Common Malfunctions of Small Biomass Pellet Mills and How to Fix Them
Low Pellet Formation Rate
Low pellet formation rate is the most common fault in small wood pellet machines. The main causes include unsuitable raw material moisture content, an excessive gap between the pressure rollers and the die, and insufficient pressing temperature. If the raw material moisture content is too high, above 18 percent, the pellets easily crumble and fail to form properly; a dryer is needed to reduce the moisture content to the 10 to 15 percent range. If the moisture content is too low, below 10 percent, the raw material lacks viscosity, and a small amount of water can be sprayed before feeding to adjust it. The normal gap between the pressure rollers and the die should be 0.1 to 0.3 mm; if the gap is too large, reduce it with the adjusting bolts, and if the pressure rollers are severely worn, replace them. Insufficient pressing temperature leads to incomplete lignin softening; the heating temperature can be raised through the control system, with feed production generally controlled at 60 to 80 degrees Celsius and energy pellets at 80 to 100 degrees Celsius.
Material Blockage in the Feed Inlet and Pressing Chamber
Material blockage in biomass pellet machines often occurs at the feed inlet and the pressing chamber, and it is mainly caused by uneven particle size of the raw materials, excessive feeding speed, or hard objects in the raw materials. If the feed inlet is blocked, stop the machine immediately, clean the residual material from the feed inlet and check whether the pulverizer is functioning properly, ensuring that the raw material particle size is within the 2 to 5 mm range. If the pressing chamber is blocked, disassemble the pressing chamber casing, clean out the clumps of material and check whether the pressure rollers are jammed. If hard objects are stuck between the pressure rollers and the die, remove them promptly and check for damage. To avoid blockage, keep the feeding uniform and avoid sudden increases in feed rate, and use screening equipment in the raw material pretreatment stage to remove stones, metal and other hard objects.
Abnormal Noise and Severe Vibration
Excessive noise or severe vibration during operation is usually caused by loose, unbalanced or worn components. First, check whether the anchor bolts are loose and tighten them with a wrench if they are. Second, check the balance of the pressure roller and the motor; uneven wear on the pressure roller causes operational imbalance, so a severely worn pressure roller needs to be replaced. Finally, check the reducer and the bearings; if the bearings lack lubrication or are worn, abnormal noise appears, and the solution is to add lubricating oil or replace the bearings.
Motor Overheating
Overheating of the pellet mill motor can be caused by overload, poor heat dissipation or electrical problems. Overload is often due to an excessive feed rate or mold blockage, so reduce the feed rate and clean the mold. If the motor cooling fan is damaged or the ventilation holes are blocked, replace the fan or clean the holes. Electrical problems, such as unstable voltage or loose wiring, require checking the circuit to ensure stable voltage and secure wiring. In addition, insufficient lubrication of the motor bearings can also cause overheating, so lubricate them regularly.
Cracked Pellets and Rough Surfaces
Cracks or rough surfaces in the pellets are mainly related to pressing pressure and uneven mixing of raw materials. If the pressing pressure is insufficient, increase the pressure parameters appropriately. If pressure adjustment is not effective, there may be a leak in the hydraulic system, and the hydraulic lines need to be inspected and repaired. Uneven mixing of raw materials leads to insufficient viscosity in some particles, so check the mixing system to ensure that additives or binders are evenly incorporated. When troubleshooting, follow the principle of starting with the easy checks and then moving to the difficult ones: first inspect the raw material pretreatment and the parameter settings, then check the equipment components. Regular equipment maintenance reduces the occurrence of malfunctions, so keep a maintenance log that records each fault and its handling.
FAQ: Maintenance and Prevention
1. What is the correct moisture range for pelletizing? The raw material moisture content should be controlled at 10 to 15 percent. Above 18 percent the pellets crumble, and below 10 percent the material lacks viscosity.
2. What is the correct gap between the pressure rollers and the die? The normal gap is 0.1 to 0.3 mm. If it is too large, reduce it with the adjusting bolts; replace severely worn pressure rollers.
3. What particle size should the raw material have? The raw material particle size should be within the 2 to 5 mm range, and screening equipment should remove stones, metal and other hard objects.
4. Why does the motor overheat and how do I fix it? Overheating is caused by overload, poor heat dissipation or electrical problems. Reduce the feed rate, clean the mold, check the cooling fan and ventilation holes, and verify the voltage and wiring.
5. How can I reduce the number of faults over time? Follow the troubleshooting principle of easy checks first, keep a maintenance log that records every fault and its handling, and inspect wearing parts regularly so that problems are caught before they stop the line.
