Case Study: Oven Control System

We were approached by a customer, to design and build a control panel for a process oven.

The oven needed to be controlled to an exact specification and to include various other auxiliary sensors, control valves and fans. We opted for a Q-series Mitsubishi PLC system.

The oven needed to rise to 110°C, hold for a period of time, then increase to 340°C, hold again, then drop back to room temperature. During this temperature control process, an even distribution of heat was required throughout the entire envelop of the oven. This was achieved using 12 thermocouples, monitored by the PLC. Fans circulated air inside of the oven, while an external process heater, pumped hot air directly into the product to eliminate cold spots inside.

Oven heaters were controlled using solid state relays and phase angle controllers, providing accurate temperature controls. Many auxiliary components, including pneumatic valves, vacuum pumps, dew point meter and mass flow controllers were also controlled and monitored by the PLC.

All values and data were displayed on a 7" Human Machine Interface (Colour display screen with membrane keypad). From this terminal, all parameters and values could be read or changed.

All temperatures, parameters and fault conditions for each production run were captured and stored in an Excel spreadsheet for analysis and certification.

The PLC provided the most cost effective solution, providing easy modification and expansion if required, while maintaining a solid platform for reliability and safety.