FAQs for Decanter Centrifuge
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FAQs for Decanter Centrifuge
Q: What is the difference between 2-phase and 3-phase decanter centrifuges, and what working conditions are they suitable for respectively?
A: A 2-phase decanter separates solid and one single liquid phase, which applies to sludge dewatering, grain lees treatment, starch residue dehydration, etc. A 3-phase decanter can separate solid, light liquid (oil) and heavy liquid (water) simultaneously, ideal for oily wastewater, waste cooking oil, ship bilge water and edible oil refining. We can provide free separation solutions based on your material samples.
Q: How does differential speed affect separation performance?
A: Differential speed refers to the rotational speed difference between the bowl and scroll, which controls solid residence time inside the machine. Higher differential speed leads to faster solid discharge with higher cake moisture content; lower differential speed extends material residence time to achieve drier cake but may cause blockage. Our equipment is equipped with dual frequency conversion to realize adjustable differential speed to cope with fluctuating feed concentration.
Q: What causes high cake moisture and turbid clarified liquid, and how to adjust the machine?
A: There are four common reasons: 1. Excessive feed flow leading to insufficient material residence time; 2. Overhigh differential speed setting; 3. Improper flocculant dosage; 4. Worn wear tiles on scroll. Corresponding solutions: reduce feed rate, moderately lower differential speed, optimize chemical dosage, and replace tungsten carbide wear tiles by factory service.
Q: The unit runs with severe vibration, can we keep it in continuous operation?
A: Continuous operation under heavy vibration is strictly prohibited, as it will damage bearings and gearbox. Root causes include uneven solid accumulation caused by fluctuating feed solid content, loose anchor bolts, aging bearings and unbalanced scroll. Solutions: stop the machine to clean the bowl thoroughly, fasten the base, inspect and replace faulty bearings, and redo dynamic balance for scroll.
Q: Can the decanter centrifuge operate automatically 24 hours a day? What control system is equipped as standard?
A: The whole machine is designed for 24/7 non-stop continuous operation, equipped with standard PLC and HMI touch screen automatic control system. It monitors real-time data including rotating speed, torque, bearing temperature, vibration and current. The system supports automatic alarm and shutdown under overload, over-temperature and excessive vibration, as well as automatic differential speed adjustment for unattended running.
Q: How to select proper material grade? What upgraded options are available for food, chemical and explosion-proof working conditions?
A: 304 stainless steel is adopted for general materials; 316L or duplex 2205 stainless steel for highly corrosive chemical media; mirror-polished sanitary 316L for food and pharmaceutical industries. For flammable and explosive sites, the explosion-proof version with Ex d II BT4 rated motor and control cabinet is optional, and CE & EAC-Ex certificates can be provided.
Q: What is the service life of core wearing parts? What is the regular maintenance cycle?
A: Tungsten carbide wear tiles have a normal service life of 8,000–12,000 hours; the design service life of main bearings reaches 15,000 hours. Gearbox lubricating oil shall be replaced every 2,000 operating hours. Daily inspection covers vibration, temperature and oil pressure; full bowl cleaning is required every six months. We offer a 12-month warranty for the whole machine.
Q: The machine is blocked and no solid is discharged from the slag outlet, how to handle the emergency?
A: Cut off feed and stop the machine immediately. Flush the interior of the bowl with clean water while jogging the unit at low speed to clear accumulated solids completely. Never force startup under blockage. An optional DN50 flushing pipeline can be installed for automatic cleaning during startup and shutdown to prevent blockage.
Q: What documents will be delivered together with the machine? Is FAT and SAT acceptance available?
A: Production will be completed within 50 days after receiving advance payment. Supplied documents include assembly drawings, P&ID diagrams, operation & maintenance manuals, material certificates, CE and EAC-Ex certification documents. Factory Acceptance Test (FAT) is available at our workshop. After delivery, our engineers can be dispatched to site for Site Acceptance Test (SAT), installation, commissioning and operator training.
Q: How to confirm the proper model specification (processing capacity, bowl diameter) for my project?
A: Three key parameters are required for accurate model selection: hourly total feed flow rate, solid content of feed material, and target cake moisture. We provide free laboratory sediment tests to match suitable bowl length-diameter ratio, G-force and power, and issue a complete quotation with full technical parameters.
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Centrifuge Complete Selection Guide (General Version for SENZ Centrifuge Projects)
Centrifuge Complete Selection Guide (General Version for SENZ Centrifuge Projects)
Core Selection Logic: Define separation process targets first → Collect complete material parameters → Select centrifuge model → Verify key structural parameters → Match material grade, explosion protection & automatic control → Conduct bench test verification if necessary
Main Models: LW/LWS Decanter Centrifuge, DBY Disc Separator, GQ Tubular Centrifuge, Pusher Centrifuge, Horizontal Scraper Centrifuge; covering mine, sugar industry, grain & oil, chemical, biological, sludge, oily sludge three-phase separation applications
I. Step 1: Collect Basic Process Data of Materials (Questionnaire for Client Data Collection)
Insufficient data will easily lead to improper selection!
