FIELD OF INVENTION
The present invention relates to a rolling mill and, in particular, to a rolling mill system
adapted for data acquisition and analysis for efficient mill performance during steel rolling
process. More particularly, the invention is directed to a rolling mill with a basic platform
where the rolling parameters are acquired for two purposes; (i) providing inputs to a
mathematical model and (n) analysis of rolling parameters for reduction of off gauge and
reduction in cobbles. The system advantageously incorporates programmable controller with
fast data acquisition modules and would thus be simple and accurate.
BACKGROUND
In a Hot Strip Mill, strips of different thickness and width are rolled from slab. Usually such
hot strip mills are known to consist of three Roughing stands and six Finishing stands. Such
a conventional hot strip mill and the disposition of the Roughing stands and the Finishing
stands and, more particularly, the usual lay out of such hot strip mill are well known to the
art.
Basically, the hot strip mills conventionally involve the combination of Roughing stands and
Finishing Stands. The first Roughing Stands is a combination horizontal stands and vertical
stand. The other two Roughing stands are four high horizontal stands. There is a delay table
after the second Roughing stand, a coil box and a crop shear at the end of the delay table.
There are six numbers of four high finishing stands and two hydraulic down coiler.
Now, involving different rolling parameters or process parameters of a hot strip mill to
facilitate operation of the hot strip mill is well known in the art.
EP 1608472 discloses a system for on-line property prediction for hot rolled coils in a hot
strip mill of a steel plant comprising a unit for providing data on rolling schedule with
chemistry from the steel making stage, multiple field devices for measuring process
parameters during hot rolling, a programmable logic controller for acquiring data of
measured parameters from said field devices and feeding said data parameters to a
processor, means for conversion of the measured data from time domain to space domain
using segment tracking, a computation module for processing said converted space domain
data for predicting mechanical properties along the length and through the thickness of the
strip being rolled and a display unit for on-line display of the predicted properties.

EP 155301 describes a method and apparatus for automatically controlling the thickness of
product emerging from a rolling mill. Signals indicative of total roll force, roll gap position,
angular position of a first mill roll and downstream product thickness are utilized to obtain
an output signal indicative of total roll eccentricity affecting the true instantaneous roll gap
position as a function of the measured mill roll angular position. The output signal may be
used to compensate an estimate of instantaneous thickness of the product for the purpose
of controlling the gap between work rolls. If preferred the output signal may be further
processed to obtain an output signal indicative of the period roll eccentricity of a set of rolls
having a common period of rotation or of a plurality of such sets.
The roll gaps of finishing stands are calculated based on certain rolling parameters. These
rolling parameters are to be acquired on line during rolling and to be given to the input of
the model. The model then outputs the no load roll gap to be set for Finishing stands to
obtain the desired target thickness. The above prior arts does not describe any data
acquisition technique or system which can be applied to outputs the no load roll gap to be
set for Finishing stands to obtain the desired target thickness in hot strip mill based on the
rolling parameters. Thus one data acquisition system is required to acquire the process
data, which is fast enough to capture all transient values, and the data will be fed as input
to the model.
Another purpose of the data acquisition is to analysis the data to find out the cause of a
cobble and the cause of off gauge. The result of the analysis is communicated to the
operator such that he can take corrective action to reduce off gauge and eliminate cobbles.

In a conventional rolling mill the data acquisition may be done at different nodes. Such
conventional data acquisition system suffers from drawbacks / disadvantages which are
discussed hereunder:
A. The interval between two successive information of rolling data is much more than
20 msec and thereby loosing some useful information.
B. No provision for storing the data.
C. No provision for analysis of the data to draw meaningful inference.
D. Data is available to the operator at different instruments but the operator can not
correlate the data to draw meaningful inference.
E. Provision for retrieving the data for strip rolled earlier was not there.
F. Analysis of data is available at different locations such that all person concern can

retrieve the data.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for a rolling mill adapted for
data acquisition on performance of the rolling mill and analysis of roiling parameter, which
would enable avoiding the drawback / disadvantages of conventional rolling mill systems
especially its data acquisition done at different nodes.
Another object of the present invention is directed to a rolling mill adapted for data
acquisition on rolling performance and analysis of rolling data which would avoid the
limitation of interval between two successive information of rolling data being more than
20m.sec and thereby the possibility of losing some useful information concerning the rolling
conditions and performance.
Another object of the present invention is directed to provide for a rolling mill adapted for
data acquisition and analysis which would favour the provision of storing of the data, which
is relevant for monitoring the rolling performance and taking corrective measures if and
when required.
Another object of the present invention is directed to a rolling mill system which would have
facilities for analysis of rolling mill performance data to thereby favour drawing meaningful
inference based thereon.

