Fault: One of the main functions of the scraper conveyor in a comprehensive mining face is to transport the coal blocks cut by the coal miner, and this function is achieved by the chain installed on the scraper conveyor. The chain itself is an elastomer and the amount of coal cut by the coal miner is not determined, resulting in inconsistent weight of the coal blocks carried by the scraper conveyor chain. After long time operation, the chain of scraper conveyor will be slack, if not dealt with in time, it will lead to safety accidents such as broken chain, stuck chain and stacked chain, which will affect the coal mining efficiency of the comprehensive mining working face in serious cases. Solution: Add chain automatic tensioning device at the end of the scraper conveyor, which is composed of PLC controller, end tensioning cylinder, solenoid valve, pressure sensor, stroke sensor, etc. When the system detects that the pressure value of the pressure sensor is not within the expected range, the PLC controller will control the solenoid valve to drive the tail tensioning cylinder to adjust the cylinder pressure value to return to the expected range, and the travel sensor will detect the distance of the tail tensioning cylinder and report to the PLC controller to participate in the logic control of the PLC controller. When the scraper conveyor runs for a period of time, the scraper chain will be too loose, then it is necessary to cut the chain operation.