Fault: One of the main functions of the scraper conveyor on the fully mechanized mining face is to transport the coal cut by the shearer, which is realized by the chain installed on the scraper conveyor. The chain itself is an elastic body, and the amount of coal cut by the shearer is uncertain, resulting in inconsistent weights of coal carried by the scraper conveyor chain. After a long time of operation, the chain of the scraper conveyor will be relaxed, if not handled in time, it will lead to broken chain, stuck chain, pile chain and other safety accidents, which will affect the coal mining efficiency of the fully mechanized mining face in serious cases. Solution: The chain automatic tensioning device is added to the tail of the scraper conveyor, which is composed of PLC controller, tail 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 controls the action of the solenoid valve, drives the action of the tail tensioning cylinder, adjusts the pressure value of the cylinder back to the expected range, and at the same time, the travel sensor detects the driving distance of the tail tensioning cylinder and reports it 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, and it is necessary to cut the chain operation.