal screw-in threads are still considered to provide the tightest bond, though other materials like polymers are also now used. Pipes that are of different size or type may be joined using compression fittings, while barb fittings are often chosen to join flexible tubing. These have a threaded end which connects to the pipe, and a single or multiple barbed cone which goes into the tube. Many people prefer the modern solution of push-in fittings, which are often used for joining air hoses. Their quick connect and disconnect design enables the easy change-over of different parts, and they come in many sizes and materials.</p><hr><h3>TUBING AND HOSES</h3><p>Tubing and hoses in a pneumatic system are two different things: <strong>hoses are typically used in high-pressure applications</strong> and are reinforced for extra strength; <strong>tubing, on the other hand, tends to be used in applications requiring lower pressure</strong>, and does not need reinforcement. Both come in many different types, with flexible pneumatic tubing or hoses being more widely used than the rigid ones. The development of strong polymers and application-specific materials make flexible tubes and hoses the most versatile parts of a pneumatic system. All you need to do is ensure that you have the <a href="https://www.rowse.co.uk/blog/post/how-to-choose-the-right-air-hose" target="_blank" title="How To Choose The Right Air Hose">right size and type</a> of hose or tubing for your devices, and that everything is compatible.</p><hr><h3>VACUUM TECHNOLOGY</h3><p>Creating a vacuum produces conditions where the air pressure is substantially below that of atmospheric air, specifically <strong>a negative pressure of 300 mbar or less</strong>. The available vacuum range is then subdivided into four categories, ranging from rough to ultra-high vacuum. In order to create a vacuum, it's necessary to remove all the air from a contained space, for which you can use a <a href="https://www.rowse-pneumatics.co.uk/pneumatics/vacuum/generators" target="_blank" title="Pneumatic Vacuum Generators">vacuum generator</a> connected to your pneumatic system. This ejects compressed air forcibly through a diffuser, leaving a vacuum in the application. The item on the workspace will then be drawn up into the vacuum by means of a <a href="https://www.rowse-pneumatics.co.uk/pneumatics/vacuum/gripping-technology" target="_blank" title="Gripping Technology">suction pad or cup</a>, and gripped there while it is processed.</p><p>Many fields of modern industry and various manufacturing processes are now using vacuum technology, including food and beverages, pharmaceuticals, metallurgy and process engineering. They are typically used for delicate pick and place applications, such as plate glass and small electronic components, or for gripping and holding items in position. One of the most recognisable uses for this technology is vacuum packaging.</p><hr><h3>AIR PREPARATION</h3><p>When air is compressed it heats up, and when it cools again it produces condensation which contaminates the supply of compressed air. Ordinary atmospheric air also generally contains impurities such as dirt, dust, oil and other particulates. If compressed air containing such contaminants is passed downstream into functioning parts of the pneumatic system, such as cylinders, valves and hoses, it will inevitably cause some damage. Even if your compressor has built-in components for filtering, drying or regulating the air intake, fittings and components along its outward journey to the application can contribute further contamination.</p><p>In order to keep your system functioning properly for as long as possible, therefore, <strong>it’s necessary that the compressed air supply is filtered</strong>. It is possible to install a simple air filter for this purpose, but the air will still have to be monitored to make sure that the correct pressure is being maintained. Furthermore, the compressed air will need to be lubricated so that downstream equipment is not damaged by an excessively dry air supply. So while all these functions can be dealt with by separate units for filtration, regulation and lubrication, it's more common these days to install a combined <a href="https://www.rowse.co.uk/blog/post/6-things-about-pneumatic-frls" target="_blank" title="6 Things To Know About Pneumatic FRLs">Filter-Regulator-Lubricator unit</a> (FRL).</p><p>For optimal performance of your pneumatic system, you should ensure that the air preparation takes place at the point of use for the machinery. This is particularly important if the compressor is a long way away from it, and provides opportunities en route for the build-up of more water and particulates. FRL units are today's integrated solution to the preparation of air, offering a broad range of filtration options, operating pressure regulation and lubrication where required. They are space-saving and cost-effective, and – if properly sized and installed – will give your pneumatic system a much longer, trouble-free working life.</p><hr><h3>SILENCERS</h3><p><a href="https://www.rowse-pneumatics.co.uk/pneumatics/silencers" target="_blank" title="Pneumatic Air Silencers">Pneumatic air silencers</a>, like the silencer on your car's exhaust, are simply a means to <strong>reduce excess noise when air is exhausted from your pneumatic system</strong>. Venting the exhaust air from a pneumatic system often makes an explosive sound, depending on the force and pressure of the flow. This increases the operational noise levels of the application as a whole, and can cause physical damage or disturbance to personnel. Installing a silencer is a cost-effective solution which can be fitted on pneumatic cylinders, 5/2-way solenoid valves, or other associated devices and fittings.</p><p>In addition, silencers can manage the airflow rate out of the unit using adjustable throttle valves. These work in a similar fashion to needle valves and can also control actuator speed. Further, the exhaust air may also contain contaminants, so an exhaust cleaner may be added to the silencer unit to protect the environment from any harmful particulates.</p><p><br></p>

