FAQ

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6.Dust Collector Filter Media Selection FAQ (2025 Edition)

1. Bag Filters vs. Cartridge Filters – When to Upgrade to Pleated Bags?

Key Differences

  • Bag Filters (Baghouse): Rugged, tolerate high dust load, easy to maintain, but lower filtration area per volume (higher A/C ratio).

  • Cartridge Filters: Pleated media provides more surface area, lower A/C ratio, stable ΔP curve, compact size; require surface treatments and pre-separation for sticky/moist powders.

  • Pleated/Star Bags: Retrofit option without changing housings; increase filtration area by 1.5–2.5×, lowering A/C by 25–50%.

Best Time to Upgrade to Pleated Bags:

  • Persistent high ΔP despite pulse cleaning.

  • Excessive energy consumption (fan running at high load).

  • Fine/slightly sticky dust but not enough to justify full cartridge conversion.

  • Need to maximize effective surface area within existing housing.

2. Why Choose ePTFE/Nano Membranes over Traditional Needle-Felt?

Advantages (Surface Filtration):

  • Keeps dust on the surface, avoids deep penetration → slower ΔP rise.

  • Lower fine dust penetration (better for PM2.5 / PM1), reducing downstream HEPA load.

  • Less blinding with sticky/oily powders; even more stable with hydrophobic/oil-repellent coatings.

Trade-Offs:

  • Slightly higher initial ΔP, higher cost.

  • Requires controlled inlet concentration and flow distribution.

Best Applications:

  • Fine powders (D50 < 20–30 μm).

  • Sticky, hygroscopic, or oily powders.

  • Cleanroom/recirculation environments.

3. Best Filter Media for Sticky Powders & High-Humidity Environments

Three-Step Strategy:

  1. Material: ePTFE/nano membranes + hydrophobic/oil-repellent treatment; add anti-static for combustible dust.

  2. Pre-Separation: Cyclone or settling chambers to reduce dust peaks; inlet deflector for uniform loading.

  3. Dew Point Control: Insulation, pre-heating, or dehumidification to avoid condensation.

Washable Option (CIP/SIP):

  • Consider sintered PE/SS tubular filters (backwashable/steam sterilizable).

  • Note: Higher initial ΔP, requires strong backwash system.

4. Do I Really Need HEPA? How to Verify with DOP/PAO?

When to Add HEPA:

  • Indoor recirculation.

  • Cleanroom or sensitive product environments.

  • Applications requiring ultra-fine particle capture.

Recommended Placement: Main Filter → Fan → HEPA → Exhaust/Recirculation.

Validation Methods:

  • PAO/DOP Integrity Test: Aerosol injection upstream, scan seals & joints; acceptance ≤0.01–0.03% leakage (per standard).

  • ΔP Monitoring: Track baseline and replacement thresholds.

  • Alternative: Particle counters (when PAO unavailable).

5. Anti-Static Standards & Grounding for Combustible Dust

Three Checks Required:

  1. Filter Media Conductivity: Surface resistivity ≤ 10⁸ Ω (depending on certification).

  2. System Grounding & Equipotential Bonding: Housings, cages, caps, hoses, and ducts grounded. Common target: ≤ 10 Ω.

  3. Certification & Zone Classification: Verify NFPA/ATEX/IECEx compliance (Zone 20/21/22).

How to Verify:

  • Request filter material certificates (ATEX/antistatic/Ex).

  • On-site testing with megohmmeter & grounding resistance meter; keep inspection logs.

6. How to Choose Between Fiberglass, P84, PPS, and PTFE in High-Temperature Acidic Gas?

Decision Logic:

  • PTFE (membrane/full PTFE): Best chemical resistance, 240–260 °C, excellent for sticky/fine powders. Higher cost.

  • PPS (Ryton): ~190 °C, excellent for sulfur/acidic gas, but sensitive to oxidizers (O₂/NOₓ).

  • P84 (Polyimide): ~240 °C, high efficiency for fine dust at high temperature, but weaker chemical resistance.

  • Fiberglass: ~260 °C, durable under high temp with low ΔP, but brittle; requires PTFE coating for acid/humidity.

Examples:

  • High temp + strong acid/humidity → PTFE.

  • High temp + sulfuric gas (controlled oxidation) → PPS.

  • High temp + fine dust capture → P84 or PTFE-coated fiberglass.

  • Ultra-high temp, stable conditions → Fiberglass + PTFE coating.

7. Vacuum Loader Filter Maintenance – ΔP Thresholds

Maintenance Guidelines:

  • ΔP Baseline: Initial 600–900 Pa; steady state 1000–1500 Pa.

  • Cleaning Strategy: Pulse-jet 0.4–0.6 MPa, ΔP-triggered + minimum intervals.

  • Seals: Regular inspection of O-rings, quick clamps, and viewing windows (vacuum systems highly sensitive to leaks).

  • Pre-Separation & Flow Distribution: Reduce ΔP spikes.

  • Grounding/Equipotential: Especially at FIBC unloading stations.

  • HEPA (if used): ΔP monitoring + annual PAO/DOP integrity test.

Intervention Thresholds (Internal Guideline):

  • Alert: ≥ 1700 Pa → Increase cleaning, inspection.

  • Intervention: ≥ 2000 Pa → Shutdown for filter replacement or A/C adjustment.

  • Rapid ΔP rise → Check for condensation, sticky dust, or cleaning failure.

  • Abnormally low ΔP → Possible leaks or filter rupture.

One-Page Specification Template (For RFQ/Acceptance)

  • Filter Type: Cartridge / Bag / Pleated Bag

  • Filter Media: ePTFE/nano-membrane [ ] | Hydrophobic/Oil-Repellent [ ] | Anti-Static [ ] | Food-Grade [ ]

  • Cleaning: Pulse-Jet 0.4–0.6 MPa (ΔP-triggered)

  • Safety: Grounding ≤10 Ω | Zone Classification (Zone __) | Explosion Isolation/Venting [ ]

  • HEPA (if applicable): H13/H14 | Placement: Main → Fan → HEPA | PAO/DOP Test ≤0.01–0.03%