Along with hoses comes a requirement for hose connectors. There are a myriad of different types and sizes of hose connections that are perfectly suitable for compressed air. However, there are only few basic connectors that are typically used.
above Figure shows two different male NPT × hose barb fittings. The combination nipple is a standard pipe nipple with a hose barb rolled on one end. These fittings are generally preferred for hoses larger than 1/2 in. Hose menders are particularly useful items to have around and should be stocked in several different sizes.
Straight NPT screw connectors are a simple and effective way to connect basic compressed air hoses. These fittings are standard on one end of most 1/4- and 3/8-in. premade air hoses. The fitting consists of a ball seat/hose barb insert with a matching nut. The threads are straight national pipe threads and the seal is made against a small chamfer on the ID of the pipe. These fittings are available in sizes ranging from 1/4 to 3/4 in.
Industrial quick disconnect fittings are very common. They are extremely convenient to use because they automatically turn off the air when disconnected. This feature makes them ideal for applications that require frequent tool changes, such as auto repair shops. They are readily available in sizes ranging from 1/4 to 3/4 in. and can be purchased with male or female NPT threads and hose barbs.
Universal hose couplings are typically used for larger compression systems. They are a quarter turn unisex design. Fittings in the 1/4- to 1-in. range will universally mate with all sizes. This feature makes them rather popular in large plants and field operations. Additionally, these fittings are very rugged and easy to service. They are available in sizes up to 2 in., but these larger sizes will not mate with the smaller fittings. The one significant drawback to these fittings is that they do not turn off the air when disconnected. These fittings must be installed in conjunction with a ball valve. To reduce the possibility of accidental disconnection while under pressure, these fittings should always be secured with a safety pin when connected.