FIELD OF THE INVENTION
The present invention relates to an improved method of non contact type HMD
based automatic kick off operation at cooling beds at merchant mill. The method
ensures the automatic detection of leading edge of moving hot bars and automatic
kick off operation of bars at cooling beds. The new methods also have a
comprehensive PLC network based centralized control automation system for cooling
beds and bar shears at merchant mill. The method has been developed using two
nos. of PLCs, six nos. of remote I/Os with new modified operator desks at Bar
Shears and Control Pulpit-10. Remote I/Os are placed inside the bar shear operator
desks in a very harsh environment. All the nodes are connected through cold
redundant communication network eliminating all multicore control cables.
BACKGROUND ART
At the locations just prior to cooling beds , Insulated earth roll detectors (IRD) are
used for initiating kick off operation that were used for kicking the bars at cooling
beds. The operation of Insulated roll detectors was to detect the bars in an earth
contact manner and initiate the kick off operation after a certain time interval as
desired by the process. Secondly the distributed hardwired relay logic based control
method in case of sequential drive operations at cooling beds and bar shears is used
in the merchant mill of DSP.
Such conventional method suffers from drawbacks / disadvantages which are
discussed hereunder:
a. Insulated roll detectors (IRD) were getting damaged frequently due to hitting
of hot bars resulting in a non-availability of signals to activate the kick off
operation.
b. Generation of Cobbles and breakdown in cooling beds where the problem
occurs.
c. Replacement or maintenance of insulated roll detectors is difficult due to
harsh environment and continuous operation of mill.
d. Any breakdown in any of the control mechanism based on relay logic leads to
mill stoppage / generation of cobbles
e. Change in control philosophy is difficult due to hardwired relay based logic
f. Multicore control cables used at bar shear areas are prone to damage and
causing multiple breakdown.
g. No online diagnostic facility is available for fault analysis.

OBJECTS OF THE INVENTION
The basic object of the present invention is thus to develop an improved method of
non contact type sensors for automatic kick off operation at cooling beds of
merchant mill.
Another object of the present invention is to develop an improved method of
centralized control system for various mechanisms at cooling beds and bar shears.
Another object of the present invention is to develop an improved centralized control
and monitoring using Programmable Logic Controllers (PLC) for ease of maintenance
& reducing downtime.
A further object of the present invention is to provide an introduction of soft logic in
place of hardwired relay logic.
A further object of the present invention is to develop an integrated system for fault
diagnostics and analysis.
A further object of the present invention is to provide on-line and historical status of
inputs and outputs.
A further object of the present invention to use of hot metal detectors are put online
for the detection of TMT bar for improved method of automatic kick off operation at
cooling beds.
A further object of the present invention is to develop remote I/O stations at
distributed locations for inputting and outputting various control parameters.
A further object of the present invention is to provide all the nodes are connected
through cold redundant communication network.
A further object of the present invention is to develop a user friendly Human
Machine Interface (HMI) screen that is capable to eliminate all manual intervention
and helping online data analysis.
A further object of the present invention is to develop RIOs (Remote input outputs)
that are to be placed inside the operator desks at a very harsh operating
environment.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a
system for non-contact type sensor for kick off operation , automatic monitoring and
centralized control of various operations of cooling beds and/or bar shear area of
mills comprising:
Online hot metal detectors adapted for detection of bars;
Operatively connected programmable logic controller (PLC) adapted for centralized
control and monitoring;
Remote I/O stations at distributed locations for inputting and outputting various
control parameters; and
Human machine interface adapted to favour online data analysis and automatic
monitoring and control operations of cooling beds and bar shear area of mills.
In the above system for non-contact type automatic kick off operation and
centralized control at cooling beds all nodes are connected through cold redundant
communication network.
Advantageously, the system for non-contact type automatic kick off operation at
cooling beds and centralized control comprise remote inputs and outputs provisions
to favour operations in very harsh operating environments.
