As critical power equipment in the industrial sector, the reliability of shaft sealing systems in centrifugal fans directly impacts operational efficiency and maintenance costs. Within the field of sealing technology for rotating machinery, shaft sealing has evolved over a century into a diverse technological landscape; this article analyzes mainstream sealing solutions from an engineering application perspective.
Labyrinth seals function as pneumatic barrier seals, utilizing a multi-stage, tortuous flow path design to achieve sealing through the dissipation of fluid kinetic energy; typical radial clearances range from 0.2 to 0.5 mm. Centrifugal fans frequently employ carbon-ring labyrinth structures, where non-contact operation ensures zero wear. However, leakage rates increase exponentially when the pressure differential exceeds 15 kPa, making them suitable for low-speed (≤3000 rpm) and moderate-temperature (≤120°C) operating conditions. A retrofit case involving an induced draft fan at a power plant demonstrated a 67% reduction in annual maintenance costs after replacing gland packing with a labyrinth seal.
Gland packing is a type of contact-based dynamic seal composed of graphite-impregnated fiber braids, achieving radial sealing through axial compression force (typically 10–15 kN/m). Key design parameters include the stuffing box length-to-diameter ratio (1.5–2.0) and the gland taper (3°–5°). In dusty operating environments, a sealing fluid system is required, with the sealing fluid pressure maintained 0.05–0.1 MPa above the process medium pressure. At a cement plant, a kiln-end fan using PTFE packing experienced hardening and failure after 8,000 hours of continuous operation at 280°C, underscoring the decisive impact of temperature on packing service life.
Mechanical seals provide precision face sealing, and the application of double-face mechanical seals in centrifugal fans is on the rise; material pairings for rotating and stationary rings typically utilize silicon carbide against cemented carbide. Balanced designs allow the face contact pressure to be controlled within the 0.3–0.5 MPa range, supporting linear speeds of up to 50 m/s. An acidic gas transport fan at a chemical plant utilized a cartridge-style mechanical seal combined with a PLAN 54 flush system, achieving three years of leak-free operation and validating the seal's reliability under harsh conditions. Engineering breakthroughs and innovations have led to the practical application of new sealing technologies. One example is magnetic fluid field-effect sealing-which creates a liquid sealing barrier by positioning ferrofluid within a magnetic field-though magnetic saturation limits its use in high-pressure-differential scenarios, restricting it primarily to clean gas environments. Another example is the adaptive gas-film seal, which integrates principles from aerodynamic gas bearings, utilizing a wedge-shaped gap to generate gas-film stiffness. In the realm of nanocomposite seals, graphene-reinforced polyimide materials have boosted the PV value to 50 MPa·m/s-a threefold increase over traditional materials. Tests on a shipboard blower demonstrated that adopting nanocomposite seal rings reduced the end-face wear rate from 3 μm/1000h to 0.5 μm/1000h and extended the service life to over 40,000 hours.
Against the backdrop of carbon neutrality, sealing technology innovation is advancing toward zero leakage and low power consumption. The combination of magnetic levitation technology and non-contact sealing has enabled maintenance-free, full-lifecycle operation for certain advanced centrifugal blowers. Looking ahead, sealing systems will be deeply integrated into equipment digital twin frameworks; by optimizing operating parameters through real-time simulation, they will usher fluid machinery into a new era of intelligent sealing.
