The reactor is a comprehensive reaction vessel, and the pressure produced in the reaction process is very demanding for the sealing of the container. The sealing effect of mechanical seals will directly affect the operation of the reaction kettle, which will cause inestimable losses, such as shutdown, safety accidents and environmental pollution.
Today, we take a look at the common failures of the mechanical seals of the chemical reaction kettle, and how to deal with these failures.

On the seal of the reaction kettle
The seal of the reaction kettle includes two kinds of static seal and dynamic seal.
Static seal:
For reaction kettle, the static seal is usually used in the leakage point of the head flange and the cylinder flange, connecting flange, manhole, hand hole, thermometer nozzle, sight mirror, pressure gauge nozzle and so on, because the sealing surface is relatively static. Static seal is better to solve, usually adopt various forms of static seal gasket.
Dynamic seal:
The leakage point between the mixing shaft and the kettle body is relative movement due to the rotation of the mixing shaft and the static kettle body (upper head). In order to prevent the leakage of the medium, we must use the dynamic seal device: mechanical seal and packing seal.
Packing seal: simple structure and convenient packing. But because of some fatal weakness of packing seal, its service life is short. It is not suitable for high parameter working conditions (high temperature, high pressure, high speed and high vacuum).
Mechanical seals: mechanical seals are widely used in reactors. According to the specific working conditions of reactors, special structural design, material selection and lubrication and cooling measures are taken into consideration for the mechanical seals of kettle, so as to meet the technological requirements.
Compared with the soft packing seal, the mechanical seal has the following characteristics:
Sealing state is reliable in long period operation, and the leakage rate is very small, and the leakage rate is usually only 1/100 of soft packing seal.
The long service life in oil and water medium can reach 1~2 years or longer, even in chemical medium, it can usually be more than half a year.
The friction power of the mechanical seal is small, and its friction power is only 10% ~ 50% of the soft packing seal.
Mechanical seal failure and treatment of reaction kettle

