Claims:We Claim:

1. A cobble carry-out processing arrangement in a hot strip mill comprising of :
a delay table configured to receive and align an elongated steel strip as it exits from the last roughing mill;
a cobble pusher arm operably connected with the delay table; wherein
a pair of Proximity Switches and an Actuator is installed on the said cobble pusher in order to limit the movement of Cobble Pusher for both ‘forward’ and ‘reverse’ direction.

2. The cobble carry-out processing arrangement as claimed in claim 1, wherein the said actuator was fixed with the cobble pusher arm with gap between Proximity Switch and Actuator.

3. The cobble carry-out processing arrangement as claimed in claim 1, wherein the said proximity switch and actuator are connected with cobble pusher control panel for power and control.

4. The cobble carry-out processing arrangement as claimed in claim 1, wherein the said proximity switch and actuator are configured to restrict overtravel of said arm.

, Description:IMPROVING THE RELIABILITY OF COBBLE CARRY-OUT PROCESSING ARRANGEMENT

FIELD OF THE INVENTION:
The present invention relates to an improvement in reliability of cobble carry-out processing arrangement installed in a roller table between a rough rolling mill and a finish rolling mill. More particularly, the present invention includes an arrangement to detect and eliminate the over travelling of Cobble Pusher arm on delay table thereby improving the reliability of Cobble Pusher on delay table during cobble removal.

BACKGROUND OF THE INVENTION:
Hot Strip Mill of Rourkela Steel Plant, as shown in Fig. 1 and 2, have a 1700 mm semi-continuous mill comprising two Walking Beam Furnaces of capacity 225 T / Hr, three Roughing Mills, i.e. one two high Reversing Mill (R0/ V0), one 4 high Reversing Mill (R1) and one 4 high Continuous Mill (R2¬), Coil Box, Six stand 4 high Finishing Mill in tandem and two Hydraulic Down Coilers. It produces saleable hot rolled coils catering to external customers and as input material like internal customers for Cold Rolling Mill, Silicon Steel Mill and Pipe Plants.
As HSM is a semi-continuous mill, bars are rolled one after another. At any point of time, 3 bars can be accommodated in the mill. So, if any type of failure or problem occurs from Coil Box to coiler, at that moment, intermediate bar rolled at roughing area needs to be withdrawn from the roller table to keep the Mill ready for further rolling. A cobble formation on a delay table in the hot strip mill is shown in Fig. 3. The only way of removing the intermediate bar is at the delay table in between Roughing Stand #2 and Coil Box with the help of Cobble Pusher. The Cobble Pusher is a device with 5-extended arms fixed with a synchronized shaft and operated by means of motor and gearbox, which can push forward the cobble of size (intermediate bar of 24mm to 30 mm thickness) out of the delay table. The cobble removal by cobble pusher from delay table and cobble removal by crane and tong from delay table is shown in Fig. 4 and 5 respectively. In the prior art, a Cam Limit Switch was fixed with the synchronized shaft of Cobble Pusher arms to limit the movement of Cobble Pusher arms in both directions during cobble removal.
During Cobble removal from Delay Table by Cobble Pusher, the failure of Cam Limit Switch fixed with the synchronized shaft of Cobble Pusher to limit the ‘forward’ and ‘reverse’ movement of Cobble Pusher, leads to over travelling of arms and lying on delay table. This was adversely affecting the Mill production.

SUMMARY OF THE INVENTION:
During this operation of removal of the intermediate bar from delay table if Cobble Pusher fails to operate, the cobble is removed with the help of crane and tong leading to delay and production loss. During operation, if the Cam Limit Switch malfunctions, then Cobble Pusher gets over travelled, became slot out and is not able to return to its home position then the Cobble Pusher arms need to be repositioned by means of cranes and sling, after removing the slider pin of every arm, which further increases the Mill down time. To bring back normalcy in operation, it was taking approximately one hour. This used to happen 12 times/ year with cumulative production delay of 11 hours and 50 minutes.
Therefore such as herein described, there is provided a cobble carry-out processing arrangement in a hot strip mill comprising of a delay table configured to receive and align an elongated steel strip as it exits from the last roughing mill; a cobble pusher arm operably connected with the delay table; wherein a pair of Proximity Switches and an Actuator is installed on the said cobble pusher in order to limit the movement of Cobble Pusher for both ‘forward’ and ‘reverse’ direction.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
Fig. 1 illustrates the flow diagram of hot strip mill in accordance with the present invention;
Fig. 2 illustrates the different component of cobble pusher in accordance with the present invention;
Fig. 3 illustrates the cobble on delay table in accordance with the present invention;
Fig. 4 illustrates the cobble removal by cobble pusher from delay table in accordance with the present invention;
Fig. 5 illustrates the cobble removal by crane and tong from delay table in accordance with the present invention;
Fig. 6(a) illustrates the modified circuit diagram of cobble pusher in accordance with the present invention;
Fig. 6(b) illustrates the modified circuit diagram of cobble pusher in accordance with the present invention;
Fig. 7 illustrates the cobble pusher with proximity switches in accordance with the present invention;
Fig. 8 illustrates the modified drawing cobble pusher with proximity switches in accordance with the present invention.

