The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 1

ISSN 2229-5518

Analysis Of Existing Rolling Mill With Prototype Soft Starting Arrangement Of Rolling Mill For Energy

Conservation – An Experimental Approach

A.M. Bisen, Dr. P.M. Bapat and Dr. S.K. Ganguly

Abstract

In this paper an analysis is done on the main drive of rolling mill which consumes about 60 to 70 % of total energy of the plant. The existing rolling mill in India are using the 3 phase induction motor and flywheel to drive the rolling mill. The electric motor transmits the power to flywheel with the help of V-belt. An attempt has made after analysis of existing mill that by using some soft starting arrangement, which can be use as a clutch in between the motor and flywheel reduces the horse power of mai n drive which save the energy consumption of rolling mill. The optimum selection of drive can help in reducing the horse power of main electric motor and at the same time capable of energies the flywheel. An experimental analysis is done by using flat bel t drive and motor sliding arrangement in order to reduce the H.P. of main electric motor.
In this paper an attempt has made after analyzing the existing rolling that a mechanical soft starting arrangement is designed and tested on prototype rolling mill. The soft starting arrangement used in this protype rolling mill analysed and concluded that in the actual rolling mill the motor used are oversized which consumes the more energy. By designing the soft starting arrangement , the motor horse power can be reduced which ultimately saves the energy consumed and hence the billing cost can be reduced.

1. INTRODUCTION

Rolling mill are mainly dependent on the electrical energy and about 60 to 70% of electrical energy is spent on rolling operation and balance is consumed on auxiliary operation like cutting of roll stock, furnace blower ,crane operation etc. The increasing cost of electrical energy made it essential for steel rolling mills in India to consider the electrical power requirement seriously. In a rolling mill, electrical power contributes major part in the cost of rolling.
Our country produces about 40 million tons of steel, out of which 50% is produced by small scale steel three high rolling mills. An average of about 400 crore units of electricity which is consumed in rolling steel bars hence there is a great scope for considerable saving in electricity by proper design of prime movers for the rolling mills. Energy conservation studies of these mills have shown that oversized prime movers causes excessive wastage of energy therefore the prime movers have to be designed to save the energy.

Asst. Prof, MATS School of Engg. &IT ,MATS University, Raipur (C.G.)

Prof. in Mechanical Engg, BIT , Durg (C.G.)

Prof. in Mechanical Engg, Cummines college of

Engg. Nagpur (M.S.)

As per the literature available regarding the consumption of power during the rolling of any product, all are based on rolling industries situated in foreign countries. In such countries the rolling process is continuous one but in India we have most of the rolling mills as open train rolling mills. In these rolling mills the energy As far as the literature available regarding consumption of power during rolling of any product, all are based on consumption pattern is different from them and no one has attempted to go through the systematic analysis and study of this subject as it is a boundary case of mechanical, electrical, and metallurgical engineering.
It has been proved by the researchers that in running condition of the rolling mill the consumption of energy required is low as compared to starting of the mill. The motor is to start the flywheel from initial condition to full speed and largest size of flywheels are frequently recommended for smooth running of rolling mills at the same time they tend to decrease the size of the motor. The main difficulty encountered in selecting large capacity flywheel or flywheel gear box system is the starting of the mill with smaller capacity electric motor. The starting characteristic of electric motor is not suitable for starting such rolling mill with very high inertia flywheel. Hence there is tendency to use high horse power motor which is capable to start the flywheel initially. In such condition it
becomes very essential to introduces the soft starting

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 2

ISSN 2229-5518

arrangement for the electric motor so that considerably small size motor can start the flywheel effectively.

2. SURVEY OF OPEN-TRAIN ROLLING MILLS IN RAIPUR REGION (C.G.) INDIA

The open-train rolling mills are commonly employed for the production of rolled sections like rods, bars, angles, flats etc. These rolling mills are from 150 to
275 mm three high six stands mills. The normal sizes of electric motors ranges from 400 H.P. to 1000 H.P. the
rolling speed ranges from 2.25 m/sec. to 3.5 m/sec.
The normal size of ingot is 90x90 mm and overall production per hour depends on the section being rolled. It is observed that an average 80 to 120 pieces can be produced per hour, independent of the section size. Hence, the maximum attainable production is from
500kg/hour to 4.5 tones /hour. The electrical motors are designed to meet any change in the section size from 6 mm bar to 75x75x6 angle.
We have observed the weekly/monthly production records of the rolling mills showing the production in tones and the energy consumption during these periods. Also, the approximate product mixes (if various sections are rolled) are recorded. On the basis of tonnage and other records, energy consumption per tonne for each section was estimated. About 25% of the energy is assumed to be consumed for operations other than rolling (this assumption is also backed by the experimental results of Russian Scientist, Gipromez instt.data.)

