Development of Rules for Certification of Fibre-Rope based Installation Systems

Transcription

1 Development of Rules for Certification of Fibre-Rope based Installation Systems Ankerhåndtering og forflytning av innretninger, Stavanger 11 - Vidar Åhjem [email protected] DNVs 25-Tonnes test machine for Mooring Components 13 November 29 2 Slide 2 1

2 Existing fibre-rope specific standards: DNV-RP-E34 Damage Assessment of Fibre Ropes for Offshore Mooring, April 5. DNV-OS-E33 Offshore Mooring Fibre Ropes, April 9. Coming up: DNV-RP-E36 Design, Testing and Analysis of Offshore Mooring Fibre Ropes. - Design considerations. - Testing of properties. - Mooring-system design. 3 Contents of this presentation Todays Rules and new Offshore Standards (near term). Development project for new rules (Offshore Standard input). Timeline foreseen. Failure mechanics of materials. Time-based safety concept. 4 2

3 Rules to Standards DNV Offshore Codes Offshore Service Specifications Offshore Standards A B C D E F H Recommended Practices 5 Rules to Standards Overview (1) User Information Warranty Surveys Rule Section New Standard Main Input Pt. Ch.1 DNV-OSS-92 Risk based Marine Operations Pt.1 Ch.1 verification Planning of Operations Design Loads Structural Design Load Transfer Operations Towing Special Sea Transportation Pt.1 Ch.2 Pt.1 Ch.3 Pt.1 Ch.4 Pt.2 Ch.1 Pt.2 Ch.2 Pt.2 Ch.3 DNV-OS-H11 General DNV-OS-H12 Design & Fabr. DNV-OS-H21 Load dtransfer DNV-OS-H22 Sea Transport α-factor (JIP) Load definitions NDT (waiting time) Friction JIP Transport Fatigue 6 3

4 Rules to Standards Overview (2) Offshore Installation Lifting Sub Sea Operations Transit and Positioning of MOU Pt.2 Ch.4 Pt.2 Ch.5 Pt.2 Ch.6 Pt.2 Ch.7 DNV-OS-H23 Rig Moves DNV-OS-H24 Offshore Inst. DNV-OS-H25 Lifting DNV-OS-H26 Subsea 7 Lay-out update Pre-laid anchors Clearances DP elaborated Lay-out update Suction anchors General update Use of soft rope slings Small lifts (<5 tonnes) Sling safety factor Complete update MWS for Pipe laying. Installation of umbilicals, spools, etc. Safety factors fibre- & wire ropes. Rules to Standards Summary New DNV Offshore Code: DNV-OSS-92 Marine Operations DNV-OS-H11 General DNV-OS-H12 Design & Fabrication DNV-OS-H21 Load Transfer DNV-OS-H22 Sea Transport DNV-OS-H23 Rig Moves DNV-OS-H24 Offshore Inst. DNV-OS-H25 Lifting DNV-OS-H26 Subsea Status: 2% completed. Exst. Hearing No. 8 4

5 Way forward for fibre-rope based winch systems after 21: Timeline for JIP proposal: Timeline for project: - Part 1: Part 2: Part 3: 214. Approval of systems in anticipation of final rules based on part 1. - Develop criteria for limited use. - Experience gathering - ref. DNV-RP-A23. - Should not need detailed knowledge of failure modes. - Generic experience as basis. First version of standard as soon as possible. - Industry must define the needs. - Number of usage cycles actually required. 9 Tension ratio (Belastningsfaktor) The tension ratio is the ratio between the ultimate strength of the rope and the highest operational tension. TR = T ultimate T max 1 5

6 Defining safety Damage Initiation phase Failure phase Lifetime 11 Fatigue in steel specimen: 1 Test data and S-N mean curves Crack initiation phase. - Miner-Palmgren summation. Crack growth phase. - NDT methods. - Engineering Criticality Assessment. Stress Range, Δσ [MPa] 1 Curve - notch test specimens (R=.1) Notched test specimen results (R=.1) Smooth test specimen results (R=.1) Curve - smooth test specimens (R=.1) 1 1,E+4 1,E+5 1,E+6 1,E+7 1,E+8 Number of cycles, N 12 6

7 Residual strength vs. residual life Diolen 855T polyester at 2 C Typical Loading plots rate: of residual 8mN/tex strength in 1s vs. life Residual Strength [%] Abrasion Corrosion Chain fatigue Fibre-rope TTR Wire-rope fatigue Fraction of life time used [-] 13 Understanding time-dependent safety. (Fibre rope.) Force TTR.1 second TTR 1 week TTR 1 month TTR 1 year TTR 1 years TTR several hundred years TTR several thousand years Elongation 14 7

8 ARELIS proposed by Rigo Bosman 1,8 normalized tension,6,4 D 1 1 week Assured Residual Life Span,2 1. weeks log (time) Force Structural Reliability Analysis vs. Rule Failure is most likely to occur if the load is unusually high, and the strength is unusually low T, tension γ S, strength Rule criteria: T C γ S C TTR several thousand years TTR 1 year TTR 1 years TTR several hundred years TTR.1 second TTR 1 week TTR 1 month Elongation T C S C SRA: Limit state Function g(x) = S T Probabilty of failure > g( X) = < for X in safeset (no failure) for X on the limit statesurface for X in failureset (failure) 16 8

9 CBOS machine at DNV - Acergy work 17 Refining DNV standards on rope-based installation systems Operational condition at which TTR accellerates. - Basis for rope discard criterion. - Linked to visual observations on the rope. (Crew.) Step-wise levels of approval. - No considerations to localised accelleration: Limited service time - quick. - Some consideration: Longer service and rigorous monitioring. - Full consideration: Maximised service time / cost optimisation. Requirements to rope manufacture will be based on DNV-OS-E33. - Including the yarn approval program. Time-based safety format will be required. 18 9

10 Important areas: Rope construction. Coating and its durability. Temperature performance. Monitoring, maintenance and repair. Heave-compensation efficiency. Visual inspection criteria. Damage Initiation phase Failure phase Lifetime Diolen 855T polyester at 2 C Typical Loading plots rate: of residual 8mN/tex strength in 1s vs. life 1 Force TTR.1 second TTR 1 week TTR 1 month TTR 1 year TTR 1 years TTR several hundred years TTR several thousand years Elongation Residual Stren ngth [%] Abrasion Corrosion Chain fatigue Fibre-rope TTR Wire-rope fatigue Fraction of life time used [-] 19 Safeguarding life, property and the environment 2 1