‌Testing Procedures for HEPA Glass Fiber Air Filters

‌Testing Procedures for High-Efficiency Glass Fiber Air Filters During Production‌

Testing during production involves three key stages: raw material inspection, process control, and finished product testing. Detailed procedures and methods are as follows:

I. Raw Material Inspection

1. ‌Filter Media Performance Testing‌

   • ‌Physical Properties‌: Measure paper thickness (accuracy: ±1μm) and basis weight (g/m²) to ensure permeability and strength compliance; analyze fiber diameter (typically 1–10μm) and distribution density via Scanning Electron Microscopy (SEM)
   • ‌Chemical Stability‌: Conduct acid/alkali corrosion resistance tests (immersion in 30% H₂SO₄/NaOH for 48 hours), and evaluate thermal shrinkage (≤1%) and strength retention (≥80%) after high-temperature exposure (200°C for 24 hours)
   • ‌Permeability Screening‌: Perform water repellency testing (spray test); premium-grade media must resist water penetration for 24 hours

2. ‌Frame and Sealing Materials‌

   • Inspect dimensional tolerances of aluminum/stainless steel frames (e.g., side length deviation: ±2mm), flatness (≤6mm), and perpendicularity (deviation: ±3°)
   • Verify integrity of sealant gasket joints to prevent air leakage

II. In-Process Testing

1. ‌Filter Core Fabrication Monitoring‌

   • Ensure uniform pleat spacing without damage; control core height tolerance (±1mm) and pleat count (e.g., 39–41 pleats)
   • Regulate polyurethane AB adhesive ratio (A=1:2.5) during potting; adhesive penetration height ≤5mm to prevent media-frame separation

2. ‌Structural Assembly Checks‌

   • Flatten and shape protective mesh to eliminate rust/deformation; ensure burr-free filter core edges and diagonal length deviation ≤3mm after mesh fixation
   • For groove-type filters, fill with non-Newtonian sealant to ensure volatility resistance and acid/alkali tolerance

III. Finished Product Testing

1. ‌Integrity Leak Testing (Core Item)‌

   • ‌Scanning Method‌: Use aerosol photometers/particle counters with upstream PAO/DOP challenge aerosol (10–100μg/m³). Scan downstream at 3cm from the surface (5cm/s speed); leakage rate ≤0.01% qualifies
   • ‌Critical Areas‌: Test for pinholes in media, media-frame adhesive joints, and gasket-support frame seams

2. ‌Performance Parameter Testing‌

   • ‌Filtration Efficiency‌: Apply sodium flame method (NaCl aerosol) or particle counting (0.1–0.3μm particles); efficiency for 0.3μm particles must be ≥99.97% (H13/H14 grade)
   • ‌Resistance & Airflow‌: Initial resistance ≤105% of nominal value at rated airflow; airflow deviation <15%
   • ‌Dust Holding Capacity‌: Load dust until resistance doubles; evaluate accumulated dust mass (g/m²)

3. ‌Safety & Durability‌

   • Fire Resistance: Materials must comply with GB 8624 fire standards (Grade 1: non-combustible)
   • Vibration Test: After simulated transport vibration, efficiency/resistance must meet factory specifications

IV. Environmental & Documentation Requirements

• ‌Production Environment Cleanliness‌: HEPA filter assembly areas must achieve ISO Class 8; ULPA requires ISO Class 
• ‌Traceability‌: Maintain leak test records per filter, documenting leak locations and repairs