Claims:We Claim

1. An improved system for automatic measurement and adjustment system for side guide gap in a hot strip mill comprising of :-
a plurality of digital incremental encoders are connected to non-drive end of each stand motor;
a plurality of drive panels with built in communication and encoder feedback card;
a PLC system operable to provide signals for open and close movement of the guide; wherein the PLC system is configured to convert the counter module output to Analog output for display of measured values in Digital Panel Meters (DPM); and
wherein the said encoders are configured to provide the real time speed data of the side guide motors to the PLC and drive system and the speed correction is calculated in the closed loop control system and corresponding open and close movement of guide is activated.

2. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the system includes couplings for connecting gear box shaft with the incremental encoders.

3. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the speed of the side guide motors of the mill stands depend on the actual guide gap requirement.

4. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the open and close movement of the guide is done for adjustment of guide gap.

5. An improved system for automatic measurement of side guide gap using incremental encoders, PLC system, DPT meter, HMI screens

6. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the system further includes HMI screen configured to display measured gap in a monitor in real time.
7. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the drives are connected with each other via CT net cable, the drive communicates with PLC through the profibus cable and PC and drive communication is through Ethernet cable.

8. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein automatic setting of side guide gap is based on measurement feedback of the encoder and PLC.

9. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein drive panels having same numbers of 46A microcontrollers based three phase, inverter grade reversible, digital variable voltage variable frequency drive.

10. The improved system for automatic measurement and adjustment system as claimed in claim 1, wherein the drives include dynamic braking resistances along with suitable punch grid resistances.

Dated: this 12th day of March, 2018
, Description:AN IMPROVED SYSTEM FOR AUTOMATIC MEASUREMENT AND ADJUSTMENT SYSTEM FOR SIDE GUIDE GAP IN A HOT STRIP MILL.

Field of the invention

The present invention relates to automatic measurement of side guide in a hot strip mill and automatic setting of side gap based on the measurement feedback. More particularly, the present invention relates to an automatic on-line guide gap adjustment system based on measurement feedback for hot strip at finishing stands.

Background of the invention

In steel plants, hot strip mills are used to roll slabs to coils in number of rolling mill stands. Schematic diagram of a typical hot strip mill is shown in Figure-1. It comprises 3 Roughing stands and 6 Finishing stands. The first roughing stand is a combination horizontal stand and a vertical stand. The other two roughing stands are 4-hi horizontal stands. There is a delay table after last roughing stand, one coil box and a crop shear at the end of the delay table. There are six numbers of 6 high finishing stands.

In hot strip mill of RSP (Rourkela steel plant), the adjustment of side guide gap for finishing stands of HSM, RSP is manual and totally dependent on the operator. The operator uses the pushbutton for opening and closing of the guides and the guide motor is finally driven by the relay logic based system. Encoders are connected with all guide motors to know the speed of motors those are used to measure the guide gaps after certain calibration. Based on existing hardware, precise control of side guide movement is not possible.

Such conventional Side guide gap adjustment system suffers from drawbacks / disadvantages like, online correction of Side guide gap during rolling is not possible because the motors cannot be stopped at the particular position precisely. It is very difficult to adjust the Side guide gap as per the required width of bar. Desired Side guide gap is not possible due to absence of speed control of guide motors.

In order to ensure proper entry of bar into the finishing mill stands, side guides are placed on entry sides of each stand of finishing mills. As the rolls in the mill have a tendency to entrain the strip to some extent, this may lead to bending or even winding up on the rolls and thus can cause severe damage to the equipment. It is of extreme importance that such guides be designed to feed the material, properly centered and moving exactly the correct direction, into the respective units so as to prevent cobbles, maintain a flat product, and eliminate the scratching and marking. The side guide gap measurement must be accurate. In the manual operation, the operator sets the side gap on the basis of measured value as per planned final strip width. If the measured value erroneous, then the operator sets the gap with the erroneous value which leads to cobble generation in the mill.

This art describes an automatic side guide measurement system and automatic side guide setting system.