In accordance with an aspect of the invention there is provided a system for non-
contact type automatic kick off operation at cooling beds and centralized control
comprising:
Two PLC and Six Remote I/O based system with appropriate interfaces adapted for
connection of all the field signals, the nodes including two programming terminals
and one HMI terminal operatively connected through cold redundant communication
network, means for generating command signals from the various operator panels
connected to the remote I/O panels installed in the individual panels.
In the above system for non-contact type automatic kick off operation at cooling
beds and centralized control for each cooling bed, one independent PLC is located
near the CVDC (Common Voltage DC) drive panels at basement of cooling bed, the
Programming terminal for the purpose of programming, trouble-shooting and
monitoring of the PLC, remote I/Os for bar shear signals inside bar shear operator
desks at each cooling beds away from PLC Panel, all solenoid operated field
operation in bar shear area including gauge heads up / down, stopper raise / lower,
hold down raise / lower, shear cut are locally terminated at a Solenoid panel which is
provided with two nos. of networking nodes in which network nodes from RIO
based bar shear operator desks are connected, the commands for the operation of
solenoids are adapted to be generated from the switches and push buttons of bar
shear operator desks;
A remote 10 based Operator desks wherein two nos. of networking nodes
interconnected with their respective PLCs through OFC (optical fibre cable) adapted
to control various field signals and multiple mode operations of drives;
Two nos. of HMDs (Hot metal detectors) adapted for sensing the material just before
entering the cooling beds and then initiating the kick off operation after a suitable
time interval for accurate and auto operation of kick off.
Preferably, the said PLCs and Remote I/Os are connected through cold redundant
communication network cable while Ethernet communication is provided for inter-
connection of PLCs, RIOs and the programming units to keep the architecture open
for up-gradation in future and interface with other systems for shop-wide MIS.
Also, the said hot metal detectors are selected such as to sense the material after
thermax cooling and should be sensitive so as to sense the material at lower
temperatures less than 300 deg. C.
Importantly also, separate PLC are selectively provided such that each cooling bed
may function independently in case of any problem in other one and each PLC
operatively connected to"three remote I/O units and each located at a control pulpit,
bar shear Operator Desk and solenoid panel, one HMI terminal is operatively
connected to the network that may exchange data with PLC system in a desirable
manner while all Remote I/Os are connected to respective control desk, operator desk
etc.
In accordance with another aspect of the invention, the Input signals for all the field
control devices have been taken to the system with proper isolation, all digital inputs
have been taken through auxiliary relays of matching specification, depending upon
the location of the field signals, relay boards have been provided at the front walls of
the Common voltage DC drive panels in both the cooling beds, relay boards have been
prepared for both the cooling beds and fixed in the front walls of drive panels, field
inputs have been taken to the PLC through separate remote I/Os installed close to
control pulpit, bar shears and solenoid panels.

According to another aspect of the invention the system for non-contact type
automatic kick off operation at cooling beds and centralized control comprises:
PLC-1 & PLC-2 installed in the basement of their respective cooling beds, three
remote I/Os, first in a control pulpit, second in operator panel and third at solenoid
panel operatively connected with PLC-1 and networked, similarly three more
Remote I/Os first In a control pulpit, second in operator panel and third at solenoid
panel are connected with PLC-2 and networked, two remote IOs at control pulpit
are connected with each other via FO Ethernet and two remote IOs at solenoid
panels are connected with CAT-VI Ethernet, thus making a ring type network. PLC-1
and PLC-2 were operatively connected separate with programming terminals,
however any PLC can be accessed with any of the programming terminals, the relay
boards corresponding to the digital output signals of each CVDC drive panels are
installed at the front walls in cooling beds, the digital input signals of each CVDC
drive panels are terminated junction boxes at the rear side of each panel preferably
with all the communication cables are laid inside the GI pipe so as to ensure their
protection from physical damage.
The details of the invention, its objects and advantages are explained hereunder in
greater detail in relation to non-limiting exemplary illustrations as per the following
accompanying figures:
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure: 1: PLC based Automation Scheme (Schematic block diagram shown).
Figure: 2: Communication Network connecting all the nodes i.e. two PLCs and six
Remote I/O stations.
DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACOMPANING
FIGURE
The improved method consists of a monitoring and control of various mechanisms of
the cooling beds and bar shear area of the mill through two PLC and Six Remote I/O
based system. Appropriate interfaces were designed and installed for connection of
all the field signals to the new PLC system. All the 11 nodes including two
programming terminals and one HMI terminal are connected through cold redundant
communication network covering a total length of 1.2 km approximately. The
command signals from the various operator panels were connected to the remote
I/O panels installed in the individual panels. This configuration enabled drastic
reduction of 220Vdc cables earlier connecting the operator panel elements to the
hardwired circuits in the basement at cooling beds.
For each cooling bed, one independent PLC is located near the CVDC drive panels at
basement of cooling bed; The Programming terminal for the purpose of
programming, trouble-shooting and monitoring of this PLC is put in a modified air
conditioned programming terminal room at a distance of nearly 50 m from PLC. The
remote I/Os for bar shear signals are placed inside the new bar shear operator desks
at each cooling beds at nearly 80 m away from PLC Panel. These have reduced the
bunch of signal cables by an Ethernet communication cable (CAT 6 in this case). All
the solenoid operated field operation in bar shear area like gauge heads up / down,
stopper raise / lower, hold down raise / lower, shear cut etc are locally terminated at
newly installed Solenoid panel under the method. This panel has two nos. of
networking nodes in which network nodes from RIO based bar shear operator desks
are connected. The commands for the operation of solenoids are given by the
operators from the switches and push buttons of bar shear operator desks.
Similarly a remote 10 based Operator desks are placed in CP -10 in which there are
two nos. of networking nodes interconnected with their respective PLCs through OFC
(optical fibre cable). Various field signals and multiple mode operations of drives are
controlled by this desk.
Two nos. of HMDs (Hot metal detectors) of Delta (USA) make , Series DC4000 with
suitable protections are installed and commissioned under the new improved method
for sensing the material just before entering the cooling beds and then initiating the
kick off operation after a suitable time interval for accurate and auto operation of
kick off. These have replaced the age old insulated roll detectors prone to frequent
failure and missing of signals. In order to address the absence of any online
diagnostics tools and indications & very high time taken for frequent fault findings,
One HMI station is provided in Electrical control room for development and
monitoring of critical operations involved.
The changeover to the new method was carried out in a phased manner and in
weekly shutdown days without hampering the scheduled production.
Network Scheme:
Both the PLCs and six Remote I/Os are connected through cold redundant
communication network cable keeping in mind the criticality of the controls.
Separate cable routes have been chosen carefully to avoid any interference and
simultaneous breakage/failure of communication network cable. Ethernet
communication was used for inter-connection of PLCs, RIOs and the programming
units to keep the architecture open for up-gradation in future and interface with
other systems for shop-wide MIS. Fibre optic Ethernet communication was used
between PLCs and RIOs at CP-10 while CAT-6 based Ethernet communication was
used in rest of the network.
Hardware selection;
The HMD is selected on the basis that it can sense the material after thermax
cooling, so HMD must be sensitive enough to sense the material at lower
temperature (less than 300 deg C). Delta make DC 4000 series HMD having
response time 5 msec is chosen for this purpose. The merchant mill has many
makes of PLCs functioning for different types of control. The most important
considerations for designing an improved method for automation of cooling beds and
bar shears were cost and future integration. The integrated system have 2 PLCs;
one for CB-1 and other for CB-2. Two numbers of PLC was taken deliberately so that
each cooling bed may function independently in case of any problem in other one.
