Why is the expansion rate low in fish feed mills?

 

 

In aquatic feed production, if an extruder malfunctions with a "low extrusion rate," it can cause floating feed to sink quickly, sinking feed to have insufficient density, and even result in "hard-core pellets"-fish feed that originally had an extrusion rate of 90% may suddenly drop to below 60%. This not only affects the feeding of aquatic animals (e.g., fish cannot eat sinking feed), but also leads to slow growth of farmed animals due to decreased feed digestibility (insufficient starch gelatinization). If not resolved promptly, it can lead to customer complaints and damage the company's reputation.

 

 

1.Insufficient starch content or inappropriate moisture content in the raw materials.

 Cause: Expansion relies on the "expansion force" generated by starch gelatinization. If the starch content in the raw materials is less than 30% (e.g., if the proportion of high-protein fish meal is too high), sufficient pressure cannot be generated after gelatinization, and the expansion rate will naturally decrease. Excessive moisture content (over 18%) will lead to excessive gelatinization, resulting in clumping and insufficient expansion. Excessive moisture content (below 12%) will result in poor fluidity in the barrel and inadequate gelatinization.

 

 Solution: Adjust the raw material formula to ensure that the proportion of starch raw materials (corn, wheat flour) is no less than 35%. Use a rapid moisture meter to check the raw material moisture content. If the moisture content is too high, dry it in a dryer (temperature 65-75°C) to 14%-16%. If the moisture content is too low, add an appropriate amount of steam (pressure 0.3-0.4MPa) to the conditioner to stabilize the moisture content of the raw materials at 15%-17% after conditioning.

 

 

2.Barrel temperature and screw speed mismatch

 Causes: If the barrel temperature is too low (e.g., the extrusion section temperature is below 110°C), the starch gelatinization rate will be insufficient (less than 75%), preventing sufficient expansion. If the temperature is too high (over 140°C), the starch will carbonize and harden its surface, inhibiting expansion. If the screw speed is too high (over 350 rpm), the residence time of the starch in the barrel will be shortened to less than 20 seconds, resulting in inadequate gelatinization. If the speed is too slow (below 250 rpm), the starch will be over-compressed, resulting in excessively dense pellets and difficulty in expansion.

 

 Solution: Adjust the barrel temperature in stages: 60-80℃ for the feeding section, 90-110℃ for the compression section, and 120-130℃ for the extrusion section (monitor in real time using a temperature control instrument); adjust the screw speed according to the characteristics of the raw materials: control the screw speed at 280-320 r/min for raw materials with high starch content, and adjust the screw speed at 320-350 r/min for high protein raw materials, ensuring that the raw materials stay in the barrel for 25-30 seconds and that the starch gelatinization rate reaches over 85%.

 

 

 

3.Improper Die Aperture and Back Pressure Adjustment

 Causes: If the die aperture is too large (e.g., using a 5mm die for 3mm granules), the material will not be extruded with sufficient pressure, leaving little room for expansion. If the aperture is too small (e.g., using a 2mm die for 3mm granules), the material will clog the die aperture, preventing smooth extrusion. If the die back pressure is too low (less than 0.5MPa), the material will not be able to build up sufficient pressure within the barrel, resulting in poor expansion. If the back pressure is too high (over 1.2MPa), the granules will be over-compacted, inhibiting expansion.

 

 Solution: Replace the die with one that matches the granule size (e.g., for 3mm granules, use a 3mm die with an aperture aspect ratio of 1:8-1:10). Adjust the back pressure using the die adjustment screw. For starch-based materials, maintain the back pressure between 0.6-0.8MPa, and for high-protein materials, between 0.8-1.0MPa. This ensures both sufficient pressure and expansion during extrusion.

 

 

 

 

MIKIM boasts extensive experience in poultry feed pellet production lines, significantly reducing the incidence of poultry diseases. Its equipment is not only widely used across various industries domestically but also exported to Southeast Asia, Europe, Africa, and South America, earning a high reputation internationally. This global presence not only demonstrates the adaptability and competitiveness of its products, but also demonstrates the company's experience in adapting to diverse market standards and logistics conditions, enabling it to provide a stable supply chain for its overseas customers. Whether serving large domestic farms or cross-border feed companies, MIKIM can leverage its global service network to ensure a consistent, high-quality experience.

 

For more information on process flow design, equipment layout, factory construction plans, individual equipment pricing, or turnkey project proposals, please feel free to contact us!!!

 

 

 

1. What is the price of the fish feed pellet making machine?

The price ranges from approximately $4,000-$22,000

2. Do you provide maintenance services for your customers?
Yes, we offer comprehensive after-sales maintenance services to our customers.

 

 

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