Pneumatic tubing is primarily measured by its Outside Diameter (OD), especially when used with common push-to-connect fittings.
Understanding Pneumatic Tubing Measurement
The method used to measure pneumatic tubing depends largely on the type of fitting it will be used with. The most prevalent method relies on the outer dimension of the tube.
Measurement by Outside Diameter (OD)
Tubing is generally measured by the OD Outside Diameter because it is used with push-to-connect fittings. These fittings grip the outer wall of the tubing, making the OD critical for a secure and leak-free connection.
Common types of pneumatic tubing measured by OD include:
- Polyurethane tubing
- Nylon tubing
- Polyethylene tubing
These materials are often rigid enough to maintain their shape and interface effectively with the internal collet and seal of push-to-connect fittings.
Measurement by Inside Diameter (ID)
While OD is the standard for many types, softer tubes that use barbed fittings or compression fittings are measured by ID Inside Diameter.
- Barbed fittings: These fittings are inserted into the tubing, relying on the inner wall for a seal and grip. The ID determines how tightly the tubing fits over the barb.
- Compression fittings: Although they compress the tube externally, some older styles or specific types might rely more on the internal support or the relation between OD and ID for the ferrule's function, or are designed for tube types where ID is the standard specifier.
Quick Reference Table
| Measurement Method | Dimension Measured | Common Fitting Types | Typical Tubing Characteristics |
|---|---|---|---|
| Outside Diameter | OD (Outer Dimension) | Push-to-Connect Fittings | Generally more rigid |
| Inside Diameter | ID (Inner Dimension) | Barbed Fittings | Generally softer |
| (May also use ID) | ID (Inner Dimension) | Some Compression Fittings | Generally softer |
Knowing how your pneumatic tubing is measured is essential for selecting the correct fittings and ensuring the integrity of your pneumatic system. Always check the tubing specifications and the requirements of your chosen fittings.
