ENHANCING OPERATIONAL SAFETY AND LOGISTICAL EFFICIENCY FOR TORPEDO LADLES Tapas Dasgupta* and Vinay Prasad** * BF Deptt, Bhilai Steel Plant, SAIL, Bhilai (C.G.) ** IT Services, MECON Ltd., Ranchi Abstract Bhilai Steel Plant will employ torpedo ladles for the first time to transfer hot metal from blast furnaces to new steel melting shop in the ongoing modernization & expansion plan. Thermographic and visual imaging with advanced automation are envisaged to provide a pro-active platform for operational safety and logistical efficiency of torpedo ladles. Thermographic imaging will be used for assessment of refractory lining in real time as dire consequences might ensue if hot metal were to leak. Operational logistic efficiency will be enhanced by utilizing visual cameras for spout inspection resulting in reduced turn over time for ladles. Enhancement in life of refractory is envisaged by evenly distributing direction of pouring of individual ladles by history based scheduling. Keywords Torpedo ladle, thermographic image, visual imaging, safety, operational efficiency INTRODUCTION Steel Authority of India Limited (SAIL) is currently undergoing a modernization & expansion plan (MODEX) to increase its hot metal (HM) production capacity from around 15 million tons per annum (MTPA) to about 23.46 MTPA in the first phase and 26.18 MTPA in the second phase. Under this plan, in the first phase, Bhilai Steel Plant (BSP) will see its HM capacity go up to 7.5 MTPA. Major new facilities envisaged in the plan for BSP include Steel Melting Shop III (4.0 MTPA), Blast Furnace-8 (4060 m3), etc. Hitherto, open top ladles have been used in BSP for transfer of hot metal. However, torpedo ladles, having a capacity of 350 tons of hot metal have been envisaged to transfer hot metal from Blast Furnace-8 (BF8) and existing blast furnaces to Steel Melting Shop-III (SMS-III). Operational safety can be an issue with torpedo ladles as any hot metal leak may seriously affect the operation of both blast furnace (BF) and steel melting shop.
This is especially true for BSP, as the brown field expansion provides no possibility of an alternate route. Because of layout limitations, the required regular after-pouring spout inspection at Torpedo Ladle Repair Shop (TLRS) will result in increase of number of torpedo ladles in circuit. Further by enhancing campaign life for torpedo refractory, operational as well as capital costs can be reduced. An advanced automation platform, namely Torpedo Ladle Management System (TLMS) has been envisaged as a real time automated system aimed to target above issues. A brief account of major functions is presented below. THERMOGRAPHIC IMAGING The Torpedo Ladle Car (TLC) will be monitored, online and in-motion, by two numbers of thermal imaging cameras installed at Thermal Imaging Station (TIS). These cameras will be installed on either side of tracks (Fig. 1) so as to take a complete snapshot of the whole ladle. Unified thermographic image of the complete ladle body will be created by using images from the two cameras. Unified image will be tagged with identity of the ladle and will be used for analysis as well as stored in the history database for comparison purposes. One portable thermal imaging camera with provision of storage will be used at pouring locations in SMS-III, for manually capturing images of fully tilted ladle. Subsequently, the portable camera will be hooked on to the TLMS network to transfer this information to the main server. In case of wear out of refractory, temperature of the metal body of ladle will increase and will be automatically detected by themorgraphic imaging. In case temperature increases beyond a certain threshold, the ladle will be taken for repair of refractory. This will ensure that no refractory wear out will go unnoticed and leakage of hot metal can be avoided. This will also ensure that ladles are not taken for relining, prematurely.
TI Camera TI Camera Figure 1: Schematic for arrangement of thermal imaging cameras AUTOMATED SPOUT INSPECTION Spout or mouth of the torpedo ladle may get blocked by deposits during the pouring process. Hence spout inspection for any abnormalities is normally carried out after each pouring operation. A special platform is required for this inspection, which in BSP s case will only be available at the TLRS. However taking TLC to TLRS will increase turn over time of ladles and will result into taking more TLCs into circuit (Fig. 2). HM Dump Pit BF 8 SMS III TLRS Existing BFs Figure 2: Indicative layout of facilities (not to scale)
In order to optimize on this, an automated spout inspection will be provided. One visual imaging camera each will be employed on the top of two tracks at TIS for the purpose of automated spout inspection (Fig. 3). Figure 3: Schematic for Visual Imaging Camera Every time any TLC returns from SMS-III after emptying, the automated spout inspection system will take an image of the spout opening while the TLC is in motion. Based on the condition of spout, the TLC may be advised to return to TLRS for further inspection / repairs, or may be taken to blast furnace for next cast. A history of abnormal spout images along with TLC identity will be maintained by TLMS for further analysis. REVERSAL TRACKING Pouring of hot metal at steel melting shop takes a heavy toll of the refractory near the spout of torpedo ladle. Refractory wear out at the spout will be appreciably higher on the side of pouring as compared to the other side. Therefore, if direction of pouring or tilting can be evenly distributed, it can result into increasing availability of the ladle. To achieve this objective, drives used for tilting of ladles will be interfaced to the system. TLMS will maintain history of the side of tilting of individual ladles at SMS-III. Accordingly it will advice incoming TLC regarding the selection of track for placement and side of tilting.
