Dual zone PID controller for Steelworks Annealing and Tempering Furnace

• Application: To achieve high level of uniformity in Annealing and Tempering furnace
• Product: 3850T multifunction controller performs Multiloop PID control, setpoint profile generation, recipe management, batch record and remote access for monitoring and maintenance purpose
• Result: Achieved +/- 0.5 °C uniformity at 900°C holding temperature

Heat treatment of metal is an industrial, thermal and metalworking process used to alter the physical, and sometimes chemical, properties of a material. This process involves the use of controlled heating and cooling phases in order to achieve the desired result such as hardening or softening of a material.
Heat treatment techniques of metal include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching.
Furnaces used for heat treatment can be split into two broad categories: batch and continuous. Batch furnaces are usually manually loaded and unloaded, whereas continuous furnaces have an automatic conveying system for loading/unloading.
To ensure the homogeneity of temperature in the furnaces, control strategies with single or multiple zones are applied according to the size of the furnace.

Precise temperature control uniformity
Furnace: Gas heated furnace of app 10 x 6 x 5 mt (33 x 20 x 16 ft) with two temperature control zones (front / rear), 8 gas burners and related control unit. It is used for annealing and tempering processes up to 1300°C (2372°F) maximum working temperature.

The load is typically iron or steel components such as large valve body for O&G fields or components of gas turbines.

Considering the wide scope of different size and material of the load, specific temperature / time profiles (Recipe) need to be maintained together with precise PID heating-cooling temperature control of this dual zone furnace.

Batch report
The temperature profile of each heat treatment batch needs to be recorded as product quality document compliant to batch production.

Remote Monitoring
Remote access of control system is required for continues plant monitoring and preventive maintenance.

Multifunction PID controllers 3850T
Core functions

• Precise and multiloop PID control
• Recipe management
• Batch data recording
• Custom graphic interface

Valued added functions for user benefits

• Wide and brilliant graphic touch display for operator’s convenience
• Multiple functions bundled in one unit for simplicity and trouble-free operation.
• Precise and pre-configured multiloop loops PID controls reduce time of commissioning.
• Data monitoring and encrypted recording (archiving) for temper proof reports for audits
• Graphic display, process mimics, local visualization to make the control interface user friendly for operators.
• Menu driven configurator tool – no special skills required for the maintenance engineers.
• Quick set up and easy configuration to suit the application – saves time for production team.
• Ethernet VNC Remote access for remote monitoring and maintenance

3850T fully meets the requirement of precise and uniform temperature control, data recording and remote access.

Temperature control and temperature profile generation

• Two independent PID control loops of the upper and lower temperature control zones, driving the burner control unit via analogue output signal of 4-20 mA.
• Structured Recipe management of different thermal profiles with alphanumeric names for easy identification
• Precise and stable control of furnace temperature, maximum error of +/- 0.5 ° C (+/- 32.9 ° F) at the holding temperature of 900 ° C (1652 ° F)

Batch data recording

• Recording of the temperature and uniformity check values (Figure 2) with reference to the production batch
• Data store security in encrypted format
• Remote backup of recorded files
• Local and remote graphic display of recorded data

Operator interface

• Intuitive graphic display for convenience of operators
• Graphic mimic pages for overview of system conditions and temperature control (Figure 3)

Remote access

• Remote access to the Multifunction Controller for maintenance purpose (Figure 4)
• Monitoring of gas flow values for plant monitoring and cost consumption analysis