Pneumatic systems are widely used in all sorts of machines, engines and industrial applications. Every pneumatic system runs on compressed air or gas, in order to move an actuator, and can be as simple as a single air-driven piston, or as complex as a mining operation with multiple actuators.

What Is Pneumatics?

<p>While some actuators and lifting devices can be purely electrical, using a screw system, it's far more likely that you'll be using some form of fluid power. This means you have a choice between hydraulics and pneumatics.</p><p>Pneumatics provides fluid power by means of pressurised air or gases. Hydraulics provides fluid power by means of pressurised liquids, such as oil or water. In choosing one of the two, cost-effectiveness, materials to be moved, availability of resources and space are all factors to be considered. Heavy lifting equipment, for example, takes up a lot of space and requires a great deal more power than the small-scale demands of robotic laboratory or food-processing equipment. Each type of power has its advantages and disadvantages, according to circumstances.</p><h2>1. Strength</h2><p>Hydraulics is the best option for strength, because the liquid medium used for its operation has a high mass density and is largely incompressible. This means that hydraulics can develop much higher levels of pressure, and can use that pressure to transmit the power that will drive your application. Industrial applications using hydraulic power may command anything from 1,000-5,000 pounds per square inch (psi) of pressure, while some specialised applications such as mining equipment or heavy lifting cranes can develop 10,000 psi or more.</p><p>The fluids used in pneumatics have low mass density and are easily compressible. In some circumstances, gas or air can be compressed up to several hundred psi, but most mechanical applications are based on an operational pressure of only 80-100 psi. This means that pneumatic systems are largely incapable of the much larger force offered by hydraulics, and are unsuited to the moving or lifting of heavy loads. Compressed air is also subject to unexpected pressure drops or fluctuations which can cause operations to become jerky or unstable.</p><h2>2. Hygiene</h2><p>Pneumatic systems win out over hydraulics in the field of hygiene, as the only thing that can leak out of your system is air. Within the system itself, the compressed air will be cleaned of oil, water or metal particles, and any other contaminants, by the filtration unit. Pneumatic systems are generally favoured by environmentally-conscious companies or those contemplating greener manufacturing practices.</p><p>You'll also be likely to choose pneumatics if you're installing systems in a clean room, a pharmaceutical laboratory, or the food and beverage industry. In these environments there must be absolutely no risk of contamination, so hydraulic systems are generally off-limits as they may be susceptible to leakage.</p><p>Whether you choose water or oil in a hydraulic system, either of these may potentially leak out via faulty seals, valves or worn hoses. This will contaminate your clean environment despite any safeguards you may put in place. The presence of liquids may also invite corrosion of the hardware, with a further risk of introducing contaminants. Storage tanks are also required for the fluids, and residues must be disposed of at the end of the operational process.</p><h2>3. Speed</h2><p>Speed is one of the pneumatic system's biggest advantages. Compressed air has a high flow rate, which enables the quick release of energy and high-speed motion of moving parts such as actuators. Pneumatic actuators can achieve high cycle speeds and increased duty cycling, which deliver greater productivity. The advantage of rapid cylinder movement is further enhanced by the availability of equipment in very small sizes, ideal for use in applications where miniaturisation is a priority.</p><p>Air has a much lower mass density, and can flow much more quickly and easily through pipework. Another advantage of the pneumatic system is that valves and cylinders can quickly alter their state or change direction by dumping their compressed air. This can be voided straight to the atmosphere and requires no further disposal.</p><p>Water and hydraulic oil have a much greater resistance than air, with the viscosity of oil making it much slower. Although it will ultimately develop a greater degree of force and maintain constant pressure, it does not have the same rapidity as air movement, and may take longer to get your system running. In the event of a leakage or emergency, hydraulic fluid may not be vented rapidly to the environment, but must be re-routed back to its tank or reservoir.</p><h2>4. Energy</h2><p>Comparing hydraulics to pneumatics with regard to energy consumption, there are several factors to consider. Both systems usually require an input of electrical power to drive them, and a pneumatic system needs the continuous running of a compressor to provide the compressed air. The air supply cannot be recycled and requires constant replenishment, so energy consumption in this respect may be high. Any&nbsp;<a href="https://www.rowse.co.uk/blog/post/how-to-find-leaks-in-pneumatic-systems" target="_blank" title="How to Find Leaks In Pneumatic Systems">air leakage</a> will also waste energy in the system.