DETAIL DESCRIPTION OF THE INVENTION:
Hot Strip Mill of Rourkela Steel Plant, having a 1700 mm semi-continuous mill comprising two Walking Beam Furnaces of capacity 225 T / Hr, three Roughing Mills, i.e. one two high Reversing Mill (R0/ V0), one 4 high Reversing Mill (R1) and one 4 high Continuous Mill (R2¬), Coil Box, Six stand 4 high Finishing Mill in tandem and two Hydraulic Down Coilers. It produces saleable hot rolled coils catering to external customers and as input material for internal customers like Cold Rolling Mill, Silicon Steel Mill and Pipe Plants.
In order to eliminate the over travelling of Cobble Pusher arm on delay table. As the existing type limit switch is obsolete and not available and it is not possible to provide other type Cam Limit Switch due to physical limitation, the team came up with an innovative solution to replace the Cam Limit Switch by Proximity Switch and Actuator to limit the movement of Cobble Pusher for both ‘forward’ and ‘reverse’ direction. To implement this creative idea, a modified electrical circuit diagram as shown in Fig 6 (a) and (b) was made ready. Two nos. of brackets were also made ready for fixing the Proximity Switches. One 220 volt AC/24 volt DC Power Supply and 2 nos. of 24 volt relays were fixed in Cobble Pusher control panel. A junction box with connector was also installed for termination of Proximity Switches. Control wiring was done as per prepared circuit diagram after laying control cable from Proximity Switch junction box to Cobble Pusher control panel.
The implementation was done on a shutdown day after removing the Cam Limit Switch from the position and fixing the Proximity Switch along with the bracket for Coil Box side arm of Cobble Pusher. The Actuator was fixed with the arm and the gap between Proximity Switch and Actuator was adjusted as shown in Fig 7 and 8. It was put under observation for 60 days. During this period and thereafter smooth operation of cobble pusher was observed and no over travel of Cobble Pusher occurred. The implementation of this innovative idea was found to be working very successfully.
Details of Financial Savings:
A: Contribution of HR coil / Ton = Rs. 3000/-
Reduction of mill delay = 11 hours and 50 minutes
Average production of HSM = 274 Ton/ hr.
Opportunity production loss due
to mill production delay (11hrs. 50 min.) = 3242 Ton
Contribution of HR coil @ Rs. 3000/Ton = 3242 T x Rs. 3000
= Rs. 97, 26,000/-
B: Cost of proximity switches (2 nos.) = Rs. 2500 x 2 = Rs. 5,000/-
Cost of 24 volt power supply (1 no) = Rs. 4860/-
Cost of 24 volt relay (2 nos.) = Rs.870 x 2 = Rs. 1740/-
Total Cost of Implementation = Rs.11, 600/-
Total Saving (A) - (B) = Rs. 97, 14,400/-

-----------------------------------------------------------------------------------------------------------------------
Data of Cobble Pusher failure due to malfunctioning of Cam Limit Switch (May’2019 to April’2020)
Month Frequency Delay (Hrs.)
May 0 0
Jun 1 0:50
Jul 1 1:05
Aug 0 0
Sep 1 1:00
Oct 1 0:45
Nov 1 0:50
Dec 2 1:45
Jan 1 1:00
Feb 1 1:10
Mar 2 2:10
Apr 1 1:15

Total
12
11:50

USEFULNESS OF THE INVENTION:
? Productivity: Elimination of Mill break down due to malfunctioning of Cam Limit Switch significantly enhanced productivity.
? Safety: Removal of cobble from the delay table in unsafe and hazardous condition completely eliminated.
? Working condition: A safe and healthy working condition ensured.
? Environment: Implementation of this highly creative and innovative idea significantly improved the working environment enhancing the employee morale and motivation. The implementation of the idea has immensely enhanced the confidence level of the employees as they feel confident that they can contribute a lot for the benefit of the department and the organization.

INDUSTRIAL APPLICABILITY:
• Steel industry having Rolling Mills with cobble pusher controlled by Cam Limit Switch facing such type of problems will be immensely benefitted by the adoption of this innovative process.
• Heavy industries using Cam Limit Switch for limiting the movement of equipment in both directions facing the problem of over travelling can gainfully adopt the innovative process.

Although the foregoing description of the present disclosure 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.

-----------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------