The sealing principle of packing mainly depends on the labyrinth effect and bearing effect.

Maze effect: The microscopic lower surface of the shaft is very uneven, and it can only partially fit with the packing, but is not in contact with other parts. Therefore, there is a tiny gap between the packing and the shaft, like a maze, and the pressurized medium is in the gap. It is throttled several times to achieve the sealing effect.

Bearing effect: There will be a thin liquid film between the packing and the shaft, which makes the packing and the shaft similar to sliding bearings and plays a certain lubrication effect, thus avoiding excessive wear of the packing and the shaft.

Packing material requirements: Due to the temperature, pressure, and PH of the sealed medium, as well as the linear speed, surface roughness, coaxiality, radial runout, eccentricity and other factors of the axially split case pump, the packing material is required to have the following characteristics:

1. Has a certain degree of elasticity and plasticity

2. Chemical stability

3. Impermeability

4. Self-lubricating

5. Temperature resistance

6. Easy to disassemble and assemble

7. Simple to manufacture and low in price.

The above material properties directly affect the sealing performance and service life of the packing, and there are very few materials that can fully meet all the above properties. Therefore, obtaining high-quality sealing materials and improving their material properties have always been the focus of research in the field of sealing.

Classification, composition and application of packing for  axially split case pumps .

Due to different working conditions, there are many types of packing materials. In order to better distinguish and select packing, we usually divide packing according to the material of the main sealing base material of packing:

1. Natural fiber packing. Natural fiber packing mainly includes natural cotton, linen, wool, etc. as sealing base materials.

2. Mineral fiber packing. Mineral fiber packing mainly includes asbestos packing, etc.

3. Synthetic fiber packing. Synthetic fiber packing mainly includes: graphite packing, carbon fiber packing, PTFE packing, Kevlar packing, acrylic-clip silicone fiber packing, etc.

4. Ceramic and metal fiber packing Ceramic and metal fiber packing mainly include: silicon carbide packing, boron carbide packing, medium-alkali glass fiber packing, etc. Since a single fiber material has more or less some materials themselves The disadvantage is that a single fiber is used to weave the packing. Since there are gaps between the packing fibers, it is easy to cause leakage. At the same time, some fibers have poor self-lubricating properties and a large friction coefficient, so they need to be impregnated with some lubricants and fillers. and special additives, etc. To improve the density and lubricity of the filler, such as: mineral oil or molybdenum disulfide grease mixed with graphite powder, talc powder, mica, glycerin, vegetable oil, etc., and impregnated polytetrafluoroethylene dispersion emulsion, and in Add appropriate amounts of surfactants and dispersants to the emulsion. Special additives usually include zinc particles, barrier agents, molybdenum-based corrosion inhibitors, etc. to reduce the corrosion of equipment caused by packing fillers.