21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions 1

NATIONAL TECHNICAL UNIVERSITY OF ATHENS LABORATORY FOR SHIP & MARINE HYDRODYNAMICS

(member of ITTC, HELLAS LAB., ISO 9001 Certified)

Minimum Propulsion Power for ship safe Operation

under adverse Weather Conditions

by G.J. Grigoropoulos, Professor NTUA

SCOPE OF THE STUDY

The study aimed at the assessment of the seakeeping performance including added resistance in wind and waves for four (4) Bulk Carriers. The ship speed and the sea conditions were derived on the basis of IMO MSC MSC-MEPC.2/Circ.11 issued on December 2012.

On the basis of these results, some conclusions are drawn with respect to the required installed power to propel the ship at a specified speed in head waves (worst case) defined in the above Circular, as well as in those specified by ISC Code 2008.

The selected ships are:

• BC HANDY DWT 30000 T

• BC SUPER-HANDY-MAX 57000 T

• BC KAMSAR-MAX 79000 T

• BC CAPE SIZE 176000 T

• MT VLCC 306000 T

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3

BC DWT 30000 T

MAIN DIMENSIONS

LBP = 168.00

BM = 26.00 m

TBAL = 5.06 m και TSCAN = 9.89 m

Minimum Power Line = 6015 kW

Installed Power = 6480 kW

Ballast Draft

Full Load Draft

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

4

BC DWT 57000 T

MAIN DIMENSIONS

LBP = 185.00

BM = 32.26 m

TBAL = 5.87 m και TSCAN = 12.8 m

Minimum Power Line = 7635 kW

Installed Power = 9480 kW

Ballast Draft

Scantling Draft

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

BC DWT 79000 T

MAIN DIMENSIONS

LBP = 222.00

BM = 32.26 m

THB = 8.209 m και TFL = 14.619 m

Minimum Power Line = 8983 kW

Installed Power = 11060 kW (+23%)

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BC DWT 176000 T

MAIN DIMENSIONS

LBP = 282.20

BM = 45.00 m

THB = 9.267 m και TFL = 18.250 m

Minimum Power Line = 14861 kW

Installed Power = 16860 kW (+13.5%)

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BC DWT 176000 T

MAIN DIMENSIONS

LBP = 320.00

BM = 58.00 m

THB = 11.570 m και TFL = 20.430 m

Minimum Power Line = 23917 kW

Installed Power = 29340 kW (+23%)

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SIMPLIFIED METHOD (BULK CARRIERS)

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SIMPLIFIED METHOD (TANKER)

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SIMPLIFIED METHOD (BC DWT 30000, 57000 & 79000 Τ)

BC DWT 30000 T

• LOADING CONDITION 06: Heavy Ballast Condition at Arrival (Displ. = 26029 mt)

• LOADING CONDITION 27: Homo. Loading with Dens=3T/m3, Short Voyage (50% Bunker) Departure (Displ. = 37760 mt)

BC DWT 57000 T

• LOADING CONDITION 09: Heavy Ballast Condition Arrival (Displ. = 43858 mt)

• LOADING CONDITION 23: Multi-Port 2ND Port Homo. Loading, Departure (Displ. =67680 mt)

BC DWT 79000 T

• LOADING CONDITION 44: Multi-Port 2nd Port Ore Loading (3.0 t/m3) Condition at Departure (Displ. = 93377 mt)

• LOADING CONDITION 10: Heavy Ballast Condition at Arrival (Displ. = 49388 mt)

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 176000 T & VLCC DWT 306000 T)

BC DWT 176000 T

• LOADING CONDITION 39: 6A Homogeneous Heavy Loading Condition at Departure (SF = 11.97 ft3/lt) (Displ. = 202617 mt)

• LOADING CONDITION 23: 2G Heavy Ballast Condition at Arrival, without AP, WBT10, WBT6P/S (Displ. = 96734 mt)

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VLCC DWT 306000 T

• LOADING CONDITION 10: Homogeneous Design Load, 40% Bunker Condition (S.G. = 0.7884)

• LOADING CONDITION 07: Gale Ballast Condition at Arrival (No. 3 C.C.O.TK)

SIMPLIFIED METHOD (BC DWT 79000 Τ)

12

0

200000

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Resis

tan

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Vs [kn]

BC79K_Full Load_Vwind = 19 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rwave

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 79000 Τ)

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Vs [kn]

BC79K_Heavy Ballast_Vwind = 19 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 79000 Τ)

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Vs [kn]

BC79K_Full Load_Vwind = 26 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rwave

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 79000 Τ)

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Vs [kn]

BC79K_Heavy Ballast_Vwind = 26 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 176000 Τ)

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Vs [kn]

BC176_Full Load_Vwind = 19 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 176000 Τ)

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0

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ce [

N]

Vs [kn]

BC176_Heavy Ballast_Vwind = 19 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rwave

