FIELD OF THE INVENTION
The present invention relates to an expert system based heating control system for
annealing cycle in batch type Bell annealing furnaces. More particularly, the heating control
system for annealing cycle in bell annealing furnace is implemented to a plurality of
furnaces in the annealing line. The time and temperatures for heating/soaking is determined
for the entire thermal regime for the annealing heating cycle for a batch of cold rolled coils
after tandem mills. Importantly, the integrated system of heating control in bell annealing
furnace according to the invention comprising a system of control for annealing heating
cycle for CR coils in Bell furnace on base wherein a hierarchical control is implemented in
steps e.g. (i) the level zero being field instrumentation, (ii) level-I is PLC based control and
(iii) level II as expert system, wherein the level I and level II control is carried out through
a specially developed software, adapted to automatically selecting and implementing set
points for heating cycle parameters like first and second heating time (thi & th2), first and
final soaking time(tsi & ts2) and also first and final soaking temperatures (Ti and T2) for a
large number of annealing bases/furnaces depending on input of CR coil parameters data
like the coil gauge, weight, width, type of steel etc. The level II expert system is
implemented in a PC workstation using VC++. It is based on several rules and guidelines
framed with the expertise of plant personnel. The Expert System allows the operators to
enter the coil parameters i.e. its number, weight, width, gauge, grade, rolling data etc.
through human machine interface (HMI) implemented through two PC based workstations.
Based on these data input, the Expert System, implemented in one workstation, selects
most appropriate annealing cycle and downloads the same to PLC through a interface driver
software for control of annealing process which finally regulates air/gas valve to control
time-temperature cycle of annealing in bell type furnace with cooling hood. The PLC and the
two workstations are connected through dual redundant 10 MBPS Ethernet. The bi-
directional data communication between expert system and level I PLC has been achieved
through an OPC (OLE for Process Control) based client software developed in VC++ and is an
integral part of expert system. All the process parameters are viewed through an interactive
HMI, including the overview, status, trends and graphs. Also, all individual PID control and
annealing cycle ramp parameters is accessed by the operator through the HMI.
Advantageously, the expert system according to the present invention also renders several
guidelines relating to for example mixed charging, stack height, Protective Gas(PG) purging
non-working of base fan etc. The expert system according to the present invention is
capable of providing optimum annealing cycle for CR coils in bell type annealing cycle
ensuring processed steel/coil quality, reduction in specific heat consumption, reduction in
material downgrading and rejections, economy in energy consumption, with reliability
improving annealing line base productivity, without direct human intervention and thus
having prospects of wide industrial application in CRM of large steel plants.
BACKGROUND ART
The cold rolled coils after tandem mill in CRM are subjected to annealing process involving
heating and soaking of CR coils at different temperature levels for different pre-defined
periods and then cooled slowly. Annealing process is adopted to improve the mechanical
properties of coils and is extremely crucial for final coil quality. Conventionally 3/4 coils in
a batch are stacked over the circular bases for annealing in bell type furnace. In order to
avoid oxidation during heating, the coils are heated in an inert environment by a gas called
Protective Gas (PG), which is a mixture of around 98% of N2 and 2% of H2. The coil stack is
covered by a bell shaped hood called PG cover inside which the inert environment of PG is
maintained. The bell shaped furnaces are kept over this PG cover. Mixed gas which is a
combination of Blast Furnace and Coke Oven gas is used as fuel for heating the furnace.
After completion of heating over one base, the furnace is lifted from that base and placed
over another base by overhead cranes. The heated coils in the previous base are then
cooled by placing another cover called cooling hood over it. Cooling hoods are equipped with
cooling fans for the purpose of cooling the coils. After completion of cooling time and coils
cooled below a certain temperature, both cooling hood as well as PG cover are removed and
coils are unloaded from the base.
