Instrumentation tube fittings encompass not only standard items such as adapters and connectors, but also non-standard types like fittings for calibration and special orifices. It is critical to the correct and long-term functionality of the instrumentation system that tubes and tube fittings are installed properly. Though the components and their assembly may look simple, errors during storage, fabrication, and installation are all too common. These errors result in sub-optimal performance and reduced lifespan of tubing systems.
Storing and Handling Tubing
Improper storage and incorrect handling of tubing are frequently-made mistakes. While tube fittings are carefully stored and handled, the tubes themselves are often left unprotected on unpadded racks or on the ground. They may also be handled roughly during unloading. We have known installers to drag bare tubing to the installation site. All this rough storage and handling can cause scratches and cracks on the tubing's outer surface, leading to poor fit or damaged finishes that cause fluid leakage.
Here are some recommendations for the correct storage and handling of tubing:
- Tubing must be supplied and stored in protective packaging or tubing.
- Do not leave unprotected tubing on the ground. Store it on padded racks instead, and avoid storing tubing with pipes on the same rack.
- Cut tubing to manageable lengths in the shop to avoid dragging excessive lengths around the worksite.
- Provide extra length while cutting to allow for trimming away scratched ends.
- Carefully inspect tubing before installing it and avoid using scratched or cracked tubing.
Proper Cutting and Deburring
Cutting and preparing tubing for installation are important steps that must be done with the right tools and procedures. For stainless steel tubing, use a cutter with hardened cutting wheels. A hacksaw and tube saw vise can also be used. Care must be taken to ensure that the tube ends are square.
Burrs created on the outer surface during cutting can lead to improper installation, as they can hinder tube insertion and prevent tubes from bottoming out. Hence, out diameter (OD) deburring of tube ends after cutting is critical to ensuring sufficient insertion depth. The inside diameter also must be deburred and the debris blown out with nitrogen or dry air to protect downstream systems.
Pre-Inspection
This step is necessary to ensure that the ferrule system is not missing any components and that the ferrules are oriented correctly. It is during pre-inspection that the proper alignment of the ferrule system and the tubing is confirmed.
Proper Installation
Here are some factors that influence the installation of tubing:
- Conform to the manufacturer's recommendations for rotating the nut.
- Verify sufficient insertion depth of the tubing.
- Scribe the tubing and nut to ensure correct rotations.
Lack of attention to these factors can cause tube fitting failure, wastage through incorrect seating of ferrules onto the tubing, or distortion and flaring up of tubes.
Post-Inspection
Conducting a post-installation inspection is critical to proper quality assurance. It consists of the following checks:
- Proper tube insertion. Since improper tube insertion is the chief reason for tube blowout, the operator must check that the tube bottom rests squarely on the internal shoulder of the fitting. This provides the necessary mechanical resistance for the ferrule system to set onto the tubing when the nut is tightened. In flareless tube fittings, it is important to ensure that the ferrule system is properly locked on the tube.
- Verification of ferrule setting. This can be done by trying to slide the front and rear ferrules along the tubing's length. This should not be possible if the ferrules are set properly—they may rotate on the tube but won’t slide longitudinally.
- Proper rotations of the nut. If the tubing walls are too thick or the tube is too hard, ferrules may not set properly. Make sure to use tubes within appropriate wall thickness and hardness guidelines as specified by ASTM standards.
Instrumentation Tube Fitting Installation Support From SSP
Instrumentation system designers have to carefully evaluate the operating environment of the installation site, check the compatibility between components, follow proper installation procedures, and conduct sufficient maintenance to ensure trouble-free operation, great performance and long life of tubing systems.
At SSP, we assist our customers at all stages of their tubing projects, from the selection of components through installation and maintenance. Our mission is to be our customers' preferred supplier by providing the highest quality products, on time, at competitive prices, and backed with exemplary service.
Contact us today to learn more about successfully installing or maintaining instrumentation tube fittings, or about any of our services and capabilities.