3. CASE STUDY OF U.P. ROLLING MILL

we have selected one of the renowned Hot Rolling Mill “U.P. ROLLING MILL” situated at Industrial area of URLA, RAIPUR(C.G.) INDIA. The total area of the plant is 10 acres whereas the layout area of the plant is
1.5 acres. The gross production of the plant is 100 tones
/day. The raw material used about 120 tones /day & storage raw material is about 200 tones /day. Some important data related to our analysis are as follows.

Table No.1

Some of the photographs taken from the mill.

Fig. 1 RAW MATERIAL Fig. 2 FURNACE

Fig. 3 PULLEY Fig. 4 FLYWHEEL

Fig. 5 FLYWHEEL ARRANGEMENT Fig. 6

OUTPUT

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 3

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4. ANALYSIS OF DATA TAKEN FROM ROLLING MILLS

We have use the non contact type electronic digital tachometer for the purpose of analysis of rpm of motor and the flywheel from the initial condition to the maximum rpm of the flywheel and same is recorded by using the video camera. The above set up is done in the rolling mill fig. no. 7,8 9 and the reading is given in table no.2 below.

Fig. 7 SETTING THE EQUIPMENTS AT INTIAL CONDITION

Fig. 8 TECHOMETER READING Fig. 9 VIDEO RECORDING

Table No.2

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 4

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70

667.2

244.2

74

702.3

244

72

680

244

1000

500

0

TIME VS MOTOR & FLYWHEEL RPM

Fig. 12 GRAPH OF TIME Vs MOTOR R.P.M.


Based on the above reading from table no.2 , the graph is plotted in between the r.p.m. of the motor along the Y axis and the time in seconds along the X axis. The result of the graph is given in the fig . no.10.

TIME VS MOTOR RPM

1000

500

0

TIME

Fig. 10 GRAPH OF TIME Vs MOTOR R.P.M.

From the table no.2 , a graph is plotted between the flywheel r.p.m. on Y axis against the time in seconds along X axis and the result of the graph is shown in fig .no.11

Fig. 11 GRAPH OF TIME Vs FLYWHEEL R.P.M.

From the fig. no. 10 and 11 , we have plotted a third cumulative graph shown in fig . no. 12 .As we can observe from the fig. no.12 that in the initial situation the motor rotates at its full speed and the flywheel is at the stationary condition for the time period of 0-2 seconds . Then slowly the motor rpm decreases with there is an increase in flywheel rpm. After that there is a continuous decrease in motor rpm as well as there is an increase in flywheel rpm as the motor is supplying the energy to the flywheel and after 44 seconds the flywheel rpm become constant and the motor r.p.m. is increasing as the flywheel attains the maximum speed and now motor tends to attains the maximum speed. After 84 seconds both motor and runs at constant maximum speed.
We have also observe that there is no change of voltage at any stage either in no load or load conditions. The voltage is constant (420 V). But there is sudden fluctuation in current from 800amp to 1400 amp of the motor , which shows that when motor runs at no load condition then the current drawn by the motor is about 800 amp. and when whenever the load comes to the mill the motor draws the higher current up to 1100 amp. depending upon the temperature of the ingots. When the temperature of the ingots is low, the motor draws the higher amp. up to1400 amp. This due to the reason of motor tends to regain the r.p.m. and torque very fast and it draws the higher current.

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 5

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5. EQUIPMENT SETUP

Based on the study of hot rolling mill in the Raipur region and since for the experimental analysis we have developed a prototype rolling mill model. In the equipment we have neglected the rolling action due to the reason that it has been proved that in running condition the power consumed by the electric motor is less as compare to in the starting period. So the main focus area for the energy conservation is in starting of the mill. In the initial condition the motor should be capable enough to drive the flywheel at maximum speed. Hence our focus area is electric motor and flywheel.

