Coupling with Quality: What to look for—What to look out for

Coupler selection may seem like a quick pick, but finding quality couplings plays a large part in success. An inferior coupling may cause quality issues, lost product, biohazards, or other problems. For this reason, finding the right coupling requires more than just an eni-meanie-minie-mo, it takes a little bit of understanding of what goes into a quality coupling.

For a quality coupling, there are three main components we need to look at: materials selection, sealing capabilities, and the hose connection.

In some applications, materials selection is not important, but for some, such as life sciences, food or chemical processing, it can mean the difference between diluted samples, corroded coupler internals, or clean samples. In some cases material selection can be determined from a chemical compatibility chart. Some materials must meet different regulations such as the national sanitary foundation (NSF) r to allow food related materials to flow through them. Other couplers must be chosen dependant on how acidic or basic they are. For bioprocessing applications, couplers often need to be free of oxygen entrained into the coupler materials. Special applications such as these may require some material selection assistance from engineers, and should be manufactured in a controlled environment.

To prevent hazards to controlled environments, the valve type and material selection makes a significant difference. A shut-off valve will always stop flow, but some disconnects have more fluid encapsulated in the valve than another. This means that some couplers will spill more than others once they are disconnected. In volatile environments where a line might contain hazardous fluids such as blood or acid, a spill may be a serious issue. To prevent this, some couplers have a “non-spill” design. With a non-spill design, the amount of liquid trapped between the two coupler ends is minimized, and the liquid that remains is a condensation on the valve. Non-spill designs also prevent dirt from entering the coupler when disconnecting and reconnecting. So in many ways, the seal will significantly impact your coupler selection.

The third component impacting coupler selection is the hose connection on the coupler. A hose connection can be a potential leak point for any coupler. If the hose connection leaks, it will not matter if the coupler is connected or not, the leak will be continuous. Again, in very hazardous situations this can be a serious issue, but it may also mean a loss of product and puddles on the floor. To prevent this, quality hose connections are a must.

The quality features affecting a hose connection depend on the style of connection you use. With hose barbs being among the most common, choosing a quality hose barb is important. Hose barb connections have three main quality indicators: the sharpness of the ridges, the removal of any plastic flash, and the proper compliance with the mating component. The ridges of the connection determine how secure the coupler is with its mating component. If the ridges are not very sharp, a tube may slip off. Plastic flash can also be problematic and may lead to small amounts of leakage. Plastic flash is caused in the molding process where the two halves are joined. When the halves pull apart, there is a little ridge where plastic sneaks through the creases between the mold halves. If this is not removed, it creates a little peak in the hose where liquid can escape. If too much of this is removed, it creates a valley in the coupler connection where liquid can escape. This makes delicate removal of flash essential for a leak-free connection. The final characteristic of quality hose barb connections is creating a tight fit with the tubing. Because of tolerance variations between different tubing manufacturers, couplers must be tested with a variety of different manufacturer’s tubing. The coupler must also be held to high tolerances to have a guaranteed fit.

Many coupler manufacturers may claim to have all of these features, but few truly do. For quality couplers for your application, contact Donald Engineering and we’ll show you the difference a quality coupler can make.