Reduction in Failure of Slag & Metal Ladle Auto Couplings
B. D. Babu & DPS Brar
Blast Furnaces, Bhilai Steel Plant,
Steel Authourity of india Ltd, Bhilai. 490001
e-mail: bdbabu@sail-bhilaisteel.com
ABSTRACT
Bhilai Steel Plant, Pioneer unit of Steel Authority of India Limited (SAIL), a Maharatna Company
in the field of Iron & Steel, is India's sole producer of Rails, 260 Mtr Long Rails & Heavy Steel
Plates and also specializes in other products ie, Wire Rods and Merchant products. BSP is
accredited with ISO 9001:2000 Quality Management System Standard and all Saleable products of
Bhilai Steel Plant come under the ISO umbrella.
Blast Furnace produces Hot Metal, which is transported as Rake of 3-4 Ladles in shortest possible
time to Steel Melting Shops so that minimum heat is lost & increase in availability of ladles for Hot
Metal Circuit. These Rakes are formed by joining Hot Metal ladle bogies with the help of Auto
Couplers. Out of 232 Auto couplers installed in locos & bogies, there were approximately 100
failures every year. Frequent Failure of these Auto Couplers was the major problems faced by
Blast Furnace, as failure leads to delay in Hot Metal Disposal, Heat Loss, Bunching of rakes, and
reduction in Hot Metal/Slag Ladle availability. Reduction in Ladle availability for tapping results
in holding furnace under low blast/Low production state. This directly effects the Blast furnace
productivity.
This Project was undertaken to identify and eliminate the problem arising breakdowns. On data
analysis of Auto Coupler failures, it was found that failure of Couplers was mainly on Shank &
Wedge area. Team studied the problem and recommended modifications in material & Design of
Shank & Wedge. The modifications had resulted in “Zero Failure in Modified Auto couplers
installed since Apr’2009” leading to tangible savings of Rs.51.59 Lakhs per annum and intangible
benefit of Rs.3.0 Crores due to reduction of Low Blast duration by 41.75 Hrs. This has also
resulted in Safe Working with minimum maintenance staff.
INTRODUCTION
Bhilai Steel Plant, the NINE times winner of Prime minister trophy, is the flagship unit of Steel
Authority of India limited (SAIL).It is an integrated steel plant producing steels for general
construction as well as special steels catering mainly to the needs of Engineering, Power, Railways,
Automotive & Defense sectors. This is the first Steel Plant in India to cross 5MT mark. As symbol;
of a “New Age” in India, Bhilai Steel Plant has been consistently performing despite several odds
and generating profits for the last twenty two years.
Historically, Bhilai Steel Plant has been into value engineering since 1972, but it got the
momentum through its Value Engineering program in 2008 One of the successful projects is the
subject of the present case study which was done in Blast Furnace and implemented in Apr’2009.
Blast Furnace is the mother of an integrated steel plant. Bhilai Steel Plant is the flagship unit with
production capacity of 5.3 MT by 7 Blast Furnace. Hot metal tapped in Ladles and is supplied to
Steel Melting Shop – I & II, Foundry and Pig Casting Machine. The slag produced is sent to slag
granulation Plant & Slag Dump through Slag Thimbles. Total 89 Hot Metal Ladles and 45 Slag
Thimbles are in circulation. All these Ladles are joined together with the help of two Auto
Couplers (One at each side). The process layout of Blast Furnace is as shown in figure below:
ABOUT AUTO COUPLER
Auto Coupler is a device used for joining two ladle cars. It works under the action of impact of
collision between two ladle cars (Shown in Fig below & next page). The couplers get engaged and
locked automatically. The operation of an external handle disengages the same.
A pair of Auto Couplers, in engaged condition, ensures the joint of two adjacent ladle cars. They
transmit the force of pull by which the whole train of ladle car moves on Rail tracks. It works to
transfer the ladle car from one place to another without detaching of any of the ladle cars in the
train during movement. The various internal components make the system to get engaged with the
other coupler on slight impact. It is automatically responsible for the transmission of the pulling
and pushing load, which moves the train of ladle cars to & fro from Blast Furnace area to Various
Customer Destination.
