First, establish a regular standardized maintenance system adopting a four-level maintenance mode: daily inspection, monthly leak test, quarterly maintenance and annual verification. Daily inspection: Conducted every day. Observe operating air resistance and air supply condition; check whether the liquid level in the gel trough is uniform without drying, overflow or impurity contamination; verify that the filter cartridge surface is intact with no dust accumulation or discoloration. Monthly leak test: Perform non-destructive on-site leak detection via the PAO test port to confirm no air leakage and stable sealing performance. Record leak test data and build maintenance logs. Quarterly maintenance: Thoroughly clean the equipment surface, test ports and surroundings of the gel trough; calibrate equipment levelness; inspect that the knife-edge is free of wear and deformation. Annual verification: Fully test filtration efficiency, air resistance parameters and sealing gel performance. Evaluate the overall operating status of the filter and determine whether filter cartridge replacement or gel renewal is required.

Sealing gel replacement is a unique core maintenance procedure for gel-seal filters. After long-term operation, the gel may accumulate contaminants, lose viscosity or deteriorate, which impairs sealing performance. Under normal cleanroom conditions, the service life of sealing silicone oil is 2–3 years. For high-dust and heavily polluted environments, the cycle shall be shortened to 1.5–2 years.

Standard gel replacement procedure:

1. Shut down and cut off power supply. Wait until system air pressure drops to zero and the equipment cools down. Extract old gel and clean sediments and residual gel inside the trough to ensure the trough is clean and dry.
2. Inject brand-new dedicated sealing silicone oil and precisely control liquid level to maintain uniform and full filling.
3. Allow standing for calibration, reset the filter cartridge, and perform leak testing. Restart the system only after sealing passes inspection. The whole replacement process must be carried out under clean conditions to prevent impurities from mixing into the gel and causing sealing risks.

Common equipment faults and targeted solutions:

1. Abnormally dropping liquid level and minor air leakage Cause: Slight gel volatilization and insufficient liquid level. Solution: Top up with the same type of sealing silicone oil, calibrate liquid level and re-run leak detection.
2. Turbid gel with accumulated impurities Cause: Dust contamination during long-term operation. Solution: Completely replace the gel, clean the trough and check whether the pre-filter system fails.
3. Sharp rise in air resistance Cause: Filter cartridge blocked by accumulated dust. Solution: Monitor air resistance parameters and replace the filter cartridge once final resistance is reached.
4. Worn knife-edge and poor sealing contact Cause: Frequent disassembly and assembly or offset installation. Solution: Calibrate knife-edge position. Minor wear can be adjusted for matching; replace the filter cartridge in case of severe wear.

In addition, three critical taboos must be avoided during maintenance:

• Inferior or non-specialized sealing gel is prohibited.
• Gel replacement and filter cartridge disassembly under pressurized or high-temperature conditions are prohibited.
• Impurities and oil contamination entering the gel sealing zone are prohibited.

Standardized maintenance management and fault handling can maximize the zero-leakage advantage of gel-seal HEPA filters, extend overall equipment service life, continuously maintain environmental standards of high-end cleanrooms and reduce maintenance & replacement costs of premium filtration equipment.