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Reasons of the Leakage of the Sleeve Pipe Joint

The ferrule nipple in pipe fittings consists of three parts: the joint body, the ferrule and the nut.


Ⅰ. What is the sealing principle of the ferrule nipple in pipe fittings?


The main sealing part of this joint is the ferrule. As the nut for compression adjustment is tightened continuously, the ferrule rubber ring in the nipple in pipe fittings moves along the axial direction of the inner cone hole of the joint body under the action of the axial force of the nut. The rubber ring's cone surface fits the joint body's cone surface, and the rubber ring's end surface fits the end surface of the joint body. When all the functional movable nuts are tightened, the front end surface of the metal ferrule contacts the inner cone surface of the rubber ring and the metal clamps. The sleeve produces a reverse force, and the cutting edge of the ferrule has different radial shrinkage under the radial action of the reaction force, which gradually eliminates the gap between the ferrule and the tube, and makes the blade contact the surface of the tube, and continue to rotate the nut and rubber ring. The outer cone surface closely fits with the inner cone surface of the joint. Due to the compression, the tapered part of the rubber ring and the pipe are tightly fitted to achieve sealing. At the same time, the cutting edge of the ferrule is also firmly cut into the pipe to ensure a safe and reliable seal. , The tail cone of the ferrule shrinks radially under the action of the force, tightly hugs the connected pipe. At the same time, the middle part is slightly arched, so the ferrule has a certain axial elastic deformation, which seals the ferrule and prevents the compression nut from loosening. All play a beneficial role.


Ⅱ. Reasons for the sealing leakage of ferrule nipple in pipe fittings


1. If the steel pipe is not inserted into the end of the metal pipe, the metal sleeve cannot be cut, and the second sealing ring cannot be formed on the metal pipe's surface, significantly reducing the sealing effect.


2. If the nut is not tightened, there will be insufficient axial thrust, resulting in the formation of the main and secondary sealing rings.


3. The outer surface of the steel pipe is severely scratched, and the scratched area may not be able to form an effective seal, and there is a hidden danger of leakage.


4. The steel pipe is not round, or the steel pipe nipple dimensions like diameter tolerance is too large. When the roundness deviation of the steel pipe is significant, an effective seal cannot be formed.


5. The steel pipe is too hard. When the steel pipe is too hard, the metal ferrule cannot be cut into the metal pipe so that an effective secondary sealing ring cannot be formed, and the sealing effect is greatly reduced.


Ⅲ. How to effectively solve the leakage of ferrule nipple in pipe fittings


1. Pre-install the ferrule's axial position on the steel pipe by the design requirements to ensure that the steel pipe is inserted to the end.


2. Tighten the available nut to the torque specified. It should not be overly tight or overly loose. A seal that is too loose will not provide enough axial force and will not form an effective seal. If the ferrule is too tight, it will yield, deform, and lose its elasticity.


3. Check whether there are scratches on the connecting part of the cold drawn tube and the ferrule. If there is a scratch, cut off a section of the scratched hard drawn tube, or replace with a qualified ferrule and reassemble it. The end of the steel pipe should be vertical without burrs


4. The structure requirements in pipe fittings manufacture of the ferrule nipple in pipe fittings must be equipped with high-precision (outer diameter) cold drawn pipes to ensure that the outer diameter of the steel pipe is tightly sealed with the installation ferrule.


5. Low-carbon steel cold drawn pipes need to be normalized, and stainless steel cold drawn pipes need to be fully annealed to ensure that the ferrule effectively cuts into the surface of the steel pipe when the functional nut is tightened.