Yet further object of the present invention is to provide for rotting mill system adapted for
data acquisition and analysis and also incorporating features enabling the availability of data
to the operator at different instruments and co-relate the said data to draw meaningful
inferences.
Yet another object of the present invention is directed to provide for rolling mill system
adapted for retrieving the data of the strip roiled to favour its analysis and ,if required, any
corrective measures.
Yet further object of the present invention is directed to a roiling mill system whereby the
analysis of data would be made available at different location such that all persons
concerned can retrieve the data.
Yet another object of the present invention is directed to a rolling mill system adapted to
favour analysis of acquired data to ascertain reason of a cobble and to find out the reason of
off gauge to thereby favour much required analysis and cause of cobble.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a rolling mill
adapted for data acquisition and analysis for efficient mill performance comprising:
a programmable controller (PLC) unit comprising analog input means , digital input means
and communication processor;
isolation devices to isolate the analog signals;
isolation devices to isolate the digital signals;
atleast one operative programming terminal for the programmable controller;
atieast one operators interface for access to the acquired and analyzed data.

In accordance with a preferred aspect the rolling mill adapted for data acquisition and
analysis comprises
a programmable controller unit comprising 48 analog inputs, 96 digital inputs and
communication processor;
isolation devices to isolate the analog signals;
isolation devices to isolate the digital signals comprising optical isolation module for
galvanically isolating the digital signals to programmable controller;
a programming terminal for the programmable controller;
an operators interface to view the analyzed performance data.
In the above disclosed roiling mill adapted for data acquisition and analysis the
programmable controller comprises of Central processing Unit having user memory
preferably 72 KB for program and 72 KB for data. Rash EPROM micro memory preferably 2
MB with defined execution time for bit operation preferably 2 p sec, counters preferably
256,timers preferably 256 with defined capacity to handle Analog input and Digital inputs
preferably 128 and 512 respectively.
According to an aspect of the present invention, the rolling mill adapted for data acquisition
and analysis comprises
three numbers of analog input modules ,each said Analog input modules providing for 16
channels, having input range of -10V DC to + 1QV DC, conversion time about 20msec; and
three numbers of digital input modules, each providing for 32 channels with rated Voltage
of 24 V DC and input voltage at M' level of 11 to 30 V DC and input voltage at "0' level of -
30 to +5 V DC.

Importantly, the rolling mill system of the invention adapted for data acquisition and
analysis comprises providing selectively from two types of isolation devices based on the
speed of response (i) fast response isolation amplifier and (si) relatively slow response
isolation amplifier.
The fast signals preferably calculated roll gap in drive and works side, measured roll gap
(signal output from the Linear Varying Differential Transformer) in drive and works side are
operatjvery connected with fast response isolation amplifiers and relatively slow response
signals preferably Roil force, roughing strand temperature finishing strand temperatures and
exit thickness are operatively connected to said slow response amplifier.
In accordance with an aspect the said fast response isolation amplifier comprises of
specifications including input range of 0 to +/- 10V DC, output range of 0 to +/- 10V DC,
response time preferably about 1 msec, power supply 24V DC, isolation level 1.5 KV,
common mode voltage 2KV, mounting DIN rail with preferred location of installation on the
PLC panel; and said ordinary response isolation amplifier comprises of specifications
induding input range 0 to +/- 10 V DC, output range of 0 to +/- 10 V DC, response time
preferably about I00msec,power supply 24V DC, isolation level 1.5 kV, mounting preferably
DIN rail and located on the PLC panel.
The said isolation device for digital signal comprises three numbers of digital signal isolation
units mounted in the programmable controller panel adapted to isolate 24V DC digital
signals from the field before connecting to programmable controller digital input each said
digital signal isolation units comprising specifications induding input '1' range of 18-32 V
DC, output *1' range of 24 V DC , input impedance 10 kQ with response time preferably
lmsec,power supply 24V DC, isolation level 1,5 kV and mounting located on the PLC panel.
The programming terminal used in the rolling mill system of the invention comprises a
personal computer located near the programmable controller , said computer further
adapted to receive data from the PLC preferably through winCC , said personal computer
provided with desired processor, cache memory, RAM,HDD,CD Drive ,monitor and operating
system.

