Analysis of the Reasons for the Use of Auxiliary Facilities in Mechanical Seals

In fluid machinery, such as pumps, compressors, agitators, and centrifuges, the harsh components used for mechanical seals are considered mechanical seals. They bear axial forces like thrust bearings and dissipate heat like heat exchangers. It is already difficult to achieve static sealing in high-temperature, high-pressure, and corrosive environments, and achieving dynamic sealing on a seal face just a few millimeters wide during high-speed rotation is even more difficult. To solve this thorny problem, people have found two ways through long-term practice: one is to start from the structure and materials of the seal to make it suitable for harsh working conditions. This approach is expensive and cannot fundamentally solve the problem. Once the seal fails, the consequences are serious. The other approach is to improve the working environment through auxiliary facilities. Currently, mechanical seals that do not use any auxiliary equipment are rare in practical work. Serial mechanical seals used in high-pressure and mechanical seals used in high-temperature pumps must adopt corresponding auxiliary facilities. By changing some harsh working environments into ones that seals can accept, the effect of mechanical seals is greatly improved, and their range of use is more widely applicable.

The frictional heat generated in the working of mechanical seals increases the temperature of the seal faces

• The temperature rise causes vaporization of the liquid film between the seal faces, intensifying wear and causing seal failure.

• The temperature rise causes thermal deformation of the dynamic and stationary rings, increasing leaks and wear.

• The temperature rise also intensifies the corrosion of the medium on the mechanical seal.

• The temperature rise causes the auxiliary sealing ring to age, deteriorate, and fail.

• The temperature rise causes impregnated synthetic resins in graphite to degrade in performance due to resin carbonization and metal-infused graphite rings to leak due to metal melting.

Using the correct auxiliary facilities for mechanical seals

Excess temperature rise is the big enemy of mechanical seal spare parts. The purpose of auxiliary facilities is to reduce this undesired temperature rise, maintain good lubrication between the seal faces, ensure that all components of the mechanical seal work well and normally; in easily-vaporized media, keep the pressure in the sealing chamber from vaporizing; in low-temperature water pump seals, serve to insulate and heat; and for seals with crystalline solid particles or strong corrosive media, to protect the seals from damage. Therefore, some countries call the auxiliary system the protection system.

Some mechanical seal spare parts work at low temperatures, pressures, and speeds, and may not require auxiliary facilities to function properly. However, from the perspective of seal stability and service life, it is beneficial to use auxiliary facilities. Therefore, auxiliary facilities should be regarded as part of the mechanical seal and selected according to different working conditions. Correct and reasonable application of auxiliary facilities has not only important significance for the stability and service life of the seal but also for safety production and reducing leakage, maintenance work and production costs. Sufficient attention must be paid to the auxiliary facilities. Some people call the auxiliary system the seal circulation protection system or simply the seal system or protection system.