The heating in annealing furnace is regulated by a 3cp electro-mechanical actuator mounted
on the furnace. The actuator drives a ratio link rod, which regulates both air and gas in a
certain ratio and fired through burners. The Protective Gas and Base temperatures are
monitored by two K-type (Chromel - Alumel) thermocouples. To maintain the flow of PG
both outside and inside of coils, suction is created by a fan called base fan. The gas
pressure in the furnace is maintained by a combustion fan, which is also mounted in the
furnace. All the electrical signals from the actuator and combustion fan are connected
through a plug and socket arrangement near base. The plugs are removed before the
furnace/hood is lifted from base by crane after each batch heat of CR coils.
The coils are heated following a certain thermal regime, usually termed as 'Annealing
heating cycle', which mainly depends on type of steel, coil weight, width, gauge etc.
Adherence to this heating cycle is extremely important for maintaining quality of coils. A
typical annealing cycle comprises of four parts: First Heating, First Soaking, Second Heating
and Final Soaking. Annealing cycle basically is directed to ascertaining and concerned with
First and Final soaking temperatures (Ti & T2), First and Final soaking time (tsi & ts2) and
First and second heating time (thi & th2).
It is known in the art of Annealing Furnace heating control conventionally implemented
through DCS or PLC based process control system. The process operator selects the thermal
regime or temperature ramp and feed it manually to control system. The control system
then controls the furnaces temperature by opening or closing air and fuel gas valves. The
control is generally carried out with respect to base temperature signal.
In conventional systems, the control system does not accepts in some cases, the heating
ramp or annealing cycle in a desired manner, so that the operator has to manually enter the
First and Final soaking temperature set points by keeping tract of time. The operator also
closes the valve manually once the heating is over. The entire heating and cooling cycle is
thus a laborious and time consuming exercise and is manpower intensive.
The manual control system thus not only lack co-relation with established scientific/logical
method but also heavily depends on a person's technical experience and timely decision
making and implementing parameter changes which always run the risks of not being
optimum. The manual system is very much labor intensive as operator have to manually
change the set-points at appropriate durations in annealing cycle stages like First heating,
First Soaking, second heating and Final soaking etc.
Moreover, as the number of bases are substantially high in annealing line, typically around
90-100 in numbers, keeping a time record of events like first heating started, first soaking
started, second heating started etc. for all the bases and changing set points exactly at
these times simultaneously are practically impossible. These inaccuracies essentially cause
variations in annealing time (e.g. thi, th2, tsi, ts2 etc.) elements in a cycle. Moreover, the
complexity and delay involved in manual operation for opening/closing of gas valve just at
the end of heating cycle is not feasible to attend causing unnecessary additional furnace
heating resulting in more energy consumption. The poor control accuracy causes quality
related problems and more energy consumption. Delayed detection of fan failures due to
absence of on-line fan status monitoring also affecting the coil quality adversely.
There has thus been a persistent need in the art to developing an integrated automation
and control for batch annealing of CR coils in base/bell type annealing furnaces, wherein the
selection of and implementation of set points corresponding to a pre-programmed annealing
cycle is decided by an expert system running on a specially developed software so as to
correlate the coil parameters to the time-temperature determinants to batch specific
requirements. The system is also having the flexibility of manual input of relevant data for a
coil batch charged in annealing furnace. A precision control system works in tandem with
the expert system for actually controlling the temperature as per cycle selected by expert
system based on coil parameters. The automated and integrated control system for the
heating control of annealing cycle for bell type heating furnace is adapted to suit
requirements of consistent quality of processed steel product, economizing energy
consumption, improving productivity in annealing line and thus favoring operation in CRM in
steel plants.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to developing an expert system
based heating control of annealing cycle for batch type Bell annealing furnace in an
accurate, economic and energy efficient manner enhancing quality and productivity of steel
products in annealing base furnace/line.
A further object of the present invention is directed to developing an integrated control
system for automatic expert system based heating control of annealing cycle for batch type
Bell annealing furnace/bases wherein the time-temperature control set points are
automatically determined by software controlled expert system and run in real time on PLC
based control of fuel/gas/air flow valves in precisely controlled instrumentation system
maintaining accurate timings and thus saving energy consumption with minimum or no
reliance on human intervention.
