"A SYSTEM FOR TIME-STAMPED FAULT DETECTION OF COBBLE IN ROLLING MILLS AND THE METHOD THEREOF"
FIELD OF INVENTION
The present invention discloses a system and method for an online time stamped fault
detection of the cobble in rolling mills. More particularly, the present invention relates to
a merchant miff protecting system wherein wrecked (cobbled) elongated metallic
material undergoing rolling (e.g. bars or rods) are located immediately without forming
any damage to the production line and therefore can be easily-removed.
BACKGROUND OF THE INVENTION
Commercial steel bars are usually fabricated on a merchant or bar mill. The method of
fabrication comprises passing the rough steel slab or billet at an elevated temperature
through a series of grooved rolls mounted on a succession of rolling stands. One
common system in use today is the straight-away continuous rolling mill, employing a
plurality of rolling stands in a straight line.
As the steel bar passes from its initial or roughmg stages to its final form, the cross-
section of the steel bar is gradually reduced by successively reducing the dimensions of
the grooves on successive rolls. The bar is carried from stand to stand by a carry-over
trough which extends between a pair of adjacent rolling stands. The rolling process is
performed at a very rapid rate, most often around 3,000 feet per minute, although there
are some mills in the 10,000 to 11,000 foot per minute rate.
Each roll stand is equipped with electrical switches, gauges, hoses, small pipes, etc.
required for the mill's operation. Mill personnel work near the mill while it is in operation.
It is not uncommon in the operation of the mill to have a wreck (cobble). Cobbles are
usually caused by the failure of a rod, exiting an upstream stand, to properly enter the
next stand downstream. The result is a mass of hot, plastic, steel bar mrashing about at
the location of the cobble. This is dangerous both to personnel and to equipment, and

has caused prolonged shutdowns of the rolling operation to cut up and remove the
cobble.
In a continuous metal casting system for forming rod wherein molten metal, is
continuously poured into a casting machine, extracted from the casting machine in solid
form and passed through a rolling mill where it is elongated and reduced in diameter and
subsequently formed into a coil, it is usually difficult to terminate the continuous
operation of the system on short notice, as when some malfunction of the system
occurs. For instance, when a cobble occurs in the rod formed from the cast bar at a
location in the system between the last roll stand of the rolling mill and the coiled rod, the
rod usually will continue to pass from the last roll stand for a short time interval before
the operation of the rolling mill can be terminated. During this time interval the cobble,
which may have occurred in the coiling mechanism or in the housing of the rolling mill, is
likely to cause the movement of the rod from the rolling mill housing to terminate while
the rod will continue to pass through roll stands of the rolling mill. The rolling mill will tend
to push the rod from the last roll stand, and since the rod is relatively flexible and tends
to bend freely the rod tends to bend and fold before it passes from the rolling mill
housing. A single bend or fold of the rod in the housing witt cause the rod to play out
from the last roll stand within the housing of the rolling mill, so that the rod tends to
accumulate within the rolling mill housing before the operation of the rolling mill is
terminated. The result is that the roll stands, spray nozzles, guide bardware and other
parts in the housing are subject to being damaged by the rod playing out within the
housing, and the accumulation of a mass of rod is difficult to remove from the housing
and from around the equipment in the housing.
In the past, efforts to protect against the cobble included shields to cover the exposed
mechanical and electrical apparatus. Not only was this completely unsatisfactory for
protection of personnel, but also the need for visual and manual access to this apparatus
necessitated cutting holes in the shields, with a resultant loss in efficiency.
One result of a sudden mill shutdown has been to produce unworkable metallic material
not only at the location of the cobble, but also at (and between) each of the upstream
mitt stands. This material may itself be cobbled (wrecked by failure to overcome the
inertia of the rapidly moving bar) or may have cooled too much for further rolling. In

