Pneumatic Fittings - A Complete Guide

Pneumatic power systems include any type of mechanised or automated processes or machinery in which motion is driven by pressurised gas or compressed air. The obvious counter-reference here would be hydraulic systems, in which motion is driven by liquids held under similar compression forces within a sealed system.

‘Pneumatic’ specifically denotes the delivery of power through controlled movement of pressurised gases (including air). In any pneumatic-powered system, the pressurised gases that drive the required mechanisms are typically delivered to where they are needed through an airtight network of rigid pipes, robust hoses, or lengths of flexible tubing.

The vast majority of these conduits are connected to each other - as well as to the various devices being powered - by a wide variety of pneumatic fittings, couplings, valves and adaptors. As a general description, a pneumatic fitting can be any type of connector designed to link components or devices in a sealed and pressurised dry-air system.

These systems and fittings are widely used today in all manner of industries and applications, ranging from construction, assembly and production line setups to a huge variety of industrial machinery, handheld tools and workbench equipment. In many workplace environments, the power that a pneumatic system delivers can often prove more versatile, reliable, cost-effective and safer than an equivalent setup powered by various electric motors and actuators.

When shopping for connectors and adaptors for this type of system, you will be presented with numerous options covering a wide variety of different assembly methods and styles. Some of the most common include:

Push-In Pneumatic Fittings

This type is designed with speed and ease of assembly/disassembly in mind, but they are also built to provide a secure and reliable join. They typically enable entirely tool-free connection and disconnection between various tubes, pipes and tools; ideal for fittings that will frequently need to be reassembled.

The most common type of push-in fitting features a collet or ‘grab ring’ around the connection point, through which the hose or pipe slides and which then automatically grips and holds the tubing in place. Pushing down on the collet with two fingers (or a quick-release tool) instantly disconnects the fitting from the tubing.

Push-in fittings can be made from plastic or various metals. Plastics are typically used for lower pressure systems whereas metal fittings may be required in higher-temperature applications or environments.

Tube-to-Tube Pneumatic Fittings

Tube-to-tube adaptors are available in a variety of diameters, sizes, and materials. They are used to connect two lengths of tubing together, either straight or at an angle, and different types can be chosen to work with a range of materials such as nylon, polyurethane or polyamide conduit.

Threaded-to-Tube Pneumatic Fittings

This type of fitting includes screw-down threading on either the inner (female) or outer (male) edge of the connector, which will be gauged to mate with matching threads on the end of a length of hose or conduit.

Fittings sold with straight threading are intended to form a solid connection between parts, but not necessarily to form an air-tight seal on their own - this threading type will require additional sealant coating or a layer of Teflon tape for use in pneumatic applications. Fittings sold with tapered threading are intended to be airtight without the need for additional coatings or tape. This may be necessary for certain working environments where sealants and coatings may lead to corrosion or contamination.

Thread-to-Barb Air Fittings

This is typically a type of push-on fitting in which the hose or tube is pushed over a barbed end for initial grip, and then a knurled nut is tightened down around the pipe and barb to provide full security of the connection for use under air pressure.

Fittings can be attached to a fairly wide range of conduit and device types - including hoses, tubing and pipe - at various points around air-powered systems. The best pneumatic fitting for your intended application and working environment will largely be dependent on the operating pressures you need the system to be running at.

However, when choosing a specific fitting type, it’s also important to be mindful of the exact sort of conduit that you are pushing the compressed air through on either side of the fitting in question. Different materials will tend to have varying properties of their own, which will often dictate the best choice of fitting to use.

Hose

A hose is typically understood to refer to a flexible type of conduit, constructed from multiple layers of robust rubberised or plastic material. It is often designed to be replaced at fairly regular intervals due to general wear and tear. For this reason, fittings designed for use with air hose may be less permanent or more easily detached, with a view to being disassembled relatively often.

Pipe

A pipe in this context usually denotes a conduit constructed from more solid materials, often in a single layer or length, and generally seen as a better option for more permanent installations or runs. Pneumatic pipe fittings may well be more firmly fixed in place than other types and are sometimes specifically designed for less frequent disassembly or detachment. Pipe is commonly graded or sized for fittings according to its inner diameter.

Tubing in pneumatic systems is often something of a halfway house between hose and pipe; a relatively rigid option but with some degree of flexibility and aimed at less permanent setups than most conduit pipe assemblies. Pneumatic tube is usually sized or gauged for fittings according to its outer diameter.