ppt

1. WELCOME

2. IMPROVEMENT OF
PRODUCTION RATE AT SBM
-PULSE-SBM
M. Aditya
P. Dada Khalandar
G. Paul Manohar
Balaji Vigneswaran K
Deepak Kr. Vishwakarma
A. Manikanta
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3. INTRODUCTION
Special Bar Mill (SBM) was envisaged in 2008 along with Wire Rod
Mill-2 and Structural Mill as part of 6.3 MTPA expansion. Key features
of the project are:
 SBM is a single strand, two-high hot rolling mill that is intended to roll
special grade steels.
 The mill was supplied and commissioned by M/s SIEMENS-VAI
Metals (now M/s Primetals Italy).
 Sections that can be produced are: 20P, 20.64P, 22P, 23P, 24P, 25P,
28P, 30P, 32P, 33.5P, 36P, 39P, 40P, 42P and 45P.
 Special grade steels like medium and high carbon steels, spring
steels, bearing steel, electrode steel, free cutting steel, case
hardening steel, cold-heading quality steel, etc., can be produced at
¼ DIN 10060 tolerance level.
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4. INTRODUCTION (CONTD…)
Salient features of the Mill are:
1. Max mill speed of 16 m/s
2. Max rolling rate of 200 Tph for select sections.
3. Rated production capacity of 0.75 MTPA
4. Provision to switch between straight bar and coil production with
quick change-over times.
5. Quick stand change devices for pre-finishing and sizing mill.
6. Two high convertible housing-less stands facilitate rolling with
minimum stand inventory while allowing a said nucleous to be used
as a horizontal stand/vertical stands as required.
7. Use of TC rings in sizing (Finishing) mill allows greater dimensional
control and stability facilitating production to meet ¼ DIN 10060
tolerance.
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5. INTRODUCTION (CONTD…)
After being commissioned in 2016, the production has improved
continuously till 2018 (Annual Production : 0.497 MT) and has slowed
down after that owing to COVID-19, input restrictions and raw material
shortages. However, this opportunity was used to initiate a number of
internal projects (QCs, QIPs and special projects) aimed at solving
major problems. Some of the projects are:
1. Switching from A/O lubrication to grease lubrication for guides.
2. Optimising/overhauling the design of troughs causing cobbles.
3. Optimising roll pass design to allow more pass life, improve
properties of finished product and to roll new sections like 23P, 39P,
RB16 and RB20 with 150x150 bloom.
4. Line change-over trough between straight and coil line
5. Cooling Bed Bar Lifter modification for better bar alignment.
6. Bundle tracking instead of encoder at VR64.
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6. After the PULSE team was constituted in
SBM with 6 members from all sections and
areas, the team under the guidance of HOD
took up two main areas of focus.
PULSE-SBM
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1. Increasing production rate
2. Minimizing the downtime

7. As a part of ramping up the production, the mill speeds
increased to reach the rated speed for all sections. However, for
sections like 20P, 20.64P, 22P & 23P, the mill level had to be capped at
14 m/s instead of 16 m/s due to the following reasons:
1.Increasing production rate
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a. Frequent failure of gear box bearings
b. Cobbles at C18 due to head bend
Due to this reason, there was a 12.5% reduction in production rate
for the said sections, which was shown as “Slow rolling” in delays to
compensate for the shortfall in production.

