Historically, tube fittings created confusion for users of medical or scientific-analysis equipment that require hand installation. Most manufacturers specify “finger tight,” a subjective measurement that introduces inconsistency because it varies from person to person. What really is finger tight, and how do you know when you’ve applied the specified torque to your fitting? The process of hand tightening fittings typically is a guessing game resulting in loose or overly tight fluid connections. Poorly torqued tubing fittings result in inconsistent, leaky processing with dead volumes and carryover problems, which can cause faulty analysis.

Take a closer look at a standard thread, such as the 1/4 -28 or other fitting and port configuration. Most current fluid connections require a compressible component such as the tubing in a flared tubing assembly, a ferrule, or a cone. Problems crop up when the compressible component is either over or under compressed by over or under tightening the fitting. The end result is an improper seal.

A threaded fastener must often apply substantial force to the compressible component, up to 35 lbs for a proper seal. The ideal way to gauge and apply the correct amount of torque to the threaded fastener is to use a torque wrench. However, the confined spaces within compact instruments often make this approach impractical.

In a standard tubing connection, the tubing is made of a semi-flexible material and compressed by the threaded fastener. With most connections such as these, the required torque is generally 15 to 40 in-oz. The initial torque is usually low (under 5 in-lbs) until the compressible component begins getting squeezed between the threaded fastener and the mating port where the fitting is being seated in the instrument. Because the tubing enters through the center of the fitting and connections are typically made in tight locations, it is difficult to reach them with a wrench.

Taking these constraints into consideration, Diba Industries Inc. introduced a threaded fitting for tubing connections. The preassembled Click-N-Seal Connection eliminates common problems and impracticalities of the standard fitting because it creates a fluid-tight connection every time it is installed. Required torque is assured, letting the user hand tighten and properly seal flared tubing assemblies without guessing if it’s been properly installed.

This new connection uses a flared tubing assembly for a continuous, “fully swept” Fluoropolymer fluid path. It maintains the tubing’s internal diameter, minimizes dead space, and maximizes wash characteristics.

The multi-use Torque-Right fitting used in the connection has two levers on the outside body of the threaded fastener which noticeably deform when pushed against by a protrusion in a custom designed cap. Tightening the fitting increases the resistance of the cap against the installer’s fingers until the correct torque is reached. At that point, the cap clicks, and further turning does not increase the applied torque. The installer can feel and hear the click indicating a properly seated fitting that creates a tight seal. This indicator lets the installer hand tighten the fittings without tools or guesswork. The ergonomic design also results in less strain on the user.

The levers on the Torque Right always allow a certain amount of interference with the protrusions on the cap. By adjusting the length and thickness of the levers, and the amount of interference with the protrusion of the cap, fittings can be produced that provide the correct torque for many different applications.

When reaching the required torque the levers on the fitting elastically deflect to prevent users from further tightening the fitting, which could potentially damage the compressible tubing. The cap can also be turned backwards without deflecting the levers off the protrusions. This allows unthreading the fitting for reuse. The fitting can be used over and over again because the levers deform elastically without permanent deformation to any of the pieces.