Field of the Invention
An infrared camera based ladle condition monitoring system is disclosed, wherein automatic detection of hot spots in ladles used in the steel making industry is carried out to avoid ladle breakout.
This invention is a result of R&D project "Infrared Camera Based Ladle Condition Monitoring System" funded by Ministry of Steel, Government of India from Steel Development Fund (SDF).
Background of the Invention
Ladles are huge containers used in steelworks for transporting molten steel to other stages of production. The ladles are covered by refractory materials that are required to withstand the molten metal temperature. The quality and performance of refractory materials are vital to safety during the production process. The refractory materials are heat proof and also thermally shock resistant. Ladle breakout is a risky affair which is always present in steel making. Ladle breakout is associated with equipment damage and loss of production. In steel plants, the refractory lining of a ladle gradually wears out due to continuous exposure to the hot metal and also due to mechanical shock during shifting of the ladle. As soon as these refractory bricks get damaged, the outside ladle surface comes in contact with the hot metal and develops cracks. When the ceramic brick refractory materials fail, the hot liquid metal spills out across the plant floor causing damage of wiring, equipment and loss of productivity. In the event of ladle breakout the plant has to face a considerable downtime period and huge cost of repair. Further, there is a potential risk of injuries to working personnel and loss of life in the event of ladle breakout. If the ladle is not relined timely it will burst open

and tons of hot liquid steel at around 1600°C will gush out in the foundry floor. The ladle shell surface temperature is the reliable indicator of the condition of refractory lining of the ladle. The present invention aims for automatic detection of hot spots in ladles used in the steel making industry. The system is based on a group of a infrared cameras and vision algorithm to achieve detection and generation of alarms for each ladle when surface temperature crosses limit.
Research in the line of early detection of refractory wear out in ladle lining is being persuaded all over the world as a programme of preventive maintenance. The present practice in steel plants is mainly through the observation of hot spot with naked eyes, which fails to take preventive action long before a critical situation occurs. Surface profiling of ladle refractory surface by using a laser range finder is another approach for refectory thickness monitoring. Here the measurement principle is based on the time of flight of the laser pulse which measures the time taken to travel to the target and back.
The limitations associated with this type of surface profiling of ladle surface are:
(i) It is difficult to ascertain whether the surface profile belongs to metal or slag or refractory surface.
(ii) Stable measurement can be achieved after one and half hour of discharging of molten metal.
(iii) Surface profiling of side walls of the entire ladle surface is not possible.
(iv) Correction of the influence of the outer shell deformation of the

ladle makes the system hardware quite complex.
The method of judging the refractory wear out of the ladle can be carried out indirectly by analyzing the cold side shell temperature distribution on the ladle surface.
US 2006/0114966 Al to Optris GmbH discloses the construction of a devices for measuring spot temperature. US 2012/0086572 Al to Hon Hai Precision integrates a microcontroller with IR Camera for generating alarm. US 2010/0260374 Al to Kratz Quintos &. Hanson, LLP discloses a method for detecting damaged region such as cavity, crack or sand streak in concrete structures with the help of an IR camera. US Patent No. 6536944 Bl to Synyx Technologies Inc. discloses a technique for high throughput determination of phase charge points of combinatorial libraries of metal alloys with the help of infrared camera to monitor temperature dependent changes in emissivity / reflectivity change in alloys. US Patent No. 4247306 to Elkem Spigerverket discloses the determination of flaws in metal members by exposing it to high frequency heating and recording temperature profile by an IR camera.
However, the above-mentioned publications relate to developments in camera technology or utilize infrared camera for different purposes, while some relate to development in spot temperature measurement techniques which is different from IR camera technology.
Summary of the Invention
To judge the refractory wear out of the ladle it is proposed to develop an inspection system by using Infrared (IR) camera and associated hardware and software. The main features of IR camera based Ladle Condition monitoring system are:

a) Continuous 24x7 Operations.
b) Very low maintenance Cost.
c) High camera life of around 10,000 hour (MTBF-mean time between failure).
d) Totally non contact operation.
e) Minimum interference with the existing plant operation.
Brief Description of the Accompanying Drawings
Fig. 1(a) shows the image of a ladle taken with a CCD camera and Fig. 1(b) shows the thermographic image of the ladle with hotspot shown in green color.
Fig. 1(a) shows an image of a ladle, taken with a CCD camera.
Fig. 1(b) is a thermographic image of the ladle. Hot spot is shown in green.
Fig. 2 is a schematic diagram of the system according to the present invention.
Fig. 3 shows the wire diagram of ladle condition monitoring system.
Fig. 4 shows the position of camera 1 at the bottom of the pillar near to steel transfer cabin no. 2 of converter no. 2 Steel Melting Shop of Rourkela steel Plant.
Fig. 5 shows the position of camera 2 at the bottom of the pillar no. N-41 opposite to LHF-2A control room Steel Melting Shop - II of Rourkela steel Plant.

