Mitigation of safety hazards at Blast Furnaces by adoption of automation & control

2. Mitigation of safety hazards at Blast Furnaces by adoption of automation & control A K Biswal DGM & HoG, C&IT Ayan Goswami AM, C&IT RDCIS

3. Various Safety Issues Associated with BF • Gas poisoning • Occurrence of heavy fumes & metal splashing at Cast House • Accidents at the charging side conveyor system • Electrocution during handling of switchgear equipments • Fire hazards in cable galleries • Explosion due to mal-operation in ladle placement • Increase of High Top Pressure of furnace beyond limit

4. Mitigation of various risk with Automation Gas Poisoning • CO is a very dangerous toxic gas which is the main ingredient of BF gas • The risks compounds when its concentration increases above 50 PPM & may results in fatal accidents • Usually, CO gas is found in hot blast stove area, furnace top area i.e. BLT & its above region due to leakage from gas valves, mal-operation or improper closing of valves due to failure of limit switches etc.

5. Mitigation of various risk with Automation Automation Intervention • The CO gas can be monitored regularly by placing portable CO monitoring devices (analog/ digital). It can also monitored through UAV with powerful sensors • Signals from these transmitters are transmitted through portable data-taker through wireless media • In the control room, the real-time CO values can be displayed at the HMI which are closely monitored by the operator • Even alarm annunciation can be generated when the CO gas level crosses the safe limit • In this way, continuous monitoring can be done & appropriate warning can be given to workmen before executing work in the gas prone area

6. Mitigation of various risk with Automation Remote monitoring of CO Gas in BF premises

7. Mitigation of various risk with Automation Heavy fumes & metal splashing at Cast House • During casting, mud-gun & drill machine are operated from electric & hydraulic control desks at the vicinity of tap-hole. • During cast opening & closing, hot metal splashes out form the furnace tap- hole and eventually falls on the control desks • There is a great chance of catching fire when the flashes comes in contact with the hydraulic oils • Frequent incidence of cable burning has been reported due to hot metal splashes. Sometimes, these may cause accidents in BF cast house premises.

8. Mitigation of various risk with Automation Automation Intervention • This problem has been solved at BF #4, RSP by introduction of RF based remote operation of mud-gun & drill machines. • In this case, operator operates the remote device from a safe distance with clear line-of-sight from tap-hole by saving himself from metal splashes. • It is a wireless transmission method which has reduced the break-down to a large extent (i.e. cable burning, damage of hydraulic valves) due to metal splashing. • To control the heavy fumes generated during casting, de-dusting motorized blowers/exhusters can be used for the extraction of fumes & dust, thus saving the workmen from suffocation & make the environment cleaner

9. Mitigation of various risk with Automation RF based remote operation of Mud Gun & Drill Machine implemented by P&C Group of RDCIS-Lead Person: I Banerjee, AGM

10. Implemented Scheme Portable Radio remote control Programming station PLC Receiver Panel Valve stand

11. Mitigation of various risk with Automation Accidents at the charging side conveyor system • Charging side of the conveyor system of the BF is a very critical & dusty area which comprises nos. of coke & ore belts. • Main conveyor is interlocked with the shuttle conveyors. • Many times during cleaning of conveyors by industrial spades, employees get entangled with the running conveyors and resulted in fatal accidents. Automation Intervention • To avoid that, control interlocking schemes in PLC /Relay logics have been provided for the motor drives in forms of pull cord limit switches, zero speed switches, belt-sway switches etc. which can be applied in emergency to stop the drive.

12. Mitigation of various risk with Automation Electrocution during handling of switchgear equipments • It has been observed over the years; few electrical accidents have taken place in BF area due to electrocution. • Large numbers of switch-gear panels are in operation for control of drives & valves • In a dusty atmosphere of BF, these panels need regular periodic cleaning. Despite that also due to dust accumulation, short circuit takes place during working at panel and resulted in flash & electrocution of the personnel working at the vicinity of the panel.

13. Mitigation of various risk with Automation Automation Intervention • Installation of smart controllers/ intelligent circuit breakers (MCBs, MCCBs, Intelligent ACBs) with type-2 co-ordination for all the drives for the faster clearance of short-circuit and earth-faults • Ensuring double electrical/ electronic earthing for the switchgear & PLC panels as per IE Rules & standards • Provision of IS marked insulation earth mat with high insulation in front of Switchgear panel

14. Mitigation of various risk with Automation Explosion due to mal-operation of ladle placement • During casting of hot metal, iron ladles are placed in metal side and metal is poured to the ladle through swiveling (hot metal) runner. • Runner changed to different positions through electrical drives & limit switches as per the position of the ladle on the railway track. • Sometimes, if the ladle is not placed properly in the bottom below the cast house & meanwhile, if operator wrongly positions the runner, then there is a possibility that entire metal will fall over the railway track. • If the hot metal comes in contact with water, blast may occurs with heavy metal flash percolating to cast house resulting in fatality/ critical accidents

15. Mitigation of various risk with Automation Automation Intervention • This can overcome, if RFID based ladle tracking is done for the proper positioning of the ladle on railway track at the bottom of the cast house. • From RFID signal, interlocking will be provided to control scheme of the motor circuit for swivelling runner. • Runner will not work unless the ladle is properly positioned. • In this way, during casting the mal-operation may be avoided & accidents can be prevented.

16. Mitigation of various risk with Automation Fire hazards in cable galleries • Cable galleries are one of the major fire prone area of BF. • Short circuits have resulted in many fire accidents in pasts. Being congested, fire easily propagates in cable galleries. • Being confined area, fires in cable galleries are discovered very late resulting in significant damages • In the past, it is observed that fire menace of the cable galleries has stopped the production for long period and created accidents & damage to the equipments.

17. Mitigation of various risk with Automation Automation Intervention • Microprocessor based fire alarm system with wireless signal transmission and provision of smoke/ fire detectors hooking the scheme at the control room’s HMI/ MIS. • Provision of emulsifier system in cable gallery • Automatic working of CO2 based fire extinguisher by sensing temperature • Application of fire retardant compounds & construction of sand barriers. • Proper dressing of electrical cables & wires with identification tag. Avoidance of loose connections which is a source of short circuit & fire.

18. Mitigation of various risk with Automation Increase of High Top Pressure of furnace ( venturi operation at GCP) • Sometimes due to number of reasons recoded below high top pressure increases beyond the top limit for few seconds, unless controlled immediately, it can damage the furnace shell & result severe accidents by metal eruption & gas leakage. • Failure of field instruments, electrics & hydraulic solenoids • Failures of PLC cards & amplifier cards. • Increase of water level inside venturi & mal function of Drain valve

19. Mitigation of various risk with Automation Automation Intervention • Control of high top pressure has been done by adding interlocks in the control circuits of bleeder valves placed at furnace top. • Bleeder valves will open automatically in that condition of high top pressure exceeding the limit for pre-set value with the timer set. • Simultaneously alarm will be created at control room HMI & hooter will be sounded, indicating emergency situation • Then fault rectification can be done by further diagnosis.

20. Thank You