Fig. 13 PROTOTYPE MODEL

Fig. 14 SLIDING ARRANGEMENT OF MOTOR

We have designed a flat belt which replaces the existing V-belt drive in the rolling mill, due to the fact that flat belt allows the slip up to 3% and comes into the category of flexible drives. This can act as a clutch in rolling mill by inserting a sliding frame arrangement in the equipment fig.no.12.In the initial condition the frame is moved towards the flywheel so that the belt becomes loose and the motor runs at no load condition as the motor attains the maximum speed the frame moves slowly away from the flywheel ,due to this the belt becomes slightly tight and motor try to rotate the flywheel. By using this type of arrangement the load does not comes directly on to the
motor and it act as a soft start. The frame again moves
away from the flywheel at constant rate till the belt becomes full tight.
The following table gives a brief idea regarding the comparison of existing rolling mill and our equipment setup-

Table No.3

Sr.

no.

Particular

Data

from industry

Our

equipment data

Ratio of

both the data

1)

Motor H.P

1000

0.5

1:2000

2)

Weight of

flywheel

10000

kg

57 kg

1:175

3)

Size of

flywheel

10 m

0.5 m

1:20

4)

Maximum

motor RPM

760

1440

1:0.52

5)

Maximum

flywheel

RPM

240

960

1:0.25

From the table no.3 , it is clear that we have use very less horse power motor which 2000 times lesser than the motor used in the actual rolling mill where as the flywheel used for this purpose is 175 times lesser than the actual ones. The motor is capable of rotating flywheel with using sliding frame arrangement and also without using the arrangement also which is experimentally proved. This shows that in actual rolling mill the motor used for the rolling are oversized. The common policy used in the rolling mill is to use the oversized motor which increases the billing cost of the plant. By using any one type of such arrangement, the billing cost of main electric motor which is about 60% of power consumption can be reduced.

6. ANALYSIS OF PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL

We have use the non contact type electronic digital tachometer which is fixed on to the panel of the set up. From initial condition to the final condition , all the readings are recorded by using the video camera and the reading are then split in to the time duration of 2 seconds. The readings of experimental set up is displayed in figure

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 6

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no. 15 to 18 and all the reading are given in the table no. 4

Fig. 15 INTIAL READING

Fig. 16 READING AFTER 9 SECONDS

Fig. 17 READING AFTER 47 SECONDS

Fig. 18 READING AFTER 90 SECONDS

Table No.4

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 7

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As we can see from the table no.4 that in the initial condition the motor rotates at its full speed and the flywheel is at the stationary condition. Then slowly the motor rpm decreases with there is an increase in flywheel rpm. After that there is a continuous decrease in motor rpm as well as there is an increase in flywheel rpm. Finally after
68 seconds both the motor and flywheel rpm become constant.

Based on the table no. 4 , we have plotted the graphs fig. no. 19 shows the motor r.p.m. vs. time in seconds. From the graph no. 19 , it is clear that the motor r.p.m. decreases with respect to time and after 68 seconds it is almost constant.

TIME VS MOTOR RPM


the fact that motor supplies the energy to the flywheel to accelerate and its r.p.m. decreases , as the flywheel fully accelerates at maximum speed than it becomes almost constant after 68 seconds.

TIME VS MOTOR &

FLYWHEEL RPM

2000

0

0 8 16 24 32 40 48 56 64 72 80 88

TIME

Fig. 20 GRAPH OF TIME Vs MOTOR & FLYWHEEL R.P.M.

7. DISCUSSION

1600

1400

1200

1000

0 8 16 24 32 40 48 56 64 72 80 88

TIME

From the table no. 3 , it is clear that in the prototype soft starting arrangement the motor used is 2000 times reduced while the flywheel used is of 175 times reduced and by using this type of soft starting arrangement we can reduce the horse power of the motor and also the starting of the motor becomes soft starts rather than hard

Fig. 19 GRAPH OF TIME Vs MOTOR R.P.M.

From the readings from the table no. 4 , we have plotted the graphs fig. no. 20which shows the flywheel r.p.m. vs. time in seconds. The graph shows that the flywheel r.p.m. increases at constant rate with respect to the time and after 68 seconds it is almost constant.
starts.
A graphs (figure no.20 )is plotted between time in seconds and the motor and flywheel rpm which shows the change in motor and flywheel rpm with respect to time. When we compare the fig no.12 and 20 , it is clear that the r.p.m. motor by using the soft starting drive is not so much reduced as compared to the motor r.p.m. used in the rolling mill, hence due to this motor is not on loading condition and may draw the maximum current.
The motor ratio is decreased is 2000 times while the flywheel ratio is decreased only by 175 times , in order to make the flywheel effective and quite enough to drive
the mill .

Fig. 20 GRAPH OF TIME Vs FLYWHEEL R.P.M.

