Mechanical seals are designed for centrifugal rotating shaft pumps, mixers, agitators and etc which pump or mix the fluids not corrosive to the synthetic rubber bellows. Mechanical seal rotate with pump shafts at a speed of less than 12m/sec and at a working pressure of less than 1.2 Mpa and at a limitted temperature from minus 30 degrees to 200 degrees. Carbon and silicon carbide and tungsten carbide materials can work as pump seal faces and ceramic,silicon carbide and tungsten carbide may operate as pump seal mating rings.