Progress Reports: June 2005 December 2004 June 2004 December 2003 June 2003 December 2002 June 2002 December 2001
MMS JIP: Full Scale Experiments on Damaged Polyester Rope
OBJECTIVE: Tests are being conducted to experimentally determine the effect of damage on the remaining strength of polyester rope. The goal is to provide information on the remaining strength of polyester mooring lines damaged either during installation or while in service. That information can then be used by the industry and the MMS to develop guidelines for dealing with damaged polyester mooring lines.APPROACH: Commercially available ropes with standard splices from Bexco, Whitehill, CSL, and Marlow are being tested. The program consists of three series of tests as shown in the test matrix below:
1. Length Effect Tests – Develop qualitative information on the influence of rope sample length on tests of damaged ropes. Small-scale rope will be used for these tests.
2. Damaged Full-Scale Tests – Develop quantitative data on the influence of damage on full-scale rope strength. These tests are the main focus of this project.
3. Verification Tests – Verify the results of the Damaged Full-Scale Rope Tests with a limited number of tests on longer full-scale rope samples.The MMS is funding one-half of the project costs, and industry JIP participants are funding the remaining half.
This project is one of several integrated projects sponsored by the MMS and/or the OTRC to assess the impact of damage to polyester rope mooring lines for deepwater structures. In addition to the project to develop a numerical model to predict the strength of damaged rope, other projects have addressed (1) characterizing installation and in-service damage, and (2) small-scale experiments of rope components up to and including subropes to provide data to calibrate the rope model and develop better understanding of damaged full-scale rope performance (CEAC). The ultimate goal of these integrated projects is to develop information for the industry and MMS to use in developing API guidelines for mitigating damaged polyester rope mooring lines.
DEPLOYMENT OF RESULTS: The test data can be directly useful in determining mitigation strategies, guidelines and criteria, and should provide valuable insight on how damaged rope fails. Results should be useful in developing API guidelines for mitigating damaged polyester rope mooring lines. Additionally, the data will be useful (1) to validate the numerical model of damaged rope being developed by Dr. Eric Williamson in a related OTRC project and (2) in developing scaling relationships for testing damaged ropes that could lead to less expensive test procedures for determining the strength and damage tolerance of new rope designs.
ANTICIPATED PROJECT DURATION: 4 yearsPROJECT PLAN FOR YEAR 4 (2004-2005):
Previous Results: The project test matrix is shown below. Test conditions include cyclic loading followed by a break test of undamaged ropes and ropes with simulated damage (5 to 15 percent of the cross-sectional area).
Test |
Break Strength (T) |
Diameter |
Length (m) |
L/D |
Total # Tests |
Test Facilities |
|
Length Effect |
35 |
36 mm (1.5 in) |
2 |
40 |
9 |
Lloyds Beal, UK |
|
35 |
36 mm (1.5 in) |
23 |
290-560 |
8 |
||
|
35 |
36 mm (1.5 in) |
35 |
1000 |
4 |
||
|
Damaged Full-Scale |
700 |
178 mm (7 in) |
10 |
40 |
26 |
Stress Engr, Houston CSL, Brazil |
|
Verification |
700 |
178 mm (7 in) |
60 |
290 |
4 |
Coordinated Equipment, USA |
|
51 |
The Length Effect Tests were completed in October 2003, and the Damaged Full Scale Tests were initiated in February 2004. Results from the Length Effect Tests showed that most failures were in rope body, and some evidence of length effects and strain localization due to damage. Damaged Full-Scale testing will be completed in October 2004.
Scope of Work: Following completion of the Damaged Full-Scale Tests in October 2004, test data and observations from the Length Effect Tests (35t) and Damaged Full-Scale Tests (700t) will be analyzed and interpreted to determine:
• Performance (failure characteristics, damage tolerance, etc.) vs construction differences
• Length effectso Observations - 35t tests vs 700t tests
o Potential causes of length effects• Scale effects - 35t vs 700t tests
• Damage tolerance of ropes of different constructionsThese results will be used to select the damage conditions for the Verification Tests.
