White Paper: Test Methodologies For Barbed Fittings

By Frank Lombardi, Value Plastics Engineering And Mark Rosneck, Value Plastics Market Development Manager

As medical disposables become more prevalent, it is crucial that all elements of the disposable be properly designed. Barbed fittings for connectors such as luers and tube-to-tube fittings are often selected through a trial and error process. Unfortunately, this can lead to field failures should the barb separate from the tubing either under fluid pressure or through stress on the tubing.

In general, the best practice is to utilize a barb style with the best combination of sealing integrity, high pull-off strength, and low assembly force for the type and size of tubing that will mate with it. The cylindrical surface behind the barb should allow the tubing to relax against the fitting. In choosing a barb style, insure that there is no parting line on the sealing surface and the barb is designed with a sharp peak allowing it to bite into the tubing. To narrow down your choice of barb style, the most practical advice we can give is to test your application first by requesting samples. This is often a fundamental mistake that designers make. Virtually all fitting vendors have a liberal sampling policy. You should make certain you have performed your testing on a large enough sample to fully understand the potential failure modes of your disposable.

The second most frequent mistake that design engineers make is not asking the vendor for technical assistance. Again, most fitting suppliers have excellent technical support groups. Take advantage of their expertise. It is likely that someone else has had a similar application and the vendor can save you time by leading you in the right direction. And if your application requires something different from one of the vendor's standard parts, custom parts are sometimes an option or the vendor can often direct you to another solution. Custom parts are often less expensive than you might expect and it's worth exploring this direction if a standard component will not meet your requirements.