The fracture of mining ring chain and compact chain can be roughly divided into 3 types according to their stress conditions:
1 strong chain break
When the impact force exceeds its static breaking load, it suddenly breaks. This form of chain breaking is also called brittle fracture. The fracture often occurs in the middle of the welded joint, the heat affected zone of the weld or the bending part of the chain link.
2 Fatigue broken chain
The force is less than its static breaking load, but fatigue failure occurs due to pulsating load for a long time. This type of fracture is also called plastic fracture. The fracture is generally at the connection between the curved part of the chain link and the straight part.
3 Hybrid Fractures
It is the fracture phenomenon that occurs under the intertwined action of pulsating load and impact force for a long time. The fracture has both obvious plastic deformation area and uneven lip.
Analysis of the cause of scraper chain breakage:
1. The chain is suddenly stuck during operation. It may be that the chute is misplaced, and the scraper or chain or chain is caught; or because the roof of the roadway is not high enough and the machine head is high, when large coal or gangue is transported to the head of the machine, it is stuck between the scraper and the roof. During this time, the chain breaks due to impact.
2. The chain is too tight, which not only increases the initial tension of the chain and shortens its service life, but also when the chain is stuck, there is no room for buffering, which increases the tension load of the chain and makes it easier to break.
3. Because the chain is too loose, severely worn, or the length of the two chains is different. When it runs to the sprocket, the tooth skipping occurs, so that the chain of the sprocket is impacted by the teeth of the sprocket, causing the chain to deform and break.
4. Overload operation, when the amount of coal transported is too large, the motor is started under the overload condition, which increases the dynamic tension of the chain and causes the chain to break.
5. The link distance of the two chains is different, so that the load is heavy on a certain chain, which makes the chain overload and cause a chain breakage accident.
6. The chain is broken due to the loss of the connecting ring screw of the chain link, the chain is disjointed and the chain is broken.
7. The deformed chain ring should be replaced in time, the meshing is not good during the operation, and the uneven force will cause the chain breakage accident.
8. The floor of the roadway on the working face is not flat or straight, which causes uneven force on the scraper chain to scrape the card and get off the groove, causing the chain of the scraper to break.
9. The scraper has a large amount of coal returned, causing the bottom chain to be overloaded and broken.
10. Mine water corrosion and wear cause chain breakage.
In summary, in actual production, it is necessary to strengthen the daily inspection and maintenance of the scraper, and take corresponding management measures:
1. Make the roadway of the working face as straight as possible, so that the scraper is laid straight and the chain is evenly stressed.
2. Adjust the length of the two chains to be the same, so that the chains will not be unevenly stressed.
3. Adjust the tightness of the chain in time, so that the tightness of the chain is moderate, and replace the severely worn chain and chain in time.
4. When the amount of coal in the chute is too large, organize workers to clean up with tools, and do not start the scraper forcibly overloaded.
5. After the scraper has been used for a period of time, remove the chain and turn it over 90 degrees, so that the horizontal chain link and the vertical chain link can be exchanged and continue to be used, and the worn position can be changed to prolong the service life.
6. Drain the water on the working surface in time, do not let the scraper work in water or shorten the time of immersion.
7. A chain breaking protection device is added to the scraper, so that the scraper can automatically stop when the scraper breaks the chain and scrapers. The working face scraper conveyor should be operated according to the regulations during the use process. In addition to daily maintenance, pay attention to check the use of the equipment when changing shifts, find problems in time, and deal with them as soon as possible to ensure safe production and maximize the efficiency of the scraper conveyor.