Pellet mill maintenance

Commonly asked questions about daily pellet mill maintenance

Step 1: Hold the hoop positioning pin broken

pellet mill parts

Cause: When installing the pellet mill hoop, one end of the screw is tightened at a time, resulting in a torn positioning pin.

Consequences: three pieces of hoop, each piece between the gap, granulator operation, because the three notches do not contact with the hoop friction, resulting in the formation of three high points, in the absence of hoop positioning pin, after replacing the ring mold, the hoop will be installed again when the hoop will be installed on top of the three high points, thus making the hoop face contact into a point contact, granulator start working, it will accelerate the wear of the hoop, which will also accelerate the wear of the drive wheel, the use of hoop and drive wheel life is greatly reduced.

Solution: When installing the pellet machine hoop, pay attention to the letters on both ends of the hoop, do “A-A,B-B,C-C”, before installing, put a layer of grease on both sides of the hoop 15° to reduce the wear caused by the hoop when the equipment starts and stops. To install, install one piece with the positioning hole first, then the other two pieces. When tightening the screws, three screws should be evenly and gradually tightened, and try to ensure the evenness of the three gaps. After pre-tightening with a ratchet, use the extension handle to gradually increase the force until it is tight.

Step 2: Abrasion resistance ring wear

pellet mill spare parts

The role of the wear ring is on the one hand to protect the drive wheel to avoid premature wear and prolong its service life, and on the other hand is to play a guiding role, so that the ring die and the drive wheel do concentric circular motion.

 Wear and tear of the pellet mill wear rings is inevitable during use, a coat of grease on the surface reduces wear and also facilitates the installation of the ring mould. If the mating surface between the ring die and the wear ring is found to be shiny, it means that the wear ring has been worn. 

Severe wear of the wear-resistant ring will also cause the ring die to rotate not in the circumference, but in a single pendulum swing, which will accelerate the fatigue of the front bearing of the empty shaft, affecting the service life of the bearing. The wear ring will protrude due to vibration when working, so each time you change the ring die, clean the mounting position of the ring die on the drive wheel and knock the wear ring back to its original position.

Step 3: Wearing of transmission health

pellet machine parts

The drive key only plays the role of positioning does not drive, ring die start the moment, ring die key groove and the drive key will occur instantaneous impact, over time, will aggravate the wear and tear of the drive key, please pay attention to timely replacement, ring die key groove part of the broken gap is due to the drive key wear and do not replace the results in time. 

To minimize the damage to the drive key from impact, we minimize the clearance between the drive key and the ring die keyway by turning the ring die counterclockwise before tightening the hoop screw.

Step 4: The use of hoop screw spherical spacer

pellet machine part

 The two spherical spacers for the hoop screw are used in groups, with the spherical side of one spacer being used in conjunction with the concave side of the other spacer, with the central role being face-to-face contact rather than point contact. 

It is difficult to ensure the position of the bolt hole is on a line because there is a gap between each piece during installation. During installation, grease between the two gaskets to facilitate staggered movement of the two under stress.

Step 5: Die cover screw assembly

 The pressure pellet mill die cover screw is a shoulder screw, which is used in conjunction with the elastic spacer to ensure that the ring die can be misaligned with the ring die when it is deformed by pressure, preventing the screw from being cut. 

The elastic spacer is elastic enough to press the pellet mill  die cover, if it is tightened too much it will cause screw damage (breakage or shoulder wear). and the “fish-eye” phenomenon. 

The fish-eye phenomenon is due to the selection of a high-strength screw that is directly tightened to pull out the ring mold threaded hole position while working. It wasn’t caused by our tightening assembly being too tight. 

Step 6: Gearbox drainage

pellet mill gear box

  The source of water in the pellet machine gearbox: one, the pelletizing room of high humidity steam may enter the gearbox through the seal; two, because the gearbox is high temperature and high pressure when working, then after the shutdown cooling, the gearbox will form a negative pressure, so that the water vapor in the air will enter the gearbox.

 If the oil inside is found to be emulsified through the oil level view mirror, it means there is water. Once the pellet mill gearbox has water to be drained in a timely manner, otherwise it will cause the surface of the pinion shaft of the big gear a little bit of corrosion phenomenon, reducing the life of the big gear, in addition to this will also affect the bearing lubrication effect. 

It needs to be drained once a week, after a 4-8 hour shutdown, when the water and oil are completely separated. If there is not much water discharged each week, it can be relaxed to a maximum of two weeks of water discharges, not too long apart, especially during the rainy season in the south. Drainage is even more important during the off-season of production.

Pellet mill maintenance structure