The type of oil press employed has a significant impact on the extraction efficiency of crude palm oil (CPO). After sterilization, stripping, and digestion, mechanical pressing extracts oil from the fruit’s mesocarp using either a single or double screw press. Each type affects throughput, oil recovery, cost, and profitability.
Understanding the Oil Pressing Stage in Palm Oil Processing
Once palm fruits are digested into a soft mash, the material is conveyed to a screw press to extract the oil. The press squeezes the digested mash under high pressure, forcing the oil out while leaving behind solid byproducts like fiber and nuts.
An efficient oil press:
- Maximizes oil recovery from the mesocarp
- Maintains low residual oil content in the press cake
- Minimizes damage to nuts and fiber for easy separation
- Handles throughput without frequent downtime
The performance of the press directly impacts the oil yield, clarity, and profit margin of your operation.
Overview of Single Screw and Double Screw Presses
🔧 Single Screw Oil Press
This is the most commonly used oil press in palm oil mills. It features a cylindrical barrel containing a single horizontally mounted screw shaft. The screw rotates and conveys the digested mash forward while applying increasing pressure, pushing oil through barrel perforations.
🔧 Double Screw Oil Press
A double screw press has two parallel intermeshing screws rotating inwardly. The digested mash is compressed between these two screws and forced along a tapered channel. High-capacity and high-efficiency operations frequently use it.
- Maintains low residual oil content in the press cake
- Minimizes damage to nuts and fiber for easy separation
- Handles throughput without frequent downtime
The performance of the press directly impacts the oil yield, clarity, and profit margin of your operation.
Working Principles: How Do They Function?
✅ Single Screw Press Operation:
- Digested mash is fed into a feed hopper.
- The rotating screw pushes the mash along the barrel.
- Compression increases as the channel narrows.
- Oil is squeezed through slotted barrels and collected in the sump.
- The remaining cake (fiber and nuts) exists at the end.
✅ Double Screw Press Operation:
- Mash is fed between two interlocking screws.
- The mash is equally compressed by the screws, which revolve in opposite directions.
- Oil flows through perforated cage walls.
- Fiber and nuts are discharged from the end.
Note: Double screw action ensures more thorough pressing and better discharge control.
Key Design Differences
| Feature | Single Screw Press | Double Screw Press |
| Number of Shafts | 1 | 2 (parallel, intermeshing) |
| Compression Style | Progressive compression along screw | Compression between counter-rotating screws |
| Construction Complexity | Simple | Complex |
| Maintenance | Easier | More demanding |
| Gear Mechanism | Single-gear motor | Dual synchronized gear drives |
Capacity and Throughput
Capacity is a key factor in press selection, especially for large-scale operations.
🔧 Single Screw Press
- Ideal for 5–20 tons of FFB/hour
- Common capacities: 1.5–3 tons/hour (per press)
- Modular—multiple units can be installed in parallel
🔧 Double Screw Press
- Designed for 20–60 tons of FFB/hour
- Handles high feed volume in continuous operations
- Higher compression efficiency per press
Verdict: For small to mid-sized mills, single screw presses offer flexibility and cost-effectiveness. For high-volume industrial plants, double screw presses reduce the number of machines required.
Oil Recovery Rate and Efficiency
✅ Single Screw
- Typical oil recovery: 90–93% of available oil
- Residual oil in press cake: 6–8%
✅ Double Screw
- Oil recovery: 93–95%
- Residual oil in cake: 3–5%
- Better control of fiber and nut separation
While both press types achieve good results, double screw systems excel in maximizing oil yield, especially in mills where every percentage point matters.
Fiber and Nut Handling
Efficient discharge of fiber and nuts affects downstream separation (fiber/nut classifiers, nut crackers).
- Single screw: Often results in slightly compressed cake with more nut breakage.
- Double screw: Produces a looser, fluffier cake, which aids in nut recovery and reduces kernel losses.
Energy Consumption and Operation Costs
| Factor | Single Screw Press | Double Screw Press |
| Power Consumption | 20–50 kW per unit | 60–100+ kW per unit |
| Maintenance Cost | Lower | Higher (more parts, gears) |
| Operator Training | Easier | Requires a skilled technician |
| Spare Parts | Widely available | May need custom components |
Conclusion: Although double screw presses extract more oil, they consume more energy and require higher maintenance costs. Single screw presses are generally more cost-efficient for mills under 20 tons/hr.
Space and Layout Requirements
✅ Single Screw Press
- Compact
- Can be installed in modular units
- Easy to integrate into existing layouts
✅ Double Screw Press
- Larger footprint
- Needs more space for gearboxes, motors, and press cake conveyors
- Better suited to greenfield projects or large facility expansions
Capital Investment Comparison
| Category | Single Screw Press | Double Screw Press |
| Initial Cost (Unit) | $15,000 – $35,000 | $50,000 – $100,000+ |
| Installation Cost | Lower | Higher |
| Number of Units | More units for the same capacity | Fewer units needed |
While double screw presses require more upfront investment, their long-term ROI is attractive in high-throughput mills.
Suitability by Mill Size
| Mill Type | Recommended Press Type |
| Micro Mills (<5 tons/hr) | Single Screw Only |
| Small Mills (5–10 tons/hr) | Single Screw |
| Medium Mills (10–25 tons/hr) | Single Screw or Hybrid |
| Large Mills (25+ tons/hr) | Double Screw Preferred |
Which One Should You Choose?
Choosing between a single screw and a double screw oil press depends on your mill size, budget, and production strategy.
- For small and medium-sized mills processing up to 20 tons of FFB/hour, the single screw press offers simplicity, flexibility, and affordability.
- For large, high-throughput operations focused on maximizing oil recovery and long-term ROI, the double screw press is the superior choice.
Here’s a quick decision matrix:
| Consideration | Best Choice |
| Low investment budget | Single Screw |
| High efficiency & recovery | Double Screw |
| Simple maintenance | Single Screw |
| High-capacity production | Double Screw |
| Modular layout | Single Screw |
| Fully automated line | Double Screw |
Ultimately, selecting the right oil press system is about finding the balance between cost, efficiency, and operational reliability. Consult with equipment manufacturers who can assess your facility’s layout, desired output, and labor availability to recommend a tailored solution that suits your business goals.
