100 years, people fill a class with a variety of sealing materials, so that the liquid from the pump housing along the axis of outward leakage decrease. Although modern pumps used in process, still widely in use of the oldest seal design - packing boxes, because of its low initial outlay, but they work for the factory staff are familiar with. However, the relationship between environmental topics, the use of the method is gradually packing seal can not be accepted, particularly for the more common modern process, in terms of corrosive liquid. Therefore, in practice, to replace the mechanical seal packing seal more and more.

The basic elements of mechanical seal sealing is the use of friction between two surfaces of the principle of operation, to seal the purpose. Installed in the pump rotating seal face of the spindle, and fixed sealing surface installed within the sealing gland. As a sealing surface is in motion, and the other sealing surface is stationary, so this type of seal is called the dynamic seal. Rotating surface and the stationary surface of the seal between the sealing performance in determining the basis of the most critical factor in the mechanical seal, of which four leakage paths need to seal: 1. Sealing surface between the channel; 2. Rotary path between the surface and the spindle ; 3. fixed path between the surface and the gland; 4. gland and stuffing box between the channels. The latter two commonly used static seal leakage paths, does not exist between the two relative motion. This part of the seal is usually called the third seal, the seal or gasket material compatible with the process liquid O-ring.

Sealed in the older design, is located under the secondary seal rotating plane left a certain gap, before and after the movement in the spindle, so easy to cause wear and premature failure. However, in the relatively new seal design, the secondary seal in a static state, so you can avoid wear and corrosion resistance appears on the subject of the spindle. In the normal control pump, the rotating surface between the surface and still packing boxes for the liquid pressure generated by the state to keep it in a sealed, the starting and stopping, the stuffing box pressure to maintain the pressure generated by the spring ( can even be replaced by the pressure of the spring.) Most of the mechanical seal is designed with soft materials to create rotating surface, it's still in the hard surface of rotating friction. Over the years, the most common combination is the use of carbon materials as the rotating surface so the surface of the ceramic still running.

Such material is still widely used, but still faces the hard choice of stainless steel or more materials, such as tungsten carbide or silicon carbide. Regardless of what material, in short, must be maintained between the contact surface layer of liquid film in order to play the role of lubrication. However, in the packing box, using spring-loaded, and combination of fluid pressure, can play a very good sealing surface between the seal. But the seal pressure is too high, it will affect the contact surface between the liquid film, leading to increased heat and premature wear. If the seal pressure is too low, the gap between the contact surface increases, causing fluid leakage easily. Seal manufacturers are constantly strive to advance the flatness of the contact surface, they use a special grinding and polishing plate. Then, using the grating monochromator board for its detection.