1. Failure and treatment of mechanical seal parts
Cause and phenomenon of failure
During the operation of the reactor, the sealing face will often wear, hot cracking, deformation and breakage. Screw, thread and spring will also relax, break and corrode for a long time. The auxiliary sealing ring also appears crack, distortion and deformation, rupture and so on.
Troubleshooting method
If a mechanical seal part fails, it will need to replace parts or improve the machining accuracy of parts. Improving the machining accuracy of the mechanical seals and the machining accuracy of other parts of the reactor is very beneficial to the mechanical seal effect.
In order to improve the sealing effect, the requirements for the smoothness and the integrity of the friction surface of the dynamic and static rings are higher. The width of the friction surface of the dynamic ring and the static ring is not large, usually between 2~7 millimeters.
2. Cause and treatment of mechanical seal vibration and heating fault
Cause and phenomenon of failure
During the operation of the reactor, mechanical wear and chemical erosion will make the surface of the static ring fit rough, and the gap between the static ring and the sealing cavity is too small, resulting in vibration due to the vibration caused by the pendulum.
Sometimes, due to the poor sealing face (corrosion and temperature) performance, or inadequate cooling or the inclusion of particulate impurities when the end faces are installed, it will also cause the vibration and heating of mechanical seals.
Troubleshooting method
If the gap between the moving ring, the static ring and the sealing cavity is too small, it is necessary to increase the inner diameter of the sealing cavity or reduce the rotating outer diameter, at least to ensure the clearance of the 0.75mm.
If the pairs of friction pairs are mismatched, the moving ring and the static ring material should be changed to make it warm and corrosion-resistant. This will reduce the vibration and heat of the mechanical seal.
3. Causes and treatment of mechanical seal leakage
The cause of leakage in the static pressure test of mechanical seal
Mechanical seals do not pay attention at the time of installation, often will seal scratches, deformation, damage, cleaning up not only with granular impurities, or because the positioning screw loosening, capping machines and equipment is not pressed, the accuracy is not enough, so that the sealing surface is not fully fit, will cause the leakage of the medium. If the shaft sleeve leakage, it is the shaft sleeve sealing ring is not pressed or compressed when the assembly is not enough or damaged.
The cause of periodic or paroxysmal leakage of mechanical seals
The periodic vibration and the axial channeling of the mechanical seal rotor will cause leakage. The seal face of mechanical seal must have a specific pressure, so that it can play a role of sealing. This requires that the spring of mechanical seal must have a certain amount of compression, give a push to the sealing face, and the reaction kettle will rotate to make the sealing cover produce the specific pressure required by the seal.
In order to ensure this specific pressure, the mechanical seal requires that the shaft should not have too large channeling, and it is generally guaranteed to be within 0.25mm. But in practice, due to the unreasonable design, manufacturing errors and assembly errors, shaft often leads to large amount of channeling and periodic or paroxysmal leakage.
Causes of frequent leakage of mechanical seals
There are many reasons for the frequent leakage of mechanical seals.
One is the frequent leakage caused by the seal face defect.
The two is the frequent leakage caused by the auxiliary sealing ring.
The three is the leakage caused by the spring defect.
Others also include leakage caused by rotor vibration. Transmission, tight and thrust parts are not good or loose, causing leakage, leakage caused by mechanical seal auxiliary mechanism, and frequent leakage due to medium problems.
Ways to reduce the leakage of mechanical seals
Clean and clean when assembling. Mechanical seal parts, tools, lubricants, cleaning materials must be clean. Seal static ring wiping with softgauze.
Trim the corner and pour it round. The chamfering of the shaft and the seal end cover should be smoothed and smooth, and the related corners of the shaft and end cover should be shined.
When the auxiliary sealing ring is assembled, the rubber auxiliary sealing ring can not be soaked with gasoline and kerosene to avoid swollen deformation and premature aging..
After the assembly is finished, the compensation ring is pressed with the hand to check whether it is in place and whether it is flexible, and whether the elastic opening ring is reliable. When the ring is installed, it must be guaranteed to move flexibly axially on the axis.
4. The vibration of mechanical seal is large and its treatment method
Cause and phenomenon of failure
The mechanical seal, if the vibration is large, will eventually lead to the seal failure. But lead to excessive vibration causes of mechanical seal mechanical seal is not always their own reasons, other parts of the reactor is the vibration source, such as shaft design, machining precision and bearing, coupling the parallel degree of difference, radial force and other reasons.
Troubleshooting method
It should be cleaned in the installation of the shaft, the sealing cavity and the mechanical seal itself, so as to prevent the impurities from entering the sealed installation part. And the balance device of the axial force is designed reasonably, so that the rotor of the equipment which is installed the mechanical seal is channeling &le in axial direction; 0.3mm is used to eliminate the axial channeling.
Selection method and principle of mechanical seal for reaction kettle

Mechanical seal according to the working conditions and the medium properties are different, high temperature resistance, low temperature mechanical seals, pressure resistant, corrosion resistant mechanical seal, light hydrocarbon medium particle medium mechanical seal and adapt easy vaporization of the mechanical seal, should choose different according to different use types and materials of mechanical seal.
1. The main parameters of selection
Sealed cavity pressure (MPA)
Fluid temperature (centigrade)
Working speed (M / S)
Characteristics of fluid
Install the effective space for sealing.
2, the basic principles of selection
According to the pressure of the sealed cavity, it is determined that the seal structure is balanced or non - balanced, single end or double end.
According to the working speed, it is determined to adopt rotating or static type, fluid dynamic pressure type or non contact type.
According to the temperature and fluid properties, the friction pairs and auxiliary seal materials are determined, and the mechanical seal circulation protection system, such as lubrication, rinsing, heat preservation and cooling, is selected correctly.
According to the effective space for installation and sealing, it is determined to adopt multiple spring or single spring or wave spring, internal or external loading.
In the design and selection of mechanical seals, we should give full consideration to its application conditions, choose suitable sealing structure and parts and materials, so as to prevent seal failure caused by improper design.
The daily maintenance and maintenance of the mechanical seal of the reaction kettle
Mechanical seal cooling liquid in each class to check again, with insufficient number of coolant to the oil pan height of about 2/3, the cooling liquid changed once a month. And make the corresponding record.
Check the mechanical seal tighten ring screw loosening every day before starting the machine, whether the spring and the spring between the compression ring and the spring seat are distorted or jump out. If there should be any adjustment, we should make timely adjustments and make corresponding records.
Content source: Qingta
Photo source: Baidu