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Tube Fitting Basics | How to Install a Tube Fitting

Did you know that more than half of fitting installers don't actually follow the proper installation guidelines? This guide details how to properly install fittings

If you've worked around tube fittings (also known as compression fittings) for very long, chances are that you've got your tube fitting installation method down to a science. However, did you know that more than half of fitting installers don't actually follow the proper installation guidelines? This can lead to some pretty unsafe conditions and work environments. Whether you're an "old-timer" or a newcomer to the industry, knowing the manufacturer's installation instructions is a must! This article will cover proper procedure in detail as well as a few tricks to make the process fast without sacrificing safety.

Tubing Prep

Before you install a tube fitting, you'll want to make sure the tube is properly prepared. To begin, be sure to select tubing that matches the tube fitting specifications for hardness and wall thickness.  Always check with your manufacturer to make sure your tubing is certified to work with the tube fitting you're using. Inspect your tubing and make sure that it's clean and free of surface scoring or deformation. Even small irregularities in the tubing surface may compromise the integrity of your fluid network, especially at high pressures. Next, you'll want to make sure that you've cut the tubing squarely and evenly and that it’s been properly deburred. Once this is complete, you're ready to install your tubing.

The Tube Fitting Installation Myth

The idea that tube fittings can be installed by feel is commonplace in the tube fitting industry. However, many don't realize that it's not the amount of force used to install tube fittings that determines their sealing potential. In reality, the depth to which the ferrules are set is what impacts how well a fitting may or may not seal. The "feel" may change based on wall thickness, tubing hardness, or even fitting size. In light of these factors, following the guide below can help you make safe, leak-free connections every time.

Standard Tube Fitting Installation Instruction

Interestingly, virtually all of the major tube fitting brands use the same standard instructions for tube fitting installation.

  1. Insert the tubing into the fitting until it bottoms out on the fitting shoulder.
  2. The shoulder is a stopping point inside the fitting body. By bottoming the tubing out against the shoulder you’re making sure that the ferrules have enough biting surface on the tubing for a strong connection.
  3. Tighten the fitting nut by hand until hand-tight.
  4. Using a marker, mark the fitting nut and body at the 6 o'clock position.
This image depicts a tube fitting being marked at 6 O'clock for proper installation.
  1. Using a wrench, tighten the nut 1-¼ turns from the hand-tight position ending with your mark at the 9 o'clock position.
This image shows the fitting clock positions, illustrating how far to tighten past hand tight.

At this stage, all of the hard work has been complete. Honestly, this is where most installers stop. Unfortunately, there is one final step that many people skip over, and it's the reason that tube fittings have such a high average of failures.

The Final Step That Everyone Skips

In every manufacturer's instructions it states that once a fitting has been tightened to the 9 o'clock position, the installer must then check the gap between the fitting body and the nut using a gap gauge. In doing so, this ensures that the fitting doesn't need additional tightening. So, why would anyone skip this step? Often, it's because gap gauge tools are forgotten or go missing. Also, many installers feel that this step wastes time. After all, they've installed hundreds of fittings, surely they can feel when it's tight, right? However, as previously stated, many factors can change the torque needed for a secure connection meaning that it might feel different every time. This is why every fitting needs to be gapped correctly.

(However, there is one thing that traditional gap gauges cannot address, and that's over tightening. Over tightening can be just as problematic as not tightening enough. If a fitting is over tightened, the ferrules can crush the tube, preventing flow and weakening the tube. This can very rapidly lead to serious problems once a system gains pressure.)

The Potential Pitfalls of Not Checking Gaps

What can go wrong if a fitting is not properly installed? If you're lucky, you'll just have a leak, and even this can be costly. However, if the ferrules have bitten too deep or not deep enough, you could be looking at a total blow out. These situations have the capability to be devastating. Tubing can shoot out of a fitting like a projectile. If that happens, machinery can sustain damage, but worst of all, workers may take a hit or be exposed to hot or potentially hazardous material that may be running through the system. That is why you should always follow the manufacturer's guidelines and always check your work with a gap gauge.

The Simple New Way to Gap Fittings

The largest factor that causes tube fittings to leak is avoidable human error. Gap gauges are a hassle to keep track of, so they get lost or left in the toolbox. Double checking the gap takes time, and production is always in a hurry. What if you could have the safety of properly gapped fittings without having to carry or remember where you left your gap gauge? The new patented i-Fitting from Superlok does just that by building a gap gauge directly onto each individual fitting.

In this image there are three circle illustrating the three steps of Superlok i-Fitting installation.

Just seat the tube against the shoulder and tighten until the red indicator ring pops away. It's that simple. Not only does this eliminate under tightening, it also prevents over tightening by letting the installer know exactly when to stop tightening. This patent has been a huge step forward for safety. The i-Fitting from Superlok is the only improvement on the tube fitting concept in the last 60 years.

Stay Safe Out There

Finally, just remember that providing safe working environments is critical. For the sake of you and your fellow workers, if you're going to install a tube fitting, use a gap gauge. If you want to maintain a fast pace and leave your gap gauge at home, use an i-Fitting.

For more information on Superlok Fittings you can contact Mako Products below. We are the exclusive home of Superlok i-Fittings and carry a comprehensive variety of all Superlok fitting and valve lines.

Contact Mako

Contact our team here.

The Author

Ethan McNeese
Marketing Specialist
Ethan is our resident content marketer, blog author, YouTube host, and general knower of things. When he's not at his keyboard working on new web pages and videos, he's usually out in the shop wrenching on valve assemblies, developing diagrams for projects, or praying for rain.

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