REFRACTORY & MAINTENANCE TRACKING Refractory tracking for TLC will comprise of tracking history of all information regarding refractory lining viz. schematic of refractory lining for TLC, heating, cooling, thermal image during operation, de-bricking, etc. The system will also keep a track of the number of times the TLC is sent for maintenance in addition to the number of heats after which it is sent for maintenance. The reason for taking TLC into maintenance will also be tracked. This data along with other information available in the system such as tilting history, etc. will be available to the technologist for assessment and to compare various kinds of refractory materials and lining techniques, and employ the best suited option for the application. OTHER FUNCTIONALITIES Material Tracking When a TLC is positioned at blast furnace and is being filled with hot metal, through interfacing with the BF system, cast number of the tapping will be tagged with the TLC. Further by interfacing with the weigh bridges and laboratory information system, weight and hot metal analysis will also be captured. This information will then be transferred to SMS-III automation system for further usage there. TLC Position Tracking TLC identification system, employed at vantage identified locations (Fig. 5), will update position of individual TLCs in the plant. Further positioning system will give information regarding direction of travel. By assimilating this information, a complete map of TLC locations will be made available to the operating personnel for logistics. Level Monitoring at Blast Furnace Frequency modulated continuous wave (FMCW) based level measurement system will be provided at filling locations in cast house of blast furnaces for measuring hot metal level in TLC during tapping. An audio-visual alarm will be provided to signal almost-full and full status of TLC. In addition, large sized
LED based display will also be employed for continuous display of hot metal level in the TLC which is receiving hot metal. Scheduling & Sequencing Scheduling and sequencing of TLCs will be done taking into consideration various operational aspects such as minimum number of TLCs available at BFs, time for inspection, time required for pouring at SMS, dumping pit, pig casting machine, etc.; time for travel between various points viz. BFs, SMS, TLRS, HM dumping pit, pig casting machine etc. Advice for placement at blast furnaces will also be generated to ensure symmetric wear-out of refractory. COMPUTATIONAL & FIELD INTERFACE SETUP TLMS is envisaged to be implemented in client-server architecture. TLMS server will be used for data acquisition, processing, analysis, history and providing inputs for user interface. This server will be deployed at TLRS. Operator stations distributed at all necessary locations will provide the user interface. The thermal imaging and visual imaging cameras will be interfaced on Ethernet to the TLMS server. For interface with field instruments and sensors, PLCs will be deployed in a distributed configuration and TLMS server will interface with it. The torpedo ladles will be transporting hot metal from BF8 and two existing blast furnaces to SMS-III. Thermographic and visual imaging will be carried out at TIS. Field instruments and sensors will be employed at all these places in addition to TLRS and hence PLC setup will be provided at all these locations. A fiber optic Ethernet ring will run through all the locations and provide necessary connectivity. TLC IDENTIFICATION AND POSITIONING Radio Frequency Identification (RFID) technology will be used to identify TLCs at various locations. Identity programmed RFID tags will be installed on the outer body on either side of each TLC. RFID readers will be installed at strategic locations so as to identify the TLC. RFID tags and readers will be fully redundant to allow fault tolerance. Positioning will be done using track based sensors. These sensors will be deployed such that they enable correct centering at pouring and tapping locations
and will also be capable of determining the direction of movement of TLC. Necessary signaling to enable correct centering will also be provided near the track. CONCLUSION The benefits expected from the TLMS system are enumerated as follows: o Zero operational accidents due to hot spots in refractory lining and avoidance of its consequences in terms of time, material & labour. o Increased refractory lining campaign and ability to do partial relines, leading to reduction in specific consumption of refractory. o Stable on-track performance due to symmetric refractory wear-out o Enhanced operational efficiency o Planned refractory relining maintenance schedule o Reduction in cost towards refractory maintenance o Improved confidence level ACKNOWLEDGMENT The authors would like to gratefully acknowledge the contribution of Mr. S. K. Verma & T. K. Biswas, DGM I/c (IT Services) of MECON, Ranchi, Piyush Kumar, S. K. Bose & Ravi Shankar of INCOS, BSP, Bhilai; H. N. Rai, C. K. Narayanan & Gujju Srinivas of Blast Furnaces, BSP, Bhilai and C. Vineet Rao of Raw Material Division (RMD) SAIL, Kolkata (earlier with BSP). REFERENCES 1. B. Wileman, S. Rickards, Process imaging solutions for the steel industry, Millennium Steel, 2008, pp.49 52. 2. FLIR Systems AB, Thermography at iron and steel works: Krupp Mannesmann ironworks use FLIR Systems ThermaCAM P series to inspect, maintain and observe production processes., FLIR Application Story, 1 2. 3. IRCON, Torpedo car inspection software product information listing, 2001, pp.1 2. 4. Land Instruments International, Land ladle safety system - automated torpedo car refractory monitoring, Application Bulletin AB LSS01, pp.1 7. 5. Mikron Infrared, Torpedo ladle management, Application Notes, pp.1. 6. Projects Directorate Steel Authority of India Limited, Modernisation and expansion plan of SAIL, Internal document.
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