What are the differences in working principles between dry and wet fish feed extruders?

 

 

When buying a fish feed extruder, you often hear the terms "dry" and "wet". Many people's first reaction is "dry means no water is added, and wet means water is added". But just looking at whether water is added or not, you can't understand why the fish feed produced by the two is different. Some dry machines produce feed that floats for a long time, while some wet machines produce feed that is softer. In fact, the core difference lies in the working principle, which has to be explained from "how to make the feed float".

 

 

Water addition method: Relies solely on the raw material's own moisture; no additional water is added. The raw materials for the dry-type extruder must be "dry." For example, the moisture content of corn flour and fish meal should be controlled at 12%-14% (similar to the humidity of sun-dried goods). No additional water is added during feeding; the reaction relies entirely on the small amount of moisture in the raw material.If the raw material is too wet (exceeding 15%), it will clump and clog the screw, so the raw material must be dried before feeding.

 

Heating principle: Heat is generated by friction between the screw and the barrel; no additional heating element is needed. The screw thread of the dry-type extruder is designed to be relatively dense. When rotating, the friction between the screw and the raw material, and between the raw material and the inner wall of the barrel, generates high temperatures (up to 120-150℃). This heat gelatinizes the starch and denatures the protein in the raw material, while simultaneously turning the small amount of moisture in the raw material into steam, forming bubbles in the pellets. After extrusion and cooling, the floating feed is produced.Simply put, it's about "heating the raw material through friction and creating air bubbles."

 

 

 

Water Addition Method: Requires additional water or steam; raw material moisture content can be slightly higher. The moisture content of the raw material for wet extruders can be as high as 15%-18%. Water is added during feeding through a dedicated "water inlet" or "steam outlet" (generally 10%-15% of the raw material's volume), making the raw material into a "wet dough" state.Without water, the raw material is too dry, the screw cannot turn, and it will wear down the barrel.

 

Heating Principle: Relies on steam heating + a small amount of friction for more stable temperature. The barrel of the wet extruder has a steam jacket (like a "kettle" for the barrel), directly heating the raw material by introducing steam (temperature can be precisely controlled at 100-130℃), combined with screw friction for auxiliary heating. Steam heating is more uniform than friction heating, resulting in more complete gelatinization of the raw materials, producing more and finer bubbles, and more stable particle buoyancy. Simply put, it is "using steam to 'cook' the raw materials and cook out bubbles."

 

 

 

 

For example, when making sinking feed for sea bass, high particle density and uniform nutrition are required. The shearing and mixing action of a twin-screw extruder allows fishmeal and starch to be fully integrated, resulting in better water resistance of the particles. However, when making floating feed for ordinary grass carp, the requirements are not as high, and the simple structure of a single-screw extruder can meet the needs, as long as the particles can be extruded.

 

 

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 prawn feed making machine?

The price ranges from approximately $6,000-$26,000

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

 

 

 

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