The goal of the Verification Tests is to verify critical results from the Damaged Full-Scale Test with a longer test sample. The damage level and pattern that caused the most significant damage tolerance finding for each rope will be re-tested using longer rope samples (60 m vs 10 m). The Verification Tests are expected to be completed in December 2004.
Results for the Verification Tests will then be analyzed and incorporated with results from the Length Effect tests and the Damaged Full-Scale Tests to develop overall results and conclusions regarding
• the impact of damage on the performance of polyester ropes on different constructions
• the damage tolerance of different polyester ropes
• practical implications
• testing and length effectsAnticipated Results: The Final Report will be completed in 2005 following the completion of the Verification Tests and the final analyses of all results.
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): E.G. Ward
Others: R Ayers (Stress Engineering Services), S. Banfield (Tension Technologies Inc.)
Date: June 2005Project Title: Polyester Rope Large Scale Experiments JIP
MMS Project: 416 TO Numbers: 18201/35982
PI: E. G. Ward
COTR: A. Konczvald
Estimated Completion Date: December 2005
Project Description: Polyester ropes are being tested to determine the impact of damage on the strength of polyester mooring lines. Ropes samples from four manufacturers are being tested: Bexco (Belgium), Marlow (UK), Whitehill (USA), and CSL (Brazil).
Small-scale ropes were tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes are being tested to determine the relationship between break strength of damaged rope and level of damage, and to compare with any length effects noted in the smaller ropes. These data and other results will be available to develop guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP. Industry participants include BP, Unocal, Petrobras, Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco.
Progress:
Analyses of data from the completed Damaged Full-Scale Rope Tests (26 samples of 700 tonne rope ~15 m length, Length/Diameter = 40) continues to focus on the relationships between observed residual strength and damage level. Correlations between residual strength and different measures of damage, e.g., loss of cross sectional area, number of cut or damaged subropes, number of damaged yarns, etc, are being studied to determine a damage measure that best describes the residual strengths for different damage levels and rope constructions.
The API 2I Task Group recently requested preliminary results from the MMS JIP to guide them in their efforts to address discard criteria for damaged rope. The MMS and Participants granted us permission to provide limited normalized data. We provided information on the ratio of break strength/calculated minimum break strength versus several measures of damage.
The Verification Tests have been initiated. Four long samples of 700 tonne rope (Length/Diameter ~ 290) are being tested at Tension Member Technology in California. The intent of this limited test series is to compare specific results from the Damaged Full-Scale Rope Tests with similar tests of longer rope samples to determine the importance of any length effects on residual strength of larger ropes. Two tests have been completed, and we expect to complete the remaining two tests by September 2005. Analyses of data from these tests have begun. Comparisons of residual strengths from the Verification Tests (L/D=290) with the Damaged Full-Scale Rope Tests (L/D=40) suggest length effects similar to those found in some of the smaller scale (35 tonne) Length Effect Tests.A Final Report will be prepared that documents the results and conclusions, and summarizes the completed analyses and test data.
Date: December, 2004
Project Title: Polyester Rope Large Scale Experiments JIP
MMS Project: 416 TO Numbers: 18201/35982
PI: E. G. WardCOTR: A. Konczvald
Estimated Completion Date: August 2005
Project Description: Polyester ropes are being tested to determine the impact of damage on the strength of polyester mooring lines. Ropes samples from four manufacturers are being tested: Bexco (Belgium), Marlow (UK), Whitehill (USA), and CSL (Brazil).
Small-scale ropes were tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes are being tested to determine the relationship between break strength of damaged rope and level of damage, and to compare with any length effects noted in the smaller ropes. These data and other results will be available to develop guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP. Industry participants include BP, Unocal, Petrobras, Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco.
