FIELD OF THE INVENTION
The present invention relates to wireless signal transmission system for rotating
turret of a continuous caster. More particularly, the invention relates to the design
and development of a wireless signal transmission system for electrical equipment
mounted on a rotating structure such as the turret of a continuous caster. The signal
transmission system has been designed using wireless modems, RTU cards, weighing
system controllers, proportional valve amplifiers mounted in air cooled and dust
proof enclosure. The system ensures reliability of signal transmission thereby
achieving reduction in downtime of equipment and enhancing reliability of the
operation favouring wide scale application of such system for Turret operation of
continuous casting machine at Steel Plants.
BACKGROUND OF THE INVENTION
In the hostile environment of steel plants, cables get burnt or cut, causing
breakdowns. There are areas where cable laying is almost impossible. Signals are
lost or distorted when transmitted by long distance cables. Modern steel plants must
operate extremely precisely in order to produce consistent, high quality output.
Reliable wireless communication systems are key components of steel production
operations to reduce maintenance workload, increase efficiency, and reduce the risk
of accidents. Wireless transmission is a technology that enables sending / receiving
of signals without any physical wires, just like mobile phones, Wi-Fi, pagers, etc,
Wireless transmission of signals is coming in a big way and is destined to become the
technology of tomorrow.
Turret is the most vital equipment of continuous casters of any steel plant. It is used
to hold molten steel in the ladle while casting continues. Since it is rotating
equipment, all the electrical signals to and from turret was routed via slip rings,
located inside the turret well. Length of control cables is around 300 mtrs for each
signal with intermediate junction boxes between field devices, mounted on Turret
and the PLC in the control room. Long distance control cables resulted in loss of
signal and made interlocking un-reliable. Position of slip ring makes maintenance
difficult and breakdown of control cable / slip ring assembly causes the caster to
stop, resulting in loss of production.

Thus the existing cable network based signal communication for control of operations
of the rotating turret of a continuous caster suffers from the following limitations:
(i) Transmission of signals by the conventional method using control cables;
(ii) All signals are routed to / from Turret via slip ring, since Turret rotates by
360°;
(iii)Load cell output (millivolt), becomes inaccurate due to long distance
cables;
(iv)Signal transmission via rotating slip ring is unreliable;
(v) Trouble shooting in the slip ring during casting is not possible;
(vi)Any breakdown in the slip ring causes stoppage in production;
The successful use of wireless technology has immense potential in steel plant
having harsh operating environment that includes dust, smoke, vibration, EMI/noise,
and extremely high temperatures.
There has been thus a need to developing a signal communication system for turret
operation of continuous caster to avoid the above stated limitations and
disadvantages, involving particularly a wireless based signal transmission system for
Turret in continuous casting machine which would be reliable for implementing
control functions as well as easy to maintain with less faults/breakdown and thus
improving productivity. The system being developed for rotating turret continuous
caster has huge possibilities of advantageous application in other Continuous Casting
Machines and also in areas like Raw Materials Handling Plant, Coke ovens, Sinter
Plants and Blast furnaces etc for status monitoring and control of conveyors network
operations.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to developing a wireless
signal transmission system for rotating turret of a continuous caster for reliable
interlocking and control of a rotating structure with reduced frequency of breakdown
and improved trouble shooting and maintenance.

A further object of the present invention is directed to developing a wireless signal
transmission system for rotating turret of a continuous caster involving development
of a reliable method of analog and digital signal transmission using wireless media.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster which would be
non contact type involving development of signal transmission from rotating
structure without using the conventional slip ring method.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster wherein a PLC
based means adapted for generating net molten metal weight enabling selectively
process monitoring, control and alarm generation.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster which would be
capable of wireless signal transmission suitable to work in the harsh ambience of
Continuous caster shop.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster which would
ensure easier fault diagnosis, troubleshooting and will facilitate the reduction of
downtime, to achieve higher productivity.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster which would
work satisfactorily and reliably in harsh operating environment that includes dust,
smoke, vibration, EMI/noise, and extremely high temperatures.
A still further object of the present invention is directed to developing a wireless
signal transmission system for rotating turret of a continuous caster which can also
be applied for Raw Materials Handling Plant, Coke ovens, Sinter Plants and Blast
furnaces etc for status monitoring and control of conveyors network operations.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine in steel plant comprising:
a wireless station on Turret ;
a wireless station in control room;
means adapted for sensing various analog and/or digital signals ;
means adapted to control Turret and tundish movement;
a PLC based means adapted for generating net molten metal weight enabling
selectively process monitoring, control and alarm generation.
A further aspect of the present invention is directed to a non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine in steel plant comprising
a Wireless station installed on Turret;
a Wireless station installed in Control room in operative wireless
communication of signals with said Wireless station installed on Turret;
a display system mounted on roof of control room;
a PLC installed in control room adapted to receive and process signals
received from turret for desired control and display of net molten metal
weight.
A still further aspect of the present invention is directed to a non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein
a) said Wireless station on Turret comprises
I. Radio Modem
II. RTU cards

