Unilok tube fittings are designed and manufactured to provide a reliable, leak-proof connection in instrumentation and process tubing systems. Unilok tube fittings consist of three precisely machined components:

1. Body
2. Ferrule
3. Nut

The single ferrule design, with the spring-like action of the ferrule during make-up, compensates for the variations in tubing materials, hardness, and thickness of the tube wall to provide leak-tight connections in an extensive range of applications.

Additionally, in fulfillment of the design criteria, all Unilok components are manufactured with extremely tight tolerances and superior surface finishes under rigorous quality control standards to assure the optimum performance of each component part.


Through the critical interaction of the precisely machined fitting components with the process tube, a leak-tight seal is achieved. The simple geometric rotation of the Unilok nut provides the axial thrust necessary to coin the ferrule to the outside diameter of the tube. To eliminate any potential stress on an existing system, the tube fittings have been designed not to transmit installation torque from the tube fittings to the tubing.

During the rotary movement of the nut, the internal surface of the nut meets with the rear surface of the ferrule to move the ferrule forward axially into the angular section of the fitting body. The leading edge of the ferrule is directed into the tube to begin the required “bowing” action of the ferrule.

Subsequently, the leading edge of the ferrule “locks” on the outside diameter of the tube to complete the sealing action and secure the tube within the fitting.

The resulting “spring-like action” of the ferrule is designed to help compensate for exposure to system variables such as vibration, pressure pulsation and thermal expansion/contraction.