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I. Assembly of ferrule-type pipe fittings (1) Pre-assembly ① The most important step in the pre-assembly of ferrule-type pipe fittings, as it directly affects the reliability of the seal. A dedicated preheater is generally required. Joints with small diameters can be pre-assembled on a vise. The specific method is to use a connector as the base, and then clamp the sleeve onto the pipe. The main types include bayonet-style straight pipe fittings, bayonet-style end-to-end straight connectors, and bayonet-style tee pipe fittings. The author found that even for a batch of products from the same manufacturer, the depth of the conical holes in these different types of connectors often varies, which leads to leaks; yet this issue is often overlooked. The proper approach is to use the same type of connector at the corresponding end as that used at one end of the pipe, which helps to minimize the risk of leaks. ②The ends of the pipes should be flush. After the pipe is cut, it should be polished smooth using tools such as grinding wheels, burrs should be removed, and it must be cleaned and blown clean with high-pressure air before use. ③During pre-installation, efforts should be made to maintain coaxiality between the pipe and the fitting; excessive skewing of the pipe can also lead to seal failure. ④The preloading force should not be too high so that the inner edge of the collet fits snugly against the outer wall of the pipe, and the collet should not suffer any significant deformation. When connecting the pipes, assemble them using the specified tightening force. The tightening force for the ф6-1 collar is 64–115 N, for 16 фmmr it is 259 N, and for ф18 mm it is 450 N. If the sleeve is severely deformed during pre-installation, it will lose its sealing function. (II). The use of sealants and other fillers is prohibited. Some people apply sealant to the collar in order to achieve a better seal, but as a result the sealant ends up in the hydraulic system, causing problems such as blockages in the orifices of hydraulic components. (III) When connecting the pipelines, ensure that the pipes have sufficient deformation allowance to avoid being subjected to tensile forces. (IV) When connecting the pipelines, avoid subjecting them to lateral forces, as excessive lateral forces can lead to poor sealing. (5) When connecting the pipelines, it should be done properly in one go to avoid multiple disassemblies, as this can also degrade the sealing performance. Installation of socket-type pipe fittings: (1) For pipes that require pickling, they must first be pickled in accordance with the requirements in Chapter 9 ； (2) Cut the pipe to the desired length using a sawing machine or specialized pipe cutting equipment; it is absolutely not allowed to use methods such as melting (e.g., flame cutting) or grinding wheel cutting ； Remove burrs on the inner and outer circles of the pipe ends, metal shavings, and dirt ； Remove the rust inhibitor and dirt from the pipe fittings ； At the same time, it is also necessary to ensure the roundness of the tube ； (3) Insert the nut and the collet onto the tube in sequence; the cutting edge at the front end of the collet (the smaller-diameter end) should be at least 3 mm away from the tube’s opening. Then, push the tube into the conical hole in the connector until it reaches the end ； (4) Slowly tighten the nut, while rotating the tube until it stops, then tighten the nut by 2/3 to 4/3 turns ； (5) Disassemble to check whether the card sleeve has cut into the pipe and whether its position is correct. The cartridge is not allowed to move axially, but can rotate slightly ； (6) After passing the inspection, tighten the nut again.