Claims:WE CLAIM:

1. A system for prevention of cobble in roughing mill through slab thickness measurement and the said system comprising of :
at least one number of Laser sensor installed before the roughing stand and near the manipulator and sending the analog signals to the Programmable Logic Controller (PLC) through communication cable ;
at least one Programmable Logic Controller(PLC) means configured for receiving of analog signals from the laser sensor and further receiving of digital signals for monitoring the health of Laser signals, processing the said signals and provide control signals;
at least one number of display means is configured for the display of the slab thickness to the operator; and
at least one number of stand means configured for the fixing of the laser sensor above the roller table for the measurement of slab thickness and for the ease of maintenance the laser sensor.

2. The system as claimed in claim 1, wherein the PLC means if further configured for processing of the received signals , sending of the signal of slab thickness to the display unit and slowing down of the roller table under the laser sensor for correct slab measurement

3. The system as claimed in claim 1, wherein the Laser sensor is configured to signaling based on time of flight principle.

4. The system as claimed in claim 3, wherein the flight principle includes a reference object which is the roller below the slab.

5. The system as claimed in claim 4, wherein the said slab comes in between the sensor and the roller table, and the difference in time of the reflected laser signal gives the thickness of the slab
6. The system as claimed in claim 1, wherein the display unit is interfaced with the laser sensor through PLC and also directly interfaced with the laser sensor.

7. The system as claimed in claim 1, wherein laser sensor is mounted on an arm of retractable type so that sensor is turned back for any maintenance purpose and / or to avoid increase of ambient temperature around the sensor.

Dated this 14th day of March, 2018
, Description:A SYSTEM FOR PREVENTION OF COBBLE IN ROUGHING MILL THROUGH SLAB THICKNESS MEASUREMENT

FIELD OF THE INVENTION

The present invention relates to a system for prevention of cobble in roughing mill through slab thickness measurement. More particularly, the present invention relates to a scheme for prevention of cobble in roughing stand as sequel to overdraft given in the roll gap by the operator due to wrong information of slab thickness given to him by the re-heating furnace operator.

BACKGROUND AND PRIOR ART OF THE INVENTION

Research & Development Centre for Iron and Steel (RDCIS), Ranchi and Bhilai Steel Plant (BSP), Bhilai have designed, installed and commissioned “A system for prevention of cobble in roughing mill through Slab thickness measurement.” This system has been installed before the roughing stand of Plate Mill just before the manipulator. This system is being utilized successfully since commissioning from February 2017 at Plate Mill, Bhilai Steel Plant.

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. This mill has three reheating furnaces. The positioning of slabs at the entry (Charging side) of the existing three reheating furnaces is done manually. The manual feeding of slabs by the operator in the furnace at times results in charging mistakes which also results in discharging mistakes i.e. wrong slab thickness feed by the operator. As a result of wrong thickness, the draft given by the roughing mill operator is erroneous. This results in rolling stoppage due to tripping of motor due to overload, cobble generation and hammering on the motors.

The present inventors have successfully designed, installed and commissioned a system for prevention of cobble in roughing mill through slab thickness measurement
OBJECTS OF THE INVENTION

One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.

A basic object of the present invention is to provide a scheme for measurement of slab thickness before roughing stand based on time of flight principle.

Another object of the present invention is to provide a scheme for display of the slab thickness to the roughing stand operator so that the proper draft (roll gap) in roughing stand can be given based on the thickness of the slab.

Yet another object of the present invention is to provide a scheme for auto slowdown of the roller table before the manipulator for the ease of measurement of slab.

These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

According to one of the aspect of the present invention there is provided a system for prevention of cobble in roughing mill through slab thickness measurement and the said system comprising of:
at least one number of Laser sensor ( based on time of flight principle) is substantially installed before the roughing stand and near the manipulator and sending the analog signals to the Programmable Logic Controller (PLC) through communication cable ;
at least one Programmable Logic Controller (PLC) means is substantially installed in the electrical control room for receiving of analog signals from the laser sensor, receiving of digital signals for monitoring the health of Laser signals , processing of the signal , sending of the signal of slab thickness to the display unit in operator’s room and slowing down of the roller table under the laser sensor for correct slab measurement .
at least one number of 7-segment display unit means is substantially installed in the operator’s cabin of the roughing stand for the display of the slab thickness to the operator.
at least one number of stand means is substantially installed near the manipulator for the fixing of the laser sensor above the roller table for the measurement of slab thickness and for the ease of maintenance the laser sensor.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawing:

Figure 1 illustrates Laser sensor with mounting arrangement in accordance with the present invention;

Figure 2 illustrates Mounting arrangement details in accordance with the present invention;

Figure 3 illustrates 7-segment Display unit in operator’s pulpit in accordance with the present invention;

DETAILED DESCRIPTION

The present invention relates to a system for prevention of cobble in roughing mill through slab thickness measurement.

The present system consists of a Laser sensor for measuring the thickness of slab. The temperature of the target object can be up to 1300. The measurement is based on time of flight principle. The reference object is the roller below the slab. When the slab comes in between the sensor and the roller table, the difference in time of the reflected laser signal gives the thickness of the slab. The slab thickness can be measured up to an accuracy of +/-10mm. Since the variation slab thickness in Plate Mill is of 20mm, this accuracy is sufficient for the operator to know the size of incoming slab and whether the furnace operator has given a correct feedback. The Laser sensor with mounting arrangement is shown in Figure-1

In the new scheme the existing PLC is used for the analog signal feedback from the laser sensor for the slab thickness. The PLC also receives signal of the healthiness of laser sensor. The PLC sends the signal of the slab thickness to the 7-segment display unit installed in the operator’s pulpit of the roughing stand. For the laser sensor to get the sufficient time for measuring the slab thickness, the PLC slows down the roller table before the manipulator as is required.

In this new scheme, a mechanical mounting platform has been designed and installed for the maintenance of the laser sensor. The mounting arm of the laser sensor is retractable type so that sensor can be turned back for any maintenance purpose. Secondly, if the hot slab is held under the sensor for a longer duration for some breakdown in the roller table, the sensor can be turned back to avoid increase of ambient temperature around the sensor. The mounting arrangement is shown in Figure 2.

In the new scheme, a 7-segment display unit is installed in the operator’s pulpit of the roughing stand. The display of the slab thickness is with accuracy of +/-10mm. This display of slab thickness gives an idea to the operator w.r.t the size of the incoming slab and the operator adjusts the draft (gap of the rolls) of the roughing stand. The display unit in the operator’s pulpit is shown in Figure 3.

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 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.

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