Screw Conveyor Engineering Guide: Design Calculation, Selection Criteria & GX vs LS Series Comparison
01 Introduction: The Role of Screw Conveyors in Aggregate Processing
At Shandong Hengtai, while our core expertise lies in crushing and screening equipment (jaw crushers, cone crushers, mobile crushing stations), we recognize that efficient material handling is critical to complete production line performance. Screw conveyors (also known as auger conveyors) serve as essential components for transporting powdery and granular materials between processing stages.
This technical guide—adapted from foundational research by Dragonlxh—provides comprehensive engineering data for screw conveyor selection, including:
Construction standards and component selection
Capacity calculation methodologies
GX series vs. LS series (ISO 1050) comparison
Power consumption formulas and efficiency optimization
Disclaimer:
This article is a technical adaptation for engineering education purposes. Original technical concepts sourced from Dragonlxh. Practical applications and product recommendations are provided by Shandong Hengtai.
02 Screw Conveyor Fundamentals
2.1 Operating Principles
A screw conveyor consists of a helical flight (screw blade) mounted on a rotating shaft within a U-shaped trough. As the shaft rotates, material particles—prevented from rotating with the shaft by friction against the trough walls—are propelled axially toward the discharge point, similar to a nut moving along a stationary bolt.
Key Advantages:
Compact footprint and simple structure
Dust-tight operation (fully enclosed)
Multiple loading/unloading points possible
Cost-effective for short to medium distances (<70m)
Critical Limitations:
High power consumption due to friction (mechanical efficiency typically 30-40%)
Significant particle attrition (not suitable for friable materials requiring size preservation)
Limited to non-abrasive, non-lumpy materials (max particle size restrictions apply)
Moderate capacity only (typically <100 m³/h)
03 Construction Components & Design Variations
3.1 Screw Flight Configurations
| Flight Type | Geometry | Best For | Special Functions |
|---|---|---|---|
| Full Blade (Standard) | Continuous helical surface | Dry, fine powders and granules | Standard conveying |
| Ribbon Flight | Interrupted helical bands | Sticky, fibrous materials | Reduced material buildup |
| Paddle Type | Discontinuous paddles | Wet, cohesive materials | Mixing while conveying |
| Cut Flight | Notched blades | Heat-sensitive materials | Enhanced agitation |
Rotation Direction:
Right-hand or left-hand helix determines material flow direction. For a right-hand screw rotating clockwise (viewed from drive end), material moves toward the discharge.
Material Specifications:
Standard: 3-8mm carbon steel plate, welded to shaft
Abrasive materials: Hard-faced steel or cast iron flights
Corrosive materials: Stainless steel 304/316 or polymer coatings
3.2 Trough Design & Bearings
GX Series (Traditional Chinese Standard):
Split tubular trough with bolted flanges
Internal hanger bearings (bush alloy or white metal)
Single or dual-end drive configurations
LS Series (ISO 1050-75 Equivalent):
Key Improvement:
Head and tail bearings moved outside the housing (sealed from material)
Hanger Bearings:
Interchangeable roller or sliding types
Sliding: Copper, alloy cast iron, or graphite-impregnated bronze bushings
Sealing:
Nylon or PTFE dust seals (low friction, high wear resistance)
Cleaning:
End-mounted cleaning devices at discharge
Noise Level:
5-10 dB lower than GX series
Maintenance:
External bearing access eliminates need to empty trough for service
04 Technical Specifications & Selection Criteria
4.1 Operating Parameters
Environmental Limits:
Ambient temperature: -20°C to +50°C
Material temperature: <200°C (standard design)
Maximum inclination: 20° from horizontal (reduces capacity significantly)
Maximum length: 70m (single drive), >35m requires dual-end drive (C2 configuration)
Material Compatibility:
✓ Suitable: Cement, fly ash, sand, fine aggregates, flour, granular chemicals
✗ Unsuitable: Large lumps (>1/4 screw diameter), highly abrasive materials, heat-sensitive products (due to friction heat)
4.2 Designation System Explained
GX Series Nomenclature:
GX [Diameter] × [Length] - [Flight Type] - [Drive] - [Bearing Material]
Example: GX600×22-B1-C1-M1
600mm nominal diameter
22m length
B1: Full blade flight (pitch = 0.8×diameter)
C1: Single-end drive
M1: Babbitt alloy (white metal) hanger bearings
LS Series Nomenclature:
LS [Diameter] × [Length] × [RPM] - [Bearing Type]
Example: LS600×22×50-M2
600mm diameter, 22m length, 50 RPM
M2: Sliding hanger bearings (cast iron)
05 Engineering Calculations: Selection Methodology
Note: The following calculations use SI units. For Imperial units, apply appropriate conversion factors.