A still further object of the present invention is directed to developing an integrated control
system for automatic heating control of annealing cycle in batch type bell annealing
base/furnace wherein the data input for a particular charge of coil parameters are put to the
system using a HMI to facilitate auto selection of annealing cycle parameters by expert
system with the help of an embedded software and its implementation through the PID/PLC
controller and precise instrumentation to achieve desired control on annealing cycle
determinants in terms of time-temperature distribution for first and final heating and
soaking in the cycle.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing base furnace wherein the HMI facilitate process overview of the entire annealing
line, generate status, trends and graphics and also enable selection of annealing cycle and
annealing extension.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing base/furnace wherein the total system has been designed following the concept of
hierarchical control system comprising the level zero being field instrumentation, level I as
PLC based control system and level II as expert system.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing base/furnace wherein level I and level II systems operate through specially
develop driver software.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing bases wherein the system enable precise control on desired heating cycle in
terms of the time temperature and other related parameters so that superior quality of the
end steel product/CR coil is achieved consistently with less fuel/energy consumption.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing furnace wherein the system provides means for on-line fan status monitoring and
detecting failure of base/fan or combustion fan in the cooling hood or furnace cover to favor
ensuring precise control on temperature by controlling flow of PG and air for achieving
desired end quality of product.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in batch type bell
annealing furnace wherein the expert system based control favor achieving the optimum
annealing cycle in a cost effective manner with minimum human intervention.
A still further object of the present invention is directed to developing an integrated control
system involving expert system based heating control of annealing cycle in bell type
annealing base furnace involving rule based expert system for selection of optimum
annealing cycle parameters to achieve improvement of on-line performance, to reduce
specific heat consumption, reduction in material downgrading and rejections and improved
productivity of the annealing line comprising plurality of batch type bell annealing furnaces.
SUMMARY OF THE INVENTION
The basic object of the present invention is thus directed to a system for automatic heating
control for batch type bell Annealing Furnaces of cold rolling mills and the like comprising:
means for entering coil parameters /specifications of the coil to be annealed ;
annealing condition determining system adapted to selectively generate the most suitable
annealing cycle based on the said coil parameters/specifications;
a PLC based control system operatively connected to said annealing condition determining
system for carrying out said selected annealing cycle by downloading the selected annealing
cycle to said PLC which is then adapted to regulate the desired control of the annealing
based on said selected cycle determined by the annealing condition determining system.
A further aspect of the present invention is directed to said system wherein said annealing
condition determining system comprises rule based system for selection of optimum
annealing cycle based on a given set of coil parameters including selectively weight, width
and gauge, steel grade etc.
Another aspect of the present invention is directed to said system wherein said annealing
condition determining system comprises provision for annealing extension, base unloading,
charge abandon and generation of operational reports and status.
A still further aspect of the present invention is directed to said system comprising a PLC
based process control for actual control of furnace temperature as per regime determined
by said annealing condition determining system.
A still further aspect of the present invention is directed to said system comprising
interfacing of said annealing condition determining system and process control through
driver interface means preferably based on OPC (OLE for process control).
A still further aspect of the present invention is directed to said system comprising Human
machine Interface (HMI) adapted for annealing line operation and status/performance
display.
According to yet another aspect of the present invention is directed to a system comprising
hierarchical control comprising:
Level-0 being field level instrumentation;
Level-I being said PLC based control system; and
Level-II being said annealing condition determining system.
A still further aspect of the present invention is directed to said system wherein said
annealing condition determining system comprises (i) said means for entering coil
parameters and (ii) based on coil parameters selecting the most appropriate annealing cycle
and (iii) generated guide lines such as for mixed charging, stack height, PG purging and
base fan operations and the like.
A still further aspect of the present invention is directed to said system comprising cascade,
auto or manual mode of operation.
The present invention and its objectives and advantages are described in greater details
with reference to the accompanying non limiting illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the conventional batch type bell annealing furnace
employed for batch annealing of CR coils on bases in annealing line, showing its different
functional elements.
