Mechanical seals, also known as end-face seals, are devices used to seal the gap between rotating shafts and the body, commonly used in rotating fluid machinery such as pumps. Therefore, mechanical seals are a universal shaft sealing device.
There are two types of mechanical seals. Currently, most use contact mechanical seals, while non-contact mechanical seals are under development and have attracted attention. Mechanical seals are non-functional parts of a machine, but they play a significant role in reducing leaks and stabilizing production.
The working principle of mechanical seals is to use two flat sealing surfaces that mutually adhere and are perpendicular to the axis of rotation, and a sealing device that rotates relative to each other. It relies on the pressure of the elastic element (such as a spring or a bellows) and the sealing medium to produce appropriate clamping force on the contacting ends of the rotating ring and stationary ring, so that these two contact surfaces are tightly fitted and maintain an extremely thin liquid film between them, thereby achieving the purpose of sealing.
Mechanical seals consist of at least one pair of end faces perpendicular to the axis of rotation, which are kept in contact and slide relative to each other under the action of fluid pressure and the elasticity (or magnetic force) of the compensating mechanism and auxiliary seals to prevent fluid leakage. They are commonly used in rotating fluid machinery such as pumps, compressors, and stirred reactors, as well as seals for gearboxes and ship tail shafts. Therefore, mechanical seals are a universal shaft sealing device.
There are many types of mechanical seal structures, and the commonly used structure is the end-face seal,including single cartridge mechanical seal and double cartridge mechanical seal. The static ring and the dynamic ring of the end-face seal form a set of friction pairs, and the function of the friction pair is to prevent medium leakage. It requires the static ring and the dynamic ring to have good wear resistance, the dynamic ring can move flexibly in the axial direction and automatically compensate for the wear of the sealing surface, ensuring a good fit with the static ring; the static ring has floating properties and plays a buffering role.
Therefore, the sealing surface requires good machining quality to ensure good fitting performance. The basic components of mechanical seals include static rings, dynamic rings, pressure cover, thrust ring, spring, positioning ring, shaft sleeve, dynamic ring sealing ring, static ring sealing ring, and shaft sleeve sealing ring, etc. Rubber is a commonly used sealing material. In addition to rubber, materials suitable for making sealing materials include graphite, polytetrafluoroethylene, and various sealing adhesives.
Currently, new technologies for various mechanical seals using new materials and processes are progressing rapidly, and there are new mechanical seal technologies such as slotted sealing technology. In recent years, various types of grooves have been opened on the sealing end face of mechanical seals to produce static and dynamic pressure effects, which are constantly being updated.
Zero-leakage sealing technology used to be believed that contact and non-contact mechanical seals could not achieve zero leakage. Israel has proposed a new concept of zero-leakage non-contact mechanical end-face sealing using slotted sealing technology, which has been used in lubricating oil pumps for nuclear power plants. Dry-running gas sealing technology is a type of sealing that uses slotted sealing technology for gas sealing. Upstream pumping sealing technology uses flow grooves on the sealing surface to pump back a small amount of downstream leakage fluid to the upstream.