A diesel single screw floating fish feed extruder machine works through a process called extrusion cooking. A diesel engine drives a high-alloy screw inside a barrel, using intense friction and pressure to heat raw materials to 110°C–135°C. This flash-cooks the ingredients and gelatinizes starches. When the dough is forced through the die into atmospheric pressure, the internal moisture turns to steam, causing the pellet to "puff" and create a porous structure that ensures long-term buoyancy.
To understand how this diesel single screw floating fish feed pellet extruder machine works, we must look at the thermodynamic and mechanical changes happening inside the barrel.
Raw materials (ground to <60 mesh) enter the barrel. The screw’s flight design begins to move the powder forward. At this stage, the moisture content (20-25%) is critical; it acts as a lubricant and a heat-transfer medium.
As the material moves, the screw flights become tighter. This creates mechanical shear.
Friction Heat: The kinetic energy from the diesel engine is converted into thermal energy.
Pressure Build-up: Pressure rises to 30–60 bar, compressing the air out of the mixture.
In the final section of the barrel, the temperature peaks.
Starch Transformation: Complex starches break down into simpler, digestible dextrins.
Pathogen Kill: The high heat (120°C+) eliminates harmful bacteria like Salmonella, making the feed safer for aquaculture.
As the cooked "dough" exits the die, it experiences a sudden pressure drop. The superheated water inside the pellet instantly flashes into steam. This creates thousands of microscopic air pockets, reducing the bulk density to below 1.0 g/cm³, which is why the pellets float.
While electric extruders are common in factories, diesel single screw floating fish feed making machines are the backbone of remote aquaculture in Africa, SE Asia, and Latin America.
No Voltage Drops: Diesel engines provide consistent mechanical energy, unlike rural power grids which suffer from brownouts that can stall an extruder.
Torque on Demand: Diesel engines naturally produce higher torque at lower RPMs, which is ideal for the heavy-duty task of feed extrusion.
As industry professionals, we recommend these three optimizations to improve your Feed Conversion Ratio (FCR):
Starch Ratio: Your formula must contain at least 20% starch (from corn, wheat, or cassava). Without enough starch, the "pockets" won't form, and the feed will sink.
Grinding Fineness: If your raw materials are gritty, the pellets will have cracks. Aim for a flour-like consistency to ensure a smooth, water-stable surface.
Cooling & Drying: Never bag pellets immediately. They must be dried to below 10% moisture to prevent mold and maintain their floating structure.
A: This usually happens for three reasons:
The extrusion temperature is too low (not enough friction).
The starch content in your formula is below 15%.
The moisture is too high, preventing the "puffing" effect.
Tip: Increase the diesel engine RPM to generate more heat.
A: A standard 150-200kg/h extruder powered by a 22HP diesel engine typically consumes 3 to 5 liters of diesel per hour, depending on the density of the feed formula.
A: Yes. To make sinking feed, you should reduce the starch content, increase the moisture slightly, and lower the extrusion temperature. This prevents the "puffing" effect, resulting in a dense, sinking pellet.
A: A properly calibrated single-screw diesel extruder can produce pellets that stay afloat for 12 to 24 hours, which is more than enough for most commercial fish species.
A: If using high-alloy steel, the screw usually lasts for 500 to 1,000 tons of production. Processing highly abrasive materials like bone meal or rice husks will shorten this lifespan.
Understanding how a diesel single screw floating fish feed pellet making machine works allows you to troubleshoot quality issues and optimize production. By mastering the balance between temperature, moisture, and starch, you can produce professional-grade floating feed that rivals expensive commercial brands, all while remaining completely off-grid.
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