III. Proportional valve amplifier cards
IV. Weighing system controller cards
V. Switchgears
VI. Panel mounted AC unit
VII. Antenna and associated cables
VIII. Male / Female connectors for changeover; and
b) said Wireless station in Control room comprises of:
I. Radio Modem
II. RTU cards
III. Switchgears
IV. Antenna and associated cables.
A steel further aspect of the present invention is directed to a non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein said Weighing system Controller comprising
Mains voltage: 85 - 265 V AC
Mains frequency: 45 - 65 Hz
Power consumption: 140 VA
Operating temp: 0 to + 70°C
Measuring error: < 0.05%
Measuring rate: 20 values/sec
Analogue outputs: 4 No.
Voltage output:0 - ± 10 V
Current output: 0 - ± 20 Ma
A further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein said Radio Modem comprising
Frequency range: 865 - 867 MHz
Channel spacing: 25Hz
Communication mode: Half-duplex
Carrier Power: 100 mW - 500 mW Programmable /SO ohm
Sensitivity: -115...-110dBm (BER<10E-3)
Interface: RS-232 or RS-422 RS-485
Operating voltage: +9... +30 Vdc

Temperature range: -25°C...+65°C
Antenna connector: TNC, 50 ohm, female
International compliance: EN 300-220-1,ETS 300-113,683, IEC 60950
yet another aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein said Radio RTU cards comprising
Supply Voltage: + 18v to +36v DC
Digital Inputs: 8 nos optically isolated
Digital Outputs: 8 nos potential free contacts, 250V-5A
Analog Inputs: 2 nos 0-20mA 12 bit resolution
Analog Outputs: 2 nos 0-20mA 12 bit resolution with internal Loop power.
Expansion Ports: Available
Communication Ports: 2 Serial PORT RS232 & RS232/RS485
Protocols: Modbus RTU, Modbus Ascii, ASCII
Operating Temperature: -20 degree Celsius to +75 degree Celsius
Expansion bus: Supports till 8 expansion module
Protocol support: MODBUS, ASCII
Mounting: Din Rail Type
A still further aspect of the present invention is directed to a non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein said Panel AC unit comprising
Rated voltage: 230, 1~,50/60 Hz
Rated current: 2.6/2.6 A
Start-up current: 5.1/6.4 A
Pre-fuse T: 10.0 A
Useful cooling output: 500/610
Power consumption: 360/380 W
Refrigeration factor: 1.4
Temperature setting range: +20 to +55°C
Dimensions (W x H x D): 280mm x 550mm x200mm
Weight: 17KG.

A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein there are total 8 load cells, 4 per arm of rotating turret for
weighing of molten metal, where load cell output is converted on Turret itself, to 4-
20mA level and sent via wireless to the ground PLC, eliminating any chances of
signal loss and interference.
A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein Weighing system controllers are used to supply excitation current
to the Load cells mounted on the Turret Arms (4 per arm).
A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein the millivolt output from the Load cells is processed in the
controller with output of the controller being 4-20mA corresponding to the load and
this 4-20mA signal is pre wired to wireless modem on Turret panel and transmitted
to the wireless station in MCR(control room) wherein this signal (Gross weight) is
connected to the PLC as analog input so that the Software in the PLC processes this
signal and displays net molten metal weight.
A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein direct wireless transmission of the digital signals eliminates the
intermediate slip ring and junction boxes, thereby increases reliability.
A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein there are 8 Limit switches, 4 per arm for turret arm position
Feedback and 2 proportional valves per Arm, one for up direction and one for down
direction and wherein signals of limit switches and proportional valves are used for
interlocking of Turret movement.
A still further aspect of the present invention is directed to said non-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein wireless transmission of all the digital and analog signals adapted
to achieve reduction in metal dumping, reduction in chances of slag going to tundish
and also increased reliability of the caster operation.

