Minimum Propulsion Power for ship safe Operation under adverse Weather Conditions

Transcription

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 1

2 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 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 The selected ships are: BC HANDY DWT T BC SUPER-HANDY-MAX T BC KAMSAR-MAX T BC CAPE SIZE T MT VLCC T 2

3 BC DWT T Full Load Draft Ballast Draft MAIN DIMENSIONS L BP = B M = m T BAL = 5.06 m και T SCAN = 9.89 m Minimum Power Line = 6015 kw Installed Power = 6480 kw 3

4 BC DWT T antling Draft llast Draft MAIN DIMENSIONS L BP = B M = m T BAL = 5.87 m και T SCAN = 12.8 m Minimum Power Line = 7635 kw Installed Power = 9480 kw 4

5 BC DWT T MAIN DIMENSIONS L BP = B M = m T HB = m και T FL = m Minimum Power Line = 8983 kw Installed Power = kw (+23%) 5

6 BC DWT T MAIN DIMENSIONS L BP = B M = m T HB = m και T FL = m Minimum Power Line = kw Installed Power = kw (+13.5%) 6

7 BC DWT T MAIN DIMENSIONS L BP = B M = m T HB = m και T FL = m Minimum Power Line = kw Installed Power = kw (+23%) 7

8 SIMPLIFIED METHOD (BULK CARRIERS) 8

9 SIMPLIFIED METHOD (TANKER) 9

10 SIMPLIFIED METHOD (BC DWT 30000, & Τ) BC DWT T LOADING CONDITION 06: Heavy Ballast Condition at Arrival (Displ. = mt) LOADING CONDITION 27: Homo. Loading with Dens=3T/m 3, Short Voyage (50% Bunker) Departure (Displ. = mt) BC DWT T LOADING CONDITION 09: Heavy Ballast Condition Arrival (Displ. = mt) LOADING CONDITION 23: Multi-Port 2 ND Port Homo. Loading, Departure (Displ. =67680 mt) BC DWT T LOADING CONDITION 44: Multi-Port 2nd Port Ore Loading (3.0 t/m3) Condition at Departure (Displ. = mt) LOADING CONDITION 10: Heavy Ballast Condition at Arrival (Displ. = mt) 10

11 SIMPLIFIED METHOD (BC DWT T & VLCC DWT T) BC DWT T LOADING CONDITION 39: 6A Homogeneous Heavy Loading Condition at Departure (SF = ft 3 /lt) (Displ. = mt) LOADING CONDITION 23: 2G Heavy Ballast Condition at Arrival, without AP, WBT10, WBT6P/S (Displ. = mt) VLCC DWT T LOADING CONDITION 10: Homogeneous Design Load, 40% Bunker Condition (S.G. = ) LOADING CONDITION 07: Gale Ballast Condition at Arrival (No. 3 C.C.O.TK) 11

12 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC79K_Full Load_Vwind = 19 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rwave Rtotal Vs [kn] 12

13 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC79K_Heavy Ballast_Vwind = 19 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rtotal Vs [kn] 13

14 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC79K_Full Load_Vwind = 26 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rwave Rtotal Vs [kn] 14

15 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC79K_Heavy Ballast_Vwind = 26 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rtotal Vs [kn] 15

16 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC176_Full Load_Vwind = 19 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rtotal Vs [kn] 16

17 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC176_Heavy Ballast_Vwind = 19 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rwave Rtotal Vs [kn] 21 st May 2014 Minimum Power for safe Operation in adverse Weather Conditions 17

18 Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC176_Full Load_Vwind = 26 m/s Rbare Rcalm Rwind Rair (w/o wind) Radded Rapp Rtotal Vs [kn] 18

19 Resistance [N] Resistance [N] SIMPLIFIED METHOD (BC DWT Τ) BC176_Heavy BC57_Ballast_Vwind= Ballast_Vwind 26 = m/s 26 m/s Rbare Rcalm Rair Rair (w/o wind) Rbare Radded Rcalm Rapp Rwind Rwind Rair (w/o wind) Rtotal Radded Rapp Rwave Rtotal Vs [kn] 19

20 SIMPLIFIED METHOD FULL LOAD (BC DWT Τ) L1 L2 L3 L4 RPM up RPM low 6480 kw 5190 kw 5490 kw 4380 kw 136 RPM 115 RPM 20

21 7/11/06 Συνάντηση Μελών ΕΝΘΥ 21

22 7/11/06 Συνάντηση Μελών ΕΝΘΥ 22

23 7/11/06 Συνάντηση Μελών ΕΝΘΥ 23

24 SIMPLIFIED METHOD FULL LOAD (VLCC DWT Τ) L1 L2 L3 L4 RPM up RPM low kw kw kw kw 76 RPM 61 RPM 24

25 CONCLUSIONS 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. 25

26 CONCLUSIONS 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) reduced sea conditions for all ships and more so for ships below 250 m to levels equivalent to Beaufort 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. 26

27 CONCLUSIONS 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. 27