Abstract: The dynamic seal of spin shaft with magnetic fluid is studied and a test unit for magnetic fluid seal is established.The new method is presented for proof the theory . In the experiment the relationship between the seal capacity of magnetic fluid and the different seal gap is determined. The result shows that the seal capacity of magnetic fluid is raised with the increase of seal stage and the decrease of seal gap at certain range . When the seal gap is between 0.05 mm and 0.20 mm the result is better and the number of seal stage has an optimum value. But it is known by investigating that the seal capacity is not better when the gap smaller that the capacity is worser when the gap too smaller.

Key words: Magnetic fluid Magnetic fluid seal, Seal gap Seal capacity