- Separation Type ✅ Two-phase: Solid-liquid separation ✅ Three-phase: Liquid-liquid-solid (oil-water-residue, olive oil, waste lubricating oil)
- Feed Parameters
- Processing capacity: m³/h (volumetric flow rate), meanwhile calculate dry solid throughput t/h (most critical! Decanters are limited by solid load instead of volumetric flow only)
- Feed solid concentration: wt% / g/L
- Solid particles: Median particle size d50, particle size distribution; particle shape (spherical/acicular/floc); hardness (high abrasion risk or not)
- Density difference between solid and liquid Δρ (smaller difference means harder separation)
- Liquid phase viscosity, material temperature
- Required separation targets (either or both)
- Liquid phase: Clarification, allowable suspended solids (SS) in clarified liquid
- Solid phase: Target cake moisture content (core index for dewatering), solid recovery rate
- Medium Characteristics
- Corrosiveness: Acid/alkali, chloride ion concentration; SS321 is prohibited for decanter bowl; common grades: 304, 316L, 2304/2205/2507 Duplex Stainless Steel
- Flammable & explosive medium? Requirement for ATEX Ex certification, EAC Explosion-proof (Russian market)
- Food/pharmaceutical GMP requirement, CIP on-site cleaning requirement
- Operation mode: 24h continuous operation / intermittent production
II. Step 2: Application Scope of Mainstream Centrifuge Models (Preliminary Model Selection)
1) Horizontal Screw Decanter Centrifuge (LW/LWS Series) 【SENZ Core Model】
Application: Continuous large-flow & high-solid slurry dewatering
✅ Feed solid content: 3%～45%
✅ Particle size: 5 μm ~ several millimeters; suitable for tailings, sludge, plasma, filter mud, three-phase oily sludge separation
✅ Advantages: Fully automatic continuous feeding & continuous slag discharge; available in two-phase / three-phase structure; moderate footprint
❌ Disadvantages: Difficult to achieve ultra-clear liquid; limited separation performance for ultra-fine particles (＜2 μm)
Typical Applications
Mine tailings dewatering, municipal/industrial sludge, sugar filter mud, three-phase oily sludge separation, fermentation broth, starch dewatering
Model Examples: LW250, LW450, LW650, LW900; LWS high-dryness decanter series
2) Disc Separator (DBY Series)
Application: Liquid-liquid separation, fine clarification of low-solid-content materials
✅ Feed solid content: 0.2%～15%
✅ Suitable for micron-sized particles, emulsion separation; equipped with automatic valve slag discharge
✅ Advantages: High separation factor, outstanding clarified liquid quality; edible oil refining, dairy, biological fermentation clarification
❌ Disadvantages: Not applicable for high feed solid concentration; high sand content materials cause severe abrasion; unable to sustain continuous large-volume solid discharge
Typical Applications
Olive oil refining, crude oil dehydration, sugar juice clarification, bacterial cell separation, vegetable oil degumming
3) High-speed Tubular Centrifuge (GQ Series)
✅ Feed solid content ＜1%, ultra-fine particles, trace impurity clarification, difficult emulsion separation
✅ Extremely high separation factor (10000～20000 G)
❌ Intermittent slag discharge, limited processing capacity; mainly for pharmaceutical, traditional Chinese medicine extraction fine filtration
4) Pusher Centrifuge / Horizontal Scraper Centrifuge (Filter Type)
✅ Suitable for large, uniform crystalline particles with good filterability (salt, mirabilite, massecuite separation via HCT massecuite centrifuge)
❌ Not applicable for flocculent, fine-particle sludge and viscous materials, prone to screen blockage
Quick Selection Comparison Table
表格
| Material Condition | Preferred Model |
|---|---|
| Large flow, high-solid slurry continuous dewatering, tailings, sludge, three-phase oily sludge | LW/LWS Decanter Centrifuge |
| Edible oil refining, liquid-liquid separation, deep clarification of low-solid feed | DBY Disc Separator |
| Trace solids, hard-to-break emulsions, high-precision clarification with small throughput | GQ Tubular Centrifuge |
| Inorganic salt crystals, sucrose crystal separation (A/B/C massecuite) | Pusher Centrifuge / HCT Massecuite Centrifuge |
III. Step 3: Key Parameter Selection for Decanter Centrifuge (Most Widely Used in Projects)
1. Separation Factor G (RCF)
Formula: \(G=1.118×10^{-5} × r × n^2\)
- G＜2500: Coarse particles, easily-settled materials (sandstone, coarse slurry)
- G=2500～3500: General applications, sugar filter mud, common industrial slurry