Progress: The Damaged Full-Scale Rope Tests (26 samples of 700 tonne rope ~15 m length, Length/Diameter = 40) were completed at Stress Engineering Services in Houston, TX and CSL in Sao Leopoldo, Brazil in October. Length Effect Tests (21 samples of 35 tonne ropes with Length/Diameter ratios of 40 to 1000) were completed previously. Analyses of these data are in progress. Some preliminary observations on the residual strength (ratio of damaged /undamaged break strength) follow.
There is a good correlation between the residual strengths of the 35 and 700 tonne rope samples with the same L/D and similar damage.
The Length Effect Test data show evidence of length effects. A simple analytical model is being used to qualitatively investigate possible length effects due to several load sharing mechanisms between damaged and undamaged subropes, including:
• Strain concentrations resulting from unequal load sharing between damaged and undamaged subropes
• Unwinding of the helical structure in a damaged rope could result in a reduced strain and improved load sharing.
• Termination geometries could result in different lengths of subropes and unequal load sharing and failures in the splice region.We are investigating the relationships between observed residual strength and damage level. We have examined correlations between residual strength and several measures of damage, e.g., loss of cross sectional area, number of cut subropes, number of damaged subropes, etc. Our analyses continue to determine a damage measure that best describes the residual strengths for the different damage levels and rope constructions.
The Verification Tests (4 samples of 700 tonne rope ~61 m length, Length/Diameter ~ 290) will be tested at Tension Member Technology (Coordinated Equipment) in California. The intent of this limited test series is to compare specific results from the Damaged Full-Scale Rope Tests with similar tests of longer rope samples to determine the importance of any length effects on residual strength of larger ropes. We expect to complete these tests in March-April 2005.
The analyses of the currently available test data continue, and will be expanded to include the Verification Test data when available. A Final Report will be prepared that documents the results and conclusions, and summarizes the completed analyses and test data.
Reports & Publications: A participants meeting was held in November 2004 to review the then-available results.
Date: June 2004
Project Name: Damaged Polyester Ropes – Large Scale Experiments (JIP)
Project Number: 416 Task Order: 18201
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2005
Project Description: Polyester ropes will be tested to determine the impact of damage of the strength of polyester mooring lines. Ropes samples from four manufacturers are being tested: Bexco (Belgium), Marlow (UK), Whitehill (USA), and CSL (Brazil).
Small-scale ropes of various lengths will be tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes will be tested to determine the break strength of damaged rope. These data and other results will be available to develop API guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP. Industry participants include BP, Unocal, Petrobras, Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco.
Progress: Results from the completed Length Effect Tests show have been studies using a simple analytical model of length effects. The results are now being further studied using a numerical model that is developed in a related project( Project 369, Polyester Rope Analysis Tool, Williamson).Damaged Full-Scale Rope Tests (700T rope strops of ~15 m length, i.e. L/D = 40) have begun. Stress Engineering Services in Houston, TX will test 18 rope samples from Bexco (Belgium), Marlow (UK), and Whitehill (USA). Initial tests have been completed with rope samples from each of these companies. CSL (Brazil) will conduct the tests on their 8 rope samples beginning in late June.
The test schedule for the 700 tonne ropes has been delayed due to slower availability of rope samples for testing from Bexco, Whitehill, and CSL. These companies are donating their rope samples to the project as in-kind participants, and several issues have delayed their sample preparations (manufacture of ropes for large commercial projects, learning to work with the different polyester fiber being used as a project standard). We expect to receive all samples and be able to complete the Damaged Rope Test series during 3Q 2004.
The Verification Tests (four tests of ~55 m ropes, one from each rope manufacturer) will then be undertaken at Coordinated Equipment (California). The intent of this limited test series is to verify specific results from the Damaged Full-Scale Rope Tests with similar tests of longer rope samples.
The analysis and interpretation of the results will include integrating results from all three different test series to develop a comprehensive understanding of the failure of damaged rope. We expect to complete the draft of the final report 2Q 2005.