Each PLC has been connected to three remote I/O units and each located at Control
pulpit 10, bar shear Operator Desk and solenoid panel. One HMI terminal is
connected to the network that may exchange data with PLC system in a desirable
manner. All Remote I/Os are connected to respective control desk, operator desk
etc. Major items that are used are HMD, Allen-Bradley make PLC & Remote I/Os and
various other processor and I/O card, Software etc used are given below:
OFC used: Between PLC - 1 and RCB-1 at CP 10
Between PLC - 2 and RCB-2 at CP 10 (shown in figure 2)
CAT-6 used: Between PLC - 1 and RIO based OD (operator desk) at BS-1
Between PLC - 2 and RIO based OD at BS-2
Between RIO based OD at BS-land RIO based solenoid panel
Between RIO based OD at BS-2and RIO based solenoid panel
(Shown in figure 2)
Field Interface:
Input signals for all the field control devices have been taken to the system with
proper isolation. All digital inputs have been taken through auxiliary relays of
matching specification. Depending upon the location of the field signals, relay boards
have been provided at the front walls of the Common voltage DC drive panels in
both the cooling beds. 14 numbers of relay boards have been prepared for both the
cooling beds and fixed in the front walls of drive panels. Field inputs have been
taken to the PLC through six separate remote I/Os installed close to CP 10, bar
shears and solenoid panels. Some of the field signals that are on the drive panels
are directly taken to the respective PLCs. Separate MCBs and relays of suitable
ratings are provided to all the field signals actuating the solenoids in bar shear
areas.
Erection of Hardware:
PLC-1 & PLC-2 are installed in the basement of their respective cooling beds. Three
remote I/Os, first in CP-10, second in operator panel at BS-land third is at solenoid
panel are connected with PLC-1 and networked. Similarly three more Remote I/Os
first in CP-10, second in operator panel at BS- 2and third is at solenoid panel are
connected with PLC-2 and networked. The two remote IOs at CP-10 are connected
with each other via FO Ethernet and two remote IOs at solenoid panels are
connected with CAT-VI Ethernet, thus making a ring type network. PLC-1 and PLC-2
were connected separate with programming terminals, however any PLC can be
accessed with any of the programming terminals. The relay boards corresponding to
the digital output signals of each CVDC drive panels are installed at the front walls in
cooling beds. The digital input signals of each CVDC drive panels are terminated in
newly designed junction boxes at the rear side of each panel. All the communication
cables are laid inside the GI pipe so as to ensure their protection from physical
damage.
Commissioning:
The complete commissioning of the system was done in-house by RDCIS and DSP
jointly. Complete I/O listing including termination details has been prepared for
more than 800 I/O signals. Total commissioning was carried out in different phases.
In absence of regular planned shut down, certain jobs were completed during shift
change over. Non shutdown jobs were to be done during weekdays and major
Commissioning work was to be carried out during weekly shutdown day. The total
Project was completed in a phased manner without taking any additional shutdown
specific for this job. Normal production of the Mill was not affected during erection &
commissioning of the system.
Safety/ Earth:
Separate earth pits were made for each PLCs and their respective Remote I/Os. The
electronic earth has been distributed from the two earth pits sources to all the nodes
to avoid any mismatch in earth potential.
Software Development:
PLC application programs have been developed for the PLC operation. The programs
are developed in a modular manner. Separate modules have been written for rotary
kick off, carry over, Shuffle bar eccentric, Shuffle bar lifting, push off, back shear
table etc. and finally integrated in one program. Precaution has been taken for all
the inter locks for the limit switches and all field signals for sequential operation of
automatic cooling beds and bar shear mechanisms.
