Simple and Effective Work Roll
Cooling Modification for Hot
Mills
Mark Armstrong - Lake Erie Steel GP Inc.
Roland Van Rijn - Applied Fluids LLC.
Agenda
•
•
•
•
•
•
•
Introduction
The Cooling Mechanism
Water Pressure
Water Distribution
Nozzle Selection
Spray Pattern and Strategy
System Balancing and Set-Up
The Cooling Mechanism
• Discrepancies between the theoretical aspects and
practical application
• Roll area coverage
– Changed angles and distances to the roll to cover more
of the roll barrel – no improvement
• Water temperature
– The thermal gradient at the roll water interface
– Noticeable improvements not expected with cooler
water
Estimated Roll Surface Temperature for One Rotation
700
600
Temperature in Degrees C
500
400
300
200
100
0
0
1
2
3
4
Radians
5
6
7
Water Pressure
• Yamaguchi et. al found no relationship
between water pressure and cooling efficacy
• Van Steden and Tellman found that the rate
of energy transfer between roll and water
increased for spray pressures up to 300 psi
• Lake Erie Steel’s average roll temperatures
decreased by 6°C to 10°C when the
pressure was increased from 35 to 185 psi
Water Pressure
• Effects of pooling
• Removal of spent water
• Ability to cut through the boundary layer
Water Distribution
Entry to Delivery
• Most opportunity for eat extraction on the delivery
side as close to the roll bite as possible
• Experiences at LES
– Original configuration 40-45% entry, 55-60% delivery
– Nozzles only modified to make the distribution 25%
entry and 75% delivery yielded a 3°C to 5°C
improvement in centerline roll temperatures
– Addition of auxiliary headers on top and bottom on the
delivery side closer to the roll bite
– No noticeable change – notice the pooling
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
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
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
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



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
Water Distribution
• Optimization of header placement
• Circumferential balancing of spray
locations and volumes applied from the roll
bite
• Stand geometry and its affects
• Roll sizes and their effect on spray coverage
and overlaps
• Uniformity of perpendicular distances
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
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
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


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

Water Distribution
Top to Bottom
• The amount of water applied to the top and
the bottom work rolls should be roughly the
same
• Small modifications to header positioning
or water volumes to account for top to
bottom variations in strip surface
temperature should be done carefully
Nozzle Selection
• KSAM – filtered nozzle with locating key
• Thickening flat type
• Straightening filter advantages
– 100% of rated flow even when 80% blocked
– Improved impingement and more organized
flow
– More efficient use of available water
Nozzle Selection
effective spray
area
wasted water
Spray Pattern from a Typical
Flat Fan Nozzle
KSAM Nozzle with adapter base
and attached filter
effective spray
area
wasted water
Spray Pattern from a Filtered
KSAM
Spray Pattern and Strategy
• Cross width flow density strategies (volume
of water applied per unit width of roll
barrel) – Blazevic’s findings
• Uniform strategy was selected by LES for
simplicity and rolling schedules
• Importance of flow density analysis
• Calculation of flow density variation
Flow Density Pattern
Header : New Top Del. Headers F4-F5
Nozzle :50 deg.-15 deg. Skew, 2.5" spacing 29 &
30 Nozzles Per Hdr., Midzones Off
Large Rolls
100.00
Small Rolls
90.00
Flow Density (%) of Total Flow
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0.00
5.00
10.00
15.00
20.00
25.00
Dist. From Mill Center Line (Inches)
30.00
35.00
40.00
Flow Density Pattern
100.00
Header : New Top Del. Headers F4-F5
Nozzle :50 deg.-15 deg. Skew, 2.5" spacing
29 & 30 Nozzles Per Hdr.
