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4.Vacuum Conveyor / Powder Loader｜Top 15 FAQs with Practical Formulas & Field Values (2025 Edition) Your Complete Buyer’s Guide for Powder Conveying Systems

1. Vacuum vs. Pressure vs. Screw Conveying – How to Choose?

Conclusion:

  • Vacuum (Negative Pressure): Enclosed & clean, short-to-long distance, frequent recipe changes, prevents dust escape (fine powders/valuable powders).

  • Pressure Conveying: Long distance (>40–60 m), high throughput, centralized feeding, multi-point distribution.

  • Screw Conveyor: Short distance (<6–8 m), stable dosing, high solids content, simple design.

  • Hybrid: Vacuum feeding → small hopper → short screw dosing; or vacuum branches + pressure main line.

SEO Keywords: vacuum conveyor, pressure conveying, screw feeder, powder conveying solutions

2. How to Quickly Estimate “System Size”?

Define 3 key factors: Capacity R (kg/h), Equivalent Length Leq (m), Powder Properties.

Leq≈Horizontal length+(Vertical length×2−3)+(Elbows×1.5−3 m/each)Leq \approx \text{Horizontal length} + (\text{Vertical length} \times 2-3) + (\text{Elbows} \times 1.5-3 \, m/each)Leq≈Horizontal length+(Vertical length×2−3)+(Elbows×1.5−3m/each)

  • For conservative dilute-phase vacuum: pipe velocity v ≈ 16–20 m/s.

  • Select pipe size to avoid plugging and excessive ΔP; leave 10–20% margin.

  • For precision: supplier validates with performance curve or test run.

3. Pipe Diameter & Velocity – What’s the Range?

Dilute-phase vacuum references:

  • Fine powders: 14–20 m/s

  • Very light/floating powders: 16–22 m/s

  • Fragile particles: 8–12 m/s (use dense-phase or larger pipe, fewer bends)

⚠ Too small = high ΔP, plugging risk. Too large = low velocity, settling risk.
Start with mid-range, then refine with ΔP trend or field data.

4. Fine / Hygroscopic / Sticky Powders – How to Avoid Plugging or Blinding?

Four-in-One Strategy:

  • Filter media: PTFE/nano membrane / nano coating, + hydrophobic/oil-repellent, + anti-static for combustible dust.

  • Pre-separation: Cyclone or dropout section to reduce high-concentration peaks.

  • Dewpoint management: Insulation/dehumidification, inlet baffles for even flow.

  • Further measures: Shorten pulse interval (ΔP-triggered), check moisture/oil content, larger receivers, or staged conveying.

5. Arching Prevention & FIBC Big Bag Unloading

  • Hopper: With arch breaker, vibration, fluidizing pads, rounded corners. Sealed outlet + local dust hood.

  • FIBC: Use conductive big bags with grounding; pre-slit + docking station to prevent sudden powder surge.

  • Weighing: Shield weighing scale or level sensor from airflow (use throttling/damping or delayed sampling).

6. Is HEPA Always Needed for Vacuum Conveying?

Yes, if: indoor return air, cleanrooms, sensitive products, or zero dust leakage required.

Recommended position: Main filter → blower → HEPA → exhaust/return (HEPA as final barrier).
Verification: PAO/DOP leak test or upstream/downstream particle count; ΔP gauges for replacement timing.

7. When Do I Need Explosion-Proof / ESD Protection?

Required if combustible dust, vapors, or static discharge risks exist:

  • Conductive hoses/pipes/wheels + grounding/equipotential bonding (periodic checks).

  • Flame isolation valves/check valves + explosion venting (safe direction) or suppression.

  • Spark detection/extinguishing for grinding/cutting processes.

  • Electricals must comply with Zone 20/21/22 classification.

8. Filter Cartridges & Pulse Cleaning – Any Standard Ranges?

  • Pulse-jet cleaning pressure: 0.4–0.6 MPa

  • ΔP Management (example):

    • Initial: 600–900 Pa

    • Normal: 1000–1500 Pa

    • Alert: ≥1700 Pa → stronger cleaning/check

    • Intervention: ≥2000 Pa → stop for service/filter change

General rule: Always use baseline + thresholds.

9. Will Vacuum Conveying Break Fragile Particles?

Yes, if velocity is high or too many bends.
Solutions: Lower velocity (dense phase or larger pipe), minimize bends/use long-radius elbows, add deflectors/cushioning at receiver.
Verify with PSD/attrition rate during SAT acceptance.

