Tube Fittings 101: Single & Double Ferrule Types

white tubes

Stainless steel tube fittings find applications in compressed air systems due to the pressure they can withstand. As a result, they are necessary for safe operations. For any fitting, its pressure rating will depend on the construction method, the fitting’s size and wall thickness. The type of the steel tubing also plays a significant role in determining pressure ratings of any fitting.

The common types of high-pressure pipes include the double ferrule and single ferrule tubes.

Single vs. Double Ferrule Fittings

Single ferrule fittings are either of brass or steel and come in different sizes: a sixteenth of an inch to two inches. The design of these fittings is very accurate to minimise any errors during the installation process that would lead to leaks. The pressure ratings for these fittings are also relatively low.

On the other hand, double ferrule ratings come in the same sizes as of the single fittings, but the materials for creating these fittings are different. These fittings are best for tubes with both thin and thick walls because they create a firm grip for tight and leak-free joints.

Double Ferrule Fittings

These fittings have four main components: body, nut, front and back ferrule. During the installation process, you will require adding another tube as an extra component for leak-free joints. The bushing on the inside is locking ferrules while that on the outside makes the sealing ferrules, both working to offer a tight hold around the tubing without risking damage to the wall.

The leak-free bonding that double ferrule high-pressure fittings offer makes these fittings a suitable choice in most compressed air systems. Nevertheless, some applications require single ferrule connections to facilitate minimal backward movement of fluids. They are also resistant to pulsation and vibration. Finally, some industrial applications demand the use of single ferrule fittings.