PROBLEM:
During train formation & movement, frequent breakdown in Auto coupler were observed. These
breakdowns resulted in delay in train movement, restricted traffic, increased cycle time in Hot
Metal & Slag Ladle Circuit, Low blast to Blast Furnace and Production & Heat/Energy loss.
APPROACH & METHODOLOGY
A cross- functional team constitutes of members from Operation, Mechanical, VE trained persons
from industrial Engineering. The team was given the task of coming up with a Value Engineering
proposal for a new cost effective solution for failure of Auto Coupler.
INFORMATION PHASE:
To study & understand the design, function and problematic area of Auto Coupler, detailed sketch
(given below) was thoroughly studied. Keeping in view all the aspects of function, design,
material, operations etc each part & Sub-parts were discussed and noted for further analysis.
EXISTING AUTO COUPLER
TOP VIEW
SIDE VIEW
OBSERVATIONS & FINDINGS
Data analysis for Breakdown pattern, Design and material of Auto Coupler was carried out in
detail. All aspects of problem were studied and discussed with concerned official to reach at the
conclusion that Shank & Wedge area of Auto Coupler are the parts of failure in this coupling.
S. No
Month
No of Breakdown
Delay in mins.
1
April
8
3.93
2
May
11
5.4
3
June
6
2.95
4
July
9
4.42
5
August
6
2.95
6
September
12
5.9
7
October
9
4.42
8
November
7
3.44
9
December
10
4.91
10
January
9
4.42
11
February
8
3.93
12
March
11
5.4
106
52.07
Total
FUNCTION PHASE:
Function analysis of Auto Coupler was elaborated and identified to describe Higher Order
Function, Lower Order Function, One Time Function and All time function. these are displayed as
under:
HIGHER ORDER FUNCTION
LOWER ORDER FUNCTION
Facilitate Train Movement
Use Shank
ONE TIME FUNCTION
ALL TIME FUNCTION
Transfer Load,
Withstand Impact,
Bending,
Shear & Shock
Connect Parts,
Hold Parts
The functional analysis of Shank in Auto Coupler is displayed as under:
FUNCTION
BASIC /
VERB
NOUN
SECONDARY
Transfer
Load
Basic
Withstand
Impact
Secondary
Withstand
Shear
Secondary
Withstand
Tension
Secondary
Withstand
Shock
Secondary
Prevent
Bending
Secondary
Connect
Parts
Secondary
Hold
Parts
Secondary
Facilitates
Fixing
Secondary
Increase
Weight
Secondary
Increase
Replacement
Secondary
The functional analysis of Wedge in Auto Coupler is displayed as under:
FUNCTION
BASIC /
SECONDARY
VERB
NOUN
Facilitates
Locking
Basic
Facilitates
Horizontal
Movement
Secondary
Withstand
Shock / Impact
Secondary
Withstand
Shear
Secondary
Withstand
Tension
Secondary
Facilitates
Maintenance
Secondary
Facilitates
Fixing
Secondary
Withstand
Wear
Secondary
Prevent
Bending
Secondary
FUNCTION-COST –WORTH ANALYSIS
Function Cost –Worth Analysis was carried out by comparing the Cost of Shank & Wedge
separately with respect to worth taking Manual Coupling Cost as basis of Worth. The value gap &
Value Index was thus evaluated as below:
S. No
Items
Existing
Cost
(C)
Worth
(W)
1
Shank
20500
10250
2
Wedge
890
665
Basis of
Worth
Manual
Coupling
Cost
Value gap
(C-W)
Value
Index
(C/W)
10250
2
225
1.33
FAST Diagram for Auto Coupler
How?
Why?
Hold
Parts
Facilitate
Train
Movement
Transfer Load
Withstand
Impact
Withstand
Shear
Connect
Parts
Withstand
Shock
Use
Shank
Withstand
Bending
Increase
Replacement
Increase
Weight
CREATIVITY PHASE
In the creativity phase, the Team generated 07 ideas by brainstorming during the workshop, out of
which 4 ideas were for Shank and 3 ideas were for Wedge. One idea each for Shank & Wedge
were selected due to their outperformance in feasibility ranking matrix.
