1. Feeding System Faults (Blocking, No Feeding, Material Backflow)

Fault 1: Feeding hopper blocking, no material discharging

• Raw material moisture content is too high or too low; powder agglomeration or excessive oil adhesion causes screw sticking.
• Screw feeder speed is too low, feeding capacity cannot match main host pushing speed.
• Long-term residual materials in the feeding bin cause material bridging.
• Crushed raw material particle size is too coarse with poor fluidity.

• Stop the machine and clean all agglomerated materials. Control raw material moisture at 12%–18%. Mix oil evenly in advance instead of adding oil separately in the later stage.
• Increase the frequency of the feeding inverter to match the main machine output (standard 600–800kg/h for 85 model).
• Install a vibrator on the feeding bin and clean residual materials on the inner wall after each shift.
• Sieve raw materials through 40–60 mesh to improve powder fluidity.

Fault 2: Material backflow and powder spraying at feeding inlet, steam backflow

• Screw and bushing wear leads to increased gap and insufficient material pushing pressure.
• Excessive steam pressure causes high-pressure steam to flow back to the feeding section.
• Sudden feeding reduction leads to screw idling and reverse pressure outflow in the chamber.

• Check the wear degree of screws and liners, replace worn screw sleeves and wear-resistant parts in time.
• Reduce pre-conditioning steam pressure to the standard 0.2–0.3MPa and feed steam slowly.
• Ensure continuous and uniform feeding; prohibit main machine idling without materials. Immediately close steam and reduce main machine speed once material breakage occurs.

2. Main Host Faults (Vibration, Abnormal Noise, Stuck, Overload Trip)

Fault 1: Severe machine vibration and loud resonance noise

• Anchor bolts are loose, base shock absorption pads are aging or damaged.
• Hard impurities (stones, iron blocks) stuck inside the screw barrel.
• Screw misalignment, deformed screw blades, or worn coupling buffer rubber pads.
• Unstable feeding volume causes drastic fluctuation of internal chamber pressure.

• Stop the machine to fasten all anchor bolts and replace aging shock absorption rubber pads.
• Disassemble the screw to clean hard foreign matters, and install a permanent magnet iron remover at the front end to filter metal impurities.
• Calibrate screw concentricity, replace coupling buffer pads, repair or replace deformed screws.
• Stabilize the feeder inverter to ensure uniform and continuous feeding.

Fault 2: Main machine overload trip, sudden high current, motor stalling

• Low raw material moisture increases friction resistance and leads to excessive load in the extrusion chamber.
• One-time excessive feeding causes screw overload.
• Die hole blockage prevents material discharge and causes pressure holding stalling.
• Insufficient lubricating oil leads to increased resistance of gearbox bearings.

• Add steam in the conditioning section to increase raw material moisture; add water appropriately for dry material production.
• Start the feeder at low speed and increase output gradually, prohibit full-load feeding at one time.
• Disassemble the die plate to clear all blocked holes and clean coked materials inside the screw.
• Check the gearbox oil level regularly and fill with special gear oil on schedule.

Fault 3: Screw friction and harsh metal abnormal noise

• Too small gap between screw and bushing causes dry friction.
• Hard foreign matters enter the extrusion chamber and cause metal scraping.
• Damaged bearings and worn transmission shafts.

• Adjust the screw assembly gap to the standard wear-resistant gap specified by the manufacturer.
• Use magnetic separation equipment throughout production and screen raw materials in advance to remove impurities.
• Disassemble the gearbox and replace damaged bearings.

3. Discharging Particle Abnormal Faults (Sinking, Cracking, Uneven Size, Blackening, Adhesion)

Fault 1: Feed pellets sink, cannot float on water

• Insufficient extrusion temperature leads to low puffing degree and few internal pores of pellets.
• Low starch content in raw materials (fish feed starch content ≥20% is recommended).
• Unmatched large die hole size and incorrect cutting speed.
• Insufficient conditioning steam results in poor curing effect.

• Increase the heating temperature of each section of the main machine to raise the shear temperature in the extrusion chamber.
• Increase high-starch raw materials such as corn and wheat in the formula to improve expansion rate.
• Replace with small-aperture die plates and synchronously increase the cutter speed.
• Increase conditioning steam supply and extend material curing time.

