Experimental visualization of the lifetime and self-healing of magnetic fluid seals

The lifetime of magnetic fluid seals (MFSs) affects the ability to determine the relationship between their lifetime, operating conditions, and gaps. In this study, we designed an MFS device with a nonconductive poly magnetic shaft structure to visualize the lifetime of MFSs, seal failure, and seal self-healing. The kinetic state of the fluid can be divided into two phases: squeezing and rupturing. At sealing pressures exceeding 70% of the maximal sealing pressure and sealing gaps of 0.6 mm and above, a cliff appeared; seals exhibited significant leakage and no secondary sealing capacity. At sealing pressures of 70% and higher of the maximal sealing pressure and sealing gaps of 0.4 mm and smaller, slippery slopes were observed and the seals exhibited secondary sealing. Under dynamic sealing conditions, the lifetimes of the magnetic seals decreased as the gap, sealing pressure, and speed increased, and secondary sealing did not occur. The magnetic seals failed at speeds exceeding 1000 rpm. This study provides a reference for the design and application of MFS.