Ideas generated for Shank:
1. Change in material composition to provide adequate Strength (IS:2708 GrII).
2. Improve Design by altering Shape and Size ie, Increase thickness from 20 mm to 25mm.
3. Improve alignment by installing Support Springs on both sides.
4. Avoid Malfunction / Mal-operation by educating Porter & Driver.
Ideas generated for Wedge
1. Replace Wedge arrangement by Heat Treated Cylindrical Pin Arrangement.
2. Avoid additional support plate at the Impact area (Si-Mn Spring Steel).
3. Provide greasing at the contact points of Cylindrical Pin.
EVALUATION PHASE
IDEN
TITY
A
B
C
D
E
F
G
H
RELA
IBILITY
EASE
OF
OPER
ATIO
N
I
MAIN
TAIN- WEIG
ABILI
HT
TY
SCOR
E
COST
QUAL
ITY
TIME
SAFE
TY
FEAS
IBIL
ITY
A
B3
C2
D3
E2
F3
G2
H1
A1
2
B
B3
D3
B2
B2
G2
B1
B2
14
C
D3
E2
F2
G1
C2
C1
6
D
D2
D0
D2
D3
D2
19
E
F2
G2
H1
E1
6
F
F2
F2
F1
13
G
G2
G2
12
H
H1
4
I
1
3
points
for
Major
Differe
nce
2
points
for
Mediu
m
Differe
nce
1 point
for
Minor
Differe
nce
No
points
for
No
Differe
nce
DECISION MATRIX
Based upon the evaluation phase, ideas were further evaluated based on decision matrix for wedge
& Shank of Auto Coupling.
FEASIBILITY
RELAIBILITY
DX
19
4
EX
6
3
FX
13
4
GX
12
2
HX
4
2
1X
1
4
Material
Strengthenin
g
2
56
6
76
18
52
24
12
4
Improve
Design
1
2
2
4
4
3
42
2
28
3
1
6
2
12
3
3
57
2
38
3
3
18
1
6
4
3
39
1
13
3
2
24
1
12
4
3
12
1
4
3
2
Improve
Alignment
Avoid
Maloperation
8
42
18
57
24
39
48
12
2
2
2
1
1
RANKING
SAFETY
CX
6
1
TOTAL POINTS
TIME
BX
14
4
WEIGHT
QUALITY
AX
2
1
IDEAS
Weightage
MAINTAINABILITY
COST
CRITE RIA
EASE OF
OPERATIO
N
Detail of Decision Matrix for Shank is as given below:
250
I
202
III
119
IV
249
II
TIME
SAFETY
FEASIBILIT
Y
RELAIBILIT
Y
EASE OF
OPERATIO
N
MAINTAIN
ABILITY
Weightage
BX
14
4
CX
6
2
DX
19
4
EX
6
3
FX
13
4
GX
12
4
HX
4
4
1X
1
2
Heat Treated
Cylindrical
Pin
Additional
Support
Plates
8
56
12
76
18
52
48
16
2
2
3
2
3
2
3
2
3
2
4
42
12
57
12
39
24
12
Provide
Lubrication
2
3
2
3
3
4
4
3
1
4
42
12
57
18
52
48
12
1
2
RANKING
QUALITY
AX
2
4
IDEAS
WEIGHT
COST
CRITE RIA
TOTAL POINTS
Detail of Decision Matrix for Wedge is as given below:
288
I
204
III
246
II
RECOMMENDATIONS
It was decided to take up the top ranking proposals of Shank & Wedge respectively for
implementation. The proposals for implementation For Shank is to change the specification (From
M:201 Gr B to IS:2708 Grill )of Auto Coupler to avoid Mal-operation and for Wedge Installing
heat treated Cylindrical Pin for fixing coupler.
