Dehulling & Separation Equipment — Technical Specification
1. Process Objective
Remove the fibrous hull from pre-conditioned flaxseed while minimising endosperm breakage, then classify the stream into hulls, coarse middlings, and clean kernels. Design capacity: 3 MT/hr input. Target dehulling efficiency: 85–90 %.
2. Equipment Configuration — ASCII Flow Diagram
Pre-conditioned flaxseed (3 MT/hr, from tempering)
|
v
[ 1. Centrifugal Impact Dehuller ] ← 3,000–4,500 rpm Primary break
| (impeller + stator ring)
|
v
[ 2. Roller Dehuller ] ← 0.3–0.8 mm gap Secondary break
|
v
[ 3. Air Classifier — Zigzag Column ] ← Hull removal (light fraction)
|
v
[ 4. Gravity Separator — Deck table ] ← Kernel / mid-density separation
|
v
+──→ Hull fraction (to pelletising / waste)
+──→ Middlings (to grinding)
+──→ Clean kernels (to packaging / further processing)
3. Equipment Table
| Unit |
Type |
Model (Example) |
Capacity (MT/hr) |
Power (kW) |
Material (food-contact) |
Manufacturer (suggested) |
| Centrifugal Impact Dehuller |
Vertical impeller with tungsten-carbide pins & stator ring |
Retsch ZM-500 / custom |
3–4 |
22–30 |
SS304 chamber, WC-Co pins, SS304 stator |
Hosokawa / Retsch / custom |
| Roller Dehuller |
Twin paired rolls, differential speed |
Bühler MDDL-800 |
3–5 |
2 × 7.5 |
Chilled cast-iron rolls, SS304 frame |
Bühler / Satake |
| Air Classifier (Zigzag) |
Zigzag column + fan + cyclone |
Rhewum ZAZ-600 |
3–6 |
11 (fan) + 1.5 (feeder) |
SS304 column & cyclone |
Rhewum / Hosokawa Alpine |
| Gravity Separator |
Reciprocating deck, air-table |
Forsberg GC-48 |
3–4 |
5.5 (fan) + 1.5 (drive) |
SS304 expanded-metal deck, polycarbonate cover |
Forsberg / Oliver |
4. Detailed Technical Parameters — Set Points & Tolerances
4.1 Centrifugal Impact Dehuller (3,000–4,500 rpm)
| Parameter |
Set Point |
Tolerance |
Notes |
| Impeller rotational speed |
3,600 rpm |
±100 rpm |
VFD-controlled |
| Tip speed (impeller outer Ø 400 mm) |
75 m/s |
±5 m/s |
Critical for hull release |
| Number of impact pins (impeller) |
12 |
— |
Replaceable tungsten-carbide |
| Number of impact pins (stator ring) |
24 |
— |
Tungsten-carbide coated |
| Pin-to-pin gap (stator vs. impeller) |
8 mm |
±0.5 mm |
Adjustable via shims |
| Feed rate per rotor |
3 MT/hr |
±0.3 MT/hr |
— |
| Product temperature at inlet |
35–50 °C |
±5 °C |
From tempering |
| Dehulling efficiency (target) |
85 % |
±3 % |
Sieve + visual count |
| Broken kernel / fines generation |
≤ 5 % |
— |
Target < 2 % for premium |
| Amperage (no-load) |
15 A |
±2 A |
At 380 V, 50 Hz |
4.2 Roller Dehuller
| Parameter |
Set Point |
Tolerance |
Notes |
| Roll diameter |
250 mm |
±0.5 mm |
Chilled cast iron |
| Roll length |
800 mm |
±1 mm |
— |
| Fast roll speed |
800 rpm |
±10 rpm |
— |
| Slow roll speed |
450 rpm |
±10 rpm |
Ratio ~1.78:1 |
| Roll gap (nip) — fixed side |
0.5 mm |
±0.05 mm |
Adjustable by eccentric |
| Roll gap — floating side |
0.5 mm |
±0.05 mm |
Spring-loaded |
| Differential speed ratio |
1.78 : 1 |
±0.05 |
— |
| Feed rate |
3 MT/hr |
±0.3 MT/hr |
Even curtain across roll width |
| Motor load (each roll) |
≤ 7.5 kW |
— |
Thermal overload relay |
| Roll surface hardness |
58–62 HRC |
±2 HRC |
— |
4.3 Air Classifier — Zigzag Column
| Parameter |
Set Point |
Tolerance |
Notes |
| Air velocity in column |
6.0 m/s |
±0.5 m/s |
Adjustable damper / VFD fan |
| Column height |
2,000 mm |
±50 mm |
8 zigzag stages |
| Zigzag angle |
45° |
±2° |
— |
| Cut point (d50) |
1.2 mm |
±0.1 mm |
Hulls < 1.2 mm rise |
| Feed rate |
3 MT/hr |
±0.3 MT/hr |
— |
| Fan volume |
120–150 m³/min |
±10 m³/min |
— |
| Static pressure at fan inlet |
−1.5 kPa |
±0.2 kPa |
— |
| Hull recovery (light fraction) |
≥ 90 % |
— |
Hull purity ≥ 85 % |
| Kernel loss to hull fraction |
≤ 5 % |
— |
Target < 3 % |
4.4 Gravity Separator (Deck Table)
| Parameter |
Set Point |
Tolerance |
Notes |
| Deck air velocity |
3.0–4.5 m/s |
±0.3 m/s |
Adjustable plenum |
| Deck vibration frequency |
600–800 rpm |
