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3.Automated Dust Collection Systems & Dust Control – FAQ with Quick Formulas (2025 Edition)Accurate Answers for Common Industrial Dust Collector Questions (with Lazy Formulas Pack)

1. How to Calculate Dust Collector Airflow? Any Easy Formula?

Core principle: Start with source capture airflow (hood face velocity), then check conveying velocity in ducts, and finally add diversity factor and future margin.

Quick Formula (Source Capture):

Q (CMM=m3/min)=Vf (m/s)×A (m2)×60Q \, (CMM = m^3/min) = V_f \, (m/s) \times A \, (m^2) \times 60Q(CMM=m3/min)=Vf​(m/s)×A(m2)×60

Example:
Weighing hood opening: 0.6 m × 0.5 m, face velocity = 0.6 m/s
Q = 0.6 × 0.3 × 60 = 10.8 CMM

Reference Face Velocity (Powder Operations):

  • Weighing / dumping hood: 1.0–1.2 m/s (higher for fine/light powders)

  • Grinding / cutting hood: 1.2–1.5 m/s (depends on energy of release)

Conveying Velocity in Ducts (to prevent settling):

  • General powders: 14–18 m/s

  • Metal chips / heavy dust: 18–22 m/s

Check airflow per pipe size to ensure main and branch ducts meet minimum transport velocity.

Diversity + Margin:
Simultaneous-use ratio × total airflow, then add 10–20% expansion margin.

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2. Where Should HEPA Filters Be Installed? How to Verify?

Rule of thumb: HEPA should be the final barrier—all leaks must pass through it.

Two common setups:

  1. Main filter → Blower → HEPA → Exhaust/Return (most common, ensures HEPA is final filter)

  2. Main filter → HEPA → Blower → Exhaust (protects blower, but blower leaks may bypass HEPA)

For indoor recirculation / cleanroom: use setup (1) with sealed HEPA housing + ΔP gauges before/after.

3. How to Avoid Filter Blinding with Sticky / Oily / Wet Powders?

Four actions simultaneously:

  • Match filter media: PTFE/nano membrane, surface coating, hydrophobic/oil-repellent, anti-static (for combustible dust).

  • Pre-separation: Cyclone, dropout section, or dust drum to reduce load.

  • Dewpoint & flow control: Insulation, pre-heating, or dehumidification; inlet baffles and diffusers to prevent dust concentration.

  • Bonus methods: Pre-coating with inert fine powder; track ΔP curves for preventive maintenance.

4. When to Use Wet Scrubber or ESP (Electrostatic Precipitator)?

  • Wet Scrubber (Water-Wash Collector):

    • High spark / hot particle risk (e.g., aluminum, magnesium, tungsten grinding)

    • Very sticky/hygroscopic powders where dry filters fail

    • When soluble gases/acid/alkali need scrubbing

    • ⚠ Requires wastewater treatment, anti-corrosion materials, demister

  • ESP (Electrostatic Precipitator):

    • Submicron fume, smoke (<1 μm), metal fumes, oil mist

    • Low ΔP requirement, particles chargeable and collectable

    • ⚠ Sensitive to gas humidity, electrical conditions; strict compliance/maintenance required

5. Do Combustible Dust Applications Always Require Explosion-Proof Motors?

Not always. The overall explosion protection strategy and zoning classification matter most:

  • If fan/motor is located outside hazardous area (clean-side, outdoor), standard motor may suffice.

  • If installed inside Zone 20/21/22, explosion-proof Ex motors/electrics are required.

  • More important: system-level protection—explosion venting/suppression, flame isolation valves, grounding/bonding, spark detection, and Dust Hazard Analysis (DHA).

  • Pneumatic drive may be used in no-electric or high-risk zones.

6. At What ΔP Should the System Shut Down?

No absolute value—use baseline + thresholds:

  • Record baseline: New filters initial ΔP (e.g., 600–900 Pa); steady-state (1000–1500 Pa).

  • Set dual thresholds:

    • Alert: ≥1700 Pa → system increases cleaning / operator check

    • Intervention: ≥2000 Pa → shutdown, maintenance, filter change or blockage inspection

  • Abnormal rise: even below thresholds → investigate sticky peaks, condensation, failed cleaning.

  • Abnormally low ΔP: possible leakage/broken filter → immediate check.

7. Are There Standard Hood Sizes & Face Velocities?

No universal size, but practical ranges and validation logic exist:

  • Close capture is key: Hood closer = better efficiency.

  • Face velocity: ~1.0–1.2 m/s for powders; higher for strong dispersion sources.

  • Bigger opening = higher airflow: use Q = Vf × A × 60 for quick estimates.

  • Baffles/deflectors: reduce required airflow by controlling turbulence.

Example:
Dumping hood: 700 × 500 mm, Vf = 1.2 m/s
Q = 1.2 × 0.35 × 60 = 25.2 CMM (add diversity + margin)

On-site validation:

  • Smoke rod / paper strip airflow test

  • Hot-wire anemometer / flow hood measurements

  • Adjust hood angle/shape to operator posture (slotted, side-draft, etc.)

Quick Action Checklist

  • Estimate each source airflow with Q = Vf × A × 60.

  • Check duct transport velocity: powders 14–18 m/s; metals 18–22 m/s.

  • Place HEPA last, verify with PAO/DOP test or particle count.

  • Sticky/oily/wet dust: PTFE/hydrophobic media + pre-separation + dewpoint control.

  • Combustible dust: zone-classified Ex motors only when required, plus venting/suppression/isolation/grounding.

  • Hood design: 1–1.2 m/s starting point; validate with smoke & velocity test.