The automation of the mill and flour silo in the flour processing company JSC «Rigas Dzirnavnieks» (JSC Rigas Dzirnavnieks)

Used controller: Siemens Simatic S7-400.

Used visualization program: based on Siemens WinCC .

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The wheat mill and flour silo of the JSC "Rigas Dzirnavnieks" are located in separate blocks, the automation was made by separate controllers, but the process visualization and the control was managed from unified control program. There were used the newest process control technologies to automate these objects. The highest level of the managing system hierarchy is the Industrial Ethernet that connects server, operator computer and programming logical parameters (PLC) providing data transmission speed 10 Mbit/sec.

The wheat mill is created on a basis of equipment and technology of the company "Buhler".

Flour silo provides the transport, dosage, homogenisation and storage of different kind and quality flour. All in all there are 40 containers, 6 conveyers and 2 elevators in the bulk store.

The controller connects with the system elements of the flour silo in five ways:

  1. The inputs/outputs of the central controller are connected directly to the MCC to provide the engine control commutation signal, its turning on/off and overload control. The direct connection between the central controller and MCC is reasoned with securing the safety requirements of exploitation.
  2. The frequency inverters are controlled using the PROFIBUS communication line. This line is used also for connection with the DP/AS interface converters.
  3. All solenoid valves, level sensors, pressure sensors, line motion sensors and valve end-switches are connected to the input/output modules that through the AS interface provides the information exchange with the central controller. These input/output modules are connected to the appropriate AS interface of the producing line. One module has 4 digital inputs and outputs. Models for analogue signals have two inputs and outputs.
  4. Connection with the computer is provided using the Ethernet line.
  5. Connection with the electronic scales is provided using the communication processor CP-441-2.

It is possible to provide the opportunity that the sensors could be connected directly to the centralized inputs in case of the necessity to provide faster accounting of any parameter.

Similar scheme was used in wheat mill automation.

Such connection scheme is the most efficient using the AS interface modules within maximum. Such variant enables to reduce the capacity of installation wires, provide comfortable expanding of the system, well clearness for diagnose and renovation.

Operator controls and manages the producing process using the computer operator desk. Overall there are 4 operator desks (two in the wheat mill and two in the flour silo) that are interconnected with Industrial Ethernet.

The program of the process visualization performs the following functions:

  1. Executive mechanism management and position control using manual and automatic regime.
  2. Blocking of the executive mechanism switching on in case of technical or operator mistakes. The blocking turns up according to the blocking parameters (delay of switching on time, sequence, mutual blocking etc.) of each executive mechanism. These parameters are gained from the table of mutual interaction of the executive mechanisms. This table can be edited and improved by users not changing the process control program.
  3. The flour transportation path can be assigned by stages or calculated automatically specifying the beginning and finishing points, as well as the characteristic intermediate points.
  4. Automatic performance of the planned tasks. Operator defines flour-processing tasks (transportation path, stir proportions, weight, screening intensity etc.). These tasks are performed automatically in the assigned sequence.
  5. Automatic choice of the complete product in the mill. Operator defines the amount of each quality flour that mill has to proceed during the fixed time period. Then grain is automatically navigated in different flows for processing to ensure the planned production.
  6. Automatic generation of messages during the prevention. The representative of user can edit and improve the time of each executive mechanism prevention.
  7. The issue, fixing and archiving of the warning messages. It is possible to review the warning message register by time periods and message types.
  8. Diagnose of the electrical power equipment position.
  9. Automatic control of the operations performed by the operator.
  10. Determination of different access levels.

The process visualization was realized using the development tools of Siemens WinCC program. Some specific additional solutions (for example, position tables) were made using Delphi programming facilities. The examples are mill and bulk store visualization.

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NORD MILLS specialists and consultants controlled and managed the automation of these objects. The automation of the mill was realized according to the "Buhler" defined technological process.




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