PEEPL Automation's high accurate weigh Feeders are specially designed to do a continuous weighing on flowing materials and controlling of material feeding rate as per desired set point which we set on our machine.There are two single Point Load cells model and four single point load cells model. The loadcells are connected in the silent zone of the conveyor belt so that the vibrations and other disturbances will not affect the loadcell's ouput. The loadcells are connected to a loadcell module which converts the loadcell's output to a readable value for the controller. In a second 30-40 weighments are done for bulk material, running for desired accuracy. Optical encoder is fitted on return/driven roller which generates 1000 PPR (pulses per revolution) of belt speed sensing roller. The optical encoder converts slow speed of the conveyor in to high speed pulses to get desired accuracy.
The microcontroller based weigh feeder controller receives the weight in terms of kg/m from Load transmitter and speed in terms of pulses/min from optical encoder.
It processes these two inputs received from the field and calculates the feed rate in the form of Tons per hour (i.e. TPH) also calculate the cumulative weight passed through the Weigh feeder.
Set point TPH and start command can be given from the 3 locations (i.e. Local Panel , WF Panel & Master PLC) based on the selection switch (i.e. mode of operation) provided on WF Panel, whereas stop command can be given from all the locations irrespective of mode of operation.The accuracy particularly depends on the calm tape operation and consistent material spread on carrying belt.There is a provision to adjust the Load cell height and to remove the material deposited on the conveyer (on line) to get better accuracy.
Screw WEIGH Feeders do a continuous weighing and controlled feeding of bulk material to next process as per desired set point. The screw feeder receives material from pre-feeder i.e. in this case Rotary Airlock Valve. Two ‘S’ type Load cells of required capacity are installed below screw Weigh feeder. These load cells are connected to Load cell input of Controller to convert the weight signal into Kg/m. As the material moves out of through the screw feeder the material weight will acts on the load cells in turn controller derives kg/m parameter. In a second 30-40 weighments are done for bulk material load for desired accuracy. The controller displays all time kg/m load.
Optical encoder is fitted at non driven end of screw feeder which generates pulses per revolution of shaft and with the help of this the travel of the screw shaft is derived which is converted to meters/second (i.e. m/s).
The Micro controller based screw Weigh feeder controller receives the above two signals and processes to calculate the feed rate in the form of Tons per hour (i.e. TPH) also calculate the cumulative weight carried by screw feeder in Tons. The rate is calculated by multiplying kg/m and m/s. The totaliser is upgraded by integrating the rate with respect to time.
Set point TPH and start command can be given from the 2 locations (i.e. Screw Weigh feeder Panel & Master PLC) based on the selection switch (i.e. mode of operation) provided on Screw feeder Panel, whereas stop command can be given from all the locations irrespective of mode of operation.
Firstly, operator needs to decide mode of operation by selection switch provided on Screw Wigh Feeder Panel and give set point from selected location. On receiving the start command to Screw Feeder controller, it start the motors of screw Feeder & RALV, derives actual feed rate as explained above, compares it with set point and generates error output for Variable frequency drive to correct the speed to achieve desired feed rate (i.e. set point) in few seconds by using software PID function. Thus the system runs in a close loop giving out the material at required rate.
The accuracy particularly depends on the calm operation and material build up inside screw feeder. The system can be operated either in Gravimetric mode or in volumetric mode as per the user requirement. In gravimetric mode the feedback is taken from load cells and Encoder. In volumetric mode the feedback is taken from encoder only.
(Note: Please refer attached diagram)
Remote Mode (Screw Feeder Panel) operation:
The user can control Screw feeder remotely from the Screw Weigh feeder panel itself by using controls provided on controller. If remote mode is selected then only one can change the set points and give ON commands for SF from SWF panel itself. Controller shall give required data to Master PLC as explained above. SF shall stops on receiving the OFF command from Master PLC, SF panel or emergency stop switch operation from the field
Master Mode (PLC) operation:
For Master mode operation, the user sets the set points from the PLC and read into Screw weigh feeder panel through AI in turn updates the set point in SWF controller. (If required communication bus can be provided
SWF controller controls the feed rate on getting the ON command from PLC and gives required data to Master PLC as explained above. SF shall stops on receiving the OFF command from Master PLC, SWF panel or emergency stop switch operation from the field.
Interfacing with Master PLC/DCS:
Screw feeder controller can communicate with master PLC/DCS by RS485 port, Ethernet port or Digital and Analog signals as per user’s requirement. This interfacing shall be discussed at later stage.
Screw feeder mechanicals:
Main frame MOC is steel with necessary stiffeners and supports, rigid heavy duty construction
Load cells in Alloy Steel housing, precise temperature compensated load cell for drift-free operation and control.
Digital speed sensor mounted on non drive end of shaft to sense the actual speed.
AC 415 V, 3 phase motor for driving the Screw. Motor and Gears reputed make will be provided.
Capacities up to 2 Tones / Hr
Special linings used for corrosive & abrasive ingredients.
Feeding and discharging chutes provided
Slow screw speed that avoids product abrasion
Durable modular construction
Pre-feeder Rotary Airlock Valve provided.