either case the material must be cut up and removed from all of these locations before
the mill can be returned to an operational state, further adding to mill shutdown time.
SUMMARY OF INVENTION
Briefly described, the present invention compnses a online cobble relief / detecting
mechanism for a rolling mill that functions to relieve the buildup of rod within the rolling
milt housing due to the malfunction of a component of the system downstream from the
last roll stand of the roiling mill.
Therefore such as herein described the main objective of the invention is to find the
exact location of the cobble and pin point the cause of the same by analyzing the data
stored in the DVR.
For achieving the discussed objective there is provided a system for time-stamped fault
detection of cobble in rolling mills comprising of: CCD (Charged Coupled Device)
cameras placed at strategic locations; Multi-channel Digital Video Recorders (DVR) to
record the real time images of mill operation; a display for the viewing of the images
captured from the CCD camera and processed by DVR on continuous basis; and a
memory for recordal of the said images
Also provided a method for time-stamped fault detection of cobble in rolling mills
comprising the steps of: capturing the real time images of the operation of the rolling mill
employing a plurality of CCD (Charged Coupled Device) cameras placed at strategic
locations; recording of the real time images of the mill operation employing multi-channel
Digital Video Recorders (DVR); displaying the real time images captured from the CCD
camera and processed by DVR on continuous basis, recording the captured real time in
a memory with a date and time stamp.
Thus, further object of this invention to provide a cobble relief mechanism for a rolling
mill that reduces the hazard of damaging the components of the rolling mill that might
occur if the rod is allowed to accumulate within the rolling miff housing.

Another object of this invention is to provide a means of reducing the hazard of
damaging the components of a roiling mill while allowing the rolling mill to continue its
operation in a continuous casting system when a cobble has occurred in the system
downstream from the last roll stand of the rolling mill.
As per another object of the present invention the system is programmed to store the
information with date and time stamped and further once the problem is identified
accurately, rectification action is takerr-up immediately to make the mill avaitabte for next
operation.
As per one of the exemplary embodiment of the present invention ther is provided
additional CCD cameras at the charging and discharging ends of re-heating furnaces for
enhancing the operational flexibility at the shop floor and reducing the man hour cost
substantially.
As per another exemplary embodiment of the present invention there is provided a
database, which records the history of the analysed faults of a rolling mill and also
comprises of general records of faults for reference
Other objects, features, and advantages of the present invention will become apparent
upon reading the following specification, when taken in conjunction with the
accompanying drawing,
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 illustrates the layout of re-heating furnaces and location of pulpits with respective
field of view in accordance with the present invention;
Fig.2 shows the formation of cobble at rolling stand no.9 in the merchant mill in
accordance with the present invention;
Fig. 3 illustrates the complete layout of merchant mill including the furnace and mill area
with the locations of CCD camera installed in position in accordance with the present
invention;
Fig 4 illustrates the general scheme for viewing red hot billet moving at high speed on
dark roller table in accordance with the present invention;

Fig.5 illustrates the clutter free wiring diagram showing VDA, Quad Switch, DVR, Monitor
& LAN in accordance with the present invention;
Fig.6 illustrates the live images of cobble at CT1 and Stand 9 with date & time stamped
in accordance with the present invention;
Fig.7 is the graph illustrating the section-wise percentage cobble generation at MM, BSP
in accordance with the present invention.
DETAILED DESCRIPTION
Merchant Mill (MM) of Bhilai Steel Plant (BSP) utilizes three pusher type re-heating
furnaces and twelve stands for the production of various finished sections such as
rounds, TMT, angles, channels, beams and flats from the input material known as bitfet
on continuous basis. The layout of re-heating furnaces and location of pulpits with
respective field of view is shown in Fig 1. In general, any two out of three re-heating
furnaces are being used where charging and discharging of biltet is controltecl from
either of the two available pulpits. In the present configuration, none of the pulpit
operators can monitor furnace operation efficiently because of view restrictions; for
example if re-heating furnace 1 and 3 are in operation then the operators either at pulpit
2A or at 2 cannot view charging end of re-heating fumaces 1 or 3 clearly. This leads to
improper charging of billets into the furnace causing cross falling and jamming of red hot
billet at the discharge ends which in turn cause delay in operation affecting mitt
productivity severely.
Besides, rolling operations at stand 8, 9, 10, 12 and Chain Transfer 2 (CT2) are very
critical and cobble prone in nature. A cobble is a phenomenon which occurs when fast
moving red hot billets hits any obstruction on its way either at the roller tabte or at the
stands during a rolling process. This may be due to various reasons like misalignment,
over speed, presence of another billet in front of an incoming billet etc. Fig.2 shows a
typical cobble generation at a rolling stand of merchant mill. In the event of a cobble, the
mill stops and the affected zones are examined thoroughly to detect and clear the cause
of such catastrophic phenomenon. Hence, considerable time is lost reducing mill
availability and production.
In order to enhance operational flexibility and to reduce mill delay, a scheme for
monitoring the process and also to find the cause of cobble through image processing