IMPLEMENTATION / SUPPORTING DATA SHEET
PLAN FOR SHANK
RECCOMENDATIONS
Change in Material
Specification of Auto
Coupler from M:201 Gr.B
to IS:2708 Gr. II
ACTION
RESPONSIBILITY
Incorporate Material
Specification in drawing
Issue enquiry to supplier
Receive Quotation
Evaluate Quotation
Place Order
Procurement
Implementation
MB Sarkar &
BD Babu
MB Sarkar
BD Babu
TDN Naidu
V Mathai
DPS Brar
COMPLETION
DATE
31-01-2009
30-04-2009
15-06-2009
30-06-2009
31-07-2009
31-12-2009
15-01-2010
PLAN FOR WEDGE
Discussions
Installing Heat Treated
Cylindrical Pin for fixing
Coupler
15-01-2009
Replacement of Work
order with priority
Cylindrical Pin collection
Implementation
MB Sarkar &
BD Babu
31-01-2009
All Team Members
28-02-2009
10-03-2009
MODIFIED AUTO COUPLER
TOP VIEW
SIDE VIEW
BENEFITS
DIRECT BENEFIT CALCULATION
Installed Auto Couplings in BF’s
= 274 Nos.
Auto Coupling replacement on Failure (2008-09)
= 106 Nos.
Cost of Existing Auto Coupling
= Rs. 29400/Projected Auto Coupling replacement (Apr’09 – Aug’11)
= 256 Nos.
Expected Expenditure for Projected Replacement
= Rs. 7532000/Cost of Modified Auto Coupling
= Rs. 47158/Modified Auto Coupling replacement (Apr’09 – Aug’11)
= 150 Nos.
Expenditure on Modified Auto Coupling
= Rs. 7073700/Reduction in replacement of Auto Coupling
= 106 Nos.
Saving due to reduction in replacement
= Rs. 5000000/Mandays Saving for 106 replacements
= 159 Mandays
Savings in Cost of Mandays @1000/= Rs. 159000/TOTAL SAVINGS
:
51.59 Lakhs
INDIRECT BENEFIT CALCULATION
Reduction in Delay in Disposal of Hot Metal may be accorded against failure of auto coupling.
Auto coupling Failure 2008-09
= 106 Nos
Total Delay in Hot Metal Disposal(DDHM) 2008-09
= 173.55 Hrs
DDHM due to Coupling Failure
= 52.07 Hrs
Auto coupling Failure 2009-10
=
64 Nos
Total Delay in hot metal disposal(DDHM) 2009-10
= 180.80 Hrs
DDHM due to Coupling Failure
= 31.44 Hrs
Auto coupling Failure 2010-11
=
38 Nos
Total Delay in hot metal disposal(DDHM) 2009-10
= 180.80 Hrs
DDHM due to Coupling Failure
= 19.24 Hrs
Considering 7 % Breakdown in Total Ladle Cars (274)
= 20 Nos
Expected DDHM Duration
= 10.24 Hrs
DDHM Duration before implementation
= 52.07 Hrs
Average Saving in delay Hrs (Annual)
= 41.83 Hrs
Delay Cost/Hr due to Low Blast/Stoppage
= Rs. 6 Lakhs
Benefit (Cost of delay)
:
2.51 Crores/Yr
POST IMPLEMENTATION BENEFIT ASSESMENT
Direct Savings Calculation
Total Auto Couplings
Annual Auto coupling replacement pre-implementation
Projected Auto Coupling replacement without modification
Cost of Old design Auto Coupling
Cost of One Modified Auto Coupler
Modified Auto Coupling Installed
Extra Cost for Modified Auto Couplings Installed
Failure of Modified Auto Coupling
Savings in No of Auto Couplers replacement
Savings due to reduction in failure
Net Savings due to reduction in Auto Coupler requirement
Mandays Saved for 344 replacements @1.5 Mandays/replacement.
Savings due to Mandays reduction for replacement
(Contractual Highly Skilled Worker Wages @ Rs.350)
Total Savings
Say Total Savings of Rs 1.34 Crores
ACHIEVEMENT:
“ZERO FAILURE” in all Modified Auto Couplings
since installation (Apr’2009 – Till Date)
274
106
345
29400
47200
170
3026000
1
344
16236800
13210800
516
180600
13391400