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Card sleeve fittings precautions

The ferrule type pipe joint has the advantages of simple structure, convenient use and no welding. However, in the medium and high pressure hydraulic system, if it is not properly operated, it will cause leakage and affect its promotion and use. After years of practice, the author has summarized some experiences and achieved good results.
As shown in the drawing, the ferrule type pipe joint is mainly composed of a joint body 1 having a tapered hole of 24 degrees, a ferrule 2 having a sharp inner edge, and a compression nut 3 serving as a pressing force. When the nut 3 is tightened, the ferrule 2 is pushed into the tapered hole of 24 degrees and deformed accordingly, so that the ferrule forms a spherical contact seal with the tapered surface of the joint body; at the same time, the inner cutting edge of the ferrule is embedded in the outer wall of the steel pipe 4, A circular groove is pressed out on the outer wall to serve as a reliable seal. The best choice of steel pipe is to eliminate stress-annealed 20# fine-drawn pipe, which is beneficial to the inner edge of the ferrule embedded in the outer surface of the steel pipe to provide a reliable sealing effect.
(1) pre-installed
The pre-assembly of the 1 ferrule fitting is the most important link, which directly affects the reliability of the seal. A dedicated preloader is generally required. Joints with small pipe diameters can be pre-assembled on vise. Specifically, a joint body is used as a mother body, and the nut and the ferrule are pressed onto the tube. There are mainly types of sleeve-type straight-through pipe joints, ferrule-type end straight-through heads, and ferrule-type three-way pipe joints. The authors found that even the same batch of the same manufacturer, the depth of the tapered holes on these joints are often different, resulting in leakage, and this problem is often overlooked. The correct approach should be to what type of connector is used at one end of the pipe, and the corresponding connector is pre-assembled with the same type of connector to minimize leakage.
2 The end face of the pipe should be flush. After the pipe is sawn, it should be ground and smoothed on tools such as grinding wheels, and the burrs should be removed, cleaned and washed with high-pressure air before use.
3 When pre-installing, the coaxiality of the pipe and the joint body should be kept as much as possible. If the pipe is too skewed, the seal will be invalid.
4 pre-installation force should not be too large. The inner edge of the ferrule should be inserted into the outer wall of the tube, and the ferrule should not be significantly deformed. When connecting the pipes, assemble them according to the specified tightening force. The tightening force of the φ6-10mm ferrule is 64-115n, φ16mmr 259n, and φ18mm is 450n. If the ferrule is severely deformed during pre-assembly, the sealing effect will be lost.
(2) It is forbidden to add fillers such as sealant. In order to obtain a better sealing effect, a sealant is applied to the ferrule, and as a result, the sealant is rushed into the hydraulic system, causing malfunctions such as blockage of the hydraulic component orifice.
(3) When connecting the pipeline, the pipe should have sufficient deformation allowance to avoid the tensile stress of the pipe.
(4) When connecting the pipeline, avoid the lateral force, and the lateral force is too large to cause the seal to be tight.
(5) When connecting the pipeline, it should be tight at one time to avoid multiple disassembly, otherwise the sealing performance will be deteriorated.

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