Sterile (aseptic) connectors/disconnectors
Multiple design options offer the user or system designer a choice of options to make tubing connections outside of a hooded
environment. Major benefits of these connectors are to provide sterile connection and disconnection options in uncontrolled
environments. Sterile connectors are available in genderless and gendered designed. The gendered designs can provide an additional
indication of intended process flow direction.
Barbs. Plastic barb-style connectors provide designers with a capability to accommodate the widest possible range of tubing properties
and application conditions, including a multitude of configurations such as tees, "y"s, elbows, and manifolds. A number of
barb designs are available—each with unique characteristics to tailor connection performance to specific needs—for handling
assembly forces, tensile resistance, and blow-off resistance without the need for clamps.
Barbs derive their holding capability by expanding tubing above its nominal ID, creating some amount of interference for a
secure seal and good mechanical retention. The tube expansion can vary dramatically, from lower profile, easier connections
to much more aggressive interferences, depending on the pressure and tensile pull requirements.
The selection of the barb style is important to the connector's tube-holding capability. The cylindrical surface behind the
barb should allow the tubing to relax against the fitting. In choosing a barb style, it should be ensured that the barb is
designed with a sharp peak, allowing it to "bite" into the tubing for optimal retention.
Some tubing or hose connectors may use a multibarb, which can make for an inferior tube connection and seal. Multibarbs cannot
create a sharp bite on the tube, inhibiting retention, and do not allow the tube a chance to relax behind the barb, also resulting
in poor tensile pull strength.
Multibarbs are also relegated to a manufacturing process that leaves a parting line on the sealing surface, creating a potential
leak path. This is an inherent design flaw, yet all multibarb connector designs, including metal connectors, display this
liability. An optimally designed and properly injection molded connector will incorporate a singular barb with no parting
line, a sharp bite, and a clean sealing surface.
The latest generation of plastic connector technology affords designers and manufacturers wide latitude of flexibility to
design and set-up applications that custom fit to their specific needs. Some connector manufacturers provide comprehensive
design centers to help single-use system designers and assemblers to achieve the highest level of performance from their connectors.
With good consultation up front on the user's application requirements, the pitfalls of inappropriate connection technologies
can be avoided and optimal system designs can be executed.
The author wishes to acknowledge Ken Davis of Value Plastics for his contribution to this column.
Jerold Martin is senior vice-president of Global Scientific Affairs at Pall Life Sciences, email@example.com