Fig. 6 shows the position of camera 3 at the bottom of the pillar near to the end of ladle transfer car line from converter no. 1 Steel Melting Shop - II of Rourkela steel Plant..
Fig. 7 shows the junction box near to camera No. 1 showing LIU and media converter.
Fig. 8 shows the media converters, power supplies, switch, LIU mounted inside the junction box in the control cabinet.
Fig. 9 shows the Graphical User Interface (GUI) of the MECLAD software developed for ladle monitoring. The hot spot generated by using Isotherm (green colour) is also shown in Fig. 9.
Fig. 10 shows the camera capturing the image of the slag tapping hole and giving a false temperature value, the error caused due to high ladle position relative to camera position.
Fig. 11 shows the second camera giving maximum temperature of 312.682°C which is due to presence of reflected image from crane surface, the error caused due to reflected hot metal temperature at crane surface.
Fig. 12 shows two ladles coming in the field of view of camera at the same time for which the camera gives, false reading, the error reading due to two ladles image in same frame.
Fig. 13 shows the day-wise maximum shell temperature variation of Ladle No. 10 Steel Melting Shop - II of Rourkela steel Plant.

Fig. 14 shows the day-wise maximum shell temperature variation of Ladle No. 12 Steel Melting Shop - II of Rourkela steel Plant.
Fig. 15 shows the day-wise maximum shell temperature variation of Ladle No. 18 Steel Melting Shop - II of Rourkela steel Plant. The dotted line show trend line which follows the expected increase in cold side shell temperature with the increase in ladle life.
Fig. 16 shows the thermographic picture of Ladle No. 12 Steel Melting Shop - II of Rourkela steel Plant.
Detailed Description of the Invention
The most convenient method of estimating the refractory life is from temperature distribution monitoring of the cold side of the container shell of the ladle with the help of infrared camera.
Here the machine vision based automatic detection of the hot spot of the ladle is carried out to avoid ladle breakout. The present invention aims for automatic detection of hot spots in ladles used in the steel making industry. The system is based on a group of infrared cameras and vision algorithm to achieve detection and generation of alarms for each ladle when ladle shell temperature crosses limit. Three cameras are placed at 120° apart to grab the thermographic image of the whole of ladle surface area. For automatic detection and recording the ladle is required to be positioned in front of three cameras.
The measurement principle is based on the estimation of spatial distribution of temperature over the cold side surface area of the ladle and detection of localized high temperature zone (hot spot). In Fig. 2 three IR cameras are placed at 120° apart to grab the thermographic

image of the ladle surface area. LIUs (Light Interfacing Units) are used for conversion of electrical signals to optical signal for transmission over optical fiber and back. The long wave infrared cameras are used because of the inherent advantages in the long wave range such as reduced background clutter (due to the effect of fires and flares), better performance in fog, dust, winter haze, carbon dioxide, hydrocarbons etc and higher immunity to atmospheric turbulence. For automatic detection and recording the ladle is required to be positioned in front of three cameras. A CCD camera is also used to ascertain the position of the ladle. All the four cameras are integrated via optical fiber cable into an industrial PC for image analysis and to generate alarm when the hot spot temperature rises above a certain predefined limit. Three long wave infrared cameras (Make: FLIR-Model A315) are commissioned at the following three locations near to LHF-2A control room of Steel Melting Shop - II of Rourkela Steel Plant considering the ladle to be inspected is positioned on ladle relining position near LHF-2A control room.
(i) Bottom of the pillar near to Steel Transfer Cabin No. 2 of Converter No. 2
(ii) Bottom of the. Pillar No. N-41 opposite to LHF-2A Control Room
(iii) Bottom of the pillar near to the end of ladle transfer car line from Converter No. 1
The distance between the camera and the ladle is around 15 meters. Power supply is provided at three camera locations for powering cameras and fiber optic converters. The industrial computer mounted inside the control panel is housed in LHF-2A control room. The wire diagram of ladle condition monitoring system is shown in Fig.3. Three long wave cameras are used to grab the three sides of a ladle. To protect the

