What is Pneumatics?
Pneumatics is the study and use of compressed gasses to generate forces and transmit energy. The transmission of forces is controlled by manipulating the working pressures within pneumatic systems. The output of many pneumatic systems is via a pneumatic cylinder.
The most common application of pneumatics is in your lungs. As we breathe in, forcing air into our lungs, we compress the air, which results in an expansion of our lungs. The air within our lungs is then stored energy allowing us to exert a force with our breath. For example, if shooting a dart from a tube. In pneumatic systems, this stored energy from compressed gases helps create a force.
Air is the most common gas used in pneumatic systems, although other gases are used. However, some gases are more suitable than others, such as nitrogen and carbon dioxide. Air is the most popular gas for pneumatic systems because there is a sustainable supply from the atmosphere.
What Are Pneumatic Systems?
Pneumatic systems consist of a combination of components fitted together to transport compressed gases to do work. Pneumatic systems are commonly used across the world and in varying industries. The reason for its common use is its ease of use. Furthermore, pneumatic systems tend to be very reliable and easily maintained.
Pneumatic System Components
The core principle of pneumatic systems is the distribution of compressed gases (mainly air) to complete work. Therefore, many pneumatic systems have similar components. See below a list of pneumatic system components:
– Compressor – Compressors are mechanical devices that increase the pressure of a gas, achieved by reducing its volume.
– Air (gas) Reservoir or Accumulator – Compressed air is not transported directly from the compressor. It is transferred to a tank or air reservoir that will hold the compressed air and release the air as required preventing irregular air surges. Importantly the air reservoir helps accommodate the peaks of the demand of the system and helps with efficiency.
– Check Valves – Check valves are also known as one-way valves. The role of a check valve is to prevent any backflow of the air. They tend to be fitted on the air reservoir and other positions to prevent air from flowing back into the compressor. Check valves allow the system to be reliable and safe.
– Pressure Gauges – Pneumatic Systems will operate at specific pressures depending on the application (higher pressures for larger components). The pressure gauges tell the pneumatic system software if the operating pressures are correct.
– Regulators – Regulators are either electrically or mechanically operated. The regulator has the role of releasing compressed from the air reservoir/accumulator to the circuit.
– Feed Lines / Hoses – The compress air must have a transport system and hoses are used to transport the Feed Lines / Hoses – The compressed air must have a transport system, and hoses are used to transport the compressed air. The hoses are usually made of a thick material to reduce the possibility of air leaks due to hose defects.
– Pneumatic Cylinder / Actuator – The output of the pneumatic systems is generally achieved by the use of pneumatic cylinders and actuators. We go into more detail on them below.
What Are Pneumatic Cylinders and Actuators?
Pneumatic Cylinders, also known as pneumatic actuators, are mechanical devices to produce a linear or rotary motion and force as an output for pneumatic systems. Applications of pneumatic cylinders include automated systems, machines, rail vehicle brakes etc. Compressed gas powers the devices and provides the appropriate movement.
Pneumatic cylinders tend to require little maintenance, making them an efficient solution and popular across industries. A contributory factor to the minimal maintenance is that any leaks in the system will not contaminate the surrounding parts because air is the working fluid.
The core components of pneumatic cylinders include a piston, a piston rod, an operating cylinder, an end cap and various seals.
How Do Pneumatic Cylinders and Actuators Work?
Pneumatic cylinders work by the input of compressed air, generating a force against the piston. The force generated by a pneumatic cylinder is related to the area of the piston.
F = P x Ae
F = Force
P = Applied pressure on the surface
Ae = Effective Area
The two common types of pneumatic cylinders are single acting and double acting. Single-acting cylinders have just one input port. When compressed air enters the single-acting cylinder, it forces the piston to move. The piston arrives back to its original position when the compressed air is released, by the force of a spring. In double-acting cylinders, input and output ports are located at either end of the cylinder. The position of the ports allows the compressed air to move the piston in both directions by manipulating which end the compressed air enters.
The forces for both directions are not equal in double-acting cylinders. The reasoning is that the piston rod reduces the effective area on the outward stroke, whereas the inwards stroke is not affected by the piston rod.
How Do Pneumatic Systems Works?
Pneumatic systems have a range of uses and hence have a range of components. The pneumatic system components described above are joined in a circuit to allow functionality.
The core functionality of a pneumatic system is to supply compressed air (from a compressor) to an output device (pneumatic cylinder) to give the desired output. Additionally, pneumatic systems are designed to be fail-safe in the event of a leak or drop in pressure.
There tend to be two circuits in a pneumatic system that have a safety-critical application. The application of compressed air activates the first circuit but suppresses the second circuit. The compressed air will be working against a spring in the second circuit to prevent the fail-safe application. Conversely, in the event of a gas leak, the spring in the second circuit will become active and act to stop the operation of the pneumatic circuit.
Common Pneumatic Symbols
Examples of Pneumatic Systems
– Rail vehicle brake applications – Compressed air is supplied to a pneumatic cylinder, forcing the brake pads to squeeze against the brake discs.
– Bike Pumps – Air is pressurised when entering the bike pump resulting in it moving from a high-pressure environment (in the bike pump) to a lower pressure environment (flat bike tyre).
– Jackhammer – Compressed air forces the pile driver down and controls the reciprocating motion.
– Nail Guns – When the trigger is pulled, a valve opens allowing compressed air to enter the chamber, driving the piston down and hammering the nail. Correspondingly, when the trigger is released, the air is dissipated through small holes at the bottom of the cylinder.
Advantages of Pneumatic Systems
– Low maintenance requirements make them reliable
– Plentiful supply of air
– Can be applied across many sectors and applications
– Efficient solution
– The operation of pneumatic systems are simple
– Pneumatic systems have a good track record for being safe
Disadvantages of Pneumatic Systems
– Pneumatic systems are sensitive to extreme temperature changes
– Although there is a plentiful supply of air, compressors are expensive to operate
– They can generate lots of noise
– Leaks can occur easily