Large Rolls
Small Rolls
90.00
Flow Density (%) of Total Flow
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0.00
5.00
10.00
15.00
20.00
25.00
Dist. From Mill Center Line (Inches)
30.00
35.00
40.00
Spray Pattern and Strategy
• Spray patterns should be designed to
achieve a flow density variation that does
not exceed 5%
• Mill geometry and the range of roll
diameters used must be examined to ensure
that the flow density variation is acceptable
for all operating conditions
System Balancing and Set-Up
• Balancing the total flows, header flows and
stand flows is critical to implementation
• Accurate flow estimation is key
• Flow estimation and balancing can be done
with some work in excel
• Using header pressures and flow curves for
the selected nozzles will yield accurate
results
Entry
Delivery
F4
Delivery
F5
Top
Bottom
Top
Bottom
Top
Bottom
Top
Bottom
Top
Bottom
10.62
9.765
9.155
9.29
8.6
9.695
9.895
8.275
8.635
8.305
10.62
9.765
9.155
9.29
8.6
9.695
9.895
8.275
8.635
8.305
10.62
9.765
9.155
9.29
8.6
9.695
9.895
8.275
8.635
8.305
10.62
9.765
9.155
9.29
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
Spray Length
Min. WR Max. WR
11.05
6.54
9.31
6.87
8.64
6.53
8.51
6.88
7.67
6.58
9.26
6.80
9.92
6.47
7.56
6.16
7.94
6.36
7.80
5.96
11.05
6.54
9.31
6.87
8.64
6.53
8.51
6.88
7.67
6.58
9.26
6.80
9.92
6.47
7.56
6.16
7.94
6.36
7.80
5.96
11.05
6.54
9.31
6.87
8.64
6.53
8.51
6.88
7.67
6.58
9.26
6.80
9.92
6.47
7.56
6.16
7.94
6.36
7.80
5.96
11.05
6.54
9.31
6.87
8.64
6.53
8.51
6.88
Average
Perpend.
Length
8.50
7.81
7.33
7.43
6.88
7.76
7.92
6.62
6.91
6.65
8.50
7.81
7.33
7.43
6.88
7.76
7.92
6.62
6.91
6.65
8.50
7.81
7.33
7.43
6.88
7.76
7.92
6.62
6.91
6.65
8.50
7.81
7.33
7.43
Overlap
as a % of
Perp.
Length
Branch Loss
(psi)
Bottom
Spacing
between
Nozzles
Average
Overlap
Top
Min. WR Max. WR
13.34
7.9
11.24
8.29
10.43
7.88
10.27
8.31
9.26
7.94
11.18
8.21
11.98
7.81
9.12
7.43
9.59
7.68
9.42
7.19
13.34
7.9
11.24
8.29
10.43
7.88
10.27
8.31
9.26
7.94
11.18
8.21
11.98
7.81
9.12
7.43
9.59
7.68
9.42
7.19
13.34
7.9
11.24
8.29
10.43
7.88
10.27
8.31
9.26
7.94
11.18
8.21
11.98
7.81
9.12
7.43
9.59
7.68
9.42
7.19
13.34
7.9
11.24
8.29
10.43
7.88
10.27
8.31
Skew Angle
Entry
Delivery
F3
Bottom
Main
Midzone
Main
Midzone
Auxiliary
Main
Midzone
Auxiliary
Main
Midzone
Main
Midzone
Main
Midzone
Auxiliary
Main
Midzone
Auxiliary
Main
Midzone
Main
Midzone
Main
Midzone
Auxiliary
Main
Midzone
Auxiliary
Main
Midzone
Main
Midzone
Main
Midzone
Avg.
Distance
from Roll
Face
Spray Angle
Delivery
Entry
Entry
Delivery
F2
Location
Side
Entry
Stand
F1
Top
Header
Perpendicular
Distances
6.00
5.31
4.83
4.93
4.38
5.26
5.42
4.12
4.41
4.15
6.00
5.31
4.83
4.93
4.38
5.26
5.42
4.12
4.41
4.15
6.00
5.31
4.83
4.93
4.38
5.26
5.42
4.12
4.41
4.15
6.00
5.31
4.83
4.93
70.6
68.0
65.9
66.4
63.7
67.8
68.4
62.2
63.8
62.4
70.6
68.0
65.9
66.4
63.7
67.8
68.4
62.2
63.8
62.4
70.6
68.0
65.9
66.4
63.7
67.8
68.4
62.2
63.8
62.4
70.6
68.0
65.9
66.4
51
25
26
41
44
39
55
50
24
49
28
38
27
51
11
44
43
48
36
46
27
45
28
36
47
38
55
47
32
48
29
49
31
40
Pressure (psi)
Nozzle ID Number
Current New Current
20
20
5050
46
46
5090
45
45
5050
30
30
5050
27
27
50250
32
32
50150
16
16
50100
21
21
50200
47
47
50100
22
22
5090
43
43
5050
33
33
5050
44
44
5050
20
