Failure of mine-use round-link chains and compact chains They can be roughly classified according to their load-bearing conditions. 3 Species:

1 Strong chain break

When the impact force exceeds its static fracture load, the chain breaks suddenly. This type of chain failure is also referred to as brittle fracture. The fracture surface typically occurs at the middle portion of the weld joint, the heat-affected zone of the weld, or the curved section of the chain link.

2 Fatigue fracture

The force applied is less than its static fracture load; however, due to prolonged exposure to pulsating loads, fatigue failure occurs. This type of fracture is also referred to as ductile fracture. The fracture surface typically appears at the junction between the curved and straight sections of the chain link.

3 Mixed fracture

It is the fracture phenomenon that occurs under the combined action of prolonged pulsating loads and impact forces. The fracture surface exhibits both a clearly visible region of plastic deformation and uneven, irregular lip edges.

Analysis of the Causes of Scraper Chain Breakage:

1.  The chain suddenly got stuck during operation. This could be due to misalignment of the chute joints, which caught on the scraper blades or the chain links; or it could be because the roof of the roadway is not high enough, causing the machine head to be relatively high. When large coal chunks or gangue are transported to the machine head, they become lodged between the scraper blades and the roof, creating an impact on the chain and leading to its breakage.

2. If the chain is tightened too much, not only will its initial tension increase and its service life be shortened, but when the chain gets jammed, there will be no room for cushioning, thereby increasing the tensile load on the chain and making it more prone to breakage.

3 Due to excessive chain slack, severe wear, or unequal lengths between the two chains, when the chain reaches the sprocket, it skips teeth, causing the chain links to be impacted by the sprocket’s teeth, resulting in deformation and breakage of the chain links.

4 Overloading operation: When the coal-carrying capacity exceeds the motor's rated load, starting the motor under overload conditions increases the dynamic tension on the chain, ultimately leading to chain breakage.

5 The different link spacing between the two chains causes the load to be concentrated on one chain, leading to overloading and ultimately resulting in chain breakage.

6 The chain broke because the connecting-ring screw of the link was lost, causing the links to come apart and the chain to disconnect.

7 Deformed chain links should be replaced promptly. During operation, poor meshing and uneven stress distribution can lead to chain breakage accidents.

8 The floor of the working face roadway is uneven and not straight, causing the scraper conveyor chain to get caught, jammed, and subjected to uneven stress, which ultimately leads to the chain breaking.

9 The scraper conveyor has a large amount of coal return, causing the bottom chain to overload and break.

10 Chain breakage caused by corrosion and wear from mine water.

In summary, in actual production, it is essential to strengthen daily inspection and maintenance of scraper conveyors and implement appropriate management measures. ：

1 Straighten the roadway in the working face as much as possible to ensure that the scraper conveyor runs smoothly and the chain is subjected to uniform tension.

2. Adjust the lengths of the two chains to be consistent, so that the chains are not subjected to uneven tension.

3 Adjust the chain tension promptly to ensure it’s neither too loose nor too tight, and replace chains and links that are severely worn in a timely manner.

4 When the coal flow in the chute is excessive, organize workers to clear it using tools; do not attempt to start the scraper conveyor by forcibly overloading it.

5 After the scraper has been used for a period of time, remove and flip the chain. 90 Rotate the chain links so that the horizontal links and vertical links exchange positions, then continue using them. By shifting the location of wear, you can extend their service life.

6 Drain the water from the working face promptly, and avoid allowing the scraper conveyor to operate while submerged in water or shorten the duration of submersion.

7 A chain-break protection device has been added to the scraper conveyor, enabling the machine to automatically stop in case of chain breakage or scraper damage. During operation, the face scraper conveyor must be operated in accordance with established procedures. In addition to performing routine maintenance, operators should carefully inspect the equipment’s condition during shift handovers, promptly identify any issues, and address them at an early stage to ensure safe production and maximize the scraper conveyor’s efficiency.