8. A. FAILURE OF GEAR BOX BEARINGS
Problem statement:
 As the production rate of the mill increased, shaft bearings of gear
boxes of stands 7, 8, 9,10,11 & 19 started failing with increasing
frequency.
 Initially, it was thought as an issue of oil contamination/starvation and
necessary steps were taken. But the steps didn’t yield significant results,
which prompted a deeper study into the root-cause of the problem.
Analysis:
 After an in-depth analysis, it was concluded that the bearing
specification is very close to the operating speed and needed to be
higher to ensure sound operation of the gear boxes.
 When this problem with gear boxes was appraised to the mill-builder,
they studied the problems and suggested alternate designs for some
bearings and some shafts.
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9. A.FAILURE OF GEAR BOX BEARINGS
(CONTD...)
Implementation:
 On 19/08/2022, spare parts arrived onsite, all the gear boxes were
fitted with new parts according to the revised designs.
 In several cases, a number modifications had to be done to the
existing shafts, end covers, spacers and other parts which were done
in-situ to reduce the downtime.
Control:
 After the completion of modifications, the vibration characteristics are
continuously recorded and monitored.
 So far, no abnormality is observed when rolling at speeds above 14
m/sec (upto 16 m/sec).
(click for vibration data of various stands)
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10. B. COBBLES AT C18 DUE TO HEAD BEND
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11. B. COBBLES AT C18 DUE TO HEAD BEND
Problem statement:
At shear C18, frequent cobbles are observed due to
bar head bend. To avoid this, the mill speed was
maintained below 14 m/s. This directly resulted in a
reduction of production rate by 12.5%. The shear
operation, bar cutting logic to be studied to determine
the cause(s) of this problem.
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12. B. COBBLES AT C18 DUE TO HEAD BEND
Action Points:
The following issues were studied to identify the root cause of
the problem.
 Shear blades are blunt/ worn out.
 Rejected as problem occurring with new blades as well.
 Shear not reaching reference speed.
 Drive Traces confirmed that speed is reaching.
 Dip in reference speed at proxy position may be a cause
 Sufficient lead being given to compensate the drop.
 Alignment of shear funnel with blades.
 Though this is the case sometimes, problem occurring even
when alignment is checked and corrected.
 Error in calculation of reference speed.
 This could be the root cause and it was studied further.
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13. B.COBBLES AT C18 DUE TO HEAD BEND (CONTD...)
S.No. Parameter Units
Before
correction
After
correction
1 Speed of incoming bar m/s 9.45 9.45
2 Bar size mm 33.5 33.5
3 Shear ratio - 2.5646 2.5238
4 Knives dia m 0.91 0.96
5 Internal lead % 3.73 3.73
6
Shear reference with
internal lead
RPM 528.685 492.166
7 Shear lead from HMI % 25 34
8 Final shear reference RPM 660.85 659.5
Upon modelling the calculation of shear reference speed, it was
observed that the values used for parameters Shear (Gear) Ratio and
Knives Dia in the calculation of reference speed were different from the
actual values. A synopsis of parameter values is given below for 28P.
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14. COBBLES AT C18 DUE TO HEAD BEND (CONTD...)
Implementation:
 The following parameters were modified on 27/09/2022 in
accordance with the field observations
S.No. Parameter Old Value New Value
1 Shear Diameter 0.91 m 0.96 m
2. Gear Ratio 2.5646 2.5238
3.
HMD Distance from
shear
9 m 9.45 m
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15. COBBLES AT C18 DUE TO HEAD BEND (CONTD...)
With these parameters, rolling was done in all the problematic
sections and the issue of head bend cobbles is almost eliminated. One
significant observation was that due to this correction, the shear
reference (without lead) went down by 8% which had to be
compensated with “Shear Lead” parameter from HMI.
Section
Previous
Shear Lead
(%)
New Shear
Lead (%)
20P 25 40
20.64P 25 35
22P 25 50
23P 25 35
25P 25 38
28P 25 34
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16. B.COBBLES AT C18 DUE TO HEAD BEND (CONTD...)
20P 20.64P 22P 23P 25P 28P
Improvement 1.4 0.04 2.32 2.03 1.2 2.1
Before 14.5 14.56 13.58 12.89 14.72 12.8
0
2
4
6
8
10
12
14
16
18
Mill
speed
(m/s)
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Click for Head Bends’ Data

17. Control:
 The original issue of Head-bend has come under control. But, it has
been observed that sometimes the head piece which gets cut , is
getting rebound and obstructing the material.
 It has been noticed that head rebound problem is happening when
bar head crop length is too high.
 Also, when entry funnel height is not proper this is happening.
 Presently, these two are being monitored and C18 performance is
being observed.
 In addition, a head piece guiding mechanism could be developed to
avoid the head hitting the bar.
B.Cobbles at C18 due to head bend (Contd...)
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18. Problem statement:
 Guide change of a (vertical) stand 4 requires the stand to be
shifted to tilter and tilted to horizontal position.
 Time that can be saved: 1.5-2 Hrs
 Equipment required for present procedure: Tilter, EOT
crane, tools &
tackles
A provision to change guide in-line would greatly reduce the
down-time thus, reducing the man and machine hours required to
execute the job.
2.Minimizing the down-time
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19. Minimizing the down-time (Contd…)
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20. Analysis:
To design a jig for guide changing, the following
measurements/observations were made:
 Overall dimensions & weight of the guide from guide manual.
 Height of the rest bar in rolling line.
 Minimum clearance between the guide and cassette when
rolling in last pass.
Minimizing the down-time (Contd…)
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21. Minimizing the down-time (Contd…)
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Working Design:

22. Implementation:
A feasible design was finalised for the jig to allow guide changing in-
line. The necessary equipment/items required for fabrication are as
follows:
1. 16mm thick plate
2. 20mm thick plate
3. Hydraulic cylinder to lift jig (weight~400kgs)
4. Valves and pump for the hydraulic cylinder
5. Counterweight
6. Rollers and bearings for guide trolley
The aforementioned items are being sourced and the
fabrication will begin once all the items are available.
Minimizing the down-time (Contd…)
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23. Thank You
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