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The Central Mixer VFD through the use of a 150 HP Variable Frequency Drive and PLC is capable of changing the rotational speed of the mixer drum to increase the life of the equipment. The system monitors the activity of the batch plant and reduces the rotational speed of the mixer drum at times when the mixer is inactive between batches or when a load has been in the drum longer than the mix time. Reducing the rotational speed of the drum at these times will increase the life of rollers, roller track, pinion gears and ring gear as well as reduce the wear on drum liners and paddle liners. When tilting the mixer drum the speed can be reduced to eliminate the amount of splatter created when discharging and effectively increase the speed of discharge into a ready-mix truck.
This systems is a completely stand alone unit from the batch control, the basic operation does not require any interfacing with the batch control. -The PLC monitors the aggregate batcher discharge open, cement batcher discharge open and water batcher discharge open. Anytime activity is seen on one of these functions, it will speed the mixer drum up to full speed, anticipating the drum is being loaded with materials. -After the drum has been charged with material and it does not tilt for a predetermined amount of time (example: 90 seconds) after the open signals stop, it will slow to 1/3 full speed. -When tilting, the drum will slow to a programmable speed to get the desired discharge. -Upon righting the drum, the mixer will go back to full speed, anticipating that it will be charging once completely righted. -If not charged once it has righted for a predetermine amount of time (example:180 seconds) the mixer will slow to 1/3 full speed until activity is seen on any of the scale discharge opens. -An input is available into the PLC to override the PLC and run the mixer at full speed from the batch control. This can be used when washing out the mixer or when needed to mix longer than PLC is programmed to mix at full speed.
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