Tanker Spills: Prevention by Design (1991)
Chapter: Appendix K: Committee Estimates of Oil Outflow Relative to MARPOL Standard
Appendix K
Committee Estimates of Oil Outflow Relative to MARPOL Standard (100%)
Outflow estimates were provided by Det norske Veritas (DnV) for several design alternatives; the committee made its own estimates for other alternatives using the DnV individual estimates of grounding and/or collision performance. This performance rating is stated as an outflow index relative to the conventional MARPOL tanker (designated by DnV as ''original" in their report) whenever possible.
The cases for which the committee made its own estimates are marked with an "x" in Table K-1. The figures and calculations leading to the committee estimates are on the following pages.
TABLE K-1 Ratings Derived by Committee
|
Design Alternative |
Tanker Size |
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|
|
VLCC (Table 5-5) |
40,000 DWT (Table 5-6) |
|
Intermediate oil-tight deck with double sides |
× |
× |
|
|
Double sides with hydrostatic control |
× |
× |
|
|
Double hull with hydrostatic control |
× |
× |
|
|
Hydrostatic control |
Calculated by DnV |
× |
|
|
Small tanks |
|
Calculated by DnV |
× |
|
|
|
VLCC |
|
|
|
|
Reference: DnV Outflow Figures from Chapter 5: |
|
|
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|
Figure 5-13 Speed: 5 Knots |
Figure 5-14 Speed: 10 Knots |
|
Intermediate Oil Tight Deck with Double Sides |
DnV Arrangement Number |
|
|
|
Double sides with hydrostatic control collision |
(3 B) |
30 |
19 |
|
Intermediate oil tight deck grounding |
(8) |
2 |
4 |
|
|
|
__ |
__ |
|
Total |
|
32 |
23 |
|
Double Sides with Hydrostatic Control |
DnV Arrangement Number |
|
|
|
Double sides collision |
(3 B) |
32 × .91 = 29 |
19 × .9 = 17 |
|
Hydrostatic control grounding |
(9) |
3 |
4 |
|
|
|
__ |
__ |
|
Total |
|
32 |
21 |
|
|
|
Reference: DnV Outflow Figures from Chapter 5: |
|
|
|
|
Figure 5-13 Speed: 5 Knots |
Figure 5-14 Speed: 10 Knots |
|
Double Hull with Hydrostatic Control |
DnV Arrangement Number |
|
|
|
Double hull collision |
(1A or 1B) |
33 × .9 = 30 |
20 × .9 = 18 |
|
Double hull grounding |
(1A or 1B)2 |
(0 + 1)/2 = 0 |
(6 + 3)/2 = 4 |
|
|
|
__ |
__ |
|
Total |
|
30 |
22 |
|
|
40,000 DWT TANKER |
||
|
|
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Reference: DnV Outflow Figures from Chapter 5: |
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|
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Figure 5-15 Speed: 5 Knots |
Figure 5-16 Speed: 10 Knots |
|
Hydrostatic Control + Base |
DnV Arrangement Number |
|
|
|
Base collision |
(1) |
55 × .9 = 49 |
34 × .9 = 31 |
|
Intermediate oil-tight deck grounding |
(8) |
3 |
3 |
|
|
|
__ |
__ |
|
Total |
|
52 |
34 |
|
|
|
Reference: DnV Outflow Figures from Chapter 5: |
|
|
|
|
Figure 5-15 Speed: 5 Knots |
Figure 5-16 Speed: 10 Knots |
|
Smaller Tanks |
|
|
|
|
Assume base ship (1) with twice as many transverse bulkheads. This would make collision index about 0.5 and grounding index about 0.9 compared to MARPOL base. |
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|
Base grounding × 0.5 |
|
55 × .5 = 27.5 |
34 × .5 = 17 |
|
Base collision × 0.9 |
|
45 × .9 = 40.5 |
66 × .9 = 59 |
|
|
|
__ |
__ |
|
Total |
|
68 |
76 |
|
Intermediate Oil-tight Deck with Double Sides |
DnV Arrangement Number |
|
|
|
Double sides collision |
(6)3 |
55 |
34 |
|
Intermediate oil-tight deck grounding |
(8) |
2 |
2 |
|
Total |
|
57 |
36 |
|
Double Sides with Hydrostatic Control |
|
|
|
|
Double sides collision |
(2) |
75 × .9 = 67 |
44 × .9 = 40 |
|
Hydrostatic control grounding |
(Use VLCC Values) |
3 |
4 |
|
|
|
- |
- |
|
Total |
|
70 |
44 |
|
|
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Reference: DnV Outflow Figures from Chapter 5: |
|
|
|
|
Figure 5-15 Speed: 5 Knots |
Figure 5-16 Speed: 10 Knots |
|
Double Hull with Hydrostatic Control |
DnV Arrangement Number |
||
|
Double hull collision |
[Avg. of (5+6+7)] × .9 = 60= 37 |
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|
Hydrostatic control |
Average hydrostatic control + "Perfect" |
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|
- or |
= 1.5 |
= 1.5 |
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|
(3 + 0)/2 |
|
|
|
|
|
- |
- |
|
Total |
|
61 |
39 |
|
1 0.9 assumes all cargo tanks are 90% filled for the hydrostatic control design. 2 Grounding averages 1A + 1B (double hull) and 9 (hydrostatic control). 3 Uses DnV arrangement number 6 (double hull with centerline bulkhead) being the more representative of double side that would be DnV arrangement number 2 (with no centerline bulkhead). |
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