The operator's interface comprises of a PC desired specifications to facilitate the viewing of
the analyzed data in the speed cabin and take corrective measures based thereon.
It is thus possible by way of the above disclosed roll mill system to provide a rolling mill
having an improved data acquisition system for acquiring data, provide input for the model,
analysis of the acquired data to obtain information on the cause of a cobble and cause of an
off gauge by way of a combination of a programmable controller (PLC) unit with analog
inputs, Digital inputs, and Communication processor, Isolation devices to isolate the analog
signals, Optical isolation module for galvanically isolate the digital signals to programmable
controller; a programming terminal for the programmable controller; a Human Machine
Interface (HMI) for the operator where the result of the analysis can be shown.
DETAIL DESCRIPTION OF THE INVENTION
The details of the invention, its objects and advantages are explained hereunder in greater
details in relation to non-limiting exemplary illustration of the data acquisition and analysis
means incorporated in the roll mill system of the present invention in relation to non-
hmiting accompanying figures wherein:
Figure 1: illustrates a lay out of a conventional Hot Strip Mill;
Figure-2: is a schematic diagram of the system for data acquisition and analysis used in the
Hot Strip Mills in accordance with the present invention;
Figure 3: is a circuit diagram of the digital isolation unit used in the system of the invention.
Figure 4(a): shows temperature variation after R2 stand along the length of the strip.

Figure 4(b): shows temperature variation after R2 stand along the length causing roll force
variation.
Figure 4(c): illustrates a method of reducing off gauge.
Figure 4(d): shows checking looper tension and correlating with speed variation.
Reference is first invited to accompanying Figure 1 which shows a lay out of a conventional
Hot Strip Mill. As shown in the said figure, the same basically consists of 3 Roughing stands
and 6 Finishing stands. The first roughing stand (Ro/V0) is a combination horizontal stand
and a vertical stand. The other two roughing stands (Ri and R2) are 4 high horizontal
stands. There is a delay table after R2 stand, one coil box and a crop shear at the end of the
delay table. There are six numbers of 4 high finishing stands (Fj to F6) and two hydraulic
down coilers.

The roll gaps for F4 to F6 stands are calculated based on a few roiling parameters. These
rolling parameters are to be acquired on line during roiling and to be given to the input of
the model. The model then outputs the no load roll gap to be set for Fx to F6 stands to
obtain the desired target thickness. The above (ay out and performance reveals the need for
one data acquisition system to acquire the process data, which is fast enough to capture all
transient values, and the data will be fed as input to the model.
Also, such data acquisition can be further used to analyze the data to find out the cause of a
cobble and the cause of off gauge. The result of the analysis can then be communicated to
the operator such that he can take corrective action to reduce off gauge and eliminate
cobbles.
Reference is invited to accompanying figure 2 which illustrates by way of schematic diagram
the data acquisition and analysis system adapted for incorporation in the hot strip mills in
accordance with the invention.
As shown in said figure 2 the system basically involves a programming terminal which can
be programming PC which would favour programming the input parameters for the rolling
operations and its analysis in the system of the invention. The acquired data and the
analyzed data can be provided in a suitable viewable form in an operator's terminal at the
speed cabin which can be also a PC based interface. .
As dearly represented in Figure 2 the input parameters can selectively include R2
temperature, F4 temperature, F6 temperature, Roll force Fi-Fs , Stand Speed Ft -F6, LVDT
values for hydraulic cylinder, Work Roll diameter Fi-Fs and the target thickness. The
possible networking of the data acquisition unit with other devices is also shown in the
figure.
The system for data acquisition and analysis thus basically comprises of the following
components (i) Programmable controller system,(0) Analog Input Module,(tii)Oigital input
module(iv) Isolation device for analog signal (v)Isolation devices for digital signal
(vi)Programming terminal for programmable Controller and (vii) Human Machine Interface
for the operator

Programmable controller system
The programmable controller comprises of Central Processing Unit (CPU), having preferably
the following specifications;
User memory: 72 KB for program and 72 KB for data
Rash EPROM (micro memory): 2 MB
Execution time for bit operation: 2 u sec
Counters: 256
Timers: 256
Capacity to handle Analog Inputs: 128
Capacity to handle Digital inputs: 512
Any other CPU having equivalent specification will also serve the purpose.
Analog Input module:
Three numbers of analog input modules have been used for this purpose. Each analog input
module used for this purpose can preferably have the following specification:
Number of channels per module: 16
Input range: -10 V DC to + 10 V DC
Conversion time: Around 20 msec
Any other Analog Input module having equivalent specification will also serve the purpose.
Digital Input Module:
Three numbers of digital input modules each of 32 channels has been used. Each digital
input module used for this purpose can preferably have the following specification:
Number of channels per module: 32
Rated Voltage: 24 V DC
Input voltage at '1' level: 11 to 30 V DC
Input voltage at *0' level: - 30 to + 5 V DC
Any other Digital Input module having equivalent specification will also serve the purpose.

