Should You Be Using Couplings or Fittings?

Designers of products that incorporate fluid transfer face many challenges when it comes to connecting hoses and tubing efficiently and cost effectively. While all fluid transfer lines found on motorcycles, inkjet printers, medical devices, or portable hydration units need a connection device, such as a coupling or fitting, the requirements for each can differ dramatically.

As such, the choice of connection type is dependent on a variety of considerations, including the required frequency of connection/disconnection, servicing and safety needs, and user expertise. With so many determining factors, what is the best approach to choosing the right solution for a specific project? First, let’s define couplings and fittings.

Couplings Vs. Fittings & Valves
A fitting is a simple device used most often as a permanent connection for hoses or tubing. Fittings are typically used with threaded or hose barb connections. Tools are often required to install and remove fittings.

Instant fittings are also used as a permanent connection, but do not require tools for installation of the tubing. It is important to note, however, that most fittings do not stop flow when disconnected. In order to regulate or stop flow with a fitting, a separate valve must be used.

Couplings are devices used to quickly connect and disconnect tubing or hoses. They may incorporate automatic shutoff valves to stop flow when disconnected. Designed for repeated connection and disconnection cycles, standard couplings — with or without valves — can be connected and disconnected without the use of tools. Couplings with nonspill shutoff valves provide the added security of virtually drip-free connection and disconnection.

Frequency of Connection
The first question to ask at the start of the selection process is how often the fluid line will be disconnected during equipment use. If the assembly or use of the product would benefit from repeated connections and disconnections, a coupling should be considered. Fittings are a popular choice for fluid lines that need to be connected once during the assembly process and do not require the disconnection of equipment or parts at any point during development or use.

Serviceability
The next item to consider is the speed of the connection. If machinery needs to be assembled quickly and includes fluid lines that must be disconnected for servicing or repair, then a coupling is the recommended choice. Equipment maintenance and repair contribute to overall process downtime. Couplings help minimize service-related downtime by providing quick and easy access to fluid lines that may need to be disconnected during repair processes. In addition, couplings with integrated valves save time by eliminating spill cleanup and reducing the need to purge air from the fluid lines. Fittings can take a longer time to disengage and reinstall, but may be the connection of choice if disconnections are not time sensitive.

User Expertise
Take into account user expertise and convenience. A well-trained technician or operator who regularly uses tools on the job can work capably with fittings, making repeated connections and cutting tubing easily and accurately. Untrained users of medical, printing or food-service equipment require less training and need fewer service calls when making quick disconnections with couplings.

Safety
Evaluate the safety requirements of the final product — this includes both user and equipment safety. Fluid handling of caustic chemicals or harmful gases can be tricky if fittings need to be accessed. Even for a fitting installed with a valve, tools are usually required to disconnect and then reconnect. This is quite risky for a user dealing with dangerous media that may spill if the valve and fitting are separated.

Couplings designed with integrated shutoff valves can virtually eliminate leakage upon disconnection thereby minimizing user risk and "spills." Nonspill couplings also provide safety when drips or spillage could damage critical equipment. For example, in liquid cooling of electronics a single drop could compromise crucial equipment and data. Therefore, nonspill couplings would be best in such applications.

Additional Options
Fluid connections can also be designed with a variety of other special features that enhance security and safety. Couplings offer "keying" capabilities in applications where it is critical that multiple fluid or gas lines are not cross-connected. Fittings and couplings are both available in colored options to assist in quickly identifying fluid lines. Couplings can also incorporate RFID (Radio Frequency Identification) technology to provide an even greater level of security and create more intelligent systems.

Cost
Fittings are more basic in design and function, so cost is generally lower compared to couplings. Their simplicity can make them a cost-effective connectivity solution in many applications. Couplings on the other hand, with their added features, can bring increased overall value to an operation or user. Innovative coupling suppliers can offer cost-effective solutions that make operations cleaner, simpler, safer, and even smarter.

Aligning with the Right Supplier
In addition to the above considerations, before making a final connection selection consult with a supplier about detailed specifications, such as material, size, and termination types. Review factors such as media compatibility and flow requirements, space challenges, and mounting needs. While there are various options to choose from, a knowledgeable supplier will work with you in the early design stages to ensure you specify the optimum connection for your application.

Andy Hass is business unit manager for Industrial Markets at Colder Products Company. Mr. Hass has been with Colder for 11 years, working in a variety of capacities, including new and custom product development and business development. He earned a bachelor’s degree in Mechanical Engineering from the University of Minnesota Institute of Technology and an MBA from St. Thomas University. Mr. Hass can be reached at [email protected] or 651 603-255.

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