1. Learning from mooring incidents
Arne Kvitrud
Petroleum Safety Authority Norway
At the seminar
Anchor Handling and Rig Move Operations
Stavanger, 5 November 2013

2. Subjects Regulations Polyester fibre ropes Steel wires Chains Links
Pay outs of anchor lines
Pennant wires
Other subjects
Bolsters
Summary

3. Framework regulation section 11 (Rammeforskriften § 11)
Comply with the regulations. + "In addition, the risk shall be further reduced to the extent possible”. “In reducing the risk, the responsible party shall choose the technical, operational or organisational solutions that, according to an individual and overall evaluation of the potential harm and present and future use, offer the best results, provided the costs are not significantly disproportionate to the risk reduction achieved.”

4. Handle with care during installation
Polyester fibre ropes
Three fibre ropes broken because of mechanical damage.
Handle with care during installation
"In addition, the risk shall be further reduced to the extent possible”.

5. Steel Wires Four steel wires broken due to overload.
Investigators claims the industries load calculations are not conservative – line dynamics and slow drift.
Steel wire capacity is reduced by about 11% because of bending in fairlead.
Holding force on winches are dependent on length of wire out. Example:
100% holding capacity with 850m out
70% holding capacity with 430m out.
"In addition, the risk shall be further reduced to the extent possible”.

6. Chains Four chains broken due to fatigue
+ two chains broken due to overload.
Overload failures with load < than proof load. Bending and twisting introduce additional loading?
Fatigue analysis.
Too long time in the same position.
Hydrogen?  Quality during manufacturing + CP?
Quality of inspections.
Use of jaws
"In addition, the risk shall be further reduced to the extent possible”.

7. Links Two links have failed.
Wrong type of socket  failure at 100 ton tension.
A three year old Kenter link failed in fatigue.
«Few» members but a significant failure frequency.
"In addition, the risk shall be further reduced to the extent possible”.

8. Pay outs of anchor lines
average: 3,5 incidents a year
Scarabeo 5 – line #6 paid out Failed
COSLPioneer – line #1 paid out Failed the same day.
"In addition, the risk shall be further reduced to the extent possible”.

9. Pennant wires "In addition, the risk shall be further reduced
to the extent possible”.

10. Some other observations from investigations
The ATA (automatic thruster assist) systems did not function as they should.  Intermediate water depth + too much pretention in lines. Competence + information systems.
The load cells are not calibrated, and sampling frequency are wrong.
Does changes in line stiffness introduce problems not handled properly?
"In addition, the risk shall be further reduced to the extent possible”.

11. Bolsters
"In addition, the risk shall be further reduced to the extent possible”.

12. Silent deviations
Deviations from the regulation have to be handled properly.
Recent deviations:
Model testing
Wind tunnel testing
Sampling frequency of tension
No tension measurements on FPSOs
As a minimum you shall comply with the regulations.
In addition, the risk shall be further reduced to the extent possible.

13. Summary Failing elements:
Polyester fibre ropes
Steel wires
Chains
Links
Pay outs of anchor lines
Pennant wires
ATA systems
Tension measurements
Bolsters
"In addition, the risk shall be further reduced to the extent possible”.