Isolation device for Analog Signal
The analog signals are isolated before feeding to the analog input channel of the
programmable controller. There are two types of isolation devices based on the speed of
response, used in this work. The fast signals like calculated roll gap in drive and works side
for F3 to F6 stand, measured roll gap (signal output from Linear Varying Differential
Transformer) in drive and works side for F3 to F6 stand are connected with fast response
isolation amplifiers. Preferable specifications of these isolation amplifiers are given in Table
-1.

The relatively slow signals like Rod force, R2 temperature, F6 temperature, Exit thickness
are connected to ordinary isolation amplifier, whose preferable specifications are given in


Reference is now invited to accompanying figure 3 which illustrate preferred embodiment of
the circuit diagram of a digital isolation unit. The Isolation device for digital signal having
the circuit diagram as shown in Figure 3 can be used in the system.
There can be three numbers of digital signal isolation units mounted in the programmable
controller panel. These are used to isolate 24 V DC digital signals from field before
connecting to programmable controller digital input. Preferred specification of the Digital
signal Isolation unit is given in Tabie-3. These isolations devices are build around opto
coupler.

Programming terminal: A PC has been used as a programming terminal for the
programmable controller. This PC is preferably located near the programmable controller.
This PC is also used to receive data from the PLC through WinCC. The preferred specification
of the PC is as given in Table-4.


Human machine interface: The HMI terminal is kept in the speed cabin for the operator to
view various screen and take corrective actions. This PC is having similar specification as
that of programming terminal.
The data acquisition and analysis system in accordance with the present invention thus
provides
(i) Rolling parameters at required time interval (20 m sec) to a model for calculating no
load roll gap.
(n) Analysis of reason of cobble and off gauge.
The operation of the arrangement of the system can be further explained with the
supportive illustration from the accompanying figure 4(a-d).
In the present system, as the back end of the strip crosses R2 stand, the graph of
temperature variation is seen in the HMI terminal. A sample graph is as shown in figure
4(a), once it is found that temperature variation is large, it can be predicted that there will
be thickness variation. Due to temperature variation in R2 and subsequently in Fl, there will
be roll force variation. Due to this roll force variation there will be thickness variation. This
is as shown in figure 4(b).
The method of reducing off gauge is explained in figure 4(c). In this method first the R2 and
Fl temperature variation is checked. If the variation is high, this will be reflected in the roll
force and this is checked in the graph. The large roll force variation shall reflect in the
thickness variation/The correction can be taken in the next bar by feed back action.
The method of reducing cobbles in the finishing stands is to check the looper tension
variation. The looper tension shall be almost stable during stable rolling. However if the
tension varies widely, it is a matter of concern and expecting a cobble due to unstable
operation of the mill. The accompanying figure 4(d) indicates the looper tension variation
and corresponding speed variation. From the looper tension graph if the variation is wide
then unstability may occur which leads to a cobble.
The invention thus enables providing rolling mill system adapted for data acquisition and
analysis for efficient mill performance during steel rolling process. More particularly, the

invention would provide a basic platform where the rolling parameters are acquired for two
purposes; (i) providing inputs to a mathematical model and (n) analysis of rolling
parameters for reduction of off gauge and reduction in cobbles. The system advantageously
incorporates programmable controller with fast data acquisition modules and would thus be
simple and accurate.