Fault 2: Longitudinal cracking, easy breaking and fragile pellets

• Excessively high raw material moisture causes rapid water evaporation and pellet cracking after puffing.
• Worn screws lead to unstable extrusion pressure.
• Too far distance between cutter and die plate causes pulling and cracking during cutting.
• Excessively high extrusion temperature leads to over-puffing and pellet embrittlement.

• Reduce water addition in conditioning, control feeding moisture at 14%–16%.
• Replace worn screws and bushings to stabilize extrusion pressure.
• Adjust the cutter to be close to the die plate to realize close-fit cutting.
• Lower the main machine heating temperature to avoid over-puffing.

Fault 3: Pellet adhesion and agglomeration

• Excessive oil addition causes surface viscosity and mutual adhesion of pellets.
• Insufficient cooling air leads to high pellet surface temperature and incomplete shaping.
• Over-standard moisture causes soft and sticky pellets.

• Adopt post-spraying for oil addition instead of heavy oil mixing in the early stage.
• Turn on the supporting air-cooling conveyor to fully cool and shape pellets before screening.
• Reduce conditioning steam and water addition to lower feeding moisture.

Fault 4: Black pellets, burnt materials and burnt odor

• Long-term over-high extrusion chamber temperature causes material carbonization.
• Residual materials in the screw are baked and carbonized due to incomplete cleaning before shutdown.
• Long-term accumulated coked materials in screw dead corners mix into new materials.

• Adjust and lower the temperature of each heating section to monitor stable temperature curve.
• Clean the screw with pure corn flour before shutdown to completely discharge residual materials.
• Disassemble the die plate and screw after each shift to clean coked residual materials.

Fault 5: Uneven pellet size and length

• Worn or notched cutter blades cause uneven cutting length.
• Unstable feeder speed leads to fluctuating discharging flow.
• Partial die hole blockage causes unbalanced discharging.

• Polish or replace blunt cutters and adjust cutter speed properly.
• Lock feeder inverter parameters to stabilize feeding speed.
• Clear all blocked die holes to ensure uniform discharging of each hole.

4. Heating & Steam System Faults

Fault 1: Slow temperature rise, unable to reach set temperature

• Burnt heating rings or poor contact of thermocouple temperature probes.
• Blocked steam pipeline or damaged pressure reducing valve leads to insufficient steam supply.
• Falling or damaged insulation layer causes excessive heat loss.

• Test heating rings with a multimeter, replace damaged heating elements, and fix temperature probes firmly.
• Clean scale in steam pipelines, overhaul pressure reducing valves, and stabilize steam pressure at 0.2–0.3MPa.
• Rewrap the main machine with thermal insulation cotton to reduce heat loss.

Fault 2: Temperature out of control, continuous over-temperature alarm

• Faulty temperature controller and distorted thermocouple temperature measurement.
• Stopped cooling circulating water leads to ineffective cooling.

• Replace temperature sensors and calibrate temperature control instruments.
• Check cooling water pumps and pipelines to ensure normal circulating water flow.

5. Gearbox & Electrical System Faults

Fault 1: Gearbox oil leakage and over-high oil temperature

• Aging and damaged oil seal, excessive lubricating oil level.
• Damaged cooling fan leads to poor gear heat dissipation.
• Deteriorated lubricating oil with excessive impurities.

• Replace skeleton oil seals and adjust lubricating oil to the standard scale level.
• Overhaul the cooling fan to ensure continuous heat dissipation.
• Replace special gear lubricating oil every 3 months regularly.

Fault 2: Inverter alarm, motor fails to start

• Overload protection triggered by material blockage and stalling.
• Unreset emergency stop button and poor circuit contact.
• Motor phase loss and unstable voltage.

• Clean blocked materials and reset inverter overload fault codes.
• Check all emergency stop switches and fasten electrical terminal connections.
• Detect three-phase voltage and install voltage stabilizer to stabilize power supply.

6. Daily Preventive Maintenance Guide (Reduce 80% Machine Faults)

• Screen and magnetically separate all raw materials before production to prevent metal and hard stone impurities from entering the main machine.
• Clean the screw with corn flour before each shutdown to completely discharge residual materials and avoid coking.
• Inspect 5 core systems daily: feeding system, cutter system, steam system, temperature control system and lubrication system.
• Regularly check the wear degree of screws, bushings and die plates, and replace vulnerable parts in advance.
• Match four core parameters stably: raw material moisture, steam pressure, extrusion temperature and feeding speed, avoid random large adjustment.
• Prohibit long-time idling of the main machine without materials to prevent severe screw wear.