A still further aspect of the present invention is directed to saidnon-contact wireless
signal transmission system for control of rotating Turret in a continuous casting
machine wherein direct transmission of signals from Turret to PLC reduce the
possibility of breakdown to thereby increasing the availability of Turret which lead to
better Caster operation.
The various other objects and advantages of the present invention is described in
greater details with reference to the following non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 : shows Present scheme of signal transmission between Turret and PLC;
Figure 2 : shows Implemented Scheme for wireless signal transmission according to
the present invention;
Figure 3 : shows Signal Flow and Changeover Scheme for Limit Switch;
Figure 4 : shows Signal Flow and Changeover Scheme for Proportional Valves;
Figure 5 : shows Signal Flow and Changeover Scheme for weighing system;
Figure 6 : shows Layout of the wireless panels;
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to wireless signal transmission system for rotating
turret of a continuous caster and more particularly, for controlling electrical
equipment mounted on a rotating structure. For the first time in Indian Steel Plant,
wireless signal transmission has been successfully implemented in one of the most
hazardous area of steel making namely rotating Turret of a Continuous Caster. The
system is totally indigenous and comprises of radio modem based signal transmitter
and receiver, weighing system controllers, hydraulic valve amplifiers, PLC system
and special fire resistant panels. The application and control software has been
developed in-house.

The wireless signal transmission system for rotating turret of a continuous caster
have been developed comprising the following stages:
a) Design of a comprehensive schematic of wireless signal transmission system
b) Selection of proper equipment like radio modem , weighing controllers, valve
amplifiers
c) Interfacing with the load cells and proportional valves
d) Installation of the system in phased manner with minimum shutdown of
caster
e) Integration of the new system with existing automation system
f) Development of software to control the process.
With the installation of the new wireless signal transmission system, dependency on
the slip ring and control cables is eliminated for signal transmission. The deployment
of the system helped overcome loss of signal due to long distance cabling. The
system will also result in easier fault diagnosis, troubleshooting and will facilitate
the reduction of downtime, to achieve higher productivity.
The wireless signal transmission system for rotating turret of a continuous caster
according to the present invention comprises both hardware and software. The
followings are the hardware components;
c) Wireless station on Turret comprises of:
IX. Radio Modem
X. RTU cards
XI. Proportional valve amplifier cards
XII. Weighing system controller cards
XIII. Switchgears
XIV. Panel mounted AC unit
XV. Antenna and associated cables
XVI. Male / Female connectors for changeover
d) Wireless station in Control room comprises of:
V. Radio Modem
VI. RTU cards
VII. Switchgears
VIII. Antenna and associated cables
e) Display system mounted on roof of control room

The software component consists of a program which performs the following
operations:
i) Sensing of different analog & digital signals, conversion of these signals into
Engineering units
ii) Writing software to control Turret and Tundish movement
iii) Conversion of gross metal weight to net molten metal weight in a PLC
iv) Displaying the net molten metal weight
v) Process monitoring, control and alarm generation;
The technical specification of the major hardware components as given above, used
in the wireless signal transmission system, are as follows:

Reference is first invited to Figure 1 shows existing scheme of signal transmission
between Turret and PLC, wherein the location of the slip ring is shown i.e, inside the
Turret well. All the field equipment such limit switches, proportional valves and load
cells are connected to the moving brush. The slip ring is stationary and all the signal
cables are connected to the slip ring. Control cable from the field equipments are
routed to the PLC via brush, slip ring and intermediate junction boxes. Presently
Load cell signals are routed to PLC room via slip ring and control cables
approximately 300 meters in length. Load cell output is in millivolt. Chances of signal
loss and interference is high, due to long distance cable. Presently limit switch and
proportional valve signals are routed to PLC room via slip ring and control cables
approximately 300 meters in length. Moreover, in the existing system location of the
slip ring is such that it cannot be accessed during Casting and trouble shooting any
problem in slip ring or associated cables etc inside the Turret well puts the
technicians at risk.
Reference is now invited to accompanying Figure 2 that schematically shows the
newly implemented wireless signal transmission based control scheme for rotating
turret for continuous caster, where the slip rings and control cables are totally
eliminated for signal transmission. There are two wireless stations, one on the Turret
and the other in the Control Room. The panel on Turret has wireless modem, I/O
cards, Valve amplifiers and weighing system controllers. Weighing system controllers
are used to supply excitation current to the Load cells mounted on the Turret Arms