WE CLAIM:
1. A rolling mill system adapted for data acquisition and analysis for efficient mill
performance comprises:
data acquisition and analysis involving rolling parameters during rolling and outputs no load
roll gap to be set for finishing stands of the rolling mill system to obtain desired target
thickness and including
a programmable controller (PLC) unit (1) comprising analog input means (2), digital input
means (3) and communication processor;
isolation devices (4) to isolate the analog signals;
isolation devices (5) to isolate the digital signals;
atleast one operative programming terminal (6) for the programmable controller;
atleast one operators interface (7) for access to the acquired and analyzed data enabling
stable rolling.
2. A rolling mill system adapted for data acquisition and analysis as claimed in claim 1
comprising the system for data acquisition and analysis to acquire rolling parameters during
rolling and outputs no load roll gap to be set for fishing stands of the rolling mill system to
obtain desired target thickness comprising
a programmable controller unit (1) comprising 48 analog inputs (2), 96 digital inputs (3)
and communication processor;
isolation devices (4) to isolate the analog signals;
isolation devices (5) to isolate the digital signals comprising optical isolation module for
galvanically isolating the digital signals to programmable controller;
a programming terminal (6) for the programmable controller;
an operators interface (7) to view the analyzed performance data.
3. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 2 wherein the programmable controller (1) comprises of Central processing Unit
having user memory preferably 72 KB for program and 7-2 KB for data ,Flash EPROM micro
memory preferably 2 MB with defined execution time for bit operation preferably 2 u sec,

counters preferably 256,timers preferably 256 with defined capacity to handle Analog input
and Digital inputs preferably 128 and 512 respectively.
4. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 3 comprising
three numbers of analog input modules (2) ,each said Analog input modules providing for
16 channels, having input range of -10V DC to + 10V Deconversion time about 20msec;
and
three numbers of digital input modules (3), each providing for 32 channels with rated
Voltage of 24 V DC and input voltage at '1' level of 11 to 30 V DC and input voltage at '0'
level of -30 to +5 V DC.
5. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 4 comprising providing selectively from two types of isolation devices (4,5)
based on the speed of response (i) fast response isolation amplifier and (n) relatively slow
response isolation amplifier.
6. A rolling mill system adapted for data acquisition and analysis as claimed in claim 5
wherein the fast signals preferably calculated roll gap in drive and works side , measured
roll gap (signal output from the Linear Varying Differential Transformer) in drive and works
side are operatively connected with fast response isolation amplifiers and relatively slow
response signals preferably Roll force, roughing strand temperature finishing strand
temperatures and exit thickness are operatively connected to said slow response amplifier.
7. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 5 or 6 wherein
said fast response isolation amplifier comprises of specifications including input range of 0
to +/- 10V DC, output range of 0 to +/- 10V DC, response time preferably about 1 msec,
power supply 24V DC, isolation level 1.5 KV, common mode voltage 2KV, mounting DIN rail
with preferred location of installation on the PLC panel; and
said ordrnary response isolation amplifier comprises of specifications including input range 0
to +/- 10 V DC,output range of 0 to +/- 10 V DC, response time preferably about

100msec,power supply 24V DC, isolation level 1.5 kV, mounting preferably DIN rail and
located on the PLC panel.
8. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 7 wherein said isolation device (5) for digital signal comprises three numbers of
digital signal isolation units mounted in the programmable controller panel adapted to
isolate 24V DC digital signals from the field before connecting to programmable controller
digital input each said digital signal isolation units comprising specifications including input
'1' range of 18-32 V DC, output '1' range of 24 V DC , input impedence 10 kΩ with response
time preferably lmsec,power supply 24V DC, isolation level 1,5 kV and mounting located on
the PLC panel.
9. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 8 wherein said programming terminal (6) comprises a personal computer
located near the programmable controller , said computer further adapted to receive data
from the PLC preferably through WmCC , said personal computer provided with desired
processor, cache memory, RAM, HDD, CD Drive monitor and operating system.
10. A rolling mill system adapted for data acquisition and analysis as claimed in anyone of
claims 1 to 8 wherein said operator's interface (7) comprises of a PC desired specifications
to facilitate the viewing of the analyzed data in the speed cabin and take corrective
measures based thereon.

ABSTRACT

A rolling mill data acquisition and analysis system for efficient mill performance
In a rolling mill no load roll gap is set based on mathematical model. This mathematical
model requires a set of parameter which is to be acquired at an interval of 20 m sec and
provide these inputs to the model. The data is to be analyzed to find out the reason of off
gauge and the reason of a cobble. The rolling mill system of the invention is adapted to
acquire data using a programmable controller with fast response analog and digital input
module and provides inputs to a model. The invention also provides for data analysis to
find out the reason of a cobble and reason of off gauge. The system basically comprises of
a programmable controller (1), analog and digital input modules (2,3), Isolation devices
(4,5+), programming terminal (6) and HMI unit (7) for operator's guidance.