What Causes a Floating Fish Feed Pellet Extruder to Clog During Startup?

Floating fish feed pellet making machine clogging at startup is a common issue that can halt the production process, wasting time, materials, and resources. This problem is especially troublesome for novice operators. By understanding the phenomena, causes, and quick fixes, operators can minimize downtime and ensure smooth machine operation from the outset.

I. Specific Phenomena of Extruder Clogs During Initial Start-up

Phenomenon Description:

After preheating, raw materials are fed in, and the machine seems to operate normally, but:

• No material is discharged from the die or only a minimal amount is output.
• Material backflows and steam leakage occur at the feed inlet.
• There is a slight burnt smell or abnormal noise from the machine chamber.
• The main unit current spikes (usually exceeding 1.2 times the rated current), causing some machines to trigger overload protection and shut down automatically.
• After disassembly, material clumping and blockages are found in the machine chamber, die, and screw surface, as well as ungelatinized raw materials.

These phenomena are most commonly observed after:

• Equipment debugging.
• Raw material changes.
• Restarting after long periods of inactivity.

II. Core Causes of Machine Blockage During Initial Start-up

1. Insufficient Preheating of the Milling Chamber

• Cause: Not following the recommended preheating process, or insufficient preheating time (less than 20 minutes) results in the chamber temperature failing to reach the minimum required temperature (above 140°C).
• Consequence: Raw materials are not fully softened and gelatinized, making them flow poorly and prone to clumping and agglomeration, which causes die orifice blockages.
• Impact: This is the most common cause of blockages, accounting for 52% of cases.

2. Raw Material Parameters Not Meeting Requirements

• Moisture Content Too Low: If moisture content is below 12%, raw materials are too dry, making them hard to bind and causing stagnation and clumping.
• Particle Size Issues: If the particle size is too large or uneven, it exceeds the die orifice size, preventing smooth material passage and causing blockages.
• Foreign Objects: Metal fragments, stones, and other debris in raw materials can directly jam the screw or block the die orifice, leading to a clog.

3. Improper Start-up Operations

Cause: Not performing a no-load test run before feeding raw materials.

Consequences:

• Sudden material accumulation in the machine chamber.
• Screw speed not gradually increased, causing immediate clogging.
• Feeding speed too fast, overwhelming the machine's initial processing capacity.
• Lack of required initial material (such as cooked flour) causing stagnation.

4. Equipment Component Installation or Wear Issues

• Die Head or Distributor Plate Installation: Misalignment or improper installation can obstruct material flow.
• Screw and Screw Sleeve Wear: Severe wear reduces the screw's pushing capacity, preventing the material from being effectively pushed to the die.
• Die Head Nut Installation: Improper installation can cause the screw to seize, blocking normal operation.

III. Emergency Handling and Prevention Measures for Blockage at Start-up

Emergency Handling Steps (Safety First):

1. Immediately stop the machine and disconnect the power to prevent further damage.
2. Close the steam valve to prevent steam leakage and burns from high-temperature materials.
3. Wear protective equipment such as high-temperature gloves and protective masks.
4. Disassemble the die head and flow divider, then clean out the blocked material and foreign objects.
5. Gradually clean lumps inside the machine chamber by heating and gelatinizing them.
6. Check screw and core installation and adjust to the correct position.
7. Reinstall the die head and flow divider, ensuring everything is properly secured.

Standardized Start-up Procedure:

• Preheat the machine chamber:
• Ensure the temperature reaches 150-180°C for at least 20 minutes.
• Monitor the temperature in real-time using a temperature controller.
• Run the machine with no-load for 3-5 minutes to confirm smooth screw operation.
• Gradually increase screw speed once the die is discharging material normally.
• Avoid sudden material feeding to prevent accumulation.

Raw Material Control Measures:

1. Screen raw materials before feeding to remove foreign matter (e.g., stones, metal fragments).
2. Adjust moisture content: Aim for an optimal range of 12-15%.
3. Low moisture can be adjusted by spraying water and stirring evenly.
4. Ensure uniform particle size (20-40 mesh) to promote even flow and gelatinization.

Pre-Operational Equipment Inspection:

1. Check component installation:
2. Ensure the die head, flow divider, screw, and core are correctly aligned and secure.
3. Inspect screw and threaded sleeve wear:
4. Replace if worn, as worn parts hinder material movement and increase clogging risk.
5. Clean residual material from the die holes and discharge channel to prevent blockages.
6. Ensure no obstructions in the die head or manifold feed holes.

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