Push-In Fitting - How They Work

Pneumatic push-in fittings

Pneumatic push-in fittings, also called push to connect fittings, provide a leak-free means of easily connecting hoses in your compressed air system. Fittings can have between 1-6 inlet/outlet ports or may have additional functionality such as an integrated pressure gauge or silencer.

Table of Contents

How to install pneumatic push-in fittings

The hose is easy to install by pushing it into the release ring-end of the fitting until it stops. The internal lock claws will automatically clamp around the hose for an immediate and secure connection. See Figure 1.

How to uninstall pneumatic push-in fittings

Push the release ring inward towards the fitting to disengage the lock claws and pull back on the tubing to remove it. The opposite end may be another push to connect fitting, threaded male, threaded female or a threaded male with an inner hex-type connection. The threaded connections usually have a pre-applied thread lock coating. The tube must be fuller inserted for a proper seal, as seen in Figure 1 point A. Figure 1 point B shows an incomplete insertion of the tube, creating a leak in the seal.

Left image shows proper tube installation. Right image shows incomplete insertion

Figure 1: Left image point A shows proper tube installation. Right image point B shows incomplete insertion.

Video Overview

Pros

The greatest advantage of push-in fittings is the quick release system which allows for simple and easy installation by hand, eliminating the need for tools and adhesive. Due to the ease of connecting and disconnecting air lines, it allows for frequent changing of air lines at a low cost. They are offered in a wide range of tube sizes, connections, and thread combinations to suit the desired outcome. Tameson fittings are RoHS compliant.

Cons

Push-in fittings require firmer tubing with harder walls to resist being damaged by the internal claws. Firm tubing will be less flexible; therefore, it may not be suitable for systems where hoses will be routed around tight turns. If flexible tubing is desired, we recommend using hose tail barbed fittings instead of push-in fittings. Nylon, Polyethylene (PE), or Polyurethane (PU) tubing material is ideal for push-in fittings. It is also best suited for pneumatic (air) applications; however, it can be used for water applications (see datasheet).

Normal vs unequal fittings

Some fittings are available in normal or unequal variations. Normal fittings use the same diameter across all inlet and outlet ports whereas unequal fittings have ports with different diameters (larger or smaller) to connect different sized hoses.

Connection points

Fittings can have multiple connection points ranging from one to six connections. All fittings have at least one port as a push-in fitting (excluding plugs). How they route the air (straight, elbow, etc.), normal vs unequal, and other connection port methods (plug-in, threaded, etc.) make the differences in types.

One connection

These fittings have one connection port, so they end the flow of the air.

Plug and cap fitting

Cap push-in fitting Plug for push-in fittings (right)

Figure 2: Cap push-in fitting (left) and a plug for push-in fittings (right)

Plug and cap fittings are used when the flow of air needs to be temporarily terminated or capped. A cap, Figure 2 left, is used to terminate a pneumatic hose with a plug-in fitting. A plug, Figure 2 right, is used to seal a pneumatic push-in fitting and is installed/uninstalled in the same manor.

Two connections

Two connection fittings have a single push-in type port and a single threaded (male or female) or push-in type secondary port. The air flows from the inlet port to the outlet port.

Straight fitting

Straight push-in male fitting Straight push-in female fitting

Figure 3: Straight push-in male fitting (left) and female fitting (right)

Straight fittings connect a hose in a straight line with a male or female threaded secondary port. See Figure 3 for examples.

Inner hex straight fitting

Inner-Hex Straight push-in fitting

Figure 4: Inner-Hex Straight push-in fitting

Inner hex straight fittings have a male threaded secondary port and an inner-hexagonal connection. Inner hex straight fittings have a male threaded secondary port to connect it to a valve and/or a component. The inner-hexagonal can be tightened after the threaded connection is made and a hex key can come in from the push-in fitting side to tighten the threads. See Figure 4 for an example.


 

Elbow fitting

Elbow 90-degree push-in fitting

Figure 5: Elbow 90-degree push-in fitting

Elbow fittings connect hoses at 90 or 45-degrees to change the direction of air flow. They have a male or female threaded secondary port. Normal elbows have arms that are the same length, whereas long elbows will have one longer arm. See Figure 5 for an example of a 90-degree elbow fitting.


 

Union straight fitting

Union straight push-in fitting

Figure 6: Union straight push-in fitting

Union straight fittings have a push-in type connection at each end to connect two hoses in a straight line. Unequal union straight fittings have different diameter ports to connect hoses of different sizes. See Figure 6 for an example.


 

Union elbow fitting

Union elbow push-in fitting

Figure 7: Union elbow push-in fitting

Union elbow fittings connect two hoses and has a 90-degree bend to it. Each port has a push-in type connection. See Figure 7 for an example.