camera from harsh environment of LHF area, it is housed inside an environmental enclosure and is cooled by plant air supply. Compressed instrument air is supplied to environmental enclosures for camera cooling. Advances in Infrared technology and development of long wave infrared focal plane array (FPA) facilitate the development of cost effective, low maintenance, compact IR imaging system. The cameras are compatible with GigE (Gigabit Ethernet) protocol. Gigabit Ethernet Cameras are used in applications that require multiple cameras, fast data transfer rates up to 1000 Mb/s, or long cable lengths. Gigabit Ethernet Cameras are imaging cameras that have been designed to interface with computer systems using GigE ports. Gigabit Ethernet Cameras may additionally be used in a number of locations far from a dedicated computer because of the long cable length allowed by Gigabit Ethernet technology. The camera control signals and the video signals are transmitted over the fiber-optic lines and connected to the processing industrial computer through Light Interfacing Units (LIUs) and media converters.
For proper positioning of the ladle, a CCD camera is being used which is positioned with one of the IR cameras. Power is provided at three camera locations for powering, cameras and fiber optic converters.
Fig. 4, Fig. 5 and Fig. 6 show the locations of three cameras in the LHF-2A area of Steel Melting Shop - II of Rourkela steel Plant.
The industrial computer mounted inside the control panel is housed in LHF-2A control room at SMS-II, RSP. Fig. 7 and Fig. 8 show the junction boxes containing media converters and LIUs for fiber-optic transmission.
The MECLAD (MECON Ladle Monitoring) software is developed using National Instruments LabVIEW development platform by using vision

development module. The hardware integration and software of the system is developed by Research and Development Division of MECON, Ranchi and the system was commissioned in SMS-II area of Rourkela Steel Plant in March 2014. Three IR cameras simultaneously capture images of three surfaces of the ladle for storage.
The software analyzes the radiometric images and detects any generation of hot spot on the ladle surface. The processing starts with continuous image acquisition and selection of Region of Interest (ROI) of the ladle image. As soon as the temperature of hot spot of any IR Camera exceeds the given limit, the alarm signal is triggered to activate buzzer and beacon light. The three IR cameras can be separately focused using Focus Control tools in the software. The Temperature scale and Isotherm can be activated in the software using button controls. The Camera parameters and Object parameters are to be fed in the software initially. The images from three IR cameras as well as from the CCD camera is shown in the GUI. The hot spot generated by using Isotherm (Green Color) is shown in Fig. 9. By using Isotherm the location of the hot spot on ladle surface can be found out The software gives maximum temperature, minimum temperature and average temperature of each face of the ladle.
After developing the software, temperature calibration was done by comparing the temperature readings obtained from the same camera using MECON developed Software and OEM (Original Equipment Manufacturer) software (FLIR Tools+ & FUR researcher software). The readings were found in limits of accuracy of the camera measurement capability.
Data from three designated Ladle Nos. 10, 12 and 18 were collected for analysis. The thermal images of the ladles are acquired before entry to

LHF. The day wise maximum shell temperature variations of the ladle are plotted as shown in Figs. 13, 14 and 15. For Ladle No. 10 rise in maximum temperature with the increase in ladle life shown as number over the marker of the plot was observed. For Ladle No. 12 increase in ladle shell temperature was observed after ladle life 13 crossed 380°C at ladle life 34 indicates deteriorating condition in refractory linings and called for immediate attention. The thermographic picture of Ladle No. 12 is shown in Fig. 16. However the ladle temperature again comes down which may be attributed to change in ladle holding time after tapping from BOF converter and before entering into LHF, tapping temperature at BOF as well as the accuracy in the measurement by thermal camera which is around ±2% of the temperature reading. The ladle was taken out of circulation at ladle life 38. Similar results were also observed for Ladle No. 18. Here also a peak around 380°C was observed. The dotted line in the plots of Fig.13, 14 and 15 show trend line which follows the expected increase in cold side shell temperature with the increase in ladle life.
During the execution and testing of the Ladle Condition Monitoring System at LHF (Ladle Heating Furnace) area of SMS-II of RSP it was found that the movement of Ladle is not taking place in a consistent manner. When the ladles are travelling at large height, the IR images do not come properly in the field of view of the three cameras. The camera captures only the lower portion of ladle. The camera captures the image of the slag tapping hole and gives a false temperature value which is shown in Fig. 10.
Sometimes the camera catches the reflected hot metal temperature in the crane beam for which camera gives false reading. In Fig. 11, the second camera is giving maximum temperature of 312.682 °C which is due to presence of reflected image from crane surface.

Sometimes two ladles come at the same time in field of view of camera for which the camera gives false reading which is shown in Fig. 12.
The following operational procedures are required to be adapted in order to enhance the effectiveness of the system:
(i) The hot side temperature of the ladle is required to be measured for using as a reference temperature just before placing it in front of the cameras. This can be made possible by measuring the temperature of the liquid metal at LHF (TLHF) and finding the temperature ratio as (TLHF-TMAX)/TLHF. The effect of ladle holding time on measured temperature can be minimized in this manner. The temperature ratio value is shown in Fig. 9.
(ii) The ladle is required to be kept in stand still condition in front of three cameras for a minimum period of 20 seconds in order to process three infrared images.
(iii) The minimum distance of 10 meters of ladle shell from cameras is required to be maintained in order to record the complete height and breadth of the ladle shell.
(iv) No heat source with comparable ladle shell temperature other than the ladle to be measured should come in the field of view of the thermal cameras.
As per AISE Technical Report No. 9, the cold face for ladles constructed with a carbon steel shell should not exceed 400°C in order to prevent permanent ladle shell deformation. In view of the above observations and technical recommendations enumerated in points (i)-(iv) above, the

system is found to be effective for temperature monitoring of the ladle shell.

