Reliable industrial fluid systems are essential for safety, efficiency, and profitability in your plant—and their ability to operate dependably relies on many factors. Some of the most important include proper tube and tube fitting installation as the system is initially assembled and maintained throughout its useful life.
For these reasons, fluid system professionals must equip themselves with the basic skills required to properly install tube fittings. In this article, you’ll learn how to select and prepare the proper tubing for your installation, how to install tube fittings, and why proper installation is key to industrial workplace safety.
Because of the available variety, however, it is important to be cognizant of the type of tubing you are using for any given installation. For example, a common reason for leakage in tube fittings is under-tightening during fitting makeup. This can occur when a technician pulls up tube fittings by feel. Many installers will say they have pulled up so many fittings, that they have intuition when to stop based on how the fitting feels. But each variable impacts the amount of force required to pull up a tube, and all it takes is to change one of these variables—size, wall thickness, hardness—and the fitting will feel very different to the installer.
Installers should also validate that tubing is softer than the tube fitting, which will allow the fitting to effectively grip the tube. The size, shape, and overall condition of the tubing should also be validated. Excessive scratches, depressions, raised portions, or other defects can lead to imperfect seals, particularly in gas service. Tubing that is slightly oval in shape can also cause trouble and may not fit properly through fitting nuts, ferrules, and bodies.
✔ Determine the number of tube fittings and length of tubing required in the system design before beginning the installation process. When making these determinations, it is important to select enough tubing that will allow every cut to fit into the fitting bodies.
✔ When deciding the location of your connections, keep accessibility in mind. Tube fittings may need to be serviced over the course of their working life—making them easily accessible to technicians can lead to speedier maintenance.
✔ Be sure to run your tubing in appropriate routes in conjunction with other critical systems in equipment. For example, never run tubing in front of critical instrument panels. This may cause inaccessibility and potential safety concerns. Also avoid running tubing at handrail or footrail heights. This can help prevent any inadvertent contact from plant personnel, which could be a safety risk.
✔ Utilize proper tubing support across longer runs of tubing. Optimal support systems will help reduce system vibration and increase the useful life of tubing and fittings, supporting safer and more reliable system operation over the long term.
If a tube cutter is not available, a hacksaw can be used as an alternative. This will likely result in a rougher cut.
In either case, the cutting process will result in some burring on the tube ends. These burrs should then be removed with a deburring tool. Deburring is important for proper fitting function as well as for clean, leak-free systems. Burrs also have the potential to break off and cause damage to components in other parts of the system by lodging in small holes or vents, or by scratching valve seats or soft seals such as O-rings. For these reasons, tubing should be deburred before proceeding to tube fitting installation.
Installation of two-ferrule, mechanical grip tube fittings—such as the Swagelok® tube fitting—can be completed in three simple steps.
Step 1: Insert the tubing into the tube fitting. Make sure the tubing rests firmly on the shoulder of the fitting body and that the nut is finger tight.
Step 2: Mark the nut of the fitting at the six o’clock position.
Step 3: Hold the fitting body steady and tighten the nut one-and-a-quarter turn.
After initial assembly is complete, technicians should then use a gap inspection gauge to confirm the fitting has been sufficiently tightened. Position the gap inspection gauge next to the gap between the nut and body hexes of the fitting and gently attempt to push it into the gap. If the gauge will not enter the gap, the fitting is sufficiently tightened. If the gauge will enter the gap, additional tightening is required.
Interchange is when a tube fitting from one manufacturer that has been installed on a piece of tubing is then disassembled, and the tubing, nut, and ferrules are then reassembled into a tube fitting body from another manufacturer.
Intermix is when tube fitting components, including the nuts, ferrules, and bodies from two or more manufacturers are mixed and then assembled to make a completed fitting.
Avoiding interchange and intermix is important primarily because there is no industrywide commercial design standard for tube fittings. This means every individual manufacturer follows its own design standards and processes. Therefore, tube fitting components from different manufacturers are not designed to work together. An intermixed or interchanged fitting is essentially a new, untested design.
Some manufacturers may claim their products are interchangeable with other brands. But no manufacturer can reliably and uniformly replicate designs from those of a competitor. Interchanging and intermixing tube fitting components can lead to unpredictable performance, increased costs, and potential safety hazards. It may also void your warranty, which can lead to even higher costs if and when a problem occurs. To avoid performance issues, leaks, higher costs, and safety concerns, it is best practice to never intermix and interchange tube fittings.
By following the steps outlined in this article, you’ll be better equipped to make reliable connections during your next install. Interested in learning more about the installation process and the nature of leaks, tubing materials, why two-ferrule mechanical grip fittings outperform comparative options, and more? Swagelok offers comprehensive tube fitting training for technicians of any level of experience and skill. Participants learn how to install Swagelok tube fittings with reliability you can count on. The benefits of proper tube fitting installation can help your facility become safer and more profitable.