Crew Transfer Vessel (CTV) Performance Benchmarking. Presented by Stephen Phillips of Seaspeed Marine Consulting Ltd

Transcription

1 Crew Transfer Vessel (CTV) Performance Benchmarking Presented by Stephen Phillips of Seaspeed Marine Consulting Ltd

2 BACKGROUND - CT OWA : The Carbon Trust Offshore Wind Accelerator (OWA) brings together nine offshore wind energy developers to work towards reducing the cost of renewable energy. - R&D : One area of their research is into reducing the cost of windfarm access novel vessels, transfer devices and benchmarking of CTV Performance. - DEVELOPERS : For the Developers, this benchmarking process has enabled an improved assessment of the benefits of new designs, improved O&M modelling and improved CTV contracting arrangements (ability to specify and deploy more suitable vessels for each specific site and to assure the achieved performance). - DESIGNERS : For Designers/Builders/Owners/Operators of CTVs, they are now able to demonstrate performance benefits using the benchmark as a basis.

3 BENCHMARKING RESEARCH PROGRAMME - MARKET STUDY : Market assessment to establish the make-up of the CTV sector. - STANDARDS : Development of standardised sea trial procedures for investigating Transit, Approach and Transfer performance. - SEA TRIALS : Undertaking of sea trials on a range of vessels to establish actual performance. Investigate typical limiting parameters (vertical and lateral accelerations, roll, fender slip etc) - BASELINE HULL STUDIES : Development of baseline hull forms and undertaking of computer simulations and scale model tests to better understand vessel performance and limitations. - R&D FINDINGS : Presentation of results in the form of Performance Plots and a summary of findings from the research.

4 MARKET ASSESSMENT - Market study undertaken in 2015

5 SEA STATISTICS Typical UK Sea Statistics Sea Area Category Limited Fetch (short period on P-Plots) Exposed (standard period on P-Plots) Ocean (long period on P-Plots) Hsig, m % Exceed nc Average Modal Period To, sec Spread of Modal Period To, sec % Exceed nc Average Modal Period To, sec Spread of Modal Period To, sec % Exceed nc Average Modal Period To, sec Spread of Modal Period To, sec Reference : HSE OTC 2001/030 Report Wind and wave frequency distributions for sites around the British Isles

6 SEA TRIAL AND ANALYSIS PROCEDURES - DNV GL / Seaspeed study resulted in document Conduct of offshore access performance evaluation trials, OWA-S2-A-Y2-1 October Simple tests : For Transit, run at a range of speeds and headings, measuring/recording triaxial accelerations, pitch and roll, significant wave height and wave period and for Transfer, also fender slip and/or loss-ofcontact frequency along with other environmental and vessel conditions. - Analyse data: rms, mean, max & min values - Analyse wave conditions: Hsig, Hmax, Tz - Record any other adverse conditions such as tidal current, swell, shallow water etc

7 SEA TRIALS - Transit - Transfer - Approach / loiter - Short / long term monitoring

8 SIMULATION - Development of baseline hulls and computer simulation - Scale model simulation

9 ACCEPTABILITY THRESHOLD PARAMETERS CTV Performance Acceptability Criteria Transit Acceleration and Motion Limits Vertical acceleration, rms 1.5 m/s 2 (approx g) Lateral acceleration, rms 1.0 m/s 2 (approx. 0.1 g) Pitch, rms Roll, rms Friction limit Roll limit, rms Freeboard limit Transfer Motion Limits 5 deg 6 deg 95% waves pass with no slip above 300mm (or one ladder rung) 3 deg 95% of waves below the average* freeboard Note * average freeboard is the average of the wet-deck freeboard and the bow freeboard. This parameter is used for computer assessments of performance and is not expected to be used on sea trials assessments.

10 TRANSIT P-PLOT 22m Catamaran Hsig = 2.0 metres Head Sea Beam Sea Stern Sea

11 TRANSFER P-PLOT 22m Catamaran

12 P-PLOTS WITH SEA TRIALS RESULTS 26m Catamaran

13 BENCHMARK P-PLOTS

14 BENCHMARK P-PLOTS

15 RESEARCH PROJECT SUMMARY Results now available for public comment

16 SEMINAR SUMMARY Practical Application of P-Plots No versatile means of comparing vessel performance was previously available P-plots allow a vessel of any configuration to be compared to an industry benchmark (with respect to Transit and Transfer) Developers have a better understanding of what performance can be expected from CTVs, more realistic performance data for O&M modelling and have a basis for the performance assessment of new vessel proposals The results of long term performance monitoring can be presented in a simple format and compared to a known benchmark

17 RESEARCH FINDINGS Effects on Performance of : - Vessel Type - Vessel Size - Bollard Thrust - Freeboard - Speed - Sea State - Heading - Shallow Water - Tidal Current - Docking Pole Inclination

18 RESEARCH FINDINGS Effect on Performance of : Figure A.1 - Transit P-Plots for 22 metre Monohull, Catamaran and Swath VESSEL TYPE

19 RESEARCH FINDINGS Effects on Performance of : VESSEL SIZE 18 metre CTV 22 metre CTV 26 metre CTV

20 RESEARCH FINDINGS Effects on Performance of : VESSEL SIZE

21 RESEARCH FINDINGS Effects on Performance of : BOLLARD THRUST Figure A.3 - Transfer P-Plot for 22m catamaran showing effect of bollard thrust

22 RESEARCH FINDINGS Effects on Performance of : FREEBOARD Figure A.4 - Transfer P-Plot for 22m catamaran showing effect of freeboard

23 RESEARCH FINDINGS Effects on Performance of : SPEED Figure A.5 Vertical acceleration rms of 22m monohull showing effect of speed

24 RESEARCH FINDINGS Effects on Performance of : SEA-STATE AND HEADING Figure A.6 Vert. acceleration rms of 22m monohull showing effect of Hsig

25 RESEARCH FINDINGS Effects on Performance of : SHALLOW WATER TIDAL CURRENT DOCKING POLE INCLINATION : Generally steeper waves and thus greater pitch, roll motions and accelerations. More likely to encounter confused seas : For transfer this can reduce the operational window and can make approach far more difficult, depending on relative headings : This was studied during the model tests, with inclinations up to 7 degrees from the vertical. No appreciable difference in operational performance was seen.

26 RESEARCH FINDINGS Effect of Propulsion Arrangement

27 RESEARCH FINDINGS Effect of Access Devices

28 CTV PERFORMANCE BENCHMARKING Thank you for your attention Questions?

29 DEFINITIONS Environmental Condition Assessment - Wave height; Hmax, Hsig - Wave period; Zero up crossing period, Tz, modal, To and crest period, Tc - Other important parameters - wind speed and direction, water depth, tidal current speed and direction, spreading of wave energy

30 TRANSIT P-PLOTS 22m Catamaran