Problem 1: Irregular feed.

 

Reason 1: Irregular feed

Solution:

•  The product builds bridges in the hopper.
• Modification of the hopper or fitting of a vibrator.

 

Reason 2 : The steam goes back along the loading hopper.

Solution:  Check the operation of the minimum level gauge feeler in the hopper and  of the steam valve.

 

Reason 3: Too much molasses in the mixture.

Solution: Reduce the quantity of molasses and/or  mill with fine grid

 

Insufficient production with not full-load motor.Problem 2: 

 

Reason 1: The screw feeder turns too slow

Solution : Replacement of the motor pulley and/or of the driven pulley.

 

Reason 2: The screw feeder spirals have an insufficient pitch and/or the paddles of the feeder shaft have too little inclination.

Solution : Correction of the spiral pitch or of the inclination angle of the paddles.

 

Reason 3: The spirals and/or paddles are encrusted.

Solution : Cleaning of spirals and/or paddles.

 

Reason 4: Paddles are worn out.

Solution : Replacement of paddles.

 

Reason 5: The belts slip.

Solution : Restore the correct stretch of the belts or replace them if they are worn out.

 

Reason 6: The feed motor is not fitted correctly.

Solution : Check the fitting and alignment of the motor.

 

Reason 7: Return of the material into the inlet of the die because its specific weight is too low.

Solution :

 - Increase of the speed of the die.

- Finer milling.

- Study of methods to avoid the return.

 

Reason 8: Failing receipt of materials on part of the die owing to:

- the material is too greasy  

- excessive clearance between rolls and die

- problems on rolls and/or die

 - the thickness of the die is too much

 - not saturated steam and presence of water in the mixture

Solution :

- Less steam and/or control of the steam   line are required

- Add less molasses

- Adjust the rolls

- Check the thickness of the die

- Check the discharge of the steam trap

- See also the following section

 

Problem 3: Insufficient production with full-load motor.

 

Reason 1: Overload of the mill motor, owing to the gelling of the product:

- too much steam

- die too thick

- low quality steam

- too humid steam

Solution :

- Less steam is required

- Replace the die

- Check the steam line

 

Reason 2: Product is not conditioned al its best

Solution : Steam is to be increased.

 

Reason 3: Too much clearance between rolls and die

Solution : Rolls are to be adjusted.

 

Reason 4: Pellet are too hard

Solution : Use thinner dies

 

Reason 5: Corrosion in the inside of the holes of the die

Solution : Use stainless steel dies

 

Reason 6: Only one part of the drilled die strip is operating.

Solution :

 - Clean the rows of the clogged holes.

- Give the right direction to the product by means of the deflectors

 

 

Problem 4: Remarkable variations in the absorption of power

 

Reason 1: Feeding problems.

Solution : Check the operation of the feeder

 

Reason 2: Wear of the deflectors or paddles of the feeder

Solution : Change the deflectors or paddles of the feeder

 

Reason 3: Faulty adjustment of the rolls

Solution : Rolls are to be adjusted

 

Reason 4: Irregular milling or presence of powders.

Solution : Finer milling is required.

 

Reason 5: Insufficient mixing of the liquids.

Solution : The direction of the paddles is to be adjusted.

 

Reason 6: The paddles of the mixer are not directed properly

Solution : Cleaning of spirals and/or paddles.

 

 

Problem 5: Pellet  mill vibrates too much

 

Reason 1: The bearings of the driving unit have too much backlash.

Solution : Adjustment the backlash of the driving unit

 

Reason 2: The bearings of the rolls have too much backlash.

Solution : Adjustment the backlash of the rolls is required.

 

Reason 3: The die is not perfectly aligned with the roll holder.

Solution : Check the wear conditions of the die holder and of the wear ring; if necessary overhauling might be also required.

 

Reason 4: The rolls are not adjusted at the same clearance from the die.

Solution : Adjustment of the rolls is required.

 

Reason 5: Rolls slip because of too much molasses.

Solution : Use of rolls with corrugated closed roll shell is required

 

 

Problem 6: The pellet mill does not vibrate but is noisy

 

Reason 1:

- The bearings of the driving unit are worn out

- The bearings of the rolls are worn out

- The bearings of the transmission or of the motors are worn out.

 

Solution : Check the origin of the noise; to this regard first move away the rolls and then

  loose the belts. When the origin of the noise has been ascertained, replace the

 worn out bearings.

 

 

Problem 7: The main bearings are noisy

 

Reason 1: Normal wear

Solution : Adjust the backlash of the bearings and eventually replace them

 

Reason 2: Abnormal wear, shorter life because of:

- Use of unproper grease

- Time interval of the lubrication and quantity   do not comply with the instructions.

- Bad clamping condition of the die and/or rolls with consequent strong vibration of the machine.

 

Solution :

- Use the grease according to the instructions.Do not mix different greases.

- Time interval of the lubrication and quantity do not comply with the instructions.

- Replacement of the wear ring.

- Replacement of the die and/or rolls shells

- Eventually overhaul the die.

- Checking and/or cleaning of the magnetic separator