How to deal with common failures of mechanical seals on rotating equipment

If the mechanical seal parts fail, it is necessary to replace the parts or improve the machining accuracy of the parts. Improving the machining accuracy of the mechanical seal itself and the machining accuracy of other parts of the pump body is very beneficial to the effect of the mechanical seal.

In order to improve the sealing effect, the smoothness and unevenness of the friction surface of the dynamic and static rings are required to be higher. The width of the friction surface of the static and dynamic ring is not large, generally between 2 and 7 mm.

1. The principle of mechanical seal leakage

The leakage of the mechanical seal is caused by a variety of reasons, and we need to deal with specific problems in detail. In order to minimize the amount of leakage, the mechanical seal must be assembled in strict accordance with the technical requirements when installing the mechanical seal, and the following matters must also be paid attention to.

1) The assembly should be clean and smooth. The parts, tools, lubricating oil, and wiping materials of the mechanical seal must be very clean. The sealing end face of the moving and static ring should be wiped with a soft gauze.

2) Trimming and rounding of chamfers. The chamfers of the shaft and the sealing end cover should be trimmed and smooth, and the rounded corners of the shaft and the end cover should be sanded and polished.

3) When assembling the auxiliary sealing ring, the rubber auxiliary sealing ring cannot be soaked and washed with gasoline or kerosene to avoid swelling and deformation and premature aging. After the dynamic and static rings are assembled, press the compensation ring by hand to check whether it is in place and flexible; whether the elastic split ring is reliable in positioning. After the moving ring is installed, it must be ensured that it moves flexibly in the axial direction on the shaft.

2. Treatment of mechanical seal vibration and heat

If the gap between the static and dynamic rings and the seal cavity is too small, increase the inner diameter of the seal cavity or reduce the outer diameter of the rotation to ensure a gap of at least 0.75mm. If the friction pair is not properly matched, the dynamic and static ring materials must be changed to make it resistant to temperature and corrosion. This will reduce the vibration and heat generation of the mechanical seal.

Three, the treatment of large amount of pump shaft displacement

Reasonably design the balance device of the axial force to eliminate the axial displacement. In order to meet this requirement, for multi-stage centrifugal pumps, the design scheme is: balance disk plus axial thrust bearing, the balance disk balances the axial force, and the axial thrust bearing axially limits the pump shaft.

4. Treatment measures for pump vibration

In the manufacturing and assembly process of pump products, strictly follow the standards and operating procedures to eliminate vibration sources. When installing auxiliary equipment such as pumps, motors, bases, and on-site piping, strictly control them to eliminate vibration sources.

Five, increase the auxiliary flushing system

The sealing medium in the seal cavity contains particles and impurities, so it must be washed, otherwise the spring of the mechanical seal will fail due to the precipitation of crystals and the deposition of particles and impurities. If the particles enter the friction pair, the mechanical seal will be quickly damaged. Therefore, the auxiliary flushing system of the mechanical seal is very important. It can effectively protect the sealing surface, cooling, lubricating, and flushing away debris.

The above is the application of mechanical seal on rotating equipment and the treatment method after failure. When encountering the problem of mechanical seal failure, first consider the influencing factors of the mechanical seal itself, and then some influencing factors outside the mechanical seal. For example: when analyzing the causes of mechanical seal quality accidents, it is necessary to consider the impact of other parts of the pump on the operation of the mechanical seal, and take measures to continuously improve the effect of the mechanical seal.