Objective of the invention

The objective of the invention was to develop a system for automatic measurement of side guide gap in a hot strip mill.
Another objective is to develop a system for automatic real time setting of side gap based on measurement feedback so that the need of manual setting of side guide gap by operators is eliminated.

Summary of invention

Therefore such as herein described there is disclosed an improved system for automatic measurement and adjustment system for side guide gap in a hot strip mill comprising of a plurality of digital incremental encoders are connected to non-drive end of each stand motor; a plurality of drive panels with built in communication and encoder feedback card; a PLC system operable to provide signals for open and close movement of the guide; wherein the PLC system is configured to convert the counter module output to Analog output for display of measured values in Digital Panel Meters (DPM); and wherein the said encoders are configured to provide the real time speed data of the side guide motors to the PLC and drive system and the speed correction is calculated in the closed loop

control system and corresponding open and close movement of guide is activated.

Brief description of accompanying drawings

Figure-1 illustrates schematic diagram of a typical hot strip mill wherein side guides are installed in the finishing stands of the mill;
Figure-2 illustrates a schematic diagram of automatic side guide measurement system in accordance with the present invention;
Figure-3 illustrates schematic diagram of coupling connecting gear box and encoder in accordance with the present invention;
Figure-4 illustrates schematic diagram of data transfer to automatic side gap setting system in accordance with the present invention;
Figure-5 illustrates photograph of encoder fitted with coupling in accordance with the present invention;
Figure-6 illustrates photograph of display of automatically measured side guide gap values in a hot strip mill in accordance with the present invention;
Figure-7 illustrates screenshot of operator guidance screen in accordance with the present invention;

Detailed description of the Invention

Rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness and to make the thickness uniform. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its re-crystallization temperature, then the process is known as hot rolling. In a Hot Strip Mill of modern steel Plants, Steel Slabs are rolled into strips and final product is in coil form. A slab is first rolled in roughing stands then it passes through a delay table and finally into the finishing stands as shown in Fig 1. The coil box and crop shear are located at the end of the delay table. A crop shear is used to cut the head end and tail end of transfer bar. The shear is located after coil box and before entry to finishing stand. After finishing stands, Strip passes through Run out table and then finally goes to Coiler. Side guides of finishing stands were operated by pushbuttons, relay logic system and driven by three phase, slip ring Induction motors. Encoders are

connected with all guide motors to know the speed of motor and are used to measure the guide gaps. By this system, guide operator is able to achieve desired guide gap from strip edge within a range from the centre line.
Side guide gap position for effective hot rolling is dependent on the controlled operation of guide motors in the finishing stands. The disclosure herein is intended to meet the operational requirements of optimized guide gap as per the width of rolling strip. The Automatic Side Guide Gap adjustment System for effective hot rolling at Finishing Stands of Hot Strip Mill has been envisaged by development of automatic control system. The automatic side guide measurement and setting system is shown schematically in Figure-2. The gap between two guides is measured by an incremental encoder. The encoders used for precise position sensing of the guides. The digital incremental encoders are connected to non – drive end (NDE) of each stand motor. These encoders actually give the present speed of the side guide motors to the PLC and drive system. The speed of the side guide motors of the mill stands depend on the actual guide gap requirement. The speed correction is calculated in the closed loop control system and corresponding open and close movement of guide operation took place. The drives are connected with each other via cable. Separate panel has been used for each drive and associated circuit accessories. The panel has the back access for power connection. The drive part is in the front side of the panels. The drive has the two main parts namely power unit and controller unit. The controller units of all the drives are connected via the CT-net cable. The drive communicates with PLC through the profibus cable. The PLC gives command for open and close movement of the guide and thus adjustment of guide gap took place. The Ethernet cable has been used for PC and drive communication.

The output signal of the encoder is connected to a counter module of a Programmable Logic Controller (PLC). The output of counter module is processed by the central processing unit (CPU) of the PLC where the signal is converted to analog values. The calculated analog values are sent to display meter through an analog output module and a signal isolation unit. The control logic for automatic side guide gap adjustment system is designed and implemented with a minimum error using the drive’s position control feature.

