Pneumatics|Published Sep 1, |Updated Aug 19, |8 MIN READ

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Everything You Need to Know About Pneumatic Systems

Diving into the world of engineering, pneumatics stands as a pivotal concept. It's in our daily devices and at the core of industrial machines. In this concise guide, we'll explore its indispensable role and specifics. Let's explore the world of pneumatics together.

What is Pneumatics?

Pneumatics is a crucial engineering discipline. It involves the use of pressurized gas or air to produce mechanical motion, based on the principles of fluid dynamics and pressure. The use of pneumatics extends from compact handheld devices to large-scale machines, highlighting its versatility. This field has seen significant development and diversification, becoming an indispensable part of modern engineering.

In its simplest form a pneumatic system uses compressed air to complete work. It starts with a compressed air source which is most often a compressor. A typical compressor will convert electrical energy to potential energy in the form of compressed air. It is this potential energy that is stored and distributed through the air lines for a variety of purposes

One of the most common examples of a pneumatic actuator is the simple air cylinder.  In a cylinder as pressurized air forced into one side of the cylinder, it pushes onto the piston. With the opposite side open to the atmosphere, there is a force imbalance across the piston. This imbalance creates motion. It is this force imbalance and action that is used to do work.

Applications of Pneumatics

Pneumatic systems are diverse in their applications, including:

• Transportation: Pneumatics powers the braking systems in most vehicles.
• Manufacturing: Pneumatic tools are often used in product assembly lines.
• Medicine: Devices like respiratory ventilators and pressure regulators use pneumatics.
• Construction: Many heavy-duty tools, like jackhammers, operate on pneumatic systems.
• Home appliances: Everyday devices like vacuum cleaners and spray cans utilize pneumatics.

5 Benefits of Using Pneumatics

• Reliable/Low Maintenance – A properly designed pneumatic system supplied with clean, dry air is exceptionally safe and requires next to no maintenance. Components are rated for tens of millions of cycles, and the majority of modern equipment no longer needs lubrication.
• Simple- Pneumatic systems are relatively simple. Circuits are base on logic, and their outputs are typically linear or rotary motion.
• Ability to stall–Great for pressing and clamping applications. Pneumatics can supply a constant force indefinitely without the worry of burning out motors or drives.
• Self Cooling-Due to properties of expanding gases, pneumatic actuators cool themselves as they cycle back and forth. No need to worry about overheating.
• Inexpensive- Relative to their hydraulic and electrical counterparts, pneumatic components are much less expensive.

Basic Terminology

Dew Point Temperature at which moisture in the air condenses into water droplets Atmospheric Dew Point Temperature at which moisture in the air condenses into water droplets at atmospheric air pressure Pressure Dew Point Temperature at which moisture in the air condenses into water droplets at working air pressure Relative Humidity Current moisture content in air vs theoretical maximum moisture content Compression Ratio A measure of how much air is compressed Condensation Formation of water droplets from water vapor CFM  Cubic Feet Per Minute L/min Litres per minute SCFM Standard cubic feet per minute Nl/min Normal Litres per minute Standard Conditions

• A generally accepted definition of standard consolidations by which values can be compared
• 7 psia, temp 68 decF, relative humidity 36%

ANR

• Similar to Standard Conditions
• 1 bar, 20 deg C, 65% relative humidity

Mist Separation/Coalescing

• Removal of oil mist from air.

NO vs NC Auto drains 

• NO – Normally open, drains fluid when de-pressurized
• NC – Normally closed, drains fluid only when full

Main Parts of a Pneumatic System

Compressor

A compressor compresses air up to the required pressure. It converts the mechanical energy of motors and engines to potential energy of compressed air. This is where it all begins. Compressors typically feed air into a tank where the air is allowed to cool, removing some of its moisture. Tanks also act as a storage for pneumatic energy and also eliminates pulses generated by piston compressors.  Dryers are typically  connected after the tank to remove the moisture created in the compression process.

