Filling Sealing:

Gland packings, also known as packing seals or simply packings, are a traditional type of sealing structure. In ancient China, they were used in water-lifting machinery to stop leaks by packing cotton yarn. Gland packings are favored by many industrial sectors due to their simple structure, affordable price, and widespread availability. They are primarily used in the mechanical industry for dynamic seals in process machinery and moving parts, such as centrifugal pumps, compressors, vacuum pumps, mixers, reactor shaft seals, reciprocating pumps, reciprocating compressors, and the valves of spiral motion gates. The working principle of gland packings is as follows: after the packing is inserted into the gland cavity and compressed axially by the gland nut, when the glass-lined reactor agitator shaft moves relative to the packing, the plasticity of the packing generates radial force, making it tightly contact with the shaft. At the same time, the lubricant soaked into the packing is squeezed out, forming an oil film between the contact surfaces. Due to the uneven contact state, the contact areas exhibit "boundary lubrication" known as the "bearing effect." Uncontacted concave areas form small oil grooves with a thicker oil film, creating an irregular maze-like structure between the contacting and non-contacting areas, which serves to prevent fluid leakage, known as the "maze effect." This is the mechanism of gland packings. Clearly, a good seal depends on maintaining both the "bearing effect" and the "maze effect," meaning maintaining proper lubrication and tension. Poor lubrication or excessive tension can break the oil film, causing dry friction between the packing and the shaft, leading to shaft burning and severe wear.

Therefore, it is necessary to frequently adjust the tightness of the filling material so that after the lubricant in the filling material has been lost after running for a period of time, some lubricant can be extruded, and at the same time, compensate for the relaxation of the clamping force caused by the volume change of the filling material. Clearly, frequently squeezing the filling material will deplete the impregnant, so regular replacement of the filling material is necessary. Moreover, to maintain the liquid film and carry away the friction heat, it is also necessary to intentionally allow a small amount of leakage at the filling material.