While a low expansion rate in floating fish feed pellet making machines is a commonly recognized issue, excessive expansion is often overlooked. However, it can result in products that are too soft, loosely structured, and prone to breakage. This significantly increases losses during transportation and storage, negatively impacts product taste and shelf life, and drives up production costs.
Details
I. Specific Phenomena of Excessive Expansion Rate
Phenomenon Description:
- Excessive Volume Expansion: The product expands to a volume much higher than desired, resulting in a low density and an overly soft texture.
- Fragility: The product breaks easily with a light touch and is difficult to mold.
- Internal Pores and Structure: The internal pores are too large and unevenly distributed, often with voids connecting the pores, leading to poor structural integrity.
- Surface Quality Issues: The appearance of the product is often deformed, with a rough, dull surface. Some products may even have scorched edges or spots.
- Handling and Packaging Problems: During transportation and packaging, the product is easily broken and pulverized, leading to a loss rate exceeding 15%, severely affecting product qualification and profitability.
II. Core Causes of Excessive Expansion Rate
1. Excessive Chamber Temperature
- Over-Gelatinization: When the temperature in the expansion zone exceeds 200°C, the material becomes excessively gelatinized. Upon demolding, moisture vaporizes too quickly, resulting in excessive expansion force.
- Faulty Temperature Control: If the heating elements are too powerful or the temperature control instruments malfunction, the chamber temperature may rise uncontrollably, failing to stabilize within the optimal range.
- Over-Insulation: An excessively thick chamber insulation layer prevents heat dissipation, leading to localized overheating and exacerbating the problem of excessive expansion.
2. Abnormal Steam and Raw Material Parameters
- High Steam Pressure: If the steam pressure exceeds 0.5 MPa, a sudden drop in pressure upon material demolding leads to rapid moisture vaporization, causing excessive expansion.
- Low Raw Material Moisture: Raw materials with moisture content below 12% lead to poor flowability within the chamber. This results in localized high temperatures during shearing, causing excessive expansion.
- High Starch Content: Materials with excessive amylose content (such as glutinous rice) are more prone to excessive expansion after puffing, leading to a higher-than-required expansion rate.
3. Improper Component and Parameter Settings in Floating Fish Feed Pellet Maker Machine
- Small Die Orifice: A die orifice that is too small results in slow discharge speed, excessive pressure buildup in the chamber, and over-expansion as material exits the die.
- Excessive Screw Speed: High screw speeds increase shearing and extrusion, which leads to excessive starch gelatinization. If the residence time is too short, this prevents the formation of a stable puffed structure.
- Slow Feeding Speed: When the feeding speed is too slow, the raw material stays in the die chamber too long, resulting in over-gelatinization and excessive expansion.
4. Process and Formulation Issues
- Excessive Leavening Agent: An over-addition of leavening agent leads to excessive material expansion force, resulting in an excessively high puffing rate.
- Unbalanced Raw Material Formulation: A formulation lacking sufficient binders to support the puffed structure results in an overly soft and over-expanded product.
- Fluctuating Temperature and Pressure Parameters: Excessive fluctuations in temperature and pressure during production prevent the formation of a stable puffing environment, aggravating the issue of over-expansion.
III. Solutions and Prevention for Excessive Expansion Rate
1. Temperature and Pressure Parameter Adjustment
- Lower Expansion Zone Temperature: Set the temperature in the expansion zone to the optimal range of 160-180°C to prevent over-gelatinization.
- Check Heating Elements: Regularly inspect the heating elements and temperature controllers to ensure stable temperature control and avoid overheating.
- Adjust Steam Pressure: Set the steam pressure to 0.3-0.5 MPa to maintain a stable steam supply, preventing excessive vaporization of moisture.
- Adjust Insulation Layer: Ensure that the insulation layer is not too thick, allowing for proper heat dissipation and maintaining temperature stability.
2. Raw Material and Formula Optimization
- Adjust Moisture Content: Control the moisture content of raw materials within the optimal range of 12%-15%. This increases material viscosity, which can inhibit excessive expansion.
- Enhance Binder Content: Add an appropriate amount of binder to the raw material formula to improve the product's structural support, preventing excessive softness and expansion.
- Leavening Agent Control: Limit the leavening agent to 0.5%-2% of the raw material weight to ensure uniform mixing and prevent over-addition, which can lead to excessive puffing.
3. Component and Parameter Adjustment for Floating Fish Feed Pellet Extruder Machine
- Replace Die Head: Use a die head with a slightly larger orifice to facilitate faster material discharge and reduce pressure buildup in the chamber.
- Adjust Screw Speed: Reduce the screw speed to minimize excessive shearing, which helps control the gelatinization of starch and prevents over-expansion.
- Increase Feeding Speed: Increase the feeding speed to better match the screw speed and temperature parameters, which shortens material residence time in the chamber and avoids excessive expansion.
4. Daily Management and Prevention
- Monitor Parameters: Establish a parameter monitoring log to track temperature, steam pressure, screw speed, and other key metrics. This helps promptly identify and correct fluctuations.
- Regular Calibration: Calibrate temperature controllers and pressure sensors regularly to ensure accurate readings and maintain stable parameters.
- Trial Production: Before each large batch, conduct small-batch trials, adjusting parameters to optimal levels before mass production to prevent excessive puffing.
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