FRL – Filter, Regulator and Lubricator (Combination Units)

1. Filters remove particulate from the air,  as small as 5 microns. Some also remove water droplets using centripetal force. Mist Separators or Coalescing filters can be added to remove oil from the air.
2. Regulators control working pressure. Typical regulators have system air working against spring force across a diaphragm. As you adjust the handle on a regulator, you compress the spring more, requiring higher pressure to create a balance. When you need more force, this is what you adjust. Some electro-pneumatic regulators convert an electronic signal to pneumatic pressure settings.  Regulators as the name imply create a stable pressure output.  Most pneumatic systems run at 70-80 psi.
3. Lubricators supply a steady stream of oil droplets into the airlines. Earlier generations of pneumatic components used to require this source of lubrication to work correctly. Today, most parts come from the factory don't require lubricators

Control Valves

1-Directional Control Valves are similar to electronic relays. They convert a small control signal to a larger signal used to move actuators back and forth, rotary actuators to spin CW or CCW or grippers to open or close.

2-Solenoid Valves Solenoid valves are known for their efficient power usage, impressive flow rates, rapid response, and sleek, modern designs. They find wide-ranging applications in industries such as semiconductor, automotive, packaging, medical, specialty machinery, and machine tools.

Pneumatic actuators

Pneumatic actuators are the workhorses of a pneumatic system, transforming compressed air energy into mechanical motion. They come in various forms, capable of linear, rotary, or reciprocating movement, to suit different applications. Round body and tie rod cylinders offer robust linear motion, rodless cylinders provide a compact solution, rotary actuators enable rotational movement, and grippers are perfect for manipulating objects. Each type serves its unique purpose, ensuring that whatever the task, there’s a pneumatic actuator designed to handle it efficiently.

Contact us to discuss your requirements of Electro Pneumatic Valve. Our experienced sales team can help you identify the options that best suit your needs.

Pneumatic Tubes

Pneumatic tubes are hollow pipes, made from materials ranging from rubber and nylon to stainless steel, used to transport compressed air in pneumatic systems. They are crucial for ensuring a smooth flow of air between components, similar to how wires function in electrical circuits. The choice of material is vital, with options like polyurethane and polyethylene providing resistance to various environmental factors, including high temperatures and corrosion.

Pneumatic Connectors

Pneumatic connectors provide secure, removable connections between tubing and pneumatic components such as valves and actuators. Typically utilizing push-to-connect fittings, these connectors ensure a tight seal to prevent leaks, while also allowing for easy assembly and maintenance. They accommodate a variety of tubing materials and include silencers to minimize noise from exhausting air.

5 Things to Consider About Pneumatics

1. Air Quality - Moisture– When compressing air, you concentrate all that is in it. Especially includes moisture. Even on cold, dry days, there is sufficient moisture in the air to create a problem. Water in airlines corrodes metal parts they come into contact with, causing valves to seize, damaging seals and other components. It is vital to ensure the air in the system is dry by installing an appropriate air dryer system to remove moisture.
2. Air Quality – Particulate – Keeping air clean is critical to maintaining a reliable pneumatic system. At a minimum, air should filter down to 5 microns. It's recommended filter elements should be replaced every two years or when the pressure drop across the filter exceeds 14 psi.
3. Meter In vs Meter Out –There's an old saying in fluid power "When in doubt, meter out." Metering out is when you control or limit the airflow exiting a component. Metering in is controlling or restricting the airflow entering a part. In most scenarios, you'll want to meter out. Doing so will ensure smooth motion of actuators, especially at low speeds. Metering in can result in a stuttering motion. Why would you meter in? One example would be for single-acting actuators. You can't control the air leaving the cylinder, so you have no choice but to control what's entering it. The spring force acting against the piston will help eliminate the stuttering motion.
4. The proximity of valves to actuators - You'll want to physically mount valves as close as you can to the actuators they control. Minimizing the lengths of airlines to flow through from the valve to control the actuator. Longer tube lengths mean there's more volume needed to fill to reach working pressure. On the retract stroke, that's extra air needs to be vented and has to travel farther to do so. Adding cycle time and needlessly consumes compressed air.
5. Speed– Typically, the most significant factor in limiting the speed of an actuator is the air exhausting from the low-pressure side. As pressure decays, there is less energy available to move air particles through tubing and out through the exhaust port. As stated above, having needlessly long tubing lengths compounds this problem. One solution is a quick exhaust. These get plumbed near the cylinder port. During the high-pressure cycle, these stay closed. During the low-pressure period, they open up and allow air to vent to the atmosphere right at the cylinder port, dramatically reducing restrictions on the exhaust air, increasing speed. Always keep in mind, maximum speed specifications and implementing some form of shock absorption should cylinders be travelling the entire stroke length at high speed.

What do Pneumatics run on?