(4 per arm). The millivolt output from the Load cells is processed in the controller.
Output of the controller is 4-20mA corresponding to the load. This 4-20mA signal is
pre wired to wireless modem on Turret panel and transmitted to the wireless station
in MCR. This signal (Gross weight) is connected to the PLC as analog input. Software
in the PLC processes this signal and displays net molten metal weight.
Change over scheme has been provided for all the signals of turret. During
stabilization period, if required, the system can be operated on either the new or the
old scheme. For creating the changeover scheme we use, male-female connectors.
Accompanying Figure 3 shows Signal Flow and Changeover Scheme for Limit Switch
which performs the task of providing position feedback for the turret arms.
Accompanying Figure 4 shows the Signal Flow and Changeover Scheme for
Proportional Valves which performs the task to move the turret arm up / down at
slow / fast speed. Accompanying Figure 5 shows Signal Flow and Changeover
Scheme for weighing system which indicate how the load cell signals are connected
to the old and new route, and Figure 6 shows layout of wireless panels in MCR and
on Turret which indicate the layout of various equipments in both the panels.
The gross weight, transmitted from the turret wireless station is received in the MCR
station in form of 4-20mA signal. This signal is connected to PLC as analog input. In
the PLC we have made a provision to tare the gross weight. In a subtractor module,
ladle weight and skull weight is subtracted from the gross weight. Output of the
subtractor is taken out through a analog output module. This signal is sent to a Big
display mounted on the roof of MCR.
The above stated wireless signal transmission system for rotating turret of a
continuous caster in steel plants thus ensures:
a) Enhanced accuracy of the weighing system as in the new system, load cell
output is converted on Turret itself, to 4-20mA level and sent via wireless to
the ground PLC, eliminating any chances of signal loss and interference. Also
the digital load cell controller used in the developed system is latest, and with
many diagnostic and troubleshooting features.
b) Enhanced reliability of digital signal transmission by direct wireless
transmission of the digital signals eliminating the intermediate slip ring and
junction boxes, thereby increasing reliability.

c) Increased availability of Turret as signals of limit switches and proportional
valves are used for interlocking of Turret movement and direct transmission
of these signals from Turret to PLC reduce the possibility of breakdown and
ensure improved availability of Turret which leads to better Caster operation.
d) Improved safety of operating/maintenance personnel due to direct wireless
transmission of the digital signals eliminating the intermediate slip ring and
junction boxes.
e) Comprehensive package for signal transmission: A general-purpose wireless
signal transmission system has been introduced for control of process
parameters. The package developed can be horizontally transferred to other
hazardous areas of heavy industries.
The system according to the present invention is thus a wireless signal transmission
system for process control in a heavy industry. It is a non-contact wireless signal
transmission system suitable for rotating ladle turret of continuous caster in steel
plants.
It is thus possible by way of the present invention for the first time in Indian Steel
Plant, to successfully develop and implement a wireless signal transmission system
in one of the most hazardous area of steel making namely rotating Turret of a
Continuous Caster. The system is totally indigenous and comprises of radio modem
based signal transmitter and receiver, weighing system controllers, hydraulic valve
amplifiers, PLC system and special fire resistant panels. The complete application and
control software has been developed in-house for operation of the said wireless
signal transmission system. The successful use of wireless technology has immense
potential in steel plant having harsh operating environment that includes dust,
smoke, vibration, EMI/noise, and extremely high temperatures. The system
developed has huge potential for technology transfer in areas like Raw Materials
Handling Plant, Coke ovens, Sinter Plants and Blast furnaces etc for status
monitoring and control of conveyors network operations.

We Claim:
1. A non-contact wireless signal transmission system for control of rotating Ladle
Turret in a continuous casting machine in steel plant comprising:
a wireless station on Turret;
a wireless station in control room;
means adapted for sensing various analog and/or digital signals ;
means adapted to control Turret and tundish movement;
a PLC based means adapted for generating net molten metal weight enabling
selectively process monitoring,control and alarm generation.
2. A non-contact wireless signal transmission system for control of rotating Turret in
a continuous casting machine in steel plant as claimed in claim 1 comprising
a Wireless station installed on Turret;
a Wireless station installed in Control room in operative wireless
communication of signals with said Wireless station installed on Turret;
a display system mounted on roof of control room;
a PLC installed in control room adapted to receive and process signals
received from turret for desired control and display of net molten metal
weight.
3. A non-contact wireless signal transmission system for control of rotating Turret in
a continuous casting machine as claimed in anyone of claims 1 or 2 wherein
said Wireless station on Turret comprises
XVII. Radio Modem
XVIII. RTU cards
XIX. Proportional valve amplifier cards
XX. Weighing system controller cards
XXI. Switchgears