5.1 Capacity Calculation
The theoretical volumetric capacity (Q) of a full-flight screw conveyor:
Q = 47 ⋅ D² ⋅ S ⋅ n ⋅ ϕ ⋅ ρ ⋅ C [m³/h]
Where:
D = Screw diameter (m)
S = Pitch (m) — typically S = 0.8D (full blade) or S = D (ribbon)
n = Rotational speed (rpm)
ϕ = Fill factor (0.15-0.30 for abrasive materials, 0.30-0.45 for free-flowing powders)
ρ = Bulk density (t/m³)
C = Inclination factor (1.0 horizontal, 0.8 at 15°, 0.5 at 20°)
Standard Fill Factors (φ):
| Material Characteristic | Fill Factor | Examples |
|---|---|---|
| Free-flowing, non-abrasive | 0.40-0.45 | Grain, sand |
| Average flow, slight abrasiveness | 0.30-0.35 | Portland cement, fly ash |
| Sluggish, abrasive | 0.15-0.25 | Wet clay, slag |
5.2 Critical Speed Limitation
To prevent material from centrifuging (which causes excessive wear and reduced efficiency), the maximum rotational speed is:
nₘₐₓ = A / D [rpm]
Where:
D = Screw diameter (m)
A = Material constant (typically 60-80 for light materials, 40-50 for heavy materials)
Standard operating speeds range from 20-100 rpm, with slower speeds for larger diameters and abrasive materials.
5.3 Diameter Selection & Validation
Step 1: Calculate required diameter based on capacity:
D ≥ √( Q / (47 ⋅ S ⋅ n ⋅ ϕ ⋅ ρ ⋅ C) )
Step 2: Validate against particle size constraints:
For screened materials: D ≥ (4 to 6) × dₘₐₓ
For unscreened materials: D ≥ (8 to 10) × dₘₐₓ
Where dₘₐₓ = maximum lump size (m).
Standard Diameter Series:
150, 200, 250, 300, 400, 500, 600 mm
If calculated diameter falls between standard sizes, round up to next standard size and recalculate speed or fill factor to maintain required capacity.
5.4 Power Calculation
The total power required (P) includes friction, lifting (if inclined), and operational losses:
P = [ Q ⋅ (L ⋅ ω + H) / 367 ] ⋅ K [kW]
Where:
Q = Capacity (m³/h)
L = Horizontal projection of conveyor length (m)
H = Vertical lift (m) — positive for upward, negative for downward
ω = Resistance coefficient (typically 1.2-4.0 depending on material and flight type)
Light, free-flowing: 1.2-1.5
Average: 2.0-2.5
Heavy, abrasive: 3.0-4.0
K = Power margin factor (1.1-1.2 for lengths <20m, 1.2-1.4 for lengths 20-70m)
Drive Selection:
Add 15-20% safety margin to calculated power for motor selection.
06 Engineering Application: Integration with Crushing Circuits
At Shandong Hengtai, we specify screw conveyors as auxiliary equipment in crushing plants for:
1. Dust Collection Systems:
Transporting baghouse dust from crushers back to product stream
Specification: LS series with full blade, M2 bearings (dust-resistant), C1 drive
Critical: Sealed troughs prevent dust emission
2. Fines Recovery:
Handling <5mm crusher fines from vibrating screens
Challenge: High abrasiveness requires hardened flight surfaces
Solution: GX series with alloy steel flights, reduced speed (n < 30 rpm)
3. Additive Metering:
Precise addition of moisture-conditioning agents or binders
Advantage: Screw conveyors provide consistent, controllable feed rate
Configuration: Variable frequency drive (VFD) for speed adjustment
Selection Example for Aggregate Plant:
Application: Transporting limestone dust from jaw crusher discharge to silo
Capacity required: 45 m³/h
Distance: 25m horizontal, 8m vertical lift (15° incline)
Material: Limestone dust, ρ = 1.4 t/m³, dmax = 3mm
Selection:
LS400×25×60-M2 (400mm diameter, 25m length, 60 rpm, sliding bearings)
Power:
Calculated 11.2 kW → Selected 15 kW motor with gearbox
07 Maintenance & Troubleshooting Guide
| Issue | Probable Cause | Solution |
|---|---|---|
| Excessive power consumption | Overfeeding or material buildup | Reduce fill factor; check for obstructions |
| Premature flight wear | Abrasive material; excessive speed | Reduce RPM; install hard-facing on flights |
| Bearing overheating | Inadequate sealing; misalignment | Replace seals; check shaft alignment |
| Material leakage | Worn end seals; overfilling | Replace gland packing; reduce feed rate |
| Vibration | Uneven loading; loose hanger bearings | Center feed point; tighten hanger bolts |
08 Conclusion & Engineering Best Practices
Screw conveyors remain cost-effective solutions for controlled transport of bulk materials over short to medium distances. When properly sized using the calculations above, they provide reliable service with minimal maintenance.
Key Selection Principles:
Never exceed 70m single-drive length
Size for 80% of theoretical capacity to accommodate surge loads
Use LS series (ISO 1050) for abrasive or temperature-sensitive materials
Specify dual-end drive (C2) for lengths exceeding 35m to reduce hanger bearing loads
Source Attribution:
This engineering guide is adapted from technical documentation by Dragonlxh. Practical applications, selection examples, and integration guidelines are provided by Shandong Hengtai Intelligent Manufacturing Equipment Technology Co., Ltd.