Figure 2: is the illustration of a typical ideal annealing cycle showing the four separate
stages of the cycle having first and second heating time/rate and also the first and final
soaking temperatures and time durations.
Figure 3: is the illustration of the sample display screen for HMI data input relating to coil
parameters used by expert system to determine annealing cycle to follow.
Figure 4: is the schematic illustration of the annealing cycle selected by the expert system
according to the invention after processing the input data for coil parameters through HMI
using the specially developed software.
Figure 5: is the schematic illustration of the hardware configuration of the integrated
heating control system for annealing cycle according to the present invention, clearly
showing the three tier deployment of its components e.g. the level 0, level I and level II for
control of instrumentation, PLC/PID controller via the I/O card interfaced with the
instrumentation, and the Expert system respectively, for software enabled ascertainment of
the annealing parameters.
Figure 6: is the schematic illustration of the display screen depicting actual process trend
with precise temperature control indicating the trends of set temperature determined by
expert system, base temperature and the protective gas (PG) temperature.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to an expert system based automatic integrated heating
control system for annealing cycle in Bell type annealing furnaces on bases and in
particular, to a system for annealing cycle in bell type annealing furnace adapted to any
selective number of furnaces in the annealing line simultaneously by selective control on
deciding parameters like the time and rate of heating, first and final soaking temperatures
and durations corresponding to the variable coil parameter data in order to meeting the end
quality and mechanical related properties of the processed CR coils in CRM.
Reference is first invited to the accompanying Figure 1 that schematically illustrate the
conventional batch type bell annealing furnace employed for batch annealing of CR coils on
bases in annealing line showing its different components. The coil stack comprising 3 or 4
coils is covered by a bell shaped hood called protective gas (PG) cover on annealing base,
inside which the inert environment of PG is maintained. The bell shaped furnaces are kept
over this PG cover. Mixed gas which is a combination of Blast Furnace and Coke Oven gas is
used as fuel for heating the furnace. After completion of heating over one base, the furnace
is lifted from that base and placed over another base by overhead cranes. The heated coils
in the previous base are then cooled by placing another cover called cooling hood over it.
Cooling hoods are equipped with cooling fans for the purpose of cooling the coils. After
completion of cooling time and coils cooled below a certain temperature, both cooling hood
as well as PG cover are removed and coils are unloaded from the base. An inert
environment by a gas called Protective Gas (PG), which is a mixture of around 98% of N2
and 2% of H2 is provided for heating coils avoiding oxidation. Annealing plays an important
role in improving the mechanical properties of coils and maintain superior quality reducing
spoilage and rejections.
The heating in annealing furnace is regulated by a 3f electro-mechanical actuator mounted
on the furnace. The actuator drives a ratio link rod, which regulates both air and gas in a
certain ratio and fired through burners. The Protective Gas and Base temperatures are
monitored by two K-type (Chromel - Alumel) thermocouples. To maintain the flow of PG
both outside and inside of coils, suction is created by a fan called base fan. The gas
pressure in the furnace is maintained by a combustion fan, which is also mounted in the
furnace. All the electrical signals from the actuator and combustion fan are connected
through a plug and socket arrangement near base. The plugs are removed before the
furnace/hood is lifted from base by crane after each batch heat of CR coils.
It is known in the art of Annealing Furnace heating control conventionally implemented
through DCS or PLC based process control system. The process operator selects the thermal
regime or temperature ramp and feed it manually to control system. The control system
then controls the furnaces temperature by opening or closing air and fuel gas valves. The
control is generally carried out with respect to base temperature signal.
In conventional control systems, the heating ramp or annealing cycle in not executed in
desired manner, so that the operator has to manually enter the First and Final soaking
temperature set points by keeping tract of time. The operator also closes the valve
manually once the heating is over. The entire heating and cooling cycle is thus a laborious
and time consuming exercise and is manpower intensive.