</p><p>You also have to take into account the fact that pneumatic systems lose energy through heat produced by the compression process – though there are several measures that can be taken to make your system more energy-efficient. Fortunately, air is still free of charge, so there is no need to expend energy in obtaining, replenishing or disposing of waste products.</p><p>Hydraulic fluids can use the same oil or water over and over again after the initial start-up. Provided you have a good filtration system and keep it properly maintained, a hydraulic system can be very energy-efficient in the long run. However, electrical power is still generally required to drive the pump, and much of the energy consumed by the pump is wasted. This is because the fluid medium is in constant circulation to maintain system pressure, even though only short periods of actuation may be required to drive the application. The more viscous the fluid medium, the more energy will also be required to move it. However, significant improvements are being achieved, with technological advancements involving different types of pump and the potential of modulating drives.</p><h2>5. Safety</h2><p>Considering hydraulics and pneumatics in the industrial environment, pneumatics is undoubtedly the safer option. A leakage of compressed air is not going to cause contamination, since air is not poisonous or corrosive, although other gases used in stand-alone or portable equipment may be hazardous. Compressed air does not generally pose a risk of fire and it won't explode, but the forcible escape of air through mechanical failure may cause physical injury.</p><p>Hydraulic fluids, on the other hand, are always at risk of potentially dangerous leaks. Even water can cause damage if it's hot enough to scald. Other fluid media such as oil, ethylene glycol, plasma and fluid synthetics may be corrosive and/or poisonous. The fluid media may be combustible and require extra safety precautions, and used oil or fluids must eventually be drained and safely disposed of. In general, hydraulic systems incorporate fewer mechanical parts, but these may be subject to corrosion and potential component failures.</p><h2>6. Complexity</h2><p>Hydraulic systems typically have fewer moving parts and may be easily controlled with push buttons and simple levers. On the other hand, hydraulics rely on complex engineering that requires a system of valves and hoses, as well as a pump powered by an external energy source and a tank for storage of the liquid medium. It is possible to install a centralised power unit in a manufacturing plant in order to control several different hydraulic applications. Newer technology is introducing much better systems of managing speed, pressure and power.</p><p>Pneumatic system designs are also typically very simple, and operate at a much lower pressure, so their component parts may be made from cheaper and less complex materials. Since the fluid medium is not corrosive or combustible, precautions do not need to be built in against these safety hazards. Technological advances have increased the variety of uses for pneumatic systems, with miniaturisation and new materials helping to reduce weight as well as bulk.</p><h2>7. Maintenance</h2><p>Pneumatic systems are cleaner and easier to maintain than hydraulic ones, since the fluid medium is air. A regular schedule of inspection and preventive maintenance is usually all that's required to keep a pneumatic system running, e.g. checking the seals and making sure there is no leakage of air. The air does need to be cleaned of contaminants, and one of the most important maintenance procedures is the cleaning and regular replacement of the&nbsp;<a href="https://www.rowse.co.uk/blog/post/when-to-replace-pneumatic-filters" target="_blank" title="When To Replace Pneumatic Filters">filter-regulator-lubricator unit</a>.</p><p>With hydraulic systems, the main issue is corrosion. Unless you’re able to install pipes made of non-corrosive material, such as galvanised steel, regular monitoring will be required to assess how the pipes are being affected by the fluid medium. Water may cause oxidation, and oils or other media may leave deposits that will cause corrosion. Regular checks and replacements will be required for critical components such as seals, hoses and valves.</p><h2>Context is Everything</h2><p>The flexibility of air flow, and its precision in use, make pneumatics an obvious choice for such applications as medical tools, dental drills and small-scale robotics. Pneumatics are best employed in specialised environments where hygiene or green practices are paramount, but they are generally impractical for large-scale or heavy lifting duties. Hydraulics are ideal for such high-force applications, and are often found in construction or mining environments. They provide constant torque and force, in spite of any variations in speed, and maintain positional rigidity. At the end of the day, while technological advances continue to improve energy efficiency and performance on both sides, the hydraulic vs. pneumatics question ultimately boils down to context.</p>

Any type of modern construction or manufacturing application is probably going to incorporate one or all of three different kinds of power: electrical, hydraulic or pneumatic.

