When there is any hard foreign matter entered the pelletizing chamber or when the material flow rate is too high, the pressure between the press rollers and the ring die will exceed the normal working pressure, and then the friction resistance between the press rollers and the ring die will increase.
1. The rotor will drive the main shaft to rotate since the press rollers are installed on the main shaft and the ring die is installed on the rotor.
2. When the torque of the main shaft reaches a certain design value, the sheer force of the safety pin on the safety pin disk installed on the rear end of the main shaft exceeds the sheer force limit of the safety pin, thus the safety pin is sheared off.
3. At this time, the main shaft is rotating and drives the limit switches to act, thus stopping the motor of pelleting machine.
4. The main shaft must be reset and the safety pin must be installed again before restart.
A by-pass door is provided at feeding inlet of pelletizing chamber of pellet mill, if the speed of feeds into ring die is too fast and the feeds deposited are excessive and the motor load increased exceeds the rated value, the pneumatic device will open automatically the by-pass door, the feeds will be discharged from by-pass door; after the motor load is reset normally, the by-pass door will be closed automatically and the machine will continue to operate, see Fig 0.3.
The magnetic separating device between the discharging outlet of the conditioner and inlet of the pellet mill gate is effective for removing iron impurities mixed in materials to protect the ring die and press rollers from damage.
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