How should a floating fish feed production line be operated?

The "soaking resistance" of aquatic feed is a core indicator of quality, and this indicator is entirely controlled by the pelleting process. A feed mill in Jiangsu Province improved the soaking resistance of grass carp feed from 25 minutes to 45 minutes and reduced the uneaten feed rate from 12% to 3% by optimizing pelleting techniques, significantly increasing repurchase rates among aquaculture customers. Pelletizing techniques mainly revolve around three aspects: equipment selection, parameter settings, and process control.

Ring die selection is fundamental to pelleting and must be tailored to the specific fish species. The feeding characteristics of different aquatic animals determine the die aperture and compression ratio. For shrimp feed, ring dies with a 2-3mm aperture and a compression ratio controlled at 1:8 (the ratio of die length to aperture diameter) ensure dense, soak-resistant pellets. For grass carp, crucian carp, and other adult fish feeds, ring dies with a 3-5mm aperture and a compression ratio of 1:6 are used, balancing soaking resistance and feeding efficiency. Ornamental fish feeds use ring dies with a 1-2mm aperture and a compression ratio of 1:7, resulting in small, easily swallowed pellets. The ring die material should ideally be 38CrMoAl alloy steel, which, after nitriding treatment, achieves a hardness of HRC60 or higher, extending its service life by three times compared to ordinary steel. During operation, the ring die should be periodically flipped based on wear, and replaced immediately when the die hole diameter increases by more than 0.5mm.

Precise matching of pelleting parameters is crucial, with key controls focusing on temperature, pressure, and rotation speed. For shrimp and crab feed pelleting, the temperature needs to reach 110-120℃ to fully gelatinize the starch and form a dense structure. For freshwater fish feed, the temperature should be controlled at 90-100℃ to avoid damaging vitamins. Pressure control complements temperature; the working pressure of the ring die pellet mill should be stable at 10-15MPa. Too low a pressure will result in loose pellets, while too high a pressure will make the pellets too hard, affecting digestion by fish and shrimp. Pressure can be controlled by adjusting the gap between the pressure roller and the ring die (maintaining it at 0.1-0.3mm). The roller speed needs to be synchronized with the feed rate, typically controlled at 150-200 rpm. Excessive speed can lead to uneven particle length, while insufficient speed reduces production efficiency.

The key to process control is "real-time correction." During operation, particle quality should be checked every 10 minutes, observing for smoothness and cracks on the particle surface, and testing foam resistance by hand-rubbing. If the particle surface is rough or has burrs, it may indicate die wear or insufficient raw material moisture; in this case, the die needs to be replaced or the conditioning moisture increased. If the particles break easily, the pressure is insufficient; the gap between the roller and die needs to be reduced. If the particles are too hard, the pelleting temperature or compression ratio needs to be lowered. Simultaneously, residual raw material between the die and roller should be cleaned regularly, and the machine should be stopped every 2 hours to purge with compressed air to prevent material adhesion and uneven particle formation.

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