ANALYSIS AND COUNTERMEASURES OF LEAKAGE OF MECHANICAL SEAL OF PUMP

Mechanical seal is a dynamic seal. Its principle is to use the elastic force of the elastic element to interact with the axial force of the medium to balance it, and then play a sealing effect. At present, there are many types of mechanical seals for pumps, such as bellows with small springs and so on. However, leakage problems often occur in mechanical seals of pumps and pumps.Generally, the leakage points occur at the end of the moving ring and the end of the static ring, the end of the moving ring and the auxiliary seal, and the static ring and the auxiliary seal. Between the moving ring and the pump cover and gland.

Important factors leading to mechanical seal leakage

The cause of the mechanical seal leakage of the pump and pump is that it will cause mechanical seal failure in many ways. Therefore, we need to continuously research and analyze the cause of the mechanical seal leakage problem in practice and then formulate corresponding countermeasures to ensure that the mechanical seal is safe and reliable.

Prolonged operation 

As the mechanical seal of the pump and pump is in a long-term working state, the axial displacement of the rotor will continue to increase, and the interference between the shaft and the auxiliary seal will also continue to increase, and the friction between the moving ring and the shaft will increase accordingly. During this process, the wear of the dynamic and static rings cannot be compensated for displacement, resulting in failure of the mechanical seal. In view of this situation, it is necessary to do the daily maintenance of the mechanical seal or switch the operation of other pumps. When reinstalling, ensure that the axial displacement is less than 0.1mm. Do not connect the shaft and the auxiliary seal tightly to ensure that the moving ring can move freely on the shaft.

When the pump is working, the pump shaft is prone to periodic vibration, which will greatly reduce the service life of the mechanical seal. In response to this situation, timely inspection and maintenance should be performed in accordance with relevant technical requirements to fundamentally eliminate leakage problems caused by vibration. Also clean up the pump inlet to prevent large particles from mixing into the medium to cause leakage of the friction pair. For corrosive media, choose higher quality materials to prevent leakage caused by corrosion.

Inexperienced pump operator

When installing the pump, the relevant technical requirements must be implemented to ensure the quality of the installation and prevent the failure of the seal introduced due to unqualified installation. After the machine pump is installed, leakage may occur after the static test. At this time, the centrifugal force generated by the machine pump will prevent the hostage from leaking. Therefore, the leakage at this time may be caused by the wear of the dynamic and static ring friction pairs. The main cause of this phenomenon in practice is the lack of operator experience, friction surface separation due to operating errors, friction surface wear caused by over-tightening, and large particles in the medium entering the friction pair, resulting in dynamic and static ring wear.

Seal face wear

During the operation of the pump, some impurities will be mixed into the end face sealing elements, causing wear on the end face and causing seal leakage. In addition, when the pump is working, when the internal circulation is clogged or the circulating fluid is lost, it will cause dry friction on the sealing end surface, which will cause damage to the static ring and cause leakage problems. Fouling often occurs inside the circulation system that cools high-temperature pumps, causing damage to the inside of the seal ring and causing leakage problems.

Damage caused by corrosion

During the operation of the mechanical seal, chemical corrosion, electrochemical corrosion, and mechanical erosion will occur, resulting in damage to the sealing elements and failure of the mechanical seal.

Friction temperature

If the temperature exceeds the temperature limited by the graphite ring during the operation of the high temperature pump, it will cause carbonization of the resin around the friction surface and cause mechanical seal failure. If the temperature exceeds the limit of the sealing component, the temperature will cause the component to harden continuously, resulting in less and less elasticity, and eventually cause leakage. During the operation of the pump, if the heat energy formed on the sealing end face is not transmitted quickly, the liquid film between the end faces will be melted, causing the pump to leak.

Pressure fluctuation 

The balance value β is an important factor that determines the quality of the seal. If the value of β is too small, the amount of wear on the seal end face will become smaller, and the amount of leakage will increase accordingly. If the value of β is too large, the amount of leakage will also decrease, and the friction on the seal end face will continue to increase. The pump and pump will have abnormal conditions such as evacuation and pressure during work, causing the contact surface to separate and cause the pump to leak.

Matters to pay attention to during inspection and maintenance

There is often a misunderstanding during the inspection and maintenance of mechanical seals, which is mainly based on everyone's understanding of the important parts of the mechanical seal and the principle of sealing.

Select and install correctly. Each type of mechanical seal has its application range. Selecting the correct model according to the working environment is the first step to ensure long-term reliable operation of the mechanical seal. Before installation, carefully check the integrity and standardization of each component, and install according to the mechanical seal installation and drawing requirements. During the installation process, dial indicator, vernier caliper and other tools should be used correctly to ensure that the static ring and the shaft are not eccentric, and the dynamic ring and shaft clearance is reasonable.

Prevent friction from causing failure. In order to avoid mechanical seal failure due to friction, in addition to the friction pair, materials with good friction properties should be selected, and the flatness and roughness of the sealing surface must meet requirements. In addition, remove foreign matter on the end face during installation. During the operation, a qualified transport medium should be used to avoid impurities such as solid particles from entering the transport medium.

Prevent rubber ring failure. The rubber ring has a certain service life, and the time should be calculated and replaced in time during use. If the seal ring is found to be hardened, cracked or deformed during maintenance, the seal ring should be replaced immediately.

Improve operator skills. Prior to operation, personnel training should be strengthened to improve the operational skills of personnel. When starting the pump, the pump should be filled according to the requirements to avoid cavitation. In addition, personnel should usually be arranged to do the daily maintenance of the pump, and regularly turn the car to avoid the phenomenon of excessive deflection of the pump shaft.