Use and Applications of Pneumatic Fittings and Compact Cylinders

Pneumatic fittings are components of a pneumatic system use to make pneumatic connections that link hoses, pipes, and tubes. However, novices to the field of industrial automation may be confused as to the meaning of the pneumatic system. In simple terms, pneumatic systems are mechanical structures powered by compressed or inert gasses.  They find applications in a wide variety of machines including HVAC control systems, air engines, and vacuum pumps amongst others.

Pneumatic systems are made of various components including push in fittings and actuators such as the Festo actuators that operate on the principle of fluid power, alongside hydraulic systems. These two systems are met with their own advantages and disadvantages. However, manufacturers will choose pneumatic systems over hydraulic systems due to its reliability, its simplicity in design and control, and safety with the regards to the low incidence of fire outbreaks.

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As mentioned earlier, pneumatic fittings are connections for pipes and tubes within a pneumatic system. They are distinguished by tighter seals and operates under lower pressure values. On the other hand, hydraulic fittings – which represent the connections within a hydraulic system - are characterized by higher pressure requirements.  The application of pneumatic fitting in an air logic control system and instrumentation cannot be overemphasized. Before digging deep into the application of pneumatic fittings, some vital information needs to first be understood.

There are various kinds of pneumatic fittings. However, the exact type of pneumatic fitting can be determined by the kind of vessel it is connecting. These vessels may include:

 1. Hoses: These vessels are characterized by their flexibility and have multiple layers made from varying materials. Hose fittings are temporary since these vessels are susceptible to wear and tear which allows for replacement.

2. Pipes: The rigidity of these single layered vessels sets it apart from other vessel types. However, pipes are distinguished according to the inner diameter.

3. Tubes: These vessels are fairly rigid with only one layer composed of a single substance. They are distinguished by their outer diameter.

Pneumatic fittings come in various shapes and sizes, and they differ based on their connection types and functions. However, more attention will be given to the types of pneumatic fittings based on the function due to the cogent relationship between the uses and application of these components. According to the functions of these pneumatic fittings, some fittings add or alter direction, while there are others that link smaller pipes, and others that are solely meant for special connections or functions.

1. Fittings for altering or adding direction

Elbows: These fittings adjust the direction with respect to angles. Elbows of 45 degrees and 90 degrees are the popular ones available in the market. However, elbows with the angle of 22.5 degrees can also be found.

Tee: A 3-way connection with an intersection in the shape of the letter ‘T.’ Fluid flow with this type of fitting can either be combined or split apart.

Cross: This fitting links 4 sections. There can be three inlets and one outlet or the other way round.

2. Fittings with ends or increases pipe length

Adapter:  This links two pipes of different kinds through soldering, threading or solvent welding.

Coupling: This links two similar pipes through soldering, threading or solvent welding.

Cap: With this type of fitting, the vessel end can be sealed while making an attachment to the outer circular edges through solvent welding, soldering or threading.

Plug: It terminates fluid flow at the section’s end. It is also attached to the inner wall of the pipe through soldering, solvent welding or threading.

3. Fittings linking pipes of different sizes

Reducer: It connects multiple vessels of various sizes.

4. Fittings that allow for special connections and functions

Nipple: It allows the connection of two different fittings. These fittings are straight and possess male threads that run towards both ends.

Valve: These fittings connect two vessels but allow the regulation of fluid flow.

On the other hand, compact cylinders have been available since the 1950s when Alfred Schmidt invented the first one with the brand name Pancake. This device is used when the conventional pneumatic cylinder like Festo actuators are large enough for the space provided for it. Compact cylinders account for the longest stroke that can be gotten with the smallest envelope size on a general scale.

Manufacturers like Festo actuators use compact cylinders when there is limited space and mechanical actuation is preferred. The bore size of compact cylinders can be as low as 0.5 inches and may reach 4 inches with standard strokes varying between 1.5 mm and 100mm. Compact cylinders are sometimes referred to as short stroke cylinder since it can only attain the maximum stroke of 100mm.

Compact cylinders are typified by their piston-rod arrangement which can work in a double-acting or single-acting manner. Compressed air is used by double-acting cylinders to move the rod back and forth. Thus, a double-acting cylinder is regarded as the ideal option in pushing and pulling loads. Manufacturing tasks such as assembling, bending, clamping, lifting, punching, sorting and pressing are usually done with a double-acting compact cylinder.

Conversely, single-acting compact cylinders have one side of the piston acting as an inlet to compressed air and the other serving as an outlet to the atmosphere. The piston rod will either move backward or forward, depending on the end through the compressed air is supplied. The most common design is referred to as spring-return. In this arrangement, an internal spring returns the spring to its initial position after the compressed air runs out. There is also another arrangement known as spring-extend which allows the retraction of the piston rod due to air pressure. Consequently, the spring force results in the extension of the piston rod following the removal of air pressure.

The spring force in a single-acting compact cylinder is in one direction, and the return stroke is left without an impedance. These compact cylinders find their application in flap and lever actuation, ejection and clamping. Single-acting cylinders have massive popularity in the manufacturing industry. Notwithstanding, compact cylinders with double-acting configuration are still perfect for a handful of other applications. The uses of double-acting cylinder play out in a few other scenarios.

1. It is required that both sides of the pistons have equal displacement

2. It is necessary for the cylinder to work on both sides

3. There is a positive increase in mechanical advantage when attempting to couple loads to each end

4. The extra end can be used to mount cams for operating limit switches

Many might think that the smallness of compact cylinders makes it less preferable compared to larger pneumatic cylinders due to the power that can be generated by them. However, compact cylinders are just as powerful as the conventional cylinders. Furthermore, compact cylinders can be used linear actuation and control in a wide range of applications including robotics, automotive assembling, palletizing, semiconductor processing, packaging, bottling, food processing, conveyor systems, and material handling amongst others.