Influence of gravity on performance of magnetic fluid seal

The influence of gravity, an often ignored variable, on sealing performance of magnetic fluid seal, particularly a magnetic seal with large diameter and sealing gap, was approximated, modeled, simulated, and experimentally investigated. When the axis of magnetic fluid O-ring is horizontally oriented, gravity could strongly affect the sealing performance, possibly resulting in seal-failure, at worst. The upper limit of sealing size, defined as the largest diameter of the magnetic fluid seal, was found to depend significantly on the sealing gap. The diameter limit was estimated to be about 1.57 m for ordinary magnetic fluid seals with small sealing gap; and the larger the gap, the smaller the diameter. The diameter-limit is proportional to the ratio of the saturated magnetic induction and density of the magnetic fluid, but inversely proportional to gravitational acceleration. Besides, the diameter-limit is also proportional to the difference between the highest and lowest magnetic inductions in the sealing gap.