Principle Of Sealing Packing

After the packing is loaded into the packing chamber, it is axially compressed by the gland screw. When the shaft moves relative to the packing, it produces radial force due to the plasticity of the packing, and is in close contact with the shaft. At the same time, the impregnated lubricant in the filler is extruded, forming an oil film between the contact surfaces. Because the contact state is not particularly uniform, the contact part will appear in the "boundary lubrication" state, called the "bearing effect"; The uncontacted concave part forms a small oil groove, has a thick oil film, and the contact part and the non-contact part form an irregular maze, which prevents the leakage of liquid flow, which is called the "maze effect". This is the mechanism of packing seal. Obviously, a good seal is to maintain the "bearing effect" and "maze effect". That is to say, to maintain good lubrication and proper compaction. If the lubrication is poor, or the pressure is too tight, the oil film will be interrupted, resulting in dry friction between the filler and the shaft, and finally lead to the shaft burning and serious wear.
To this end, it is necessary to adjust the compaction degree of the packing frequently, so that after the lubricant in the packing is lost for a period of time, some lubricant is extruded, and at the same time, the relaxation of the compaction force caused by the change in the volume of the packing is compensated. Obviously, such frequent squeezing of the filler will eventually deplete the impregnation, so regular replacement of the filler is necessary. In addition, in order to maintain the liquid film and take away the friction heat, it is also necessary to intentionally allow a small amount of leakage at the filler.