10. Quick “Lazy Formulas”

  • Hood airflow: Q=Vf×A×60Q = V_f \times A \times 60Q=Vf​×A×60

  • Equivalent length: Horizontal + vertical × 2–3 + elbows × 1.5–3 m

  • A/C ratio (Air-to-Cloth): Optimize for filter loading

  • TCO rough estimate: Energy ≈ airflow × pressure head; add filter/media/maintenance/downtime

11. Relationship Between Vacuum, Airflow & Motor Power

  • Motor HP ≠ performance.

  • Always check blower curve vs. system curve.

  • Troubleshooting:

    • Low airflow → check dampers, duct blockages, leaks, high ΔP

    • High vacuum but low flow → pipe too small, high resistance, or clogged filter

12. How to Write a Procurement Specification That Won’t Get Rejected?

Include:

  • Capacity: kg/h, continuous/batch, peak + margin

  • Route: sketch with H/V, elbows/tees, inter-floor, space constraints

  • Powder properties: bulk density, particle size, hygroscopic/sticky, abrasive, friable, combustible (Kst/MIE)

  • Hygiene/materials: SS304/316, CIP/SIP, quick-release

  • Safety: grounding, isolation/venting/suppression, spark detection

  • Automation: PLC/VFD, level/weight closed-loop, recipe changeover

  • Acceptance (SAT): throughput, ΔP, leakage, noise, HEPA integrity

  • After-sales: spare list, SLA, warranty

13. SAT Acceptance – What to Test?

  • Throughput: Continuous or batch meets target

  • ΔP curve: Stable, effective cleaning

  • Leakage: joints, receiver, before/after HEPA

  • Product quality: particle size, attrition, cross-contamination

  • Safety: grounding resistance, vent/isolation/suppression function, interlocks

  • Noise: day/night compliance

  • Documentation: SOPs, PM logs, electrical drawings, BOM, spares

14. Six Common Failures & Troubleshooting Sequence

  • Low airflow: damper → ΔP → duct blockage → leakage → fan belt/impeller

  • Frequent plugging: low velocity → too many bends → sticky powder → add dehumidification/insulation → pre-separator

  • ΔP spikes: sticky/wet powder → insufficient cleaning → wrong filter → inlet concentration → HEPA clogged

  • Dust leakage: gasket/quick clamp → receiver leak → HEPA damaged

  • Unstable weighing: airflow disturbance → throttling/damping hopper → delayed sampling

  • Static discharge: loose grounding → aged conductive parts → missing equipotential bonding

15. Cost Comparison – Why Cheaper May Be More Expensive Later

  • CAPEX: Main unit, ducting, controls, explosion-proof accessories, HEPA/silencer, installation

  • OPEX: Power (airflow × pressure), filters/consumables, maintenance, downtime losses

Hidden pitfalls:

  • Poor hood/duct design → high ΔP, high power cost

  • Wrong A/C ratio → high ΔP, frequent shutdowns

  • No pre-separation → short filter life

  • No ΔP baseline → reactive maintenance, frequent failures

Takeaway: Correct design + lifecycle cost = lowest total cost (TCO).

Quick Reference Tables

A. Face Velocity & Hood Airflow

  • Dumping/Weighing hood: 0.5–0.8 m/s

  • Small openings (<0.5 m²): use higher value

  • Larger openings: add baffles/side panels to cut airflow demand

Q=f×A×60Q = f \times A \times 60Q=f×A×60

B. Filter Chamber & Cleaning

  • Pulse pressure: 0.4–0.6 MPa (ΔP triggered)

  • ΔP Range (example): 600–900 Pa (initial) → 1000–1500 Pa (normal) → ≥1700 Pa (alert) → ≥2000 Pa (shutdown/maintenance)

Procurement Template (Fill-in Form)

  • Capacity: ___ kg/h (continuous/batch, peak)

  • Route: Horizontal ___ m / Vertical ___ m / Elbows ___ pcs / Floors: Y/N

  • Powder: Bulk density ___ t/m³; D50 ≈ ___ μm; hygroscopic/sticky Y/N; abrasive high/med/low; friable Y/N; combustible (Kst/MIE: ___)

  • Materials: 304/316; quick-release Y/N

  • Safety: grounding/equipotential, isolation/vent/suppression, spark detection Y/N

  • Filters: PTFE / anti-static / hydrophobic; HEPA Y/N

  • Automation: PLC/VFD, weight/level detection, auto discharge

  • Acceptance criteria: throughput, noise, HEPA integrity

  • After-sales: spares list, warranty ___ years