Reference is now invited to the accompanying Figure 2 that schematically illustrates the
typical ideal batch annealing cycle for CR coils comprising four distinct stages. The coils are
heated following a certain thermal regime, usually termed as 'Annealing heating cycle',
which mainly depends on type of steel, coil weight, width, gauge etc. Adherence to this
heating cycle is extremely important for maintaining quality of coils. A typical annealing
cycle comprises of four parts: First Heating, First Soaking, Second Heating and Final
Soaking. Annealing cycle basically is directed to ascertaining and concerned with First and
Final soaking temperatures (Tx & T2), First and Final soaking time (tsi & ts2) and First and
Second heating time (th1 & th2).
The expert system based integrated control for automatic control of annealing parameters
according to the present invention favour selection of appropriate thermal regime -basically
comprising selecting the corresponding values of T1, T2 and thi, tsi, th2 & ts2 for a batch of
coils is very important and depends on coil parameters like weight, width, gauge, grade of
steel etc as indicated above. The present system of automation involving expert system
based integrated control favor avoiding absolute reliance on the experience and expertise of
operator and rely instead on a computerized expert system to determine the annealing
parameter values for a given set of coil parameters input data. The computerized Level - 2
expert system selects the most appropriate annealing cycle as would have been selected by
an expert operator. A precision control system is also required in such cases for actually
controlling the temperature as per cycle selected by Expert System. This ensures quality of
coils, reduces energy consumption as well as reduces coil rejection and downgrading.
Reference is now invited to the accompanying Figure 3 that schematically illustrate the HMI
display screen for manual data entry for coil parameters for a batch of coils placed on
annealing base. Such variable input for base loading data comprise the base number, coil
numbers, gauge/thickness, coil width, total stack height, weight of each coil, total charge
weight, steel grade, rolling data etc. the system also renders several guidelines like mixed
charging, stack height, PG purging, non working of base fan etc. The screen shown here is
visual presentation of the input of base-wise coil parameters.
Reference is next invited to the accompanying Figure 4 that schematically illustrate the
annealing cycle selected by the expert system of the invention based on HMI input data
relating to coil parameters. The expert system decides on the annealing cycle parameters
based on inputs on coil parameter data using specially developed software on VC++ on a PC
workstation and down load the same to PLC control. A set of 'if and 'then' rules and
guidelines have been utilized in designing the software based on expertise of the plant
personnel.
Reference is invite to the accompanying Figure 5 that schematically illustrate the hardware
configuration of the integrated heating control system for annealing cycle according to the
present invention, clearly showing the three tier deployment of its components e.g. the level
0, level I and level II - for control of instrumentation, PLC/PID controller via the I/O card
interfaced with the instrumentation, and the Expert system respectively.
The integrated expert system and heating control system has been successfully
implemented in Bell Annealing base Line of Cold Rolling Mill (CRM), in the Steel Plant of the
applicants. The line is comprised of 92 bases over which 43 movable furnaces are operated.
The total system has been designed following the concepts of hierarchical control system.
The Level - 0 being field instrumentation, Level - I as PLC based control system and Level -
II as expert system. Level - I and II systems operate synergistically through a specially
developed driver software. The concept of expert system relies on the operator's expertise
embedded in the system software to select the appropriate annealing cycle based on given
set of coil parameter data input through HMI.
The expert system also facilitates the operator with the provisions of annealing extension in
case of slow temperature rise, unloading base once coils are cooled below a pre defined
temperature and abandoning a particular heating in case of severe problems. The expert
system also generates many operational and status indicating reports and print-outs like
Loading Report, Unloading report, production report, charge report, base status report, base
under heating / cooling report etc.
When the furnace is lighted up, the selected annealing cycle is downloaded to a PLC based
control system through a special interface software. The PLC system comprises of Allen
Bradley make 1756-L63 processor and 1759 Flex Logix I/O cards. The PLC processor and
I/O cards are connected through 5MBPS dual redundant Control-net data bus. The HMI is
implemented in two PC based workstation while Expert System is implemented in one
workstation. PLC and workstations are connected through dual redundant 10 MBPS
Ethernet. All the process parameters are viewed through a separate interactive Human
Machine Interface (HMI) developed in Rockwell Automation make RS-View HMI. All process
display, trends and graphics are available in this HMI. All individual PID control and
annealing cycle RAMP parameters can be accessed by the operator through HMI. Manual
configuration of annealing cycle and annealing extension is also available in HMI. The
integrated system configuration is shown in the accompanying Figure 5.