±10 rpm |
— |
| Deck longitudinal incline |
5°–8° |
±0.5° |
Product travel |
| Deck transverse incline |
2°–4° |
±0.5° |
Side discharge separation |
| Feed rate |
3 MT/hr |
±0.3 MT/hr |
— |
| Kernel purity (heavy fraction) |
≥ 98 % |
— |
— |
| Hull purity (light fraction) |
≥ 85 % |
— |
— |
| Full separation efficiency |
≥ 90 % |
— |
Composite of all fractions |
| Parameter |
Target |
Verification Method |
Frequency |
| Dehulling efficiency (overall) |
85–90 % |
Sieve fractionation + manual hull count |
Every 2 hr |
| Broken / damaged kernels |
≤ 5 % |
Visual + sieve (0.5 mm pan) |
Every 2 hr |
| Hull removal rate (air classifier) |
≥ 90 % |
Weight of light fraction vs. calculated hull content |
Daily |
| Kernel purity after gravity separator |
≥ 98 % |
Hand-pick separation of 500 g sample |
Daily |
| Throughput |
3 MT/hr ± 0.3 |
Belt scale / weigh hopper |
Continuous |
| Power consumption per ton |
≤ 15 kWh/MT |
Energy meter |
Monthly |
6. HACCP Integration
NOTE: Dehulling stages do not constitute a CCP under standard flaxseed HACCP plans (hazards are physical/quality, not critical food safety). They are OPRPs (Operational Prerequisite Programs).
OPRP-1 — Centrifugal Impact Dehuller & Roller Dehuller
| Element |
Specification |
| Hazard |
Physical — metal fragments from pin/roll wear; Excessive fines generation |
| Control Measure |
Regular pin/roll gap inspection; metal detector downstream (CCP-2 in grinding area) |
| Monitoring |
Operator checks pin wear (visual) & roll gap (feeler gauge) |
| Frequency |
Every 4 hr |
| Corrective Action |
Replace worn pins; re-set roll gap; divert product until verified |
| Record |
OPRP log sheet |
OPRP-2 — Air Classifier & Gravity Separator
| Element |
Specification |
| Hazard |
Cross-contamination — improper separation leaving hull fragments in kernels |
| Control Measure |
Air velocity & deck incline set points; periodic analysis of outlet streams |
| Monitoring |
QC analyses of hull & kernel streams |
| Frequency |
Every 4 hr |
| Corrective Action |
Re-adjust air velocity / incline; re-screen material |
| Record |
OPRP log sheet |
7. Maintenance Schedule
7.1 Daily (shift-end, ~25 min total)
| Task |
Time (min) |
Performed By |
| Centrifugal impact dehuller — check pin wear (visual); clear any wrap-around |
5 |
Operator |
| Roller dehuller — check roll gap with feeler gauge; wipe rolls clean |
5 |
Operator |
| Air classifier — empty cyclone bag; check air velocity manometer |
5 |
Operator |
| Gravity separator — clean deck surface; check air plenum for blockage |
5 |
Operator |
| Log all readings in CMMS |
5 |
Operator |
7.2 Weekly (~2.5 hr)
| Task |
Time (min) |
Performed By |
| Centrifugal dehuller — remove impeller; measure pin tip diameter; replace if worn < 80 % original |
30 |
Maintenance tech |
| Roller dehuller — check roll surface flatness (dial gauge); re-set eccentric if runout > 0.05 mm |
30 |
Maintenance tech |
| Air classifier — clean zigzag stages; inspect for wear |
30 |
Operator |
| Gravity separator — deck fabric / expanded-metal inspection |
15 |
Maintenance tech |
| Lubricate feed screw gearboxes (food-grade oil) |
15 |
Maintenance tech |
| All belts & chains — tension check |
15 |
Maintenance tech |
| VFD parameters & motor current logging |
15 |
Electrical tech |
7.3 Monthly (~5 hr)
| Task |
Time (min) |
Performed By |
| Centrifugal dehuller — replace all stator pins; rotate impeller if applicable |
60 |
Maintenance tech |
| Roller dehuller — remove rolls; measure OD for re-grinding / replacement (min. Ø 245 mm) |
60 |
Maintenance tech |
| Air classifier — fan impeller balance check; bearing re-grease |
30 |
Maintenance tech |
| Gravity separator — deck replacement if worn; plenum seal inspection |
60 |
Maintenance tech |
| All bearings replacement (as needed based on vibration data) |
30 |
Maintenance tech |
| Clean all dust collection lines & cyclones |
30 |
Operator |
| Update spare parts inventory |
30 |
Maintenance lead |
