Introduction:
Magnetofluid sealing (also known as magnetic fluid sealing) is a high-end dynamic sealing technology based on the properties of magnetofluid. It uses a magnetic field to attract magnetofluid to the sealing gap to form a "liquid O-ring", achieving a contactless seal between the rotating shaft and the stationary housing. It is widely used in industrial equipment with high vacuum, clean, and harsh operating conditions.
Core Structure and Working Principle
The core components include a permanent magnet, a magnetic ring, pole shoes, a magnetofluid, and a bushing (or shaft).
The magnetic field generated by the permanent magnet forms a closed magnetic circuit through the magnetic ring and pole shoes, creating a strong magnetic field gradient at the tiny gap (typically 0.1-0.5 mm) between the pole shoes and the shaft.
The magnetofluid (a colloidal solution containing nanoscale magnetic particles) is adsorbed into the gap under the influence of the magnetic field, forming a continuous and stable liquid sealing film that blocks media leakage and isolates external contaminants such as air and dust.
During the sealing process, as the shaft rotates, the magnetofluid moves synchronously with the shaft, resulting in no solid friction and only extremely low viscous friction.
Core features and advantages
Ultimate Sealing Performance: Achieves zero leakage (suitable for high vacuum and high-purity media scenarios), with vacuum levels reaching 10⁻⁷ Pa・L/s, far exceeding traditional sealing methods such as mechanical seals.
Non-Contact and Low-Wear: No solid friction exists between the magnetic fluid and the rotating shaft, resulting in virtually no wear on the shaft and sealing components. This leads to a long service life (typically 3-5 times that of mechanical seals) and short maintenance cycles.
Wide Operating Range Compatibility: Withstands extreme temperature variations (-200℃~400℃, with special magnetic fluids reaching even higher temperatures), rotational speeds (0~100000 r/min), and pressures (0~10 MPa), and is compatible with various media including gases, liquids, and dust.
Clean and Pollution-Free: The magnetic fluid exhibits strong chemical stability, is non-volatile and non-decomposing, and generates no frictional dust, making it suitable for sterile and high-cleanliness environments (such as pharmaceuticals and semiconductors).
Extremely Low Energy Consumption: Viscous frictional resistance is significantly lower than that of mechanical seals, resulting in significant energy savings, especially suitable for high-speed rotating equipment.
Main types and applicable scenarios
Single-stage magnetohydrodynamic (MHD) seals: Simple in structure and low in cost, suitable for low-pressure (≤0.1MPa) and low-vacuum applications (such as ordinary vacuum equipment and small agitator shaft seals).
Multi-stage MHD seals: Composed of multiple single-stage sealing units connected in series, allowing for the aggregation of sealing pressures/vacuum levels. Suitable for high-pressure (0.1~10MPa) and high-vacuum (10⁻⁷Pa) applications (such as large reactors and vacuum coating machines).
Combined MHD seals: Combined with mechanical seals or labyrinth seals, forming a "main seal + auxiliary seal" structure. Suitable for harsh operating conditions (such as highly corrosive, high-temperature, and particulate-containing media), improving sealing reliability.
Aseptic MHD seals: Utilizing sanitary materials such as 316L stainless steel and PTFE, the MHD complies with FDA standards and supports in-line sterilization (SIP), making them suitable for aseptic applications in pharmaceuticals, vaccines, and bioengineering.
Typical Application Industries
Semiconductor/Electronics Industry: Vacuum coating machines, ion implanters, semiconductor wafer processing equipment, ensuring high vacuum environments and no particulate contamination.
Pharmaceutical/Vaccine Industry: Sterile fermenters, vacuum dryers, sterile dispensing tanks, agitator shaft seals, conforming to GMP standards, preventing media contamination and leakage.
Aerospace Industry: Satellite attitude control engines, spacecraft propulsion systems, withstanding extreme temperatures and vacuum environments, ensuring reliable sealing.
High-end Equipment Industry: Precision machine tools, high-speed centrifuges, magnetic levitation motors, achieving wear-free sealing, improving equipment precision and service life.
Chemical/New Energy Industry: High-pressure reactors, hydrogen storage equipment, lithium battery material production equipment, withstanding corrosive media and high-pressure conditions, avoiding leakage risks