 

Plug-in straight fitting

Plug-in straight push-in fitting

Figure 8: Plug-in straight push-in fitting

Plug-in straight fittings connect hoses in a straight line, whereby, one port uses a push-in type connection and the secondary port uses a stem or “plug-in” type connection. Typically, the stem is inserted into an existing push-in fitting. See Figure 8 for an example.


 

Plug-in elbow fitting

Plug-in elbow push-in fitting

Figure 9: Plug-in elbow push-in fitting

Plug-in elbow fittings connect hoses at 90-degrees using push-in and plug-in type connection ports. See Figure 9 for an example.

Three connections

Three connection fittings have two push-in type ports and one threaded or another push-in type port. The fitting can have either two inlets and one outlet to increase pressure, or one inlet and two outlets to decrease pressure and make two air flows.

Union Tee fitting

Union Tee push-in fitting

Figure 10: Union Tee push-in fitting

Union Tee fittings form a “T” shaped junction to connect three equal diameter hoses using a push-in type connection at all ports. Unequal Union Tee fittings are also available to connect a smaller diameter hose to two larger diameter hoses. See Figure 10 for an example.


 

Union Y fitting

Union Y push-in fitting

Figure 11: Union Y push-in fitting

Union Y fittings form a “Y” shaped junction to connect three equal diameter hoses using a push-in type connection at all ports. Unequal Y fittings are also available to connect a larger diameter hose to two smaller diameter hoses. See Figure 11 for an example.

Four to six connection points

Push-in fittings are also capable of having more connection points, but typically no more than 6. A few examples of fittings with more connections are double “Y”, triple “T”, or cross fittings. These fittings are for special applications, but can help reduce overall fittings to feed 1 input line and to multiple outputs.

Functional combinations

Push-in orifice fittings

Push-in orifice fittings

Figure 12: Push-in orifice fittings

These consist of a push-in fitting on one side and a threaded fitting with an orifice on the other side, as seen in Figure 12. The orifice reduces the size of the tube thus controlling the air flow to a desired rate. These fittings can be used to throttle, bleed and vent a pneumatic system. They are also known as flow control orifices, precision orifice valves and flow restrictors.

Push-in check valves

Push-in check valves

Figure 13: Push-in check valves

These valves ensure that the air goes freely only in one direction while preventing it in the opposite direction. The valve has a spring-loaded poppet pressed against the base of the orifice. When the air comes in on the poppet side, at a pressure higher than the valve’s cracking pressure, it compresses the spring, opening the orifice allowing air to move through. When it comes from the spring side it will press the poppet against the orifice’s base and block the passage. The symbol engraved in to the valve’s body indicates the direction of the air flow, as seen in Figure 13. In this case, the air flows freely from the threaded port to the push-in fitting.

Read our check valve article to learn more about this functionality.

Push-in orifice check valves

Push-in orifice check valves

Figure 14: Push-in orifice check valves

These valves consist of an orifice fitting and a check valve combination and can be seen in Figure 14. On one side they have a push-in fitting and on the other a threaded port with a check valve in it.

The orientation of the check valve within it dictates which flow is metered. If the flow is metered entering a cylinder it is a meter-in valve and if it is metered exiting the valve it is a meter-out valve.

Read our check valve article to learn more about this functionality.

Needle valves with push-in fittings

Needle valves with push-in fittings

Figure 15: Needle valves with push-in fittings

These valves are used to shut off or control the air flow by changing the size of a valve’s orifice. The size of the orifice is regulated by adjusting the needle manually. When you screw the needle in, it reduces the volume of the air flow, unless you screw it in completely which would shut it off. An example can be seen in Figure 15.

The flow rate can be adjusted during the air flow. To secure the needle in the desired position tighten the locknut. These valves affect the air flow in both directions and are useful in low flow rate applications.

Read our needle valve article to learn more about this functionality.

Push-in flow control valves

Push-in flow control valves

Figure 16: Push-in flow control valves

These valves are designed to control the flow rate in one direction and allow a free air flow in the opposite direction. They consist of a needle and an orifice check valve combination, which provides them with both of their functions.

The needle valve provides the throttling function while the orifice check valve ensures that the flow is affected in only one direction. The orientation of the check valve within the flow controller dictates which flow is metered, which can be seen on the valve’s housing (Figure 16). If the flow is metered entering a cylinder it is a meter-in valve and if it is metered exiting the valve it is a meter-out valve.

Read our needle valve article to learn more about this functionality.

Push-in quick exhaust valves

Push-in quick exhaust valves

Figure 17: Push-in quick exhaust valves

These valves consist of an inlet, an outlet and an exhaust port. The inlet and the outlet ports are connected to the pipeline. The valve’s diaphragm element allows the free flow from the inlet to the outlet port, but not in the opposite direction. When the medium returns to the outlet port it is immediately exhausted through the exhaust port thus providing faster piston movement for example. This quick exhaust function allows systems to free themselves from used compressed air without returning it to the solenoid valve.

