There are some protective device inside the belt conveyor to prevent accidents and ensure the safety when conveying materials. Protections of belt conveyor consist of belt sway protection, belt-broken protection, sliding protection and emergency stop pull switch. Belt sway, belt-broken and sliding protections are course switch with simple structure and low cost, the working principle is that the machine would stop when belt touched switch. Emergency stop pull switch rely on an electric switch and pulls the steel cord wire installed on both sides of the belt.
Speed sensors: using hall elements to detect the speed of belt conveyor. If the speed of driven wheel is in 50%-70% Va, or the speed of belt conveyor is less than or equal 50% Va or greater than or equal 110% Va, and after 5-10 seconds delay, the controller would cut off the power source automatically to protect the speed.
Disalignment transducer: be off-state in normal, and close when operation. It will cut off the power source automatically to stop belt conveyor.
Coal blocking transducer: breakover by two electrodes, through leads give the reaction of coal volume to protective device. It monitors the coal volume in bucket and bunker, and will cut off the power source when bunker is full or coal piling in machine head to achieve protection.
Scram protection: there is pull urgent stop switch installed on the control panel of each controller and the belt side, used in emergency stop when trouble.
Overtemperature protection: uses a temperature senor to monitor the temperatures of bearing and other parts of belt conveyor and environment temperature. When the temperature of the monitoring points is more than the set value, the controller will cut off the power source automatically to protect the machine and start sprinklers to cool.
Smoke transducer: when detects the smoke produced, the controller will cut off the power source and start the dust extinguishing sprinkler device.
Rip transducer: when the belt has longitudinal tear problem, the coal falls on the sensor, and the controller will cut off power source to stop the belt conveyor.
Safety protection device of belt conveyor is used to monitor and give alarms when happens troubles in operation. It can make the conveyor system safety production, proper operation and protect the safety of operating personnel. Besides, it can also facilitate centralized control and improve the level of automation.
Common protection and monitoring devices are as follows:
Longitudinal tear protection device: used to detect the belt conveyor. When there are material sharps in conveyor and the belt torn from middle, the controller will cut off power source.
Belt sway switches: used to detect the conveyor belt running deviation and distortion degree, can prevent edge damage and materials diffused to realize automatic alarm and stop the machine. A warning signal when the mild deviation, delay action, alarm and automatic shutdown when severe deviation. Generally installed in the head, middle, tail and inspection points of the belt conveyor.
Pull switch: it is a protective device for conveyor-site emergency stop when an emergency occurs, anywhere in the field to pull the switch, can be a warning signal, and then self-locking and stop. Generally pull switch mounted on both sides every 60m of belt conveyor.
Chute block switch: used to detect chute blockage of belt conveyor system. When occurs blockage, the controller will give an alarm and shut down.
Slip detector: used to detect the difference of linear speed between shaft belt and driving idler. It can give an alarm and achieve automatic tension and normal shutdown.
Overspeed detection device: used for downstream transport or transported under conditions. When the conveyor speed reaches 115% -125% of the specified belt speed, it will give an alarm and emergency stop.
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