FIELD OF INVENTION

The present invention relates to an improved system for automatic setting of roll gap & mill speed in leveler of Plate mill. More particularly, the present invention relates to a scheme for automatic setting of screw down roll gap and mill speed of the leveler-I & II based on the grade, thickness and temperature of plate.

BACKGROUND ART

Plate mill of Bhilai Steel Plant is designed to produce plates in the thickness range of 5 to 120 mm for ships, bridges, structures, boilers, pipes etc. The slabs after being rolled through the Roughing and Finishing stand into plates of desired thickness, are passed through the leveller. The Function of leveller is to remove any undulations which have been formed during the rolling process. For plates up to thickness of 20mm, the levelling is done through Leveller-I and for plates above 20-60mm the levelling is done through Leveller-II. The levelling process is a combination of setting of roller gap through screw down AC motor and the speed of mill through the Main drives DC motor. The roll gap and mill speed setting for levelling depends on the grade, thickness and temperature of plate. The process of levelling in absence of any Level-II automation system was entirely dependent on the skill and experience of the operator. As a sequel to depleting experienced man power and absence of desired automation system for auto-levelling, the quality of levelling was poor at times, resulting in rejection of plates. Moreover, because of the obsolete instrumentation for roll gap display, old relay based electrics for screw down control and analog drives for mill speed control even the experienced operators found it difficult to control the mill as per desired setting.

SUMMARY OF INVENTION

Design and implementation of a scheme for automatic setting of screw down roll gap and mill speed of the leveller-I & II based on the grade, thickness and temperature of plate.

Therefore such as herein described there is provided an improved system for automatic setting of roll gap & mill speed in leveler of plate mill comprising of a plurality of DC Drives for Mill Speed Control installed in each Leveler-I & II; a plurality of AC Drives for Screw Down mechanism installed in each leveler for the screw down mechanism; a PLC Panels using Look-up tables configured for automatic roll gap setting and mill main drive speed; a plurality of Laser Sensor configured for gap measurement; a plurality of Linear Encoder configured for gap measurement purpose; and a Pyrometer each installed in both the levelers for temperature measurement.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig. 1 illustrates the schema of automation architecture in accordance with the present invention.

DETAILED DESCRIPTION

Plate mill of Bhilai Steel Plant is designed to produce plates in the thickness range of 5 to 120 mm for ships, bridges, structures, boilers, pipes etc. The slabs after being rolled through the Roughing and Finishing stand into plates of desired thickness are passed through the leveler. The Function of leveler is to remove any undulations which have been formed during the rolling process. The process of levelling in absence of any Level-II automation system was entirely dependent on the skill and experience of the operator. As a sequel to depleting experienced man power and absence of desired automation system for auto-levelling, the quality of levelling was poor at times, resulting in rejection of plates.

The inventors successfully designed, installed and commissioned a scheme for automatic setting of screw down roll gap and mill speed of the leveller-I & II based on the grade, thickness and temperature of plate. The new look up table based automation scheme for leveller comprises of digital DC drives for mill motors, AC drives for screw down, PLC , control desk with remote IO PC based HMI for operator and instruments for feedback such as Linear encoders, Laser sensors and Pyrometer.

The scheme can be implemented in any steel rolling mill where the roll gap is mill speed to is to be set automatically as per metallurgical requirements.
The new automation of scheme for levelers comprises of digital DC drives for mill motors, AC drives for screw down, PLC, control desk with remote IO PC based HMI for operator and instruments for feedback such as Linear encoders, Laser sensors and Pyrometer. The idea of auto rolling was achieved by querying the plate details from the Plant MES. Based on information of Plant MES, the lookup table to guides the PLC system for the appropriate rolling schedule. The PLC gives speed reference to the AC & DC drives and it receives feedback from field instruments like encoders & laser sensors. The existing incoming and outgoing roller table drives are also interfaced with the new automation system through the PLC.