Trials:
Due to faster response of the new PLC based method the voltage across the
contactor coil probably shooted up momentarily. To overcome this problem
freewheeling diodes of rating (PIV = 1000V and current = 3 Amps) are put across
the coils of one CVDC drive panel. But it was found that main dc fuse of 220 amps
blows during operation. It may be due to either damaged diodes or diodes were in
forward biased. These possibilities are thoroughly checked up and only seven nos. of
drives are allowed to run with diodes, but one of the diodes get shorted and again
blowing DC fuse after five days of successful running of system forced the taskforce
to think again on keeping the diodes in the circuit. Lot of documents was collected
through internet on protection of DC Contactors and on Metrosil. The experiment
was conducted with the help of ETL (Electrical technical laboratory) to study the on
line behavior of current shoot up across the coils. Voltage pattern across the
contacts of 3TF32 (Siemens make intermediate relay) was studied by oscilloscope
from ETL because this pattern is nearly proportional to actual pattern across the
coils (three types DD 300, DD150 and DD75 in this case). The online peak voltage
was found 3.5 KV in case of DD75 and DD150 and 5.5 KV in case of DD300 during
coil pickup. Ultimately it was thought to replace the diodes by the Metrosils, which
are non linear resistors with high surge protection devices and is manufactured from
a semiconducting material with the distinctive property that its electrical resistance
depends on the applied voltage enabling it to act as an electrical safety valve to
protect equipment and insulation from the effect of over voltages. Metrosil are the
right surge protection devices because of superior energy absorption, no derating
and low maintenance. It was found as soon as diodes were replaced by the Metrosil,
the peak voltage get limited to 600V. This is a remarkable improvement and quite
safer for the protection of the coils. The diodes were removed from the circuits of all
drive panels and metrosils were put across the coils of one of the drive panels for
experimentation for one full week. The successful online trial with the metrosils
prompted us to put Metrosil in rest of the drive panels in subsequent shutdown days.
Thus Extensive trials were carried out before putting the system on-line. Each
mechanism, where interlocks are used required lot of trials so that the new system
runs trouble free. Some minor changes in the position of rotary limit switches were
made to make them work nicely with the new soft logic.
Results and Discussion:
An improved method of Automation for cooling beds and bar shears at merchant mill
was run satisfactorily during the integrated trial period. System stabilized after
series of experiments with freewheeling diodes as well as with Metrosil putting
across the coils of existing contactors. The response of the method was found to be
much faster and reliable with respect to the earlier method. Faster and reliable kick
off operation was resulted by using HMD in place of IRD.
The Communication Scheme between different nodes of network (Fig 2) is found
quite satisfactory. The bunch of cables going to bar shear area as well as CP-10 area
from the basement of cooling beds are reduced drastically thus eliminating the
cables maintenance. Besides that the response of locally placed IOs are much
satisfying to the operational requirement at merchant mill. All the solenoids
operated outputs at bar shear areas are made to operate with 24 V DC control
Voltage, thus simplifying the control circuits. Any change in control philosophy can
be easily achieved through soft logic in place of earlier complex hard wired relay
based control circuits which was difficult to maintain, modify and troubleshoot.
Further maintenance and safety are made simpler with the power to Individual
solenoids having been routed through individual MCBs and fusible terminals. The
new thumb wheel switches are now programmed with new PLC system which has
shown faster response, the option to shift entering kick off timing with the help of
HMI is also proved successful.
We Claim:
1. A system for non-contact type automatic kick off operation and centralized
control, monitoring of various operations of cooling beds and/or bar shear area of
mills comprising:
Online hot metal detectors adapted for detection of bars;
Operatively connected programmable logic controller (PLC) adapted for centralized
control and monitoring;
Remote I/O stations at distributed locations for inputting and outputting various
control parameters; and
Human machine interface adapted to favour online data analysis and automatic
monitoring and control operations of cooling beds and/or bar shear area of mills.
2. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in claim 1 wherein all nodes are connected through cold
redundant communication network.
3. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 or 2 comprising remote input and
outputs inside an operator desk provisions to favour operations in very harsh
operating environments.
4. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 to 3 comprising:
Two PLC and Six Remote I/O based system with appropriate interfaces adapted for
connection of all the field signals, the nodes including two programming terminals
and one HMI terminal operatively connected through cold redundant communication
network, means for generating command signals from the various operator panels
connected to the remote I/O panels installed in the individual panels.

5. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 to 4 wherein for each cooling bed,
one independent PLC is located near the CVDC (Common voltage DC) drive panels
at basement of cooling bed, the Programming terminal for the purpose of
programming, trouble-shooting and monitoring of the PLC, remote I/Os for bar
shear signals inside bar shear operator desks at each cooling beds away from PLC
Panel, all solenoid operated field operation in bar shear area including gauge heads
up / down, stopper raise / lower, hold down raise / lower, shear cut are locally
terminated at a Solenoid panel which is provided with two nos. of networking
nodes in which network nodes from RIO based bar shear operator desks are
connected, the commands for the operation of solenoids are adapted to be
generated from the switches and push buttons of bar shear operator desks;
A remote 10 based Operator desks wherein two nos. of networking nodes
interconnected with their respective PLCs through OFC (optical fibre cable) adapted
to control various field signals and multiple mode operations of drives ;
two nos. of HMDs (Hot metal detectors) adapted for sensing the material just before
entering the cooling beds and then initiating the kick off operation after a suitable
time interval for accurate and auto operation of kick off.
