Pneumatic fittings are used to connect pipes, tubes and hoses in a pneumatic system. These are usually found in pneumatic instruments or logic control systems. The pneumatic fittings have tighter seals than hydraulic fittings, but a much lower pressure requirement.
There are different metals used for pneumatic fittings, including, aluminium, stainless steel, brass and carbon steel. Brass pneumatic fittings are preferred for its unique properties. These are suitable for all kind of hoses, tubes and pipes. Pneumatic fittings are classified by a number of criterion. Some of these are:
According to the type of connection:
Pneumatic fittings are often named according to the type of fitting they provide.
- Ball and Sleeve Fittings: These fittings connect an outer sleeve with an inner layer. These fittings work best where a push-to-connect functionality is required, such as applications where frequent connection and reconnection.
- Compression Fittings: Here compression is used to connect the fitting. Within this category are standard compression fittings, bite-type fittings, and mechanical grip fittings and flare fittings.
- Crimp Fittings: These fittings are placed with a crimp over the tubular end. These need crimping tools to form the connection.
- End Fittings: There are two types of fittings here: clamp ends and plain ends. These are specific surfaces which allow tubes, hoses or pipes to be attached.
- Push-to-Connect: These fittings allow the tube too be pushed in at one end. The tube can be later retracted, forming a mechanism for disconnecting and reconnecting.
- Threaded Fittings: These have screw threads on their male or female surface. Simple threads are known as straight threads. These threads provide a connection, but not a tight seal. On the other hand are tapered threads which form a tight seal. Straight threads often need an extra coating for a tight seal.
According to material
Pneumatic fittings are made of metals, nonmetals or composites.
- Brass pneumatic fittings: Brass has moderate toughness, strength, good resistance to corrosion and shows good ductility in high temperature. Another of its strengths is its high machinability, which makes it easy and economical to work with. It typically works with smaller compression, lower pressures, and threaded fittings and for temperatures lower than 400º F.
- Aluminium pneumatic fittings: These are corrosion resistant and lightweight. It has a low tensile strength and is often alloyed with other elements like zinc and copper to improve strength. Because of its light weight, aluminium pneumatic fittings are used in areas like aerospace and automotive.
- Carbon steel pneumatic fittings: These are durable, strong, and have a better resistance to heat than aluminium and brass. An external coating of metals like cadmium or zinc is applied to increase resistance to corrosion. Carbon steel fittings can also sustain high pressure. These fittings are used in construction, agricultural and industrial equipment.
- Stainless steel pneumatic fittings: have an excellent resistance to corrosion and chemical. It can tolerate extremes in temperatures (–425° to 1200°F). The strength and ductility of steel makes it a highly suitable material. Despite its high cost, it is a necessary component in areas where high resistance to corrosion is critical.
- Fluororesins are fluorocarbon-based polymers, such as PVDF and PTFE. They are preferred for their chemical resistance and dielectric properties.
- Polypropylene fittings are preferred for their low price, durability and compatibility with a broad range of materials. Their resistance to environmental factors like UV radiation and weathering make them ideal for outdoor application.
These fittings combine different elements to form a composite material that combines the best of all its components. Example of composite include composites of fiberglass, carbon, and graphite.
According to function:
This is a wide classification:
- Adapters connect two dissimilar pipes to each other.
- Couplings connect two similar pipes to each other
- Union are couplings which can be disconnected without cutting.
- Caps are used to cover the end of a section.
- Plugs are used to close off flow from one end of a section.
- Elbows can changes the flow direction in an angles.
- Tee fittings connects a T-shaped intersection, creating three flow sections.
- Cross fittings are used to create 4-way connections.
- Reducers connection two or more vessels of different sizes.
- Nipple allows two separate types of fittings connect with each other
- Valve connect vessels together using a valve for better control.
These are the various types of pneumatic fittings. Widely used fitting materials like brass pneumatic fittings are available in different functional and connection types.