A tubing coupler is a connector that joins two sections of tubing together, using friction or compression to seal the connections. Tubing may be made of metal, plastic, or flexible elastomers and is used for carrying liquids and gases in lower pressure applications. Most tubing is not manufactured with connections at either end, because many applications require non-standard lengths of tubing, and it can be easily cut to a desired size.
Adding a tubing coupler allows a user to size the tubing to meet their needs, connect sections together, and complete an installation quickly. Some couplers are designed to be attached and detached repeatedly, allowing tubing to be moved, or disconnected for different accessories to be added. Others may be considered permanent connections, because the two halves are screwed together and must be removed with tools.
Friction connections can be made for low-pressure plastic tubing, because the tubing coupler is made with barbs that hold the tubing together. The barbs are a series of rings that are pressed into the end of the tubing. The rings are slightly larger in diameter than the tubing, and create a leak-proof seal that can be used for applications such as medical oxygen tubing, drain hoses, or vacuum hoses in automobiles.
Another type of tubing coupler is an angle connector, which allows tubing to change direction without being bent. Some metal tubing can collapse if a user attempts to bend it by hand. To avoid this, angled couplers can be added between two straight sections of tubing, allowing the tubing to change direction as needed.
A compression tubing coupler is often used for plastic and metal tubing, where a leak-proof and semi-permanent connection is needed, such as water supply piping. For plastic tubing, a female coupler connection is slid on the end of the tubing. Then a soft metal ferrule, which is similar to a washer, is placed at the end of the tubing and inside the female connector.
The male coupler connection is slid on the end of the other piece of tubing. When the two connections are threaded together, the male connector screws into the female, making a complete connector. As the two connectors tighten, the ferrule is compressed inside the tubing coupler and expands, creating a sealed connection. Compression couplers can be removed later, but the ferrule usually has to be cut off, because the compression deforms it and makes it unusable a second time.
A flared tubing connector is the most permanent type of tubing coupler, and uses a flaring tool to shape one end of the tubing. One half of the connector is slid on first, then the tool shapes the end of the tubing, bending it and rounding it to a shape larger than the tubing. This flared end fits into the half of the coupler placed on the other section of tubing. When the two sections are screwed together, the flared end of the tubing is compressed and is leak free.
Quick-connect couplers are useful when tubing needs to be removed regularly, or accessories added and removed. This connector is common on compressed air systems, using a quick-connect female coupler placed on the end of flexible plastic tubing. Various accessories, such as tire inflators or air nozzles, have a male connector threaded into them, and by pulling on an outer sleeve of the female coupler, the male connector fits inside and makes a complete fitting. These couplers can be disconnected repeatedly without damage, making them very useful for mechanics or homeowners using compressed air systems with different tools or accessories.