Pneumatic systems utilize compressed air or inert gases as a power source. The system comprises a network of components, including a gas compressor, transmission lines, air tanks, hoses, standard cylinders, and atmospheric gas.

How is pneumatics used in everyday life?

A Pneumatic device is a tool or instrument that operates using compressed air. Examples range from rock drills and pavement breakers to riveters, forging presses, paint sprayers, blast cleaners, and atomizers. The use of compressed air offers flexibility, cost-effectiveness, and safety.

Why is pneumatic better than hydraulic?

Pneumatic systems offer cost-effectiveness as air, which is the main component, is free. They provide enhanced safety as they can operate in potentially explosive environments and avoid overheating. Additionally, despite being small and light, they offer a relatively higher power output compared to other systems. Furthermore, Pneumatic technology is known to be cleaner.

Which is safer hydraulic or pneumatic?

When it comes to safety in the industrial setting, Pneumatic systems are a more secure choice than hydraulic ones. Compressed air leakage from Pneumatic systems does not pose a contamination risk, since air is not toxic or corrosive. However, it should be noted that certain gases utilized in standalone or mobile equipment may present hazards.

Still have questions after reading our post? Don't leave them unanswered! Contact us today for your pneumatic needs and questions.

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Hello experts,

There is a control loop with PID controller and pneumatic actuator that controls the position of the valve. Pneumatic actuator has positioner and is controlled with 4 to 20 mA.

There is one thing I don't understand and need your help and it is not that much related to controls or PLC.
On the nameplate of the pneumatic actuator is written max 6 bar, and in the installation of instrumentation air there is about 5.5 bar. However in the datasheet of the pneumatic actuator, there is so called "control pressure range" and "control force".
I don't understand what this actually means. For example, I have specific actuator with 60 mm full stroke (marked in the attached picture), and it's control range pressure is: from 0.2 up to 1.6 bar.

I don't understand why there is a range in the column "from" and there is a range in the column "to". From: 0.2-1.0 bar and To: 0.8-1.6.
I have Sipart PS 2 positioner, and I'm not sure if I need to order filter pressure reducing valve.

What is confusing to me is the fact that actuator is suitable for max 6 bar, but it's control range is only about 1.5 bar. I'm not sure how to interpret this.

As far as I know, most instrumentation air installations are 6 bar, and SIPART supports up to 7 bar, but pressure range on pneumatic actuator is only 1.5 bar.

I hope there are experts here who can clarify this to me.

Thank you!

I suspect this is your situation: There are two parts to your valve actuator. There is a cylinder that is able to exert a large force to overcome valve friction, hydrodynamic forces, etc. while moving the main valve disc or globe. That large force uses normal shop air at around 5.5 bar (80 psi) to move the cylinder's piston.

The air to the cylinder is controlled by a pneumatic positioner. It uses 0.2 to 1.4 (3-15 psi) and feedback from the cylinder to provide analog positioning. The cylinder moves until the position feedback matches the pneumatic signal, which in turn is regulated by the 4-20 mA I/P signal conditioner.

If you are supplying 6 bar (90 psi) air to the positioner you will need a pressure regulator to drop the pressure. Hello Tom and thank you for the reply. Yes, there is a pneumatic actuator that needs to develop a large force to move the valve. Actuator is air to close, spring to open. Therefore air is supplied to the actuator only on one side. This pressure will develop force to overcome spring force, and all friction and other forces including the resistant force of the fluid (water). What confuses me is the fact that 0.2 bar and 1.6 bar are mentioned as control range of the actuator. This data is not in positioner's manual. I think of 0.2 bar as pressure needed to overcome spring force in order to start moving the acruator. In that way 1.6 bar is enough for actuator to extend full stroke. I think it is only to overcome spring. The pressure in application must be greater than that because there are many other opposing forces. I believe your functional description is correct.

I suspect that the pressures stated on the actuator spec/label are for bench operation, the pressures needed to create the force needed to fully close against the spring pressure.

The PS2 positioner measures position, not pressure, so it allows its internal valve at the Y1 port to stay open as long as necessary to allow supply air to continually flow, chargin the actuator's volume above the diaphragm with more and more air, which creates a higher and higher pressure on the diaphragm until the valve stem moves to a position that matches the 4-20mA demand signal position, at which point the Y1 output valve closes.

The positioner needs a higher supply pressure than the nominal working pressure in order to overcome flow forces and stiction in the valve.

No need to diminish the supply pressure; the position will only use air as needed to create the pressure needed to position the valve stem.