Severodvinsk Bakery Complex (Arkhangelsk Region) entrusted Northern Energy Systems with the task to repair and retrofit the control system of three Rothoterm WP rack ovens made in Germany. Rothoterm WP backing cabinets are used for producing bakery and confectionery products.
The existing oven control system consisted of printed circuit boards that were arranged in a special control cabinet built into the oven. An operator could see information displayed on a 5-inch touch panel connected to the printed circuit board via the CAN interface. Due to the continuous use of ovens, the build-in control system started operating with serious faults, and the front control panels of the ovens failed. These panels could not be repaired. The cost of new original panels was very high and they could only be ordered from the manufacturer's plant in Germany. It appeared that the panels failed systematically and it represented the main challenge for the bakery complex.
Together with the personnel of Severodvinsk Bakery Complex JSC, it was decided to develop and implement a new rack oven control system based on OWEN equipment.
- Baking chamber. A trolley with future products is loaded into the chamber on a movable plate; the trolley rotates during the baking process so that hot air distributes evenly over the products
- Heating unit. The heating unit is located outside the baking chamber. It consists of three sets of 75 kW heating elements. The main air channel passes through the heating unit to heat the air
- Main fan (1.5 kW). It enables air circulation between the heating unit and the baking chamber. Thanks to air circulation, the heat is transmitted from the heating unit to the baking chamber, and the hot air is evenly distributed over the products
- Steam generator. Located in the heating unit, it is used to humidify hot air during the baking process by injecting water
- Chimney valve. It is used to redirect the air flows inside the oven, mainly at the end of the baking process, to discharge "smoke" into the factory ventilation system
- Temperature sensors. Pt100 resistance temperature sensors located in the heating unit and the baking chamber allow for controlling the current and limit temperature values
Operation Algorithm of the Control System
The following OWEN equipment was used to develop the new control system:
- Operator touch panel SP310-B
- Frequency converter PChV2
- Programmable logic controller PLC110-30 [М02]
- Analog input module MV110-2А
- Heavy-duty power supply units BP60-24S and BP30-24S
- Power supply units BP60B-12
- Meyertec screw terminals
Before starting a shift, an operator switches on the system (exits the sleep mode) by pressing the corresponding button on the control panel and selecting the necessary baking program. After that, the system starts the main fan, which spins at the speed set in the settings (speed in a standby mode), and heats up the baking chamber by switching on/off a set of heating elements as per the preset value of the chosen first cycle program.
At the stage of heating-up, if the temperature differs greatly from the preset value, the operator will not be able to start the baking process (the start and stop buttons are locked). After the oven is heated up and the temperature reaches the preset value, the operator can start the baking process, and the system informs the operator about this with a sound signal.
The operator loads the trolley with future products into the baking chamber and presses the "Start" button on the touch panel screen. The products are baked according to the selected baking program consisting of 5 subprograms and the after-baking mode.
The following indicators can be set for each program:
- Subprogram time (the total baking time is calculated by summing time of 5 subprograms)
- Fan speed
- Chimney valve position (in %)
- Steam injection (in liters of water)
The number of subprograms in the baking program is selected by setting the process data (if there is no data, then this subprogram will not be executed).
The oven control system has many protective functions that prevent the operator from interfering with the baking process. In total, there are 100 baking programs.
There is also a manual baking mode. Upon completion of the baking program, the system offers the operator to switch to the after-baking mode, with an option to preset certain values. At the end of the baking process, the control system emits a loud sound signal.
On a whole, the new system appeared to be as effective as the original one, and even outperform it. The large touch screen facilitates the operator’s tasks. The control system can be used not only with Rothoterm WP ovens but also with rack ovens of other manufacturers, such as Miwe.
The project helped to stop using expensive imported equipment. Moreover, the client benefits from prompt technical support regarding the control system, which previously was not available.