A Guide to Pneumatic Tubing
What is pneumatic tubing?
Pneumatic tubing is used to deliver compressed air to power air tools and actuators. Since tubing comes in a huge range of sizes, it is important to choose one that is fit for the purpose. Pneumatic tubing supplied in different materials that suit different applications also as a solid or other forms such as PVC.
The choice of pneumatic tubing should be guided by the required type of air supply and application. This is because airflow requirements usually determine tubing specifications. While hoses are usually classified according to their inner diameter, for pneumatic tubing this is usually done by measuring its outer diameter as well as wall thickness. Selecting the wrong pneumatic tubing can have disastrous consequences. A tube that is too small can restrict airflow, leading to pressure losses and too much fluid velocity. A tube that is overly large, on the other hand, can lead to excessive costs and be cumbersome in small spaces.
Another thing to consider when selecting pneumatic tubing is the maximum working pressure. The maximum working pressure of pneumatic tubing is measured by looking at its burst pressure at 75 degrees Fahrenheit, or 24 degrees Celsius, and dividing it by a factor of 3:1 or 4:1.
Pneumatic tubing materials
Pneumatic tubing can be made from a variety of materials. Here are just some of the most popular pneumatic tubing materials on the market.
Durable and resistant to kinks and abrasions, polyurethane, or PU, tubing is the most popular type of tubing used to supply air in pneumatic systems. It is flexible and sturdy enough to withstand not just air pressure but also oil and fuels. As such, polyurethane tubing is commonly used in pneumatic actuation systems, vacuum equipment and semiconductor manufacturing.
Lightweight, flexible and inexpensive, polyethylene, or PE, tubing is ideal for use in low pressure applications. Polyethylene tubing also has decent resistance to chemicals and solvents. One of the better known suppliers of polyethylene tubing is the manufacturer of drink dispensing equipment John Guest. John Guest Tubing is renowned for its high quality and durability.
Polyamide Parker Legris Tubing
Another popular type of pneumatic tubing is polyamide, or PA, tubing. Manufactured by Parker Legris Tubing, rigid or semi-rigid polyamide tubing is durable and resistant to chemicals and humidity. Polyamide tubing also features good vibration absorption and is perfect for various air pressures and temperatures. Plus, Parker Legris Tubing is silicone-free and comes in a range of colours for easy identification.
Parker Legris Tubing’s semi-rigid PA tubing can be used with compressed air and other fluids and can withstand pressure and vacuum up to 50 barg. Plus, it has a working temperature range from - 40°C + 100°C. Parker Legris Tubing’s rigid PA tubing can be used with compressed air and other fluids as well as lubricants.
Often used in the food industry, polypropylene tubing is chemical and UV-radiation resistant. As such, it is a great option for outdoor use.
Lightweight and relatively tough, nylon tubing is great for applications in high pressure environments. It is also flexible, which makes it a firm favourite for use in compact spaces.
Polyvinyl chloride tubing
Polyvinyl chloride, or PVC, tubing is extremely flexible and lightweight. Plus, it is chemical-resistant, which makes it well suited to sterilisation procedures and as such is often used in medical settings.
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Types of Pneumatic tube fittings
Usually made from steel alloy, aluminium alloy, copper or brass, there are many different types of pneumatic tube and hose fittings on the market. Here are just a few of the most common ones.
Pneumatic elbow fittings
Featuring two inlets / outlets at a 90-degree angle, pneumatic elbow fittings are used to connect multiple tubes, hoses or pipes. They are particularly popular for connecting nylon tubing.
Pneumatic stud fittings
Pneumatic straight fittings usually feature one threaded end and one tube connection end where the tubing is attached. They can be purchased in different thread sizes, grades and diameters and can be used as adaptors for different tube sizes.
Pneumatic Y fittings
Often used in robotics, packaging and the automotive industry, pneumatic Y fittings feature three inlets / outlets in a Y shape.
Pneumatic T fittings
Frequently used in pressure and vacuum applications, pneumatic T fittings feature three inlets / outlets in a T shape. They typically come with a push-in mechanism for secure and leak-free connection to threaded ports.
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Pneumatic tubing is often flexible, which makes it easier to store than rigid pipes and some hoses. As such, pneumatic tubing is often stored in reels or cylindrical spindles. These can be either self-retracting or cranked by hand. Reels not only keep pneumatic tubing out of the way when not in use, but they also protect it from kinks and other damage. In addition, many pneumatic tubes are also sufficiently lightweight to be mounted along various surfaces such as walls and ceilings.
Made from nylon, PU or PVC, coiled air hoses are usually used to deliver power to air tools such as air blow guns and impact wrenches. They are extremely lightweight and self-retractable so as not to take up a great deal of space. Coiled hoses are elastic enough to return to their original form after they are straightened during use. Coiled air hoses typically come with two tails - or parts of the tube that are not coiled - on either end. The tails vary in length depending on the diameter of the coil.
Whether it is an adapter or a connector, pneumatic fittings come with various assembly styles.
- Push in pneumatic fittings are perfect for fittings that require frequent connection and disconnection. This is because push-in pneumatic fittings are easy to assemble and remove without the help of tools. Push-in fittings used in low pressure systems are normally made from plastic while metal push-in fittings are generally preferred in high temperature environments.
- Thread-to-thread pneumatic fittings or stud fittings feature screw threading on the outer edge (male) or the inner edge (female) which connect with the threads on the end of a hose. Since fittings with straight threading sometimes do not create an airtight seal, they may require additional coating. Fittings with tapered threading, on the other hand, are usually airtight.
- Tube-to-tube pneumatic fittings are used to connect two tubes. They come in different sizes and diameters and connect tubing in a straight line or at an angle.
- Thread-to-barb or push on air fittings feature a barbed end that grips the tubing. To make an airtight seal, this type of connection requires a knurled nut to be placed and tightened around the barb and tubing.
Fittings can be attached to tubes, hoses and pipes in a pneumatic system. Constructed from layers of material, hoses are usually relatively flexible. They also usually require frequent replacements due to wear and tear. Pipes are more solid than hoses. They are usually made from a single layer of material and used in more permanent installations than hoses. Pipes are usually classified in line with their inner diameter. Tubing sits somewhere in between hoses and pipes in terms of flexibility. Pneumatic tubing is rated according to the size of its outer diameter.