technique has been introduced in accordance with the present invention. The system is
integrated by installing CCD (Charged Coupled Device) cameras at strategic locations
along the mill with multi-channel Digital Video Recorders (DVR) to record the real time
images of mill operation on continuous basis for fulfilling the following objectives.
(a) Viewing charging/discharging ends of reheating furnaces from pulpit 2A and ensure
single pulpit operation.
(b) Process monitoring in mill area and cobble analysis.
The recorded information in DVR can easily be analyzed to pinpoint the cause of cobble
if any, for immediate rectification and thereby make the mill available for operation at the
earliest. Additionally, with the introduction of CCD camera at the charging end of re-
heating furnace 1, single pulpit operation for charging of billets from pulpit no. 2A has
been made possible and as shown in Fig 3, which leads to better process control and
greater operational flexibility at the shop floor Incorporation of such a modem process
monitoring and cobble analysis system has improved the mill availability substantially,
leading to overall improvement in productivity, The system is quite inexpensive when
compared to the cost of mill delay due to cobble generation.
As discussed above, the main objective of the invention was to find the exact location of
the cobble and pin point the cause of the same by analyzing the data stored in the DVR,
the system is further programmed to store the information with date and time stamped,
therefore, the operator can easily search and find the location and the reason for cobble
through ultra slow motion playback option which otherwise could not be noticed easily in
naked eyes during a high speed rolling operation. Once the problem is identified
accurately, rectification action is taken-up immediately to make the mill available for next
operation. Thus, by installing this system delay on account of cobble generation has
been reduced considerably which leads to the improvement of mill availability
significantly.
Additionally, introduction of CCD cameras at the charging and discharging ends of re-
heating furnaces has facilitated single pulpit operation from pulpit no. 2A, which has not
only enhanced operational flexibility at the shop floor but also reduced the man hour cost
substantially.

Selection of CCD camera for image formation
For rolling mill application, the requirement was to view very hot and bright object
moving at a high speed clearly and also to record the same for playback at slow speed
with searchable image functions including date and time stamped on it. Viewing of
images of red hot billet (1150-1200°C) moving at an average speed of 10-12 meter per
minute (mpm) clearly without smearing and blooming is not an easy task. This is
because of the change in Refractive Index (Rl) of the environment (air) just above the
hot object. In fact, there is a Rl gradient whose value changes from low to normal as the
temperature of the space attains high (350-40 0°C) to normal room temperature (50-
65°C) between the object (billet) and camera. It may be noted that the distance between
the object and the CCD camera is also not fixed which varies from location to location
depending upon site conditions. The minimum distance between the object and the
camera was found to be 5m and maximum distance was 20m approximately. In such
condition, the light rays from the object undergoes multiple deviations before reaching
the camera lens which produces blur images at the display unit. Therefore, several CCD
cameras with different/varied technical specifications were tested at site for obtaining
sharp image of the fast moving hot billet and it was found that though the clear
panoramic view was obtained in most of the low light cameras, but the close up views of
hot objects were obtained only in cameras having sense up and high light restraining
features. The general scheme for viewing red hot billet moving at high speed on dark
rotter table is illustrated in Fig 4. Additionally, critical parameters of the CCD camera viz.
(a) Gamma correction (b) Smear rejection ratio (c) Peak detecting Mode (d)
Instantaneous response etc were optimized for simultaneous viewing of bright steel billet
moving on dark roller table clearly (Fig.4). Besides, 48 zones Back Light Compensation
(BLC), Automatic Gain Control (AGC), white balance, intelligent to restrain any high light
conditions, wide dynamic features were also considered to get the images of desired
quality. All these were necessary to monitor and record the movement of hot billet
precisely to identify the location and cause of cobble generation during a rolling process.
Digital Signal Processing (DSP) for cobble detection
Once the images of acceptable quality were obtained, the signals from CCD cameras
were fed directly to Digital Video Recorder (DVR) via Video Distribution Amplifier (VDA).