Hydraulics Vs Pneumatics

<p>Machine building has become more complex with the introduction of more automated systems, and designers must devote more careful attention to the newer safety standards that apply. Mechanical safety standards had to be supplemented with new procedures for functional safety and performance reliability. In 2006, <a href="https://www.rowse.co.uk/blog/post/iso-13849-performance-levels" target="_blank" title="ISO 13849">ISO 13849</a> was revised to incorporate safety functions for machine control systems, reflecting the move towards more software-based architecture.</p><p>Designers must anticipate every possible eventuality for the system, whether it is operational, not operating or being serviced. Incorporating standards like ISO 13849 will ensure the maximum possible safety of pneumatic circuits and components, based on risk assessment and performance level (PL) parameters. Using factors such as MTTFd (mean time to dangerous failure), CCF (common cause failures) and DC (diagnostic coverage), the PL can be calculated for each individual safety function, and a required level of performance stipulated (PLr).</p><h1>5 Key Safety Functions in a Pneumatic System</h1><p>When designing a pneumatic system, there are five key safety functions that must be considered.</p><ol><li>Protection against unplanned start-up</li><li>Exhausting</li><li>Holding, blocking and stopping</li><li>Reversing the movement</li><li>Reducing speed</li></ol><h2>1. Protection Against Unplanned Start-Up</h2><p>One of the most important safety functions in a pneumatic system, or indeed any automated system, is to protect against the machine starting up accidentally. The most common way to do this is with a pneumatic safety valve which has been built for the purpose, and certified to the appropriate PLr. For PLc a simple solenoid valve is sufficient, with a single valve element which will cut in. More sophisticated valve constructions are required for PLd or e applications, which will often need redundant valve elements to assure full safety functionality. Some products may have inbuilt electronics for this function, while others may require a safety PLC or external safe relay to comply with requirements for safety certification.</p><h2>2. Exhaust or Air Pressure Dump Protection</h2><p>Dumping or exhausting of air pressure will probably occur at the same time as an unexpected start-up, and many modern safety components combine the two functions. A pressure supply valve will shut off the air supply in the event of any failure, preventing excess air pressure building up in the system. At the same time, air pressure within the system will be dumped safely, although a manual exhaust release can also be installed as a back-up. In the two-channel, three-valve system that is commonly used with higher PL applications, the downstream flow will be greater than the input supply, so that downstream pressure can still be reduced to a safe level, even if the input valve fails to shut off. More recent technology is likely to incorporate soft-start valves and position sensors to control unexpected start-ups and pressure dumps.</p><h2>3. Holding, Blocking and Stopping</h2><p>Holding, blocking or stopping operational equipment is one of the key safety functions in a pneumatic system, and applies to all kinds of applications across a wide PL range. It may be as simple as installing a pressure-operated check valve in the cylinder port. The trapped air pressure in the cylinder will hold the load and make sure it can&#39;t move, and a pressure switch added to the circuit could provide DC.</p><p>In more complex applications requiring higher PL, a mechanical lock or brake may be installed on the cylinder&#39;s piston rod. This clamps the piston rod into position using spring pressure and an appropriate valve. Another version of the rod lock comprises a pneumatic device installed on the piston rod. This device only allows cylinder movement if air pressure is directed to a port on the rod lock itself. Increased DC can be obtained by adding a sensor to detect when the rod lock is engaged.</p><h2>4. Reversing Cylinder Movement</h2><p>In simple, low PL applications, this safety function can be accomplished in a pneumatic system by a spring-return solenoid valve. Higher PL applications will require a more robust solution, such as a servo-pneumatic unit. The safety functionality in category 4 control architecture relies on the position of each valve element being sensed and transmitted to a safety PLC. This will ensure that the cylinder may only extend if both valve elements have moved.</p><h2>5. Reducing Speed</h2><p>Reducing speed is the easiest to implement of the key safety functions in a pneumatic system. It requires the installation of simple flow controls that can be validated with the appropriate movement parameters. Tamper-resistant locks may be installed to ensure these parameters are not altered.</p><p>This post was originally posted on&nbsp;<a data-fr-linked="true" href="https://www.rowse.co.uk/blog/post/5-key-safety-functions-in-pneumatic-systems" rel="noopener noreferrer" target="_blank">www.rowse.co.uk</a>.</p>

Machine building has become more complex with the introduction of more automated systems, and designers must devote more careful attention to the newer safety standards that apply.

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What Is Pneumatics?

Hydraulics Vs Pneumatics

5 Key Safety Functions in a Pneumatic System