Assembly of sleeve type pipe fittings

（1） Pre installed

① The most important step in the pre installation of sleeve type pipe joints directly affects the reliability of the seal. Usually, a dedicated preheater is required. Small diameter joints can be pre installed on pliers. The specific method is to use a joint as the base and press the nut and sleeve onto the pipe. There are mainly types of fittings such as sleeve type straight through pipe fittings, sleeve type end straight through connectors, and sleeve type three-way pipe fittings. The author found that even for a batch of goods from the same manufacturer, the depth of the tapered holes on these types of joint bodies is often different, resulting in leakage, which is often overlooked. The correct approach is to use the same type of connector body to connect one end of the pipe, and pre install the corresponding connector end with the same type of connector, which can minimize leakage problems.

② The end face of the pipe should be flush. After sawing the pipe, it should be polished flat on tools such as grinding wheels, and burrs should be removed. It should be cleaned and blown clean with high-pressure air before use.

③ When pre installing, try to maintain the coaxiality between the pipe and the joint body as much as possible. If the pipe deviates too much, it will also cause sealing failure.

④ The pre installation force should not be too large, and the inner edge of the card sleeve should just fit into the outer wall of the pipe, and the card sleeve should not have significant deformation. When connecting the pipeline, assemble it according to the specified tightening force. The tightening force of the ф 6-1 card sleeve is 64-1 15n, 16 ф mmr 259n, and ф 18mm is 450n. If the card sleeve is severely deformed during pre installation, it will lose its sealing function.

（2） Do not add sealant or other fillers. Someone applied sealant on the card sleeve in order to achieve better sealing effect, but the sealant was flushed into the hydraulic system, causing faults such as blockage of the negative hole of the hydraulic component.

（3） When connecting pipelines, the pipes should have sufficient deformation allowance to avoid being subjected to tensile forces.

（4） When connecting pipelines, avoid subjecting them to lateral forces, as excessive lateral forces can cause poor sealing.

（5） When connecting pipelines, they should be done in one go to avoid multiple disassembly, otherwise it will also deteriorate the sealing performance. Installation of sleeve type pipe joint.

(1) According to Chapter 9, pipes that require acid washing should be treated with acid washing first;

(2) Cut the pipe according to the required length using sawing machines or specialized pipe cutting machines, and it is absolutely not allowed to use melting (such as flame cutting) or grinding wheels for cutting; Remove burrs, metal chips, and dirt from the inner and outer circles of the pipe end; Remove rust inhibitors and dirt from pipe joints; At the same time, it is necessary to ensure the roundness of the pipe;

(3) Insert the nut and sleeve into the pipe in sequence, with the cutting edge (small diameter end) of the sleeve at least 3mm away from the pipe mouth, and then insert the pipe into the tapered hole in the joint body until it reaches the top;

(4) Slowly tighten the nut while rotating the pipe until it stops moving, then tighten the nut 2/3-4/3 turns;

(5) Open and check if the card sleeve has been inserted into the pipe and if the position is correct. The card sleeve is not allowed to move axially and can rotate slightly;

(6) After passing the inspection, tighten the nut again. 2、 Prevention of leakage at pipe joints: In hydraulic systems, both metal pipe joints and hose joints are prone to leakage. For sleeve type pipe joints, leakage is mostly caused by the loosening of the sleeve or deformation of the pipe end face due to significant external or impact forces on the pipeline. At this time, it is necessary to check whether the sleeve is out of roundness, whether the cutting edge is damaged, whether the pipe end is intact, and the degree of compression of the sleeve nut. At the same time, external forces on the pipeline should also be eliminated. For expansion type pipe joints, leakage is often caused by excessive expansion, substandard quality, or repeated disassembly, resulting in deformation or cracking of the expansion. In this case, the front end can be cut off and re expanded. If a male and female cone top pressure is used for sealing, the leakage is mostly due to damage to the two conical surfaces. Grinding sand can be used to grind the conical surfaces. In some cases where an "о" ring is used to seal against the end face or outer diameter, there are several reasons for leakage: leakage caused by aging or deformation of the "о" ring; The assembly of the "о" ring is not in place, resulting in uneven pressure when connecting the two planes or leakage caused by cutting the "о" ring; The "о" ring is not compacted, resulting in insufficient elastic deformation and leakage; The "о" ring stopper groove is too deep, causing leakage. For this, it is necessary to choose a "о" - shaped ring with the same outer diameter and thicker cross-section again. The sealing surface with a stop groove can also be cut or ground to reduce the depth of the stop groove, so that the "о" - shaped ring has sufficient elastic deformation (compression should generally be between 0.35-0.65mm). For leaks at pipe joints using oil resistant rubber sheets, wool felt, soft steel cardboard, composite sealing gaskets or sealants, regardless of the material, the sealing components should first be checked for damage, deformation, aging, and excessive roughness, and then corresponding measures should be taken.