6. A system for non-contact type automatic kick off operation and centralized
control at cooling beds as claimed in anyone of claims 1 to 5 wherein said PLCs and
Remote I/Os are connected through cold redundant communication network cable
while Ethernet communication is provided for inter-connection of PLCs, RIOs and the
programming units to keep the architecture open for up-gradation in future and
interface with other systems for shop-wide MIS.
7. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 to 6 wherein the said hot metal
detectors are selected such as to sense the material after thermax cooling and
should be sensitive so to sense the material at lower temperatures less than 300
deg. C
8. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 to 7 wherein separate PLC are
selectively provided such that each cooling bed may function independently in case
of any problem in other one and each PLC operatively connected to three remote I/O
units and each located at a control pulpit, bar shear Operator Desk and solenoid
panel, one HMI terminal is operatively connected to the network that may exchange
data with PLC system in a desirable manner while all Remote I/Os are connected to
respective control desk, operator desk etc.
9. A system for non-contact type automatic kick off operation and centralized control
at cooling beds as claimed in anyone of claims 1 to 8 wherein Input signals for all
the field control devices have been taken to the system with proper isolation, all
digital inputs have been taken through auxiliary relays of matching specification,
depending upon the location of the field signals, relay boards have been provided at
the front walls of the Common voltage DC drive panels in both the cooling beds,
relay boards have been prepared for both the cooling beds and fixed in the front
walls of drive panels, field inputs have been taken to the PLC through separate
remote I/Os installed close to control pulpit, bar shears and solenoid panels.
10. A system for non-contact type automatic kick off operation and centralized
control at cooling beds as claimed in anyone of claims 1 to 9 comprising
PLC-1 & PLC-2 installed in the basement of their respective cooling beds, three
remote I/Os, first in a control pulpit, second in operator panel and third at solenoid
panel operatively connected with PLC-1 and networked, similarly three more Remote
I/Os first in a control pulpit, second in operator panel and third at solenoid panel are
connected with PLC-2 and networked, two remote IOs at control pulpit are
connected with each other via FO Ethernet and two remote IOs at solenoid panels
are connected with CAT-VI Ethernet, thus making a ring type network. PLC-1 and
PLC-2 were operatively connected separate with programming terminals, however
any PLC can be accessed with any of the programming terminals, the relay boards
corresponding to the digital output signals of each CVDC drive panels are installed at
the front walls in cooling beds, the digital input signals of each CVDC drive panels
are terminated junction boxes at the rear side of each panel preferably with all the
communication cables are laid inside the GI pipe so as to ensure their protection
from physical damage.
11. A system for non-contact type automatic kick off, monitoring and control of
various operations of cooling beds and/or bar shear area of mills substantially as
herein described and illustrated with reference to the accompanying figures.

There is provided a system for non contact type HMD based automatic kick off
operation at cooling beds at merchant mill and a method of its implementation. The
system and method ensures the automatic detection of leading edge of moving hot
bars and automatic kick off operation of bars at cooling beds. The new methods also
have a comprehensive PLC network based centralized control automation system for
cooling beds and bar shears at merchant mill. The method has been developed using
two nos. of PLCs, six nos. of remote I/Os with new modified operator desks at Bar
Shears and Control Pulpit-10. Remote I/Os are placed inside the bar shear operator
desks in a very harsh environment. All the nodes are connected through cold
redundant communication network eliminating all multicore control cables.
Maintenance and safety are made simpler with the power to Individual solenoids
having been routed through individual MCBs and fusible terminals.