XXII. Panel mounted AC unit
XXIII. Antenna and associated cables
XXIV. Male / Female connectors for changeover; and
said Wireless station in Control room comprises of:
IX. Radio Modem
X. RTU cards
XI. Switchgears
XII. Antenna and associated cables.
4. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in claim 3 wherein said Weighing
system Controller comprising
Mains voltage: 85 - 265 V AC
Mains frequency: 45 - 65 Hz
Power consumption: 140 VA
Operating temp: 0 to + 70°C
Measuring error: < 0.05%
Measuring rate: 20 values/sec
Analogue outputs: 4 No.
Voltage output:0 - ± 10 V
Current output: 0 - ± 20 Ma
5. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 4 wherein
said Radio Modem comprising
Frequency range: 865 - 867 MHz
Channel spacing: 25Hz
Communication mode: Half-duplex
Carrier Power: 100 mW - 500 mW Programmable /50 ohm
Sensitivity: -115...-110dBm (BER<10E-3)
Interface: RS-232 or RS-422 RS-485
Operating voltage: +9... +30 Vdc
Temperature range: -25°C...+65°C
Antenna connector: TNC, 50 ohm, female
International compliance: EN 300-220-1,ETS 300-113,683, IEC 60950

6. A non-contact wireless signal transmission system for control of rotating Turret in
a continuous casting machine as claimed in anyone of claim 3 to 5 wherein said
Radio RTU cards comprising
Supply Voltage: +18v to +36v DC
Digital Inputs: 8 nos optically isolated
Digital Outputs: 8 nos potential free contacts, 250V-5A
Analog Inputs: 2 nos 0-20mA 12 bit resolution
Analog Outputs: 2 nos 0-20mA 12 bit resolution with internal Loop power.
Expansion Ports: Available
Communication Ports: 2 Serial PORT RS232 & RS232/RS485
Protocols: Modbus RTU, Modbus Ascii, ASCII
Operating Temperature: -20 degree Celsius to +75 degree Celsius
Expansion bus: Supports till 8 expansion module
Protocol support: MODBUS, ASCII
Mounting: Din Rail Type
7. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 6 wherein said
Panel AC unit comprising
Rated voltage: 230, 1~,50/60 Hz
Rated current: 2.6/2.6 A
Start-up current: 5.1/6.4 A
Pre-fuse T: 10.0 A
Useful cooling output: 500/610
Power consumption: 360/380 W
Refrigeration factor: 1.4
Temperature setting range: +20 to +55°C
Dimensions (WxHx D): 280mm x 550mm x200mm
Weight: 17KG.
8. A non-contact wireless signal transmission system for control of rotating Turret in
a continuous casting machine as claimed in anyone of claim 3 to 7 wherein there
are total 8 load cells, 4 per arm of rotating turret for weighing of molten metal,

where load cell output is converted on Turret itself, to 4-20mA level and sent via
wireless to the ground PLC, eliminating any chances of signal loss and
interference.
9. A non-contact wireless signal transmission system for control of rotating Turret in
a continuous casting machine as claimed in anyone of claim 3 to 8 wherein direct
wireless transmission of the digital signals eliminates the intermediate slip ring
and junction boxes, thereby increases reliability.
10. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 9 wherein
Weighing system controllers are used to supply excitation current to the Load
cells mounted on the Turret Arms (4 per arm).
11. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 10 wherein
the millivolt output from the Load cells is processed in the controller with output
of the controller being 4-2GmA corresponding to the load and this 4-20mA signal
is pre wired to wireless modem on Turret panel and transmitted to the wireless
station in MCR(control room) wherein this signal (Gross weight) is connected to
the PLC as analog input so that the Software in the PLC processes this signal and
displays net molten metal weight.
12. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 11 wherein
there are 8 Limit switches, 4 per arm for turret arm position Feedback and 2
proportional valves per Arm, one for up direction and one for down direction and
wherein signals of limit switches and proportional valves are used for interlocking
of Turret movement.
13. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 12 wherein
wireless transmission of all the digital and analog signals adapted to achieve
reduction in metal dumping, reduction in chances of slag going to tundish and
also increased reliability of the caster operation.

14. A non-contact wireless signal transmission system for control of rotating Turret
in a continuous casting machine as claimed in anyone of claim 3 to 13 wherein
direct transmission of signals from Turret to PLC reduce the possibility of
breakdown to thereby increasing the availability of Turret which lead to better
Caster operation.