- G=3500～4500: Fine particles, sludge, biological materials, hard-to-settle materials
Note: Rotating speed shall not be increased blindly! Higher speed brings heavier load on bearings and differential gearbox, shortening service life
2. Length-Diameter Ratio L/D (Effective Bowl Length / Bowl Diameter)
- L/D=2.5～3.0: High-concentration materials, fast slag discharge, priority for cake quality
- L/D=3.5～4.0 (Standard LW): Balanced clarification & dewatering performance
- L/D=4.2～4.8 (High-dryness LWS Series): Extended settling time for lower cake moisture, applicable for fine-particle materials (activated sludge, plasma)
3. Cone Angle (Half Cone Angle)
- 8°～10°: General purpose, easy cake conveying
- 6° Small cone angle: Target lower moisture content; suitable for viscous materials
- 12° Large cone angle: Good particle flowability, high-abrasion ore slurry
4. Differential System (Top Priority)
- Small differential speed → Longer solid residence time → Drier filter cake, reduced throughput
- Large differential speed → Fast slag discharge, higher capacity, increased cake moisture Drive Configurations:
- Dual-motor dual frequency conversion (mainstream, flexible adjustment)
- Hydraulic differential gearbox (heavy-duty, large-diameter LW760/LW900, preferred for high-abrasion mine applications)
5. Solid Load Principle (Key Pitfall Avoidance)
Many buyers only focus on volumetric flow rate!
The main bottleneck of decanters is solid conveying capacity.
Example: Same feed flow of 100 m³/h
- Feed solid content 2% VS feed solid content 20% requires completely different models!
Selection Sequence: Calculate dry solid output first → Confirm minimum bowl diameter → Verify volumetric flow secondly
IV. Step 4: Material Grade, Wear Resistance & Corrosion Protection Selection (High-frequency for Export Projects)
- Bowl Material (SS321 is strictly forbidden)
- Clean water, neutral food: 304
- Weak acid, general food & chemical industry: 316L
- Chloride-containing medium, seawater, corrosion + abrasion: 2205 / 2304 Duplex Stainless Steel
- Severe corrosion: Titanium alloy
- Screw Wear Protection (High-abrasion working conditions: tailings, sandstone, filter mud)
- Option 1: Tungsten carbide spray welding on screw flights (general)
- Option 2: Embedded tungsten carbide wear tiles (heavy abrasion, standard for mine LW900)
- Seal: Standard oil seal; mechanical seal (AESSEAL) for flammable/explosive or vacuum service
V. Step 5: Explosion Protection, Electrical, Automatic Control & Compliance Standards (Overseas Projects Focus)
- Explosion-proof Class
- Domestic standard: Ex d II BT4
- EU projects: ATEX Zone1/Zone2
- Russian market: Must comply with EAC-Ex, GOST standard
- Drive: Main & auxiliary motors equipped with VFD; PLC+HMI remote control; Modbus RTU communication support
- Cleaning: CIP pipeline for food/pharmaceutical applications; closed structure to prevent material volatilization
- Lubrication: Independent forced oil lubrication for differential gearbox; online monitoring of bearing temperature & vibration
VI. Common Risks in Selection (Frequent Pitfalls in Foreign Trade Projects)
- ❌ Only consider volumetric flow while ignoring dry solid load → Equipment slag blockage & overload
- ❌ Adopt low L/D ratio for fine-particle sludge → Supernatant loss of solids, insufficient solid recovery
- ❌ Omit wear-resistant screw for high-abrasion mine conditions → Severe flight abrasion within 3～6 months
- ❌ Use standard two-phase decanter when three-phase oil-water-residue separation is required → Independent oil phase cannot be separated
- ❌ Improper stainless steel grade for corrosive medium leading to pitting corrosion (304 not suitable for high chloride environment)
- ❌ Use decanter for heavily emulsified materials; disc separator shall be adopted for pre-fine separation
VII. Simplified Data Collection Checklist (Directly Send to Clients)
- Material name, temperature, pH value
- Processing capacity: ____ m³/h; feed solid content ____ wt%
- Solid d50 particle size; density difference between solid and liquid
- Target index: Filter cake moisture ____% / Required SS in clarified liquid
- Three-phase oil-water-residue separation required?
- Flammable & explosive medium? Explosion-proof requirement (ATEX/EAC)?
- Operation duration: 24h continuous / intermittent
- Material requirement, CIP hygiene requirement for food grade
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