Beginner's Guide to Pneumatic Fittings

The different types of pneumatic fittings have different functions. For exampe, bulkhead connectors are used to connect piping or tubing together through a panel. And, a male stud is typically used on a pneumatic acutator with a threaded port, so that tubing can be connected to it. In this article, we will examine all the different types of pneumatic fittings and their usage.

1. Function of Pneumatic Fittings

Whilst the most obvious function of pneumatic fittings is to connect pneumatic components (actuators, valves, filters, air treatment) together, there are more nuances to this than at first glance. Consider the need for adjustment of connection type. The majority of pneumatic components have threaded connections whilst pneumatic tubing does not have threads, but are rather of a specific outer diameter (OD) size (usually metric, though sometimes imperial). Unlike hydraulics, it is not feasible for the airline to have threads built in. This presents both start-up engineering and cost savings, and is one aspect where pneumatics reign supreme over hydraulics. The lack of threading on pneumatic lines (i.e. tubing) means some adaptor or fittings will need to be used. This is the first function of pneumatic fittings.

Secondly, sometimes, components will need to be easily disconnected and reconnected. Push-In Fittings are helpful here. A quick press on the release ring will release tubing, whilst a sturdy thrust of tubing into the fitting will engage the lock jaws, securing the tubing for pneumatic system use. In contrast to push-in fittings, pneumatic quick couplings can also be convenient (and safer) as inline pressure will not need to be reset to 0 before every reconnection. Quick couplings usually have 2 (though, sometimes, 3) components to join two independent tubing together.

View All Pneumatic Fittings

2. Types of Pneumatic Fittings

2.1. Studs (Female and Male)

Figure 1. Male Stud	Figure 2. Female Stud

Male Studs and Female Studs (sometimes called Straight Connectors) are the simplest type of pneumatic fitting. They are

2.1 Elbow Fittings (Shop Elbow Fittings)

Figure 3. Elbow Fitting -- Push-In Port to Male Thread

Elbow Fittings are shaped at 90-degree angles. This is so that they can connect pneumatic components (actuators) with the air line in a non-obstructive manner. Imagine a cylinder mounted for use, would a male stud whereby the tubing has to exit directly, be appropriate?

Union Elbows

One type of elbow fittings are union elbows, sometimes known as equal elbows, whereby both ends of the elbow are of the same size. In pneumatics, they can be metric tubing to metric tubing, (6mm to 6mm) or thread to thread (1/8” to 1/8”).

Male Thread to Metric Tubing Elbows

These are the most common type of pneumatic elbow fittings. They connect a pneumatic component to pneumatic tubing. The component (e.g. actuator, filter) will usually have a female thread socket. The pneumatic fitting fits into the thread (with PTFE tape), and pneumatic tubing can connect to this fitting via the push-in socket.

Female Thread to Metric Tubing

This type of fitting is similar to the above type of fitting, with the sole difference of there being a female thread rather than male. A female thread to metric tubing elbow allows a male threaded fitting to connect to the elbow fitting.

Female to Female Elbows

Female to Female elbows have the primary function of connecting two male threads together in a elbow shape.

Flow Control Elbows

Flow Control Elbows control the flow rate through the fitting and can be used to adjust the actuation speed. The most common flow control elbows have male thread on one end, and a metric push-to-connect port in the other end. These flow control elbows house a small needle valve inside and, sometimes, also check valve to prevent backflow.

Our PISCO JSC series is a popular flow control valve in the United Kingdom.

2.2. Tee Fittings (Shop Tee Fittings)

Tee fittings are used to connect three pneumatic lines together. The flow path is not dictated by the tee fitting but by where the compressed air originates. There are a few different types of Tee fittings.

Figure 4. Union Tee Fitting

2.2.1 Intermediate Tee

Intermediate Tee fittings are the most basic type of tee fittings. They have push-in fittings on all three sides of the ports

2.2.2 Branch Tee

A branch tee is a type of pneumatic fitting where the central end has a male thread, but the other two ends have a push-in fitting. Branch tees can come in a variety of sizes. In pneumatics, the 6mm to 1/8”mm, and the 6mm to 1/4" are the most common.

2.2.3. Run Tee

A run tee, in contrast to the branch tee, has the male thread on one of the non-central ends of the fitting. The centre and remaining ports are push-to-connect. They allow for a pneumatic component to be connected to a tubing ‘run’ at 90 degrees.

Y fittings are similar to tee fittings in function but are of a different shape. Two of the ports are at an acute angle (< 90 degrees) with each other, and are used to

2.3.1 Intermediate Y Fittings

Intermediate Y fittings have all three ports of the same type. In pneumatics, intermediate Y fittings are often all push-to-connect fittings

2.3.2 Branch Y

In branch Y fittings, the central port is a male thread whilst the two other ports are push-to-connect ports. They are used to connect a device to two pneumatic tubes in Y shape as to be suitable in tight spaces.

2.4. Stem Adaptors

Stem adaptors are fittings that have a tubing stem on one end, and male threaded connection the other end. They are used to connect tubing to a threaded port. They are different types of stem adaptors, including stem reducers and stem increasers.

2.5. Swivel Fittings

Swivel fittings and/or rotating joints are vital system element in reducing kinking, stretching, and other stresses of pneumatic tubing. Swivel fittings allow for tubing to pivot in a 360 degree fashion, along 1, 2, or all 3 planes.

The underlying principle and construction of swivel fittings is simple: they are alike static fittings except for the fact that they incorporate a dynamic seal,

Swivel fittings can be cost-effective and pay for themselves by reducing air leaks and increasing the life cycle of pneumatic tubing.

2.6. Banjo Fittings

Banjo fittings are functionally similar to elbow fittings in that they have a push-in port and a male thread on the other side that are at 90 degrees from each other. However, banjo fittings are specifically designed for high pressure usage and have very tight seals.

Figure 5. Banjo Fitting

2.7. Ball Valve Fittings

Ball valve fittings, in pneumatics, are used to restrict or permit flow absolutely. So, unlike flow control fittings, they cannot modulate flow rate. They are used to turn off and on flow.

Figure 6. Ball Valve Fitting