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Back Common Problems in Tube Fitting Installation
Tube fittings, important components in fluid systems, are widely used across diverse fields. including oil and gas, chemical processing, hydrogen energy, and semiconductors. If tube fittings are not inspected and installed correctly during the assembly process, issues such as leaks, pressure drops, or system failures may occur. These seemingly minor mistakes can lead to very serious accidents, resulting in significant economic losses and even casualties. Therefore, it is crucial to install tube fittings correctly. Below, we will introduce some common problems in fitting installation and how to avoid them.
Intermix Fittings of Different Materials and Specifications
Mixing ferrules of different materials can affect the sealing performance of the fitting and may even damage the fitting and tube. For example, if an Alloy 625 rear ferrule is used on a 316 stainless steel fitting, the high strength and hardness of Alloy 625 could overly compress the front ferrule, damaging the fitting body and tube and preventing the rear ferrule from securely holding the tube.
Similarly, mixing components of different specifications can also compromise the sealing performance of tube fitting. Due to size differences, the sealing performance can be significantly reduced after installation. Some metric and fractional sizes are quite similar, such as the 1/4” and 6mm ferrules, making them difficult to distinguish when mixed together. Therefore, fittings of different specifications should be stored separately. Additionally, during installation, it is essential to carefully check that the specifications are correct to avoid the issues mentioned above.
FITOK has designed steps on the body and nuts of metric straight tube fittings to visually distinguish them from fractional specifications. The forged components such as elbows, tees, and crosses do not have a step on the body but are marked with metric sizes on the ports.
Installation of Defective Tubing and Fittings
Improper protection during transport or operation can lead to scratches or dents on the tube surface. Severe scratches and dents can prevent the ferrule from fitting tightly against the tube surface, leading to leaks. Before installing the tube fitting, it is essential to inspect the tube for any dents, scratches, deformations, or other damages. If necessary, operators should cut the tube if it is too long or has unsatisfactory ends to prepare the tube again. To avoid damaging the tube, protective caps should be used during transport, and tubes should not be placed on the ground or dragged. Additionally, the tubes should be kept separately by size and should not be mixed on a shelf when stored.
Scratches or damages on the sealing surface of the fitting may also prevent the ferrule from fitting tightly against the fitting body, resulting in leaks. During installation, keep the tube as level or vertical as possible when inserting it into the fitting body to avoid scratching the sealing surface of the fitting.
Inadequate Tubing Preparation
Incorrect cutting and burr removal can affect the sealing capability of the fitting and contaminate the system. Additionally, unremoved burrs will scratch the surfaces of fittings and other tubes, compromising sealing performance. After cutting the tube, it is necessary to clean the inner and outer sides of the cut ends, ensuring that the edges of the burr-free tube ends are smooth and that the inner and outer chamfers do not exceed half the wall thickness of the tube. Finally, a visual inspection should be conducted.
Lacking suitable processing tools is also an important factor. Equipping with the right tools and conducting proper operations can accelerate the installation process while minimizing the risk of failures and reducing losses.
Insufficient Tube Installation Depth
If the tube is not fully inserted into the fitting body during installation, it may cause the ferrule to be too close to the tube end, preventing normal sealing and engagement. When exposed to vibrations or impulse pressures, insufficient insertion depth poses risks of loosening or even falling off, which can lead to serious accidents. Furthermore, if the tube is not fully inserted into the bottom of the fitting body, the rear ferrule can push the tube forward, causing deformation of the front ferrule. Thus, before tightening the nut, it is essential to verify that the tube is snugly against the shoulder of the fitting body to avoid shallow installation.
Additionally, improper handling in certain operations might prevent the tube from being fully inserted into the bottom. For instance, if burrs on the tube end are not properly removed, it may hinder the tube from fitting between the front and rear ferrules. Furthermore, directly turning the nut without inserting the tube can cause the inner diameter of the ferrule to shrink, preventing the tube from fully inserting.
To prevent such occurrences, FITOK has designed depth marking tools that allow users to mark the corresponding installation depth on the tube, making it easy to check whether the tube is installed at the correct depth.
Under-Tightening or Over-Tightening in Fitting Installation
Both under-tightening and over-tightening of tube fitting can negatively impact their sealing effectiveness. Generally speaking, if a fitting is not tightened properly during installation, it may lead to leaks. Accordingly, many people will be more tend to screw the fitting nuts tighter, believing that a tighter screw can ensure better sealing between the fitting and the tube. However, this is a misconception.
Under-tightening installation of tube fittings can prevent proper sealing between the ferrule and the tube, potentially causing medium leaks during system operation. When initially installing the tube fitting, a gap gauge can be used to determine whether the fitting is tightened sufficiently, helping to avoid leaks caused by loose installation.
Over-tightening the nut can cause severe deformation of the ferrule and tube, increasing the risk of leaks. Deformed or damaged tube fittings and tubes will require repairs or replacements, resulting in additional costs. Moreover, excessive tightening can reduce the number of times a fitting can be reinstalled.
The torque and number of turns during installation depend on the material and specifications of the fitting, and it is essential to follow the manufacturer's installation guidelines strictly.
FITOK offers a variety of tube installation tools specifically designed for tube fittings, including tube benders, presetting tools, tube cutters, and deburring tools, to help customers streamline the installation process. The tube presetting tool simplifies the installation of tube fittings in tight spaces while speeding up the installation process for large numbers of fittings. Other tools can better assist operators in preparing tubes and preventing leaks from occurring.
Please refer to the Tools and Accessories catalog for more information. If you have any questions, please leave a message online, and we will get back to you as soon as possible!
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