Description:

FIELD OF THE INVENTION:
The present invention relates with elimination of frequent failure of Spindle Balancing Cylinder in Roughing Stand #2 of a rolling mill and a finish rolling mill. More particularly, the present invention includes an arrangement to eliminate the frequent failure of Spindle balancing Cylinder in Roughing Stand due to deformation and failure of pre-existing Teflon bush.

BACKGROUND ART:
Hot Strip Mill of Rourkela Steel Plant, as shown in Fig 1, having a 1700 mm semi-continuous mill comprising two Walking Beam Reheating 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.
Roughing Stand#2 is a vital equipment of Hot Strip Mill with two numbers of Work Rolls and two numbers of Back up Rolls. To drive the work rolls, there are two spindles and one pinion housing fixed in between the electrical motor and work rolls. These spindles coupled with pinion housing in one side and with wobblers of work rolls in another side as shown in Fig 2(a). During rolling to absorb the rolling thrust load, a spindle carrier support is fixed along with two water hydraulic cylinders for balancing top and bottom spindles with the work rolls. These cylinders are supporting the rotating spindles, taking the vertical acting thrust load during rolling and balancing the spindle with pinion housing and work rolls.
Spindle bearing housing holding pin is fixed with the keeper plate hole of spindle balancing carrier support with 8 numbers Teflon bushes. Due to the rolling thrust (up to 25MN) during rolling, the Teflon bushes were getting deformed and the spindle bearing along with spindle was wobbling. This was leading to lateral thrust on the cylinder causing cylinder failure as shown in fig 2(b). Due to the failure of water hydraulic cylinders in spindle balancing carrier support, it is not possible to continue rolling as the rolling thrust load directly transmitted to pinion housing through the spindle causing damage of pinion housing white metal bearing, slipper pads, slipper pad pins and other mechanical equipment. Spindle balancing cylinder had failed 26 times in a year with a cumulative delay of 14 hrs. 10 min. leading to: Kick back of slabs at Roughing Stand#1, Damage of Equipment, Risk of Safety hazards, Slipper pad Damage, break down and Production loss.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Fig 1 illustrates the flow diagram of roughing stand in hot strip mill in accordance with the present invention;
Fig 2(a), illustrates the spindle balancing support of roughing stand with failure in cylinder in accordance with the present invention;
Fig 2(b), illustrates the spindle balancing support of roughing stand with failure in cylinder in accordance with the present invention;
Fig 3, illustrates the modified drawing of brass bush in accordance with the present invention;
Fig 4 illustrates the teflon bush and brass bush;
Fig 5 (a) illustrates the keeper plate and brass bush with grease hole in accordance with the present invention;
Fig 5(b) illustrates the bracket and keeper plate with brass bush in accordance with the present invention.

DETAILED DESCRIPTION:
During rolling to absorb the rolling thrust load of Roughing Stand#2, a spindle carrier support is fixed along with two water hydraulic cylinders for balancing top and bottom spindles with the work rolls. Two numbers of spindle bearings are fixed with spindle carrier support keeper plate hole with Teflon bush. Due to the deformation of Teflon bush provided in the keeper plate and on the bearing, housing holding pin of the spindle carrier support, the spindle bearing along with spindle was wobbling during operation which led to lateral thrust on the vertically acting cylinder and causing cylinder failure. This was adversely affecting production.
The slabs are heated in the Reheating Furnaces of Hot Strip Mill at a temperature of 13000C. Then the slabs are rolled in three Roughing Mills (R0, R1 and R2). Then the intermediate bar is coiled in the Coil Box to conserve the temperature and then uncoiled and rolled in the Finishing Mills to the required thickness. After it is rolled in Finishing Mill, bar is passed through laminar cooling process in ROT, where the required metallurgical property is obtained. Then the bar is coiled in two down Coilers.
In order to eliminate the frequent failures, the Teflon bush was replaced by Brass bush of same dimension as shown in Fig. 3 in the keeper plate and on the bearing, housing holding pin of the spindle carrier support to eliminate the deformation of bushes causing cylinder failure as shown in Fig. 4. To implement this creative idea, eight numbers of Brass bushes of required dimension were made ready in HSM work shop after machining the redundant plunger of Roughing Stand #2 back up rolls collected from Roll Shop department. Hole was made in Brass bushes and keeper plate for lubrication. An auto greasing line provided for brass bush lubrication tapping from roller table greasing line as shown in Fig. 5 (a).
The Implementation was done on after replacing all the eight numbers of Teflon bushes by Brass bushes in keeper plate holes and spindle bearing housing holding pins for both top and bottom spindle and lubrication provided on brass bush as shown in Fig 5(b).
It was put under observation for three months. During this period and thereafter, no abnormality in behaviour of spindles balancing assembly and brass bush noticed, no failure of spindle balancing cylinder occurred and no wearing out of the brass bush noticed.
The implementation of this innovative idea was found to be working very successfully.

USEFULNESS OF THE INVENTION:
• Productivity: Elimination of Mill break down due to failure of water hydraulic cylinder significantly enhanced productivity.
• Cost reduction: Significant Reduction in energy consumption by elimination of idle running of machine.
• Safety: Frequent replacement of water hydraulic cylinder in unsafe and hazardous condition completely done away with.
• Working condition: A safe and healthy working condition has been ensured.
• Employee Morale: There is no substitute to the joy of problem solving. The satisfaction among the internal customer of the department is the primary gain of the invention.

INDUSTRIAL APPLICABILITY:
• Steel industry having Rolling Mills with spindle balancing system operated with water hydraulic cylinders for rolling finished steel, facing such type of problems will be immensely benefitted by the adoption of this innovative process.
• Heavy industries using water hydraulic cylinders for spindle balancing and facing frequent cylinder failure can gainfully adopt the innovative process.

Financial Savings:
A: Contribution of HR coil / Ton = Rs. 3000/-
Reduction of mill delay = 14 hours and 10 minutes
Average production of HSM = 274 Ton/ hr.
Opportunity production loss due
to mill production delay (14hrs. 10 min.) = 3882 Ton

Contribution of HR coil @ Rs. 3000/Ton = 3882 T x Rs. 3000
= Rs. 1, 16, 46,000/-
B: Cost of Implementation including
preparation of Brass bush = Rs. 42, 800/-

Total Saving (A) - (B) = Rs. 1, 16, 03,200/-

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Data of Roughing Stand #2 Spindle balancing cylinder Failure due to Teflon bush deform (June’2019 to May’2020)
Month Frequency Delay (Hrs.)
Jun 3 2:00
Jul 2 1:10
Aug 2 0:50
Sep 3 1:50
Oct 1 0:30
Nov 2 0:50
Dec 2 1:35
Jan 3 1:20
Feb 1 0:35
Mar 3 1:15
Apr 2 1:25
May 2 0:50

Total
26
14:10

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.
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Claims:We Claim:
1. A Spindle balancing Cylinder in Roughing Stand of hot rolling mill comprising of:
a spindle carrier support fixed along with two water hydraulic cylinders for balancing top and bottom spindles with the work rolls; and
a pair of spindle bearings fixed with said spindle carrier support keeper plate hole with brass bush, wherein the said brash bush is configured to prevent any lateral thrust on the cylinder causing cylinder failure.

2. The Spindle balancing Cylinder in Roughing Stand as claimed in claim 1, wherein the said brass bush has dimension matching with the keeper plate and on the bearing, housing holding pin of the spindle carrier support.

3. The Spindle balancing Cylinder in Roughing Stand as claimed in claim 1, wherein said Brass bushes are provided with lubrication in keeper plate holes and spindle bearing housing holding pins for both top and bottom spindle.