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Failure and treatment of mechanical seal of reaction kettle
Jan 28, 2020

The reactor is a comprehensive reaction vessel, and the pressure generated in the reaction process is very high to seal the vessel. The sealing effect of the mechanical seal will directly affect the operation of the reactor, which will cause incalculable losses such as production suspension, safety accident and environmental pollution.


1. Failure and treatment of mechanical seal parts


Failure causes and phenomena


During the operation of the reactor, the sealing end face will often be worn, hot crack, deformation, damage and other conditions, screw, thread, spring used for a long time will also relax, fracture and corrosion. Auxiliary seal ring will also appear cracking, distortion and deformation, rupture and other conditions.


Fault handling method


If there is a failure of mechanical seal parts, it is necessary to replace parts or improve the machining precision of parts, improve the machining precision of the mechanical seal itself and other parts of the reaction kettle machining precision is very beneficial to the mechanical seal effect.


In order to improve the sealing effect, the friction surface of moving ring and static ring is required to be more smooth and smooth. The width of the friction surface of the dynamic ring and the static ring is not large, generally between 2 ~ 7 mm.


2. Causes and treatment of mechanical seal vibration and heating failure


Failure causes and phenomena


During operation of the reactor, due to mechanical wear and chemical erosion, the fitting end face of the rotor and stator rings will be rough, and the gap between the rotor and stator rings and the sealing chamber will be too small.


Sometimes due to the sealing end face (corrosion resistance and) poor temperature resistance, or insufficient cooling or end face in the installation of particles and impurities, will also cause the vibration and heat of the mechanical seal.


Fault handling method


If the clearance between the dynamic ring, the static ring and the sealing chamber is too small, it is necessary to increase the inner diameter of the sealing chamber or reduce the outer diameter of the rotation to ensure at least 0.75mm clearance.


If the friction pair is not matched properly, it is necessary to change the ring, static ring material, make it temperature resistance, corrosion resistance. This reduces vibration and heat in the mechanical seal.


3. Causes and treatment of mechanical seal leakage


Causes of leakage during static pressure test of mechanical seals


Due to the installation of mechanical seals do not pay attention to, often will seal end surface damage, deformation, damage, clean up, there are granular impurities, or because the positioning screw is loose, the gland is not pressed, the machine, equipment precision is not enough, so that the sealing surface is not fully fitted, will cause media leakage. If the sleeve leakage, the sleeve seal ring assembly is not pressed or compressed enough or damaged.


Causes of periodic or paroxysmal leakage of mechanical seals


The mechanical seal rotor assembly periodic vibration, large axial momentum, will cause leakage. The sealing surface of the mechanical seal must have a certain specific pressure, so as to play the sealing role, which requires the mechanical seal spring to have a certain amount of compression, to the seal end face a thrust, the reaction kettle rotation so that the sealing surface produced the specific pressure required by the seal.


In order to ensure this a specific pressure, the mechanical seal requirements shaft can not have too much channeling, generally to ensure that within 0.25mm. However, in practice, due to the unreasonable design, manufacturing error, assembly error and other reasons, often lead to a large amount of shaft channeling, periodic or partical leakage.


Causes of frequent leakage of mechanical seals


There are many reasons for frequent leakage of mechanical seals:


One is due to the seal end surface defects caused by frequent leakage;


Second, the auxiliary seal ring caused by frequent leakage;


Third, spring defects caused by leakage;


Others include leakage caused by rotor vibration, poor quality or loose parts of transmission, setting and thrust, leakage caused by mechanical seal auxiliary mechanism, frequent leakage caused by media problems, etc.


Ways to reduce leakage of mechanical seals


Assembly should be clean and smooth. Mechanical seal parts, tools, lubricating oil, wiping materials to be very clean. The sealing end face of the stationary ring should be wiped with soft gauze.


Trim chamfering and rounding. The chamfering of the shaft, seal end cover, etc. should be trimmed and smoothed, and the rounded corners of the shaft and end cover should be sanded and polished.


When assembling the auxiliary seal ring, the rubber auxiliary seal ring should not be soaked and washed with gasoline or kerosene to avoid swelling deformation and premature aging.


After assembling the stationary and static ring, press the compensation ring by hand to check whether it is in place and flexible. Whether the elastic open ring is positioned reliably. After the movable ring is installed, it must be ensured to move flexibly in the axial direction on the shaft.


4. Excessive vibration of mechanical seal and its treatment


Failure causes and phenomena


If the vibration of mechanical seal is too high, it will eventually lead to seal failure. However, the reasons leading to the high vibration of mechanical seal are not all the reasons of the mechanical seal itself, and other parts of the reactor are also the root causes of vibration, such as unreasonable shaft design, processing reasons, bearing precision is not enough, coupling parallelism difference, radial force, and so on.


Fault handling method


In the installation shaft, seal cavity, mechanical seal itself should be cleaned to prevent impurities into the sealing installation site. The balancing device of axial force is designed reasonably, so that the axial momentum of the rotor of the equipment installing mechanical seals is less than 0.3mm, and the axial momentum is eliminated.

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