The exhaust port is usually equipped with a silencer (as shown in Figure 17), while some models have a needle in the exhaust port to regulate the air flow at the exhaust thus affecting the speed of an actuator.

Push-in shut-off hand valves

Push-in shut-off hand valves

Figure 18: Push-in shut-off hand valves

These valves are designed for shut off control of the air flow. To operate the valve, use a quarter-turn handle (Figure 18). Turning the handle 90 degrees opens or closes the valve by moving a spool, which has lands and valleys, upward or downward. The land is a thicker part of the spool, which closes the valve and prevents the flow while the valleys allow the air flow when they are positioned between the ports.

These valves can be two or three-directional. The three-directional valves have a residual pressure release function. This means that they vent out the compressed air after closing, which relieves the system of the built-up pressure. The two-directional valves do not have the relief function, which is useful in applications that need to keep the residual pressure.

Push-in mechanical valves

Push-in mechanical valves

Figure 19: Push-in mechanical valves

These valves control the direction of the flow with a spool. The spool closes or opens desired ports which blocks or allows the flow through them. The number of ports varies and some products have an option of adjusting the ports’ direction by rotating them independently. An example can be seen in Figure 19.

Pushing the pin moves to spool downwards to close the valve if it is normally open or opens it if it’s normally closed. The spool consists of lands and valleys. The land is a thicker part of the spool, which closes the valve and prevents the air flow while the valleys allow the air flow when they are positioned between the ports.

Ball valves with push-in fittings

Ball valves with push-in fittings

Figure 20: Ball valves with push-in fittings

These valves provide shut off control of the flow by rotating the ball. The ball has a bore drilled through it and by turning the handle 90 degrees the valve closes or opens. An example can be seen in Figure 20.

Read our ball valve article to learn more about this functionality.

3/2-way ball valves with push-in fittings

3/2-way ball valves with push-in fittings

Figure 21: 3/2-way ball valves with push-in fittings

The 3/2-way ball valve designed for directional control of the air flow. Turning the handle 90 degrees directs the flow through the two desired ports at a time. An example can be seen in Figure 21.

Read our ball valve article to learn more about this functionality.

Pressure control valves with push-in fittings

Pressure control valves with push-in fittings

Figure 22: Pressure control valves with push-in fittings

These valves reduce the inlet pressure (threaded) side and release it to the outlet (push-in fitting) side. The threaded side contains an orifice check valve, which directs the flow to a poppet. This poppet is attached to an adjusting spring which is compressed by an adjusting needle thus setting the desired output pressure rating. The check valve provides pressure control from the inlet side to the outlet side while allowing a free, unmetered air flow in the opposite direction.

These valves are usually placed between a directional control solenoid valve and a flow control valve thus providing the flow controller with only as much compressed air as needed. They reduce the supply pressure on the retracting stroke, which conserves the compressed air. An example can be seen in Figure 22.

Pressure regulators with push-in fittings

Pressure regulators with push-in fittings

Figure 23: Pressure regulators with push-in fittings

These regulators are designed to keep the outlet pressure at a desired value, encase the inlet pressure were to rise above this set value. This allows for easier and more accurate pressure control. An example can be seen in Figure 23.

To learn more about pressure regulators go to pressure regulator article.

Pressure gauges with push-in fittings

Pressure gauges with push-in fittings

Figure 24: Pressure gauges with push-in fittings

Insert the tube in the push-in fitting and the gauge will show the system’s pressure rating. An example can be seen in Figure 24.

To learn more about pressure gauges go to pressure gauges article.

Selection criteria

Pneumatic fittings should be incorporated into a system that requires connection hoses together. It is advised to keep things simple to ensure no significant pressure drop is induced. For example, don’t use a 90-degree elbow if a straight fitting is possible because the elbow will create an unnecessary pressure loss. Other considerations include:

  • Operating pressure: Most fittings have a maximum operating pressure of 1.0MPa, but the pressure should be kept below this level to ensure safe operation.
  • Operating temperature: Fittings contain o-rings and plastic parts that may become ineffective if using hot air or if the system is placed in a hot environment.
  • Special environments: medical and food industries may require fittings with a special rating or material classification.

Applications

Push-in fittings are used in all types of compressed air systems, but are most commonly used in applications having pneumatic cylinders, tools, and equipment. They can be used for water applications, but extra measures have to be taken (controlled surge pressure, water compatibility, insert ring, etc.) The push on connection method allows for rapid changing of components, so it is ideal if you have one air source for multiple tools that can be exchanged out.

Additional information

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