WE CLAIM :
1. A ladle inspection system comprising Infrared (IR) camera and associated hardware and software.
2. The system as claimed in claim 1, wherein said system is based on a group of infrared cameras and vision algorithm to achieve detection and generation of alarms for said ladle when ladle shell temperature crosses limit.
3. The system as claimed in claims 1 or 2, wherein three cameras are placed 120° apart to grab the thermographic image of the whole of ladle surface area.
4. The system as claimed in claims 1 to 3, wherein for automatic detection and recording the ladle is required to be positioned in front of three cameras.
5. The system as claimed in claims 1 to 4, wherein the measurement principle is based on the estimation of spatial distribution of temperature over the cold side surface area of the ladle and detection of localized high temperature zone (hot spot).
6. The system as claimed in claims 1 to 5, wherein LIUs (Light Interfacing Units) are used for conversion of electrical signals to optical signal for transmission over optical fiber and back.
7. The system as claimed in claims 1 to 6, wherein long wave infrared cameras are used for reduced background clutter, better performance in fog, dust, winter haze, carbon dioxide, hydrocarbons, and higher immunity to atmospheric turbulence.

8. The system as claimed in claims 1 to 7, wherein a CCD camera is also used to ascertain the position of the ladle.
9. The system as claimed in claims 1 to 8, wherein all four cameras are integrated via optical fiber cable into an industrial PC for image analysis and to generate alarm when the hot spot temperature rises above a certain predefined limit.
10. The system as claimed in claims 1 to 9, wherein three long wave infrared cameras are commissioned at three pre-determined locations.
11. The system as claimed in claims 1 to 10, wherein the distance between the camera and the ladle is around 15 meters.
12. The system as claimed in claims 1 to 11, wherein power supply is provided at three camera locations for powering cameras and fiber optic converters.
13. The system as claimed in claims 1 to 12, wherein an industrial computer is mounted and three long wave cameras are used to grab the three sides of a ladle.
14. The system as claimed in claims 1 to 13, wherein the camera is housed inside an environmental enclosure and cooled by plant air supply to protect the camera from harsh environments.
15. The system as claimed in claims 1 to 14, wherein compressed air is supplied to environmental enclosures for cooling of camera.
16. The system as claimed in claims 1 to 15, wherein the cameras are compatible with GigE (Gigabit Ethernet) protocol.

17. The system as claimed in claims 1 to 16, wherein the camera control signals and the video signals are transmitted over the fiber-optic lines and connected to the processing industrial computer through Light Interfacing Units (LIUs) and media converters.
18. The system as claimed in claims 1 to 17, wherein for proper positioning of the ladle a CCD camera is used which is positioned with one of the IR cameras.
19. The system as claimed in claims 1 to 18, wherein power is provided at three camera locations for powering cameras and fiber optic converters.
20. The system as claimed in claims 1 to 19, wherein the software analyzes the radiometric images and detects any generation of hot spot on the ladle surface.
21. The system as claimed in claims 1 to 20, wherein the processing begins with continuous image acquisition and selection of Region of Interest (ROI) of the ladle image.
22. The system as claimed in claims 1 to 21, wherein an alarm signal is triggered to activate buzzer and beacon light as soon as the temperature of hot spot of any IR Camera exceeds the given limit.
23. The system as claimed in claims 1 to 22, wherein the three IR cameras can be separately focused using Focus Control tools in the software.
24. The system as claimed in claims 1 to 23, wherein the temperature

scale and isotherm are activated in the software using button controls.
25. The system as claimed in claims 1 to 24, wherein the camera
parameters and object parameters are fed in the software and the
images from the three IR cameras as well as from the CCD camera are
shown in the Graphical User Interface, and by using Isotherm the
location of the hot spot on ladle surface can be found.
26. The system as claimed in claims 1 to 25, wherein the hot side
temperature of the ladle is required to be measured for using as a
reference temperature just before placing it in front of the cameras.
27. The system as claimed in claim 26, wherein the hot side temperature of the ladle is measured by measuring the temperature of the liquid metal at LHF (TLHF) and finding the temperature ratio as (TLHF -TMAX)/TLHF.
28. The system as claimed in claims 1 to 27, wherein the ladle is kept in stand still condition in front of three cameras for a minimum period of 20 seconds in order to process three infrared images.
29. The system as claimed in claims 1 to 28, wherein a minimum distance of 10 meters between ladle shell and cameras is required to be maintained in order to record the complete height and breadth of the ladle shell.