Similarly side gap setup reaches PLC from a computer HMI screen in case of manual mode and from automatic gap setting program in case of auto-mode. The CPU of PLC converts it into digital signals and sends these signals to entry guide motor through a digital output module through a CAM switch. The motor changes the guide gap through a gear box.

Hollow shaft incremental encoders with 1024 PPR fitted at the non drive end of the guide motors to know the speed of motors those are used to measure the guide gaps after certain calibration. A coupling is required to join the shaft of the gear box with the tachometer. Mechanical coupling set matching to existing gearboxes and motors with proper alignment with all guide motors has been designed. Schematic diagram of the guide is shown in the Figure-3. The encoder also needs a support for its placement which is shown in the figure.

In an exemplary embodiment and as example the disclosed automated system for side guide gap adjustment is designed and developed by including a plurality of squirrel cage induction motors with extended shaft at non drive end for encoder mounting in place of existing AC slip ring Induction motors have been inducted. Drive panels having same numbers of 46A microcontrollers based three phase, inverter grade reversible, digital variable voltage variable frequency drive with built in communication and encoder feedback card are used. Drives also have dynamic braking resistances along with suitable punch grid resistances. Line chokes are also considered for each drive since motors are located at distances about 200m from drives.

Figure-4 shows Schematic diagram of data transfer for measurement system for automatic guide setting. In a steel plant there is production planning & control (PPC) department which makes the schedule of initial width of slab and target width of a slab in a computer system. This is represented by VAX system in the figure. The data is transferred to the automatic guide setting software by File Transfer Protocol (FTP). The measured value of Side Guide Gap is transferred to the software by OLE for Process Control (OPC) communication system. The tuning parameters are set by programming engineers. The output setting is displayed to operators and moves through automatically to CPU of the PLC for automatic setting of gaps. Transducers, metering accessories for sensing current,

voltage and RPM are used in the system for the display of different indications in the process.

The side guide gap adjustment in the finishing stands is guided by the operational requirements in the mill. This is basically determined by the minimum guide gap requirement for effective rolling. Precise guide gap position is possible during rolling with the controlled operation of the side guide motors. This operation is basically a closed loop control system in which feedback also comes through encoders in terms of guide gap calculated in the PLC. Planned coil width information set at PLC (Programmable Logic Controller) by the operator which is available in the mill PLCs network. As an example in the implemented scheme, if planned slab width is 1250 mm, initially guides of all stands shall be opened for
1325 mm. As soon as the head end of the bar bites any of the stand, say, F1 stand (to be known from F1 roll force), the guide gap will be reduced to 1260 -
1270 mm. This is repeated in all stands of finishing mill. As soon as the bar passes through the roll, the guide gap again shifted to initial open position.

The photograph of an encoder mounted to gear box shaft through a coupling is shown in Figure-5. The support is also shown in the figure. A programmable logic controller having a central Processing Unit, standard I/O modules, Counter Module for processing the encoder signal, profibus communication module for communicating with drive profibus ports, profibus connectors at drive and PLC ends are selected and used. Figure-6 shows photograph of a typical display of analog values in the operator control room. Figure-7 shows the screenshot of display of output in a computer screen wherein operator has the option to select manual mode of gap setting or auto-mode of gap setting.

Inventive Step

• Measurement of side guide gap by fitting incremental encoders in gear box

• Fitting of incremental encoders in gear box through specially designed couplings and encoder support
• A PLC program convert the counter module output to Analog output for display of measured values in Digital Panel Meters (DPM) located at the operator cabin.

• An HMI screen was designed to display measured gap in a monitor installed at operator cabin
• Development of a computer system to automatically set the side gap

• The operator can set the side guide gap and receive the feedback through a HMI screen

Industrial Applicability
Easy monitoring and setting of side guide in a hot strip mills of steel plants. Although the foregoing description of the present invention has been shown and

described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.