7.4 Annual (during shutdown, ~16 hr)
| Task |
Time (min) |
Performed By |
| Centrifugal dehuller — replace entire impeller & stator ring assembly |
120 |
Maintenance team |
| Roller dehuller — re-grind or replace rolls; replace all bearings & seals |
240 |
Maintenance team |
| Air classifier — complete fan replacement (impeller + shaft + bearings) |
120 |
Maintenance tech |
| Gravity separator — rebuild drive mechanism (eccentric, springs, bushings) |
180 |
Maintenance team |
| All motors — Megger test (insulation > 20 MΩ) + re-grease |
120 |
Electrical tech |
| All — structural inspection; weld repair; repaint food-contact surfaces |
120 |
Maintenance team |
| Full HACCP / OPRP validation — run 8-hr qualification batch |
240 |
QC + Production |
8. Safety Interlocks & Emergency Stops
| Interlock / E-Stop |
Trigger |
Action |
Location |
| E-Stop pushbutton (red mushroom) |
Manual press |
Isolates all drive motors; brake on conveyors |
Each equipment panel + line ends |
| Centrifugal dehuller door interlock |
Access door sensor |
Stops impeller if door opened |
Dehuller chamber door |
| Roller dehuller nip guard |
Magnetic switch on roll cover |
Stops rolls; disengages clutch |
Roll cover panel |
| Air classifier fan overtemp |
PTC thermistor (set 140 °C) |
Trips fan VFD |
Fan motor winding |
| Gravity separator vibration sensor |
Excessive vibration > 8 mm/s |
Stops deck drive |
Drive housing |
| Feed chute plug detector |
Rotation sensor on feed screw |
Stops upstream feed |
Each chute |
| Compressed air low pressure |
Pressure switch < 0.4 MPa |
Stops all pneumatic systems |
Air manifold |
9. Utility Requirements
| Utility |
Specification |
Connection |
Consumption (per line) |
| Electrical power |
380–480 V, 3-phase, 50/60 Hz |
Hardwired to MCC |
45 kW (peak) |
| Compressed air |
0.6–0.8 MPa, oil-free, dry (dew point −20 °C) |
1″ NPT |
1.2 m³/min (pneumatic gates only) |
| Dust collection |
150 m³/min at −3 kPa |
250 mm duct flange |
11 kW fan |
| Lighting |
500 lux minimum at deck level |
Ceiling-mounted LED |
0.3 kW |
10. Common Spare Parts List
| Part |
Part Number (Example) |
Qty in Stock |
Lead Time |
Criticality |
| Impeller pins (WC-Co) — set of 12 |
CID‑PIN‑WC‑12 |
3 sets |
2 weeks |
High |
| Stator pins (WC-Co) — set of 24 |
CID‑STAT‑WC‑24 |
2 sets |
2 weeks |
High |
| Impeller assembly (complete) |
CID‑IMP‑400‑SS |
1 |
8 weeks |
High |
| Roller pair (matched, chilled cast iron Ø250×800) |
RD‑250‑800‑PAIR |
1 |
12 weeks |
High |
| Roller bearings — SKF 22218 E |
SKF‑22218‑E |
4 |
1 week |
Medium |
| Zigzag column panel (SS304) |
ZAZ‑PAN‑2000 |
2 |
4 weeks |
Low |
| Gravity separator deck (expanded metal) |
GC‑48‑DECK |
1 |
6 weeks |
Medium |
| Gravity separator eccentric bushing |
GC‑ECC‑BUSH |
2 |
3 weeks |
Medium |
| Fan impeller (air classifier) |
ZAZ‑FAN‑IMP‑630 |
1 |
8 weeks |
Low |
| Food-grade grease — Klüber 4-302 |
— |
5 kg |
2 weeks |
Low |
| V-belt set — SPB-2240 |
Gates / Optibelt |
6 |
1 week |
Medium |
| Manometer diaphragm (0–2 kPa) |
— |
2 |
2 days |
Low |
11. Calibration Requirements
| Instrument / Device |
Range |
Standard |
Tolerance |
Calibration Frequency |
Responsibility |
| Hand tachometer (dehuller rpm) |
0–9,999 rpm |
Stroboscope |
±5 rpm |
12 months |
Maintenance |
| Feeler gauge set (roll gap) |
0.05–1.00 mm |
Micrometer (NIST-traceable) |
±0.01 mm |
6 months |
QC |
| Anemometer (air classifier) |
0–15 m/s |
NIST-traceable Pitot tube |
±0.2 m/s |
12 months |
Maintenance |
| Pressure manometer (gravity sep.) |
0–2 kPa |
Water-column manometer |
±20 Pa |
6 months |
QC |
| VFD speed display |
0–60 Hz |
Oscilloscope + frequency counter |
±0.1 Hz |
12 months |
Electrical tech |
| Belt scale (throughput) |
0–5 MT/hr |
Test weights (50 kg certified) |
±0.5 % |
6 months |
Maintenance |
| Temperature probe (product inlet) |
0–100 °C |
NIST-traceable Pt100 |
±0.5 °C |
12 months |
QC |
Document version: 1.0 — Author: Process Engineering — Approved: QA Manager