Life tests of a rotary single-stage magnetic-fluid seal for shipbuilding applications

Use of the magnetic fluid seal technology in water is much more difficult technological problem in comparison to gas or vacuum environment. Some seals constructed up to time been are designed as hybrid, two stage sealing structures with shields or mechanical seals used as protection measures to the magnetic fluid seal. Anyway, there is always problem with immediate contact between magnetic fluid and the environmental liquid. In the paper are presented results of experiments carried out with one stage rotating magnetic fluid seal operating in immediate contact with utility water. The special test procedures have been elaborated and practically used, with the aim to define main characteristics of magnetic fluid seals and to simplify experiments. These characteristics were: critical pressure, critical motion velocity and working life of the seal. Four grades of commercial, silicon based magnetic fluids of hydrophobic properties were tested in a single stage sealing system. The results of tests are presented in the form of tables and diagrams. It is concluded that hydrophobic commercial magnetic fluids could be efficiently used in rotating shaft seals however in a limited range of motion velocity.