When the operator confirms the furnace light-up, the expert system configures the
attributes of a pre defined Ramp generator software block in PLC. This ramp block basically
generates the annealing cycle with respect to time. In cascade mode of operation, the
output of this block becomes desired instantaneous set temperature of the annealing
furnace. The system is also adapted to work in Auto mode, where operator manually enter
the set temperature. Based on actual reading of base thermocouple temperature and set
temperature, the PID control block in PLC open or closes a 24 VDC relay. This relay further
activates a 440 VAC MCC circuit, which actually opens or closes the gas/air actuator valve.
At the completion of heating cycle, PLC closes the gas / air valve thus stopping the furnace
heating at appropriate time.
The system offers a very effective Human Machine Interface (HMI) in two dedicated
operator's terminals. The HMI facilitates the entire Annealing Line process overview, status,
trends and graphics. The HMI also permits selection of annealing cycle and annealing
extension. The manual changing of control loop modes (Cascade / Auto / Manual) and RAMP
parameters are included in HMI. Alarm annunciation and logging in case of any fan failure is
also provided in HMI. All the above mentioned operations and displays (except trending) is
also available through two Panel graphics terminal.
According to a preferred embodiment of the control system for heating regime of annealing
cycle in bell annealing furnaces, the expert system of the present invention is implemented
in a PC platform and software written in VC++ (Microsoft Visual Studio Version 2005). The
PLC based control system is implemented through a Rockwell Automation make Control
Logix 1756-L63 processor. The bidirectional data communication between expert system
and Level - 1 PLC has been achieved through an OPC (OLE for Process Control) client
software developed in VC++ and is an integral part of expert system. Rockwell Automation
make RS-Linx has been used as OPC server. As already illustrated in accompanying Figure
3, operator enters coil parameters like coil number, weight, width, gauge, grade etc. Based
on this data, the expert system selects most suitable annealing cycle. When operator
confirms furnace light-up, the expert system downloads the selected annealing cycle to PLC,
which finally regulates air / gas valve to control temperature.
Reference is now invited to the accompanying Figure 6 that schematically illustrate the
display screen depicting actual process trend with precise temperature control indicating the
trends of set temperature determined by expert system, base temperature and the PG
temperature. The system for heating control for the annealing cycles carried out in
annealing line has been successfully implemented in plant scale. The actual annealing cycle
is determined by expert system and the PLC maintain the cycle with accuracy of around
± 5-10 °C under normal conditions. An actual process trend is depicted in accompanying
Figure 6. All the operational reports are being generated by the system. The initial trend
shows 8 % improvement in base productivity and 8 % improvement in specific heat
consumption.
It is thus possible by way of the present invention to developing an integrated control
system comprising level 0, level I and level II hardware configuration, involving Expert
system based heating control in batch type bell annealing furnace base line adapted to
automatically design/configure an optimum annealing cycle defining specifically the
annealing parameters e.g. the first heating, first soaking, second heating and final soaking
schedule in terms of temperatures and time durations for a batch of CR coil charged on a
base and its corresponding coil parameters data input to the system via a flexible console.
Importantly, such integrated system has the flexibility to opt for and switching among
control modes comprising Cascade, Auto and Manual mode and the Ramp parameters
provided in the HMI, by manual changing. The operators long experience and expertise
regarding control on deciding parameters has been suitably embedded in the software for
the expert system thus favoring exact and accurate parameter selection and instantaneous
annealing cycle set points/temperatures implementation with means for monitoring and
control for desired optimum end result in terms of quality, reliability, cost and energy
economy/efficiency.