The clutter free wiring diagram showing VDA Quad Switch, DVR, Monitor & LAN is
illustrated in Fig 5.
The Digital Video Recording (DVR) is the nerve centre of any image processing system
where the images are recorded on a digital medium, generally a hard disk. There are
many important issues, which were considerec for making a reliable system as digital
video recording is a process intensive multitasking application and can tax the most of
the robust systems if not configured properly. Some of the important features that need
to be considered before selecting a DVR are: PC /non-PC based system, video capture
card, frames/sec/channel, CODEC (Image compression & decompression technique)
comparison between MPEG 1/2/4, MJPEG, Wavelet JPEG and the latest H.264,
network compatibility, operating system (windows/Linux), Intelligent motion detection,
quick search function for data & image, slow/fast playback etc. A 16 channel Linux
based DVR system with MPEG-4 image compression /decompression technique was
chosen for this application. The DVR adopts on-chip technology for storing image data
on real time basis which is termed as simultaneous viewing and recording at 25 frames
per sec. per channel. The system utilizes one processing chip per camera to produce
the best possible picture quality in both split and full screen display mode maintaining a
balance between image contrast and brightness to an optimum level. The installed
system can able to transmit image over LAN using TCP/IP protocol and its intelligent
motion detection feature is also configured for each channel to maximize system hard
disk efficiency by ignoring periods of non-activity Images were viewed as live display of
rolling drive and recorded on motion detection node. This has two basic advantages,
firstly, only the relevant images are recorded making it easy to search and analyse and
secondly it saves the critical hard disk space. The user-friendly system software enables
quick image search and easy playback through ir -built data search function. In the event
of cobble, the operator can playback the recorded image in slow-motion (1/4X, 1/8X,
1/16X etc) by entering date and approximate time to find the reason for such
catastrophic phenomenon. This eventually helps to clear the fault and set up the mill
correctly for next operation at the earliest. Additionally, a database on cobble generation
can also be archived for future reference. The database therefore records the history of
the analysed faults with data and time stamp of the rolling mill under usage and also
some general records of faults for a reference during operation. Fig. 6 shows various

types of cobble captured through the system at Merchant Mill, BSP with date and time
stamped on it for easy analysis.
DVR-based CCD camera systems for rolling mill applications are found to be very useful
for efficient monitoring of the process where intelligent automation schemes such as
cobble analysis, tracking of strips, no material condition etc can easily be introduced
through simple DSP techniques. Specially, analysis of cobble generation is not very
obvious and cannot be anticipated or conceived easily by deploying similar system.
Although, in modern steel plants CCD camera systems were successfully used mainly
for process viewing of plant machineries where objects are either stationary or moving at
a slow speed in normal room temperature conditions. The present application was
considered for the Merchant Mitt of Bhilai Steel Plant where red hot billets are rotted at a
high speed to produce finished products of different shapes and sizes on continuous
basis. The system cost is comparatively low with high quantified benefits, leading to its
justification on the return on investment scale. Dasign of the system is such that it can
be deployed to any rolling mills for viewing of hot objects and can easily be extended
while the cost remains proportional to the number of cameras approximately.
• Additional information
Techno-economic evaluation
• It is revealed from basic plant data that cobble generation is maximum at Chain
Transfer (CT) 1 & 2 during rolling of angles and channels. In case of TMT bars
the maximum cobble takes place between stands 6-8 and in stand 12 as
refereed from Fig.7.
Basic Rant Data
Average rolling rate; Rt (Ton/hr) 84.6
Source: Annual statistics 2004-05, BSP
• Plant Operating Data ( Before Innovation)
Average delay due to cobble & cross falling per annum; DC1 hrs 240
Source: Annual statistics 2004-05, BSP

• Plant Operating Data (After Innovation)
There is 10 % reduction in delay time (average) after installation of the system
• Cost Data
Contribution Margin; CM
{Net sales realization (NSR) Estimated- Variable cost (VC)): US$ 350
• Procedure of Calculations
10% reduction in delay after installation of the system; DC2;
(DC2 = 10%xDC1) hr 24
Therefore, increase in mill availability; MA ;(MA = DC 2) hr 24
Extra tonnage production; Et; (Et= Rt x MA) Ton 2030.40
Total saving on account of extra tonnage production; Ts (Ts = EtxCM)
US$ thousand 710.64
• Project Cost (PC) US$ thousand 167.50
• Annual Benefit (AB) US$ thousand 710.64
Benefit to Cost Ratio (BCR) [ AB/PC} 4.24
It is revealed from basic plant data that cobble generation is maximum at Chain Transfer
1 & 2 during rolling of angles and channels. In case of TMT bars the maximum cobble
takes place between stands 6-8 and in stand 12
• Basic Plant Data
Average rolling rate; Rt (Ton/hr) 84.6
Source: Annual statistics 2004-05, BSP
• Plant Operating Data (Before Innovation)
Average delay due to cobble & cross falling per annum; DC1 hrs 240
Source: Annual statistics 2004-05, BSP
• Plant Operating Data (After Innovation)
There is 10 % reduction in delay time (average) falling after installation of the
system

