|
|
Technology
Assessment & Research (TA&R) Program
| Project Number |
416 |
| Date of Summary |
October 4, 2011 |
| Subject |
Damaged Polyester
Rope-Large Scale Experiment |
| Performing Activity |
Texas A&M
University, Offshore Technology Research Center (OTRC) |
| Principal Investigator |
Dr. E.G. Ward |
| Contracting Agency |
Bureau of Safety and Environmental Enforcement
|
| Estimated Completion |
Completed |
| Description |
Full-scale polyester ropes
were tested to determine the impact of damage on the strength of polyester
rope used as mooring lines for deepwater structures. Polyester ropes from
four manufacturers were tested (Bexco, Marlow, Whitehill, and CSL) to
determine the impact of damage on the strength of polyester mooring lines.
Small-scale rope tests were tested to examine the effect of rope sample
length on the break strength of damaged rope. Full-scale ropes at standard
test lengths (15m) were tested to determine the relationship between break
strength of damaged rope and level of damage. Longer full scale ropes were
tested to further examine the impact of length on the break strength of
damaged rope. Results will be useful in developing guidelines for deciding
how best to handle polyester mooring lines damaged during installation or
service. The project is being sponsored by the BSEE (formerly MMS) and the
industry through a JIP. Industry participants include BP, Unocal, Petrobras,
Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco. |
| Progress |
All testing and analysis were completed in 2006. The ultimate
goal of this project - to provide information on the residual strength of
damaged polyester rope for the industry and BSEE to use in developing
guidelines for mitigating damaged polyester rope mooring lines - has been
accomplished.
A coherent interpretation of the overall results was developed from a
simple qualitative analytical model; careful consideration of rope
construction details; observations of subrope behavior mechanisms; and
consistent analyses and interpretation of test results. Given that this was
the first ever attempt at testing such large and long ropes, this
comprehensive interpretation can provide useful understanding and guidance
in studying damaged polyester ropes and the developing codes and regulation
to deal with damaged polyester mooring lines.
Current codes and guidelines suggest that if a rope is damaged such that
it looses 10 percent of its strength, it should be replaced. Further, it is
suggested that that damage and strength loss are linearly related so that a
10% loss of cross sectional area due to damage would result in a 10%
strength loss.
Our results indicate that polyester rope is not that damage tolerant.
While the behavior and residual strength of damaged ropes was found to be
dependent on the details of rope construction and terminations, the
following general trends were noted. The strength loss in standard test
samples (15m length) with a 10 % cut damage generally resulted in strength
losses larger than 10%. Further, longer samples (50 - 60 m) generally had a
significantly higher strength loss, confirming the presence of length
effects noted in smaller scale tests.
The Final Report that documents the tests, analyses, results and
conclusions is included in the Reports section below, after being held
proprietary for 5 years . |
| Reports |
| AA |
Full Scale Experiments on Damaged Polyester Rope JIP, Offshore Technology Research Center, Texas A&M, College Station, TX, May 2006 |
|
|
|
|