From the figure no.19 and 20 , we have plotted a new graph in figure no. 21 which is cumulative of figure no. 19 and 20 shows that motor r.p.m. decreases while the flywheel r.p.m. increases with respect to time . it is due to
Initially the motor rpm decreases ( figure no. 12 and 20) and flywheel rpm increases as the motor supplies the energy to the flywheel and after some time when flywheel rpm becomes constant again the motor rpm increases which shows that the motor supplies the energy to the flywheel and after fully charged flywheel than recovers the energy.
In authors’ view the probable area of the energy
conservation is in the main electric motors and it has proved by the researchers [6] that the oversized motors are used in rolling mill as to drive the flywheel and the mill.
Also [3] it has been calculated that the power requirement

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The research paper published by IJSER journal is about ANALYSIS OF EXISTING ROLLING MILL WITH PROTOTYPE SOFT STARTING ARRANGEMENT OF ROLLING MILL FOR ENERGY CONSERVATION – AN EXPERIMENTAL APPROACH 8

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during the mill running is very less. Hence mechanical soft starting arrangement can be possible to run the main
motor by using the flat belt drive soft starting arrangement.

8. CONCLUSION

It is suggested that, there is large scope of minimizing the energy consumption in main electric motor of rolling mill
1. The selection of the flexible drives available in mechanical, electromechanical, chemical, electronics system and designed a suitable soft starting arrangement for the rolling mills may become the future of the rolling mills of new decade and definitely we solve the energy crises.
2. To design a system which is capable of starting the system with low horse power motor and to design a some alternative arrangement which can serve this purpose.
3. It is the opinion of the authors that the simple
design in using the flat belt drive mechanical soft starting arrangement, the energy consumed by the electric main motor can be reduced .
4. To design a some more alternative arrangement which can serve this purpose.

9. REFERENCES

1. S.M.Tekadpande, Dr. P.M. Bapat and Dr.
A.J.Katkar, “Analysis of Static Power Requirement of Existing Rolling Mills”, Proceedings of the all India Seminar on Management, ECOENERGY, 1995,Institution of Engineers, India, Nagpur, 4-5 Jan, 1995P.
2. A.J. Winchester, “How to get and use Rolling Mill
Power data”, Iron and Steel Engineer Journal, July
1964, pp 92-97.
3. Polukhin N. Fedosov, A. Korlovyov and Y.
Matveyev, “Rolling Mill Practice”,
Peace Publishers, Moscow.
4. Allen S. Hall, Affrid R. Holowenka & Herman G.
Lauaghlin (1998) “Machine Design” 313-316.
5. Electric Power Research Institute. Project summary 2000.
6. Bisen A.M.,Bapat P.M.,Ganguly S.K. “Need of Soft Starting Arrangement for Hot Rolling Mill” at Recent Trend In Technology” , National Level
paper presentation at C.S.I.T. Bhilai (C.G.)
between 06-07 Feb. 2009.
7. Tekadpande S.M.,Bapat P.M.,Katkar A.J., “ Experimental verification of simulation results of three high open train mill ” Tenth world congress on theory of machine and Mechanism , Oulu
,Finland , June 20-24 , 1999
8. Bisen A.M. ,Bapat P.M.,Ganguly S.K., “Selection of Flywheel – acomputer approach to account for drive and load characterstics ”Technologia 2008,a national level technical paper presentation ,14-15
March 2008, M.P.Christian College of Engg. Bhilai C.G.
9. Bisen A.M., Bapat P.M., Ganguly S.K “simple soft starting arrangement for hot rolling mill on the basis of 3 phase induction motor and load ” at mats university journal RAIPUR ISSN- 2250-
3889.
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12. Kay, J.A., Paes, R.H., Seggewiss, J.G., and Ellis, R.G (Nov.-Dec. 2000). Methods for the control of large medium-voltage motors: application considerations and guidelines. IEEE Transactions on Industry, Vol. 36, pp. 1688-1696.
13. McElveen, R. and Toney, M (Jan.-Feb. 2001).
Starting High Inertia Loads. IEEE Transactions on

Industry Applications, Vol. 37, pp. 137-144.

14. Rajendra Prasad, M., and Sastry, V.V (3-6 Aug.
1997). Rapid Prototyping Tool for a Fuzzy Logic Based Soft-Starter. Proceedings Power Conversion Conference, Vol. 2, pp. 877-880.
15. REO UK Ltd. Soft starter units for 3-Phase asynchronous motor. Technical manual.
16. Muhammad H. Rashid, Power electronics (2nd ed.): circuits, devices, and applications, Prentice- Hall, Inc., Upper Saddle River, NJ, 1993

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