Installed System:
• DC Drives for Mill Speed Control: Two numbers of DC drive panels have been installed in each Leveler-I & II. The DC drive panels house DC drive ABB-DCS 800-S02-1190-051 having armature current rating of 1190A and field current rating of 35A.
• AC Drives for Screw Down mechanism: Two no AC drives (ABB –ACS880-01-145-3) were installed in each leveler for the screw down mechanism. A total of four numbers of AC drive panels were installed in this project.
• PLC Panels for Automation: one number of PLC Panel has been installed in each Leveler-I & II. All the instruments such as laser sensor, encoder, pyrometer, binary display unit and drive panels are interfaced with the PLC. Wonder ware HMI is used in both the levelers. The process of levelling is automated as per automation architecture (drawing 1) using Look-up tables 1 & 2, PLC and HMI. The plate data is queried from the existing MES system. The logic for automatic roll gap setting and mill main drive speed is lookup table based which is incorporated in the PLC.
• Laser Sensor: Two laser sensors (Delta-FT1507) are installed in leveler # 1 for gap measurement purpose.
• Linear Encoder: Two Magnetostrictive linear encoders (Baumer- GMA5) are installed in leveler 2 for gap measurement purpose.
• Pyrometer: One IR radiation pyrometer (Raytek- MI3) is installed in both the levelers for temperature measurement purpose.

Table No 1: Look up Table for Leveler-I

Table No 2: Look up Table for Leveler-II

Usefulness of the Invention:
The new automation scheme for Leveler I & II is an improvement over the old system in terms of latest state of art technology, auto positioning, information made available to the operator, the diagnostic tools and facility provided and an alternative system for leveling operation in the same sequence & logic.

The new Look up table based automation system enabled the operator to do leveling operation in auto mode. Interfacing of the automation system with BSP MES now gives the updated data of Plates being rolled at both the levelers. Digital drives installed operated the mill motor smoothly and with accuracy. Laser sensor & liner encoder installed in Leveler I & II respectively guides the automation system to do the auto positioning accurately. These two sensors eliminated the error in gap measurement completely. The new automation scheme for control of the leveler with respect to the grade, thickness and temperature of the plate has helped in reducing the dependency on the operator for quality levelling of plates.

Inventive step:
Precise automatic setting of roll gap & speed control of levellers as per the grade of plate.
Less dependency on operator’s expertise for slab positioning & levelling of plates.
Reduction in electrical delays.

Industrial Applicability:
Similar schemes can be implemented in all applications where roller gap and mill speed is to be set automatically as per the operation requirement.

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. 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.

WE CLAIM:

1. An improved system for automatic setting of roll gap & mill speed in leveler of plate mill -
a plurality of DC Drives for Mill Speed Control installed in each Leveler-I & II;
a plurality of AC Drives for Screw Down mechanism installed in each leveler for the screw down mechanism;
a PLC Panel using Look-up tables configured for automatic roll gap setting and mill main drive speed;
a plurality of Laser Sensor configured for gap measurement;
a plurality of Linear Encoder configured for gap measurement purpose; and
a Pyrometer each installed in both the levelers for temperature measurement.

2. The system for automatic setting as claimed in claim 1, wherein said DC drive panels of two numbers are installed in each Leveler-I & II having armature current rating of 1190A and field current rating of 35A.

3. The system for automatic setting as claimed in claim 1, wherein AC drives of two numbers each are installed in each Leveler-I & II for the screw down mechanism.

4. The system for automatic setting as claimed in claim 1, wherein said laser sensor, encoder, pyrometer, binary display unit and drive panels are interfaced with the said PLC.

5. The system for automatic setting as claimed in claim 1, wherein said levelling is automated as per architecture components using Look-up tables, PLC and HMI.

6. The system for automatic setting as claimed in claim 1, wherein the said roll gap setting and mill main drive speed is based on lookup table incorporated in the PLC & Plant MES.

7. The system for automatic setting as claimed in claim 1, wherein laser sensors of two numbers (Delta-FT1507) are installed in Leveler 1 configured for measurement of gap.

8. The system for automatic setting as claimed in claim 1, wherein magnetostrictive linear encoders of two numbers (Baumer- GMA5) are installed in Leveler 2 for measurement of gap.

9. The system for automatic setting as claimed in claim 1, wherein said Laser sensor & liner encoder installed in Leveler I & II respectively guides the said system to do the auto positioning accurately and eliminates the error in gap measurement completely and thereby achieving reduction in electrical delays.