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Marine Operations Guidelines

This document provides specifications for towing operations including: 1. Dimensions of the vessel being towed including length, width, draft. 2. Righting areas and wind/wave/current loads on the vessel. 3. Requirements for towlines including minimum breaking load and specifications for different components like wire, shackles, weak links. 4. Calculations of minimum required bollard pull for the tug based on forecasted weather conditions and efficiencies. 5. Details of an example towing operation plan including distances, speeds, timing, and safety factors.

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Ludovic Landemaine
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353 views19 pages

Marine Operations Guidelines

This document provides specifications for towing operations including: 1. Dimensions of the vessel being towed including length, width, draft. 2. Righting areas and wind/wave/current loads on the vessel. 3. Requirements for towlines including minimum breaking load and specifications for different components like wire, shackles, weak links. 4. Calculations of minimum required bollard pull for the tug based on forecasted weather conditions and efficiencies. 5. Details of an example towing operation plan including distances, speeds, timing, and safety factors.

Uploaded by

Ludovic Landemaine
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as XLSX, PDF, TXT or read online on Scribd
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DNVGL METHOD

NOBLE DENTON MARINE SERVICES - DNVGL-ST-N001 Marine Operations and Marine warranty
1-Dimensions

Overall lenght Long 54.50 m Draft variation ΔTE 0.476 m


Wide B 28.00 m Min draft TEmin 18.06 m
Height H 26.40 m Max draft TEmax 18.54 m
Draft TE 18.30 m Min air draft TAmin 7.86 m ρair 1.226 kg/m3
Tilt ϒ 0.50 ° Max air draft TAmax 8.34 m ρseawater 1025 kg/m3

2 - Righting areas

Air mask Av 220 m²


Water mask Ac 519 m²

3 - Wind load
Cd = 0.50 * see DNVGLSTN001 §17,4,2,2; DNVRPC205 §5,8 see CFD D2M Fw = 1/2 ρair Cd Av Vv²

Wind speed Vv 20.00 m/s => 38.911 nds Fwind = 2.8 t OPLIM

4 - Wave drift force

Waves (Hs) = 5.00 m Fwave = 38 t OPLIM See note 12000 D2M linear interpolation

5 - Curent drift force


CD = 0.37 * CFD study of G-MET Fc = 1/2 ρseawater Cd Ac Vc²

Current speed Vc 0.5 m/s => 0.973 nds Fcurrent = 2.5 t OPLIM

6 - Tug efficiency
Longueur Remorqueur LOA 36.00 m see DNVGLSTN001 §11.12.2.10
Bollard Pull remorqueur BP 85.00 t
Efficience Teffstatic 56 %

7 - Minimum Towline Pull Required (TPR)

Wind - 1hr mean at 10m = 20 m/s => 2.75 t


Wave = 5.0 m => 38.00 t
Curent = 0.5 m/s => 2.51 t

Total TPR 43 t

Efficiency factor = 56%

Static required bollard pull (BP) 77 t

8 - Operational Previsional Weather Forecast OPWF

Wind at 10m height

OPLIM - Wind - 1hr average = 20.0 m/s


Wind Alpha factor = 0.71 <-- Table 2-15 ->48hr Tpop
OPWF - Wind - 1hr average = 14.2 m/s
OPWF - Wind - 10min average = 15.4 m/s => 1.64 t
Avec avancement à 1.3 m/s => 1.92 t

Wave Hs
OPLIM - Wave Hs = 5.0 m
Wave Alpha factor = 0.70 <-- Table 2-14 ->48hr Tpop Hs Drift force
OPWF - Wave Hs = 3.50 m => 15.17 t D2m 3m 13 T
OPWF - Wave Hs = 3.00 m => 13.00 t * Hs réduit à 3m

Curent

Surface curent = 0.5 m/s => 2.51 t


With advance speed at 1.3 m/s => 31.79 t

9 - Recap chart

Distance de remorquage Dist 122 nm


Vitesse de remorquage Vr 1.28 m/s => 2.49 nds
Temps de remorquage tr 40 heures * Curent de 0,5m/s 50% during tow
Effort total de remorquage maximum 47 TBP
Efficacité du Remorqueur 68%
Bollard Pull Remorqueur 68 TBP
1

5
1 Tpop 48.99 h
Dist 122 nm
Vr 1.3 m/s => 2.49 nds
2 Tc 24.50 h
50% Medium curent = 0 during tow
3 TR 73.49 h

4 Tsafe 10.84 h
27 nm distance entre 2 abris 48nm et navigation à 3nm de la cote
5 Tcease 6.00 h durée de mise en sécurité à l'arrivée au refuge

6 TWF 24.00 h
Les forecast météo sont reçus une fois par jour
7 Tpop 34.84 h durée max l'évènement et l'arrivée au refuge
TR 40.84 h durée de mise en sécurité

4 OPLIM
Wind 20.00 m/s
Hs 5m
Current 0.5 m/s
5 α Alpha factor

6 OPWF Operational for GO Towing


Wind 0.71 W 14.2 m/s
Waves 0.7 Hs 3.5 m

Weather Forecast A1 ou A2
WAVE Alpha factor 0.7
3nm de la cote
WIND Alpha factor
0.71
Element DNVGL ST001 Requirement Preconized For 120T BP
TUG Wire MBL MBL+10% 220 T
Spring 150% MBL 150% MBL 300 T
Weak link MBL MBL 200 T
Delta plate 130% MBL 130% MBL 260 T
Briddle leg ULC ULC 240 T
Shackles 130% MBL 130% MBL 260 T
Caisson Plate ULC ULC 240 T
For 85 T BP Type
210 T 6x36 ame metallique Diam 57mm (1960N/mm²)
287 T Nylon Diam136mm MBL 306T
191 T 6x36 ame metallique Diam 57mm (1960N/mm²)
249 T GN Rope CMU 55T
231 T 6x36 ame metallique Diam 60mm (1960N/mm²)
249 T Green pin 55T
231 T na
BP 120 T
MBL 200 T 6x36 * 1960N/mm

DTL 1080 m
ADL 1080 m

RTBL 200 T

ULC 240 T

MBL Shackle 260 T

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