20
5050
60
60
50100
27
27
50250
28
28
50100
23
23
50250
35
35
50100
25
25
50100
44
44
5050
26
26
5050
43
43
5050
35
35
5050
24
24
50250
33
33
50100
16
16
50100
24
24
50250
39
39
50100
23
23
50100
42
42
5070
22
22
50120
40
40
5070
31
31
50120
No. of Nozzles
New
Current New
2545
25
36
29
2545
25
37
30
2545
25
36
29
2545
25
37
30
11045 110
37
30
7045
70
36
29
5045
50
37
30
11045 110
37
30
7045
70
36
29
5045
50
37
30
2545
25
36
29
2545
25
37
30
2545
25
36
29
2545
25
37
30
7545
75
37
30
7045
70
36
29
5045
50
37
30
11045 110
37
30
7045
70
36
29
5045
50
37
30
2545
25
36
29
2545
25
37
30
2545
25
36
29
2545
25
37
30
11045 110
37
30
7045
70
36
29
5045
50
37
30
11045 110
37
30
7045
70
36
29
5045
50
37
30
2545
25
36
29
2545
25
37
30
2545
25
36
29
2545
25
37
30
Top
Main
Midzone
11.18
11.98
8.21
7.81
9.695
9.895
45
45
15
15
2.5
2.5
9.26
9.92
6.80
6.47
7.76
7.92
5.26
5.42
67.8
68.4
25
43
46
28
46
28
50150
5070
8545
6045
85
60
36
36
29
30
Bottom
Main
Midzone
Main
Midzone
Main
Midzone
9.59
9.42
13.34
11.24
10.43
10.27
7.68
7.19
7.9
8.29
7.88
8.31
8.635
8.305
10.62
9.765
9.155
9.29
45
45
45
45
45
45
15
15
15
15
15
15
2.5
2.5
2.5
2.5
2.5
2.5
7.94
7.80
11.05
9.31
8.64
8.51
6.36
5.96
6.54
6.87
6.53
6.88
6.91
6.65
8.50
7.81
7.33
7.43
4.41
4.15
6.00
5.31
4.83
4.93
63.8
62.4
70.6
68.0
65.9
66.4
27
39
27
39
33
38
44
32
44
32
38
33
44
32
44
32
38
33
50150
5070
5070
50120
5070
50120
8545
6045
2545
2545
2545
2545
85
60
25
25
25
25
36
36
36
37
36
37
29
30
29
30
29
30
Top
Main
Midzone
11.18
11.98
8.21
7.81
9.695
9.895
45
45
15
15
2.5
2.5
9.26
9.92
6.80
6.47
7.76
7.92
5.26
5.42
67.8
68.4
41
30
30
41
30
41
50150
5070
8545
6045
85
60
36
36
29
30
Bottom
Main
Midzone
9.59
9.42
7.68
7.19
8.635
8.305
45
45
15
15
2.5
2.5
7.94
7.80
6.36
5.96
6.91
6.65
4.41
4.15
63.8
62.4
38
29
33
42
33
42
50150
5070
8545
6045
85
60
36
36
29
30
Top
Bottom
Header Pressure Gradients
60
50
Pressure (psi)
40
30
20
10
0
0
5
10
15
20
25
30
35
Distance from Operator Side (in.)
Top. Del. Aux.
Bot. Del. Mz.
Top Del. Main
Bot. Ent. Mz.
Top Del. Mz.
Top Ent. Main
40
Summary
1.
2.
3.
4.
5.
6.
7.
Ensure that the cooling water pressure is adequate. Pressures for work roll cooling systems
should be in the range of 7 bar to 15 bar (100 psi to 225 psi.).
Position headers for maximum heat extraction. Headers should be positioned as close as possible
to the roll bite on the delivery side and out of the pool that is developed in the delivery guide
apron if at all possible.
Headers should be positioned symmetrically about the top and bottom work rolls
circumferentially from the roll bite. The volume of water and the positions it is applied in should
also be symmetric about the top and bottom rolls circumferentially from the roll bite.
Select nozzles that provide a concentrated spray that matches well with the effective area used in
spray overlap and flow density calculations.
Ensure system filtration of the cooling water is appropriate to prevent clogged nozzles or select a
nozzle with attached filter to provide this filtration.
Design the spray overlaps to provide a flow density distribution with a variation of less than 5%.
Use header pressures to examine each branch of the work roll cooling system to ensure that the
flows generated are balanced.