Rtotal

Minimum Power for safe Operation in adverse Weather Conditions 21st May 2014

SIMPLIFIED METHOD (BC DWT 176000 Τ)

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Vs [kn]

BC176_Full Load_Vwind = 26 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rtotal

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

SIMPLIFIED METHOD (BC DWT 176000 Τ)

0

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Vs [kn]

BC57_Ballast_Vwind= 26 m/s

Rbare

Rcalm

Rair

Rair (w/o wind)

Radded

Rapp

Rwind

Rtotal

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2 4 6 8 10 12 14 16

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tan

ce [

N]

Vs [kn]

BC176_Heavy Ballast_Vwind = 26 m/s

Rbare

Rcalm

Rwind

Rair (w/o wind)

Radded

Rapp

Rwave

Rtotal

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SIMPLIFIED METHOD FULL LOAD (BC DWT 30000 Τ)

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L1 6480 kW

L2 5190 kW

L3 5490 kW

L4 4380 kW

RPM up 136 RPM

RPM low 115 RPM

21st May 2014 Minimum Power for safe Operation in adverse Weather Conditions

7/11/06 Συνάντηση Μελών ΕΝΘΥ 21

7/11/06 Συνάντηση Μελών ΕΝΘΥ 22

7/11/06 Συνάντηση Μελών ΕΝΘΥ 23

SIMPLIFIED METHOD FULL LOAD (VLCC DWT 306000 Τ)

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L1 29340 kW

L2 23520 kW

L3 23580 kW

L4 18840 kW

RPM up 76 RPM

RPM low 61 RPM

CONCLUSIONS - 1

1. All five ships studied, very easily satisfy level 1 requirements, while some of them satisfy the requirements of level 2 – simplified assessment with more difficulty. This constitutes a major failure of rationalism, dictating that level 1 should be the strictest one. Since either level is sufficient to comply with the requirement, it follows that the simplest level 1 should not also be the easiest to fulfill.

2. Submerged lateral area of the hull, corrected for breadth effect, based on IACS formulation and incorporated in MSC-MEPC.2/Circ.11 is 55-70% higher than the actual one, both at the full load and the heavy ballast conditions and in the case of the VLCC more than 80% higher. This affects the minimum speed for manoeuvrability.

3. Estimated power requirements on the basis of MSC-MEPC.2 / Circ.11 deviate form calculated results more in the heavy ballast conditions than in the full load ones. This may be due to the fact that, following IACS supporting document, approximate formulae are based on full load condition, while the heavy ballast one is more critical in this respect, due to higher vertical dynamic responses contributing to excessive added resistance in head waves.

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CONCLUSIONS - 2

4. Level 1 – Minimum Power Lines are easily exceeded in all five cases. Installed power of the small (30000T) and the large (176000T) BC exceeds regression line by 8% and 13.5%, respectively. Margin for the two intermediate BCs is >20% and for the VLCC >23%. This shows that the bar was set quite low to allow a free pass for all designs.

5. Level 2 – Simplified Assessment power requirements are met only marginally in one of the tested conditions for the investigated BCs. Taking into account the fouling and the aging of ships, this criterion may be violated. On the contrary, they are well satisfied for the VLCC, where required minimum speed is too low for the installed main engine – propeller configuration. Oceangoing ships regardless of their size encounter similar weather and sea conditions, which affect more the smaller ones, their power margin must be increased. Instead, Res. MEPC. 232(65) - 2013 reduced sea conditions for all ships and more so for ships below 250 m to levels equivalent to Beaufort 7.

6. Minimum power requirement ignores increase of calm water resistance due to hull & propeller fouling, as well as due to aging. Commercial ships are neither new-buildings nor just launched from the dry dock.

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CONCLUSIONS - 3

7. The vessels were evaluated also for the sea and weather conditions specified by ISC 2008 (equivalent to Beaufort 10). Under these conditions, assuming the required minimum speed of MSC-MEPC.2 / Circ.11, none of them satisfies minimum power requirement, although some came very close. This indicates that there is much room to set stricter requirements than those set by resolution MEPC. 232(65).

8. Level 1 power line is satisfied by 90% of plotted sample, implying that required minimum installed power is substantially lower than actual current designs for BCs. The same holds true for tankers. It does not seem appropriate, nor conservative, to now provide an effective “IMO stamp of safety” to all ships as long as they are not within the worst 10% of data wrt engine size (underpowered ships).

9. Level 1 – power line method, adopted by resolution MEPC.232 (65) as the first level of a two or three-level assessment approach should be of the most stringent and conservative, as a matter of principle.

10. Harmonization of sea & weather environment of MSC-MEPC.2 / Circ.11 to those of the mandatory ISC 2008 is reasonable and should be attempted. A ship that can’t manoeuvre in the latter conditions is prone to grounding or to be driven against a nearby rocky shore.

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