• Cost Data
Contribution Margin; CM
INet sales realization (NSR) - Variable cost (VC)] : US$ 350
Source: Cost data book 2004-05, BSP
• Procedure of Calculations
10% reduction in delay after installation of the system; DC2;
(DC2 = 10% x DC1) hr 24
Therefore, increase in mill availability; MA ;(MA = DC 2) hr 24
Extra tonnage production; Et; (Et= Rt x MA) Ton 2030.40
Total saving on account of extra tonnage product on;
Ts (Ts = EtxCM) US$ thousand 710.64
• Project Cost (PC) US$ thousand 167.50
• Annual Benefit (AB) USS thousand 710.64
Benefit to Cost Ratio (BCR) [ AB/PC} 4.24
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it has been
presented for purposes of illustration and description and is not intended to be
exhaustive or to limit the invention to the particular embodiments and applications
disclosed. It will be apparent to those having ordinary skill in the art that a number of
changes, modifications, variations, or alterations to the invention as described herein
may be made, none of which depart from the spirit or scope of the present invention.
The particular embodiments and applications were chosen and described to provide the
best illustration of the principles of the invention and its practical application to thereby
enable one of ordinary skill in the art to utilize the invention in various embodiments and
with various modifications as are suited to the particular use contemplated. All such
changes, modifications, variations, and alterations should therefore be seen as being
within the scope of the present invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are fairly, legally, and equitably
entitled.

We claim:
1 A system for time-stamped fault detection of cobble in rolling mills comprising of:
CCD (Charged Coupled Device) cameras placed at strategic locations;
Multi-channel Digital Video Recorders (DVR) to record the real time images of
mill operation;
a display for the viewing of the images captured from the CCD camera and
prpcessed by DVR on continuous basis;
and a memory for recordal of the said images.
2. A system for time-stamped fault detection of cobble in rolling mills as claimed in
claim 1 wherein, the strategic locations for placing the camera are the charging ends of
reheating furnaces, pulpits, roller tables, discharge and and at the stands.
3. A system for time-stamped fault detection of cobble in rolling mills as claimed in
claim 1, wherein all the data recorded by DVR is stored with date and time stamped
information and further configured for ultra slow mot on playback option.
4. A system for time-stamped fault detection of cobble in rolling mills as claimed in
claim 1, wherein the CCD camera is configured for high light restraining features and for
capturing the view of red hot billet moving at high speed on dark rotter table by
controlling the parameters like gamma correction, Smear rejection ratio, Peak detecting
Mode, Instantaneous response etc.
5. A system for time-stamped fault detection of cobble in rolling mills as claimed
in claim 1, wherein the Multi-channel Digital Video Recorders is configured for 16
channel Linux based DVR system with MPEG-4 image compression /decornpression
technique for Intelligent motion detection, quick search function for data & image,
slow/fast playback.
6. A system for time-stamped fault detection of cobble in rolling mills as claimed in
claim 1, wherein the DVR transmits the recorded images over LAN using TCP/IP protocol
and its intelligent motion detection feature is further configured for each channel to

maximize system hard disk efficiency by ignoring the periods of non-activity of the rolling
mill.
7. A system for time-stamped fault detection of cobble in rolling mills as claimed in
any of the preceding claims, wherein the system further comprises a database, which
records the history of the analysed faults of a rolling mill and genera! records of faults.
8. A method for time-stamped fault detection of cobble in rolling mills comprising the
steps of:
capturing the real time images of the operation of the rolling mitt employing a
plurality of CCD (Charged Coupled Device) cameras placed at strategic locations;
recording of the real time images of the mill operation employing multi-channel
Digital Video Recorders (DVR);
displaying the real time images captured torn the CCD camera and processed
by DVR on continuous basis;
recording the captured real time in a memory with a date and time stamp.
9. A system for time-stamped fault detection of cobble in rolling mills, substantially
as herein described with particular reference to accompanying drawings
10. A method for time-stamped fault detection of cobble in rolling mills substantially
as herein described with particular reference to accompanying drawings

The present invention discloses a system and method for an online time stamped fault
detection of the cobble in rolling mills, more particularly, the present invention relates to
a merchant mill protecting system wherein wrecked (cobbled) elongated metallic
material undergoing rolling (e.g. bars or rods) are located immediately without forming any damage to the production line and therefore can be easily-removed.