The expert system based control of annealing cycle in batch type bell furnace/bases, further
enable annealing extension, base unloading, charge abandonment, operational report
generation, status report etc., as and when required. The integrated system for annealing
process control according to the present invention also involve a PLC based process control
software for actual control of furnace temperature as per regime decided by Expert System
through precision support instrumentations. Interfacing of Expert System and Process
Control Software through a driver interface software based on OPC (OLE for Process
Control) favour achieving implementation of gas/air flow control and status monitoring of
suction and combustion fans to achieve desired control and implementation of annealing
cycle parameters maintaining precision timing. The HMI is available on two dedicated
operators' terminal wherein both offers an interactive Human Machine Interface (HMI) for
Annealing Line Operation, trending and status / performance display. The console for expert
system engaged in input of coil/batch data to the system. Advantageously, the operator is
able to access all individual PID control and annealing cycle ramp parameters through the
HMI. The expert system based annealing process control according to the present invention
is thus capable of ensuring about 8% improvement in base productivity and about 8%
improvement in specific heat capacity with reliability and consistency with reduced rejection
and coil degrading, and thus favoring prospect of wide industrial application of such
annealing process control systems in annealing lines in CRM in steel plants.
WE CLAIM:
1.A system for automatic heating control of batch type bell Annealing Furnaces in cold
rolling mills and the like comprising:
means for entering coil parameters /specifications of the coil to be annealed ;
annealing condition determining expert system adapted to selectively generate the most
suitable annealing cycle based on the said coil parameters/specifications;
a PLC based control system operatively connected to said annealing condition determining
system for carrying out said selected annealing cycle by downloading the selected annealing
cycle to said PLC which is then adapted to regulate the desired control of the annealing
based on said selected cycle determined by the annealing condition determining system.
2. A system as claimed in claim 1 wherein said annealing condition determining system
comprises rule based expert system for selection of optimum annealing cycle based on a
given set of coil parameters including selectively weight, width and gauge, steel grade etc.
3. A system as claimed in anyone of claims 1 or 2 wherein said annealing condition
determining system comprises provision for annealing extension, base unloading, charge
abandon and generation of operational reports and status.
4. A system as claimed in anyone of claims 1 to 3 comprising a PLC based process control
for actual control of furnace temperature as per regime determined by said annealing
condition determining system.
5. A system as claimed in anyone of claims 1 to 4 comprising interfacing of said annealing
condition determining system and process control through driver interface means preferably
based on OPC ( OLE for process control).
6. A system as claimed in anyone of claims 1 to 5 comprising Human machine Interface
(HMI) adapted for annealing line operation and status/performance display.
7. A system as claimed in anyone of claims 1 to 6 comprising hierarchical control
comprising:
Level-0 being field level instrumentation;
Level-I being said PLC based control system; and
Level-II being said annealing condition determining system.
8. A system as claimed in anyone of claims 1 to 7 wherein said annealing condition
determining system comprises (i) said means for entering coil parameters and (ii) based on
coil parameters selecting the most appropriate annealing cycle and (iii) generated guide
lines such as for mixed charging, stack height, PG purging and base fan operations and the
like.
9. A system as claimed in anyone of claims 1 to 8 comprising cascade, auto or manual
mode of operation.
10. A system for automatic heating control for batch type bell Annealing Furnaces of cold
rolling mills and the like substantially as herein described and illustrated with reference to
the accompanying figures.

The invention relates to a system for automatic heating control for batch type Bell annealing
furnaces. More particularly, the heating control system suits operation in a plurality of
furnaces simultaneously by selective control on deciding parameters like the time for heating/soaking and the temperatures relating to the soaking / heating in the thermal regime, for processing cold rolled coils after tandem mills in annealing line. Importantly, the annealing heating control system is having a hierarchical control implemented in steps e.g. (i) the level zero being field instrumentation, (ii) level I is PLC based control and (iii) level II
as expert system, wherein the level I and level II control is carried out through a specially
developed software. The set points for heating cycle parameters/most optimum heating
cycle is decided by an expert system for the coils depending on coil parameters. Advantageously, the system for heating control of annealing cycle ensure quality, reduced
specific heat consumption, avoid downgrading and rejections, economy in energy consumption with reliability and improved productivity.