Safety PLC
Bricmont provides a PLC-based safeguard system with new furnaces and upgrades for existing furnaces. With new standards from NFPA, a PLC-based safety system can be used in lieu of the old hard-wired safety circuit. This results in more reliable safeguards for the furnace, increased feedback to the operator on the HMI, increases, for some customers, in production time, and in some cases, reduced fuel usage.
The primary task of the new Safety PLC software is to monitor and control the safety system. The safety-rated PLC will provide the following combustion monitoring and control functions:
1. Provide Alarms for Abnormal Conditions
2. Shut Down and Minimization Routines for Control in the following areas:
• Over Temperature Conditions
• Electrical Power Failure
• Loss Of Communication
• PLC Failure
3. Control of Zone Combustion Fuel and Air Valves for Purge Cycle
4. Monitor the Status of the Furnace Safety System Equipment
5. First Occurrence Detection Routine for the Safety System
6. For ultra low NOx burners, the burners, and the ultra low NOx mode of the burners, can be started and stopped from the HMI automatically based on safety protocol, the temperature of the furnace and the fuel demand.
7. Burner status will be displayed on the HMI.
8. Sequential Firing can be added to side burners, particularly in the pre-heat zones. Sequential firing can be described as: burners are turned on as production rates/demand increase and turned off “in sequence” as demand decreases. There are two benefits to sequential firing. One, flame geometry improves. This helps to contribute to temperature uniformity across the length of the piece and decreases the “end-heating” effect. Two, fuel efficiency increases as the burners closest to the charge end shut off first as demand dictates. Therefore, more heat is transferred to the steel and less is lost to the flue.