Reports & Publications: Information available to MMS and JIP sponsors.
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Date: December 2003
Project Name: Damaged Polyester Ropes – Large Scale Experiments JIP
TEES Project Number: 32558-5888Y MMS Task Order: 18201 MMS Project Number: 416
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2004
Project Description:
Polyester ropes will be tested to determine the impact of damage of the strength of polyester mooring lines. Small-scale ropes of various lengths will be tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes will be tested to determine the break strength of damaged rope. These data and other results will be available to develop API guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP. Industry participants include BP, Unocal, Petrobras, Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco.
Progress:Length Effect Tests were completed on test ropes furnished by Bexco, Marlow, and Whitehill. Tests of 35 tonne (nominal break strength) test ropes were completed at Lloyds Beal Limited in Cardiff, Wales. Three rope lengths were tested in both undamaged and damaged conditions to investigate the effect of sample length and damage location as shown below.
Elongation measurement included total elongation as measured from the cross-head as well as local elongations as measured by LVDT and optical sensors. The tests were successful and the data are providing valuable data and insight on the failure of damaged rope.
Damaged Full-Scale Rope Tests (700T rope strops of ~15 m length, i.e. L/D = 40) will be conducted at Stress Engineering Services in Houston, TX on the rope samples from Bexco, Marlow, and Whitehill and will begin in January.
This project also includes tests of composite tendons. A complete composite tendon was tested at DNV’s facilities last fall. Testing began with an intact tendon. The tendon was then progressively damaged and retested, and was shown to be able to sustain considerable damage before its failure. Two strands of the composite tendon will be tested at Stress Engineering Services, Houston, TX this spring to complete this study of the damage tolerance of composite tendons.
Reports & Publications: Information available to MMS and JIP sponsors.
Date: June, 2003
Project Name: Damaged Polyester Ropes – Large Scale Experiments
Project Number: 32558-5888Y Task Order: 18201
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2003
Project Description:
Polyester ropes will be tested to determine the impact of damage of the strength of polyester mooring lines. Small-scale ropes of various lengths will be tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes will be tested to determine the break strength of damaged rope. These data and other results will be available to develop API guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP.
Progress:Industry participants include BP, Unocal, Petrobras, Kerr-McGee, ConocoPhillips, ABB, and ChevronTexaco, and all Agreements have been signed.
Polyester Rope Tests - The preparations of the rope samples are in progress. Honeywell has furnished yarn to rope manufacturers for test strops. TTI completed the specifications for rope strops and test thimbles, and the rope strops for testing are being manufactured.
Rope testing will begin this summer. The different test series are planned to precede sequentially as follows.
· Length Effect Tests (35T rope strops of several lengths from Bexco, CSL, Marlow, and Whitehill) – These test will be conducted at Lloyds Beal Limited in Cardiff, Wales. These tests are scheduled for the second half of August.
· Damaged Full-Scale Rope Tests (700T rope strops of 15 m length) will be conducted at Stress Engineering Services, Houston, TX, (Bexco, Marlow, Whitehill rope samples) and at CSL, Sao Leopoldo, Brazil (CSL rope samples) - These tests of the undamaged ropes strops may begin in September, and damaged rope tests are expected to begin in October and continue for several months.
· Verification Tests (700T rope strops 60 m length Bexco, CSL, Marlow, and Whitehill) - We now expect to test at Coordinated Equipment. We had previously expected to test 100 m strops at Holloway in Houston (cyclic loading) and Lowry Brothers in New Orleans (break tests). Negotiations to date for those tests had not resolved some business uncertainties, and the technical uncertainties associated with cycling, then transporting the rope, and finally breaking the rope at another location remained. The advantage of testing at Coordinated is that the rope can be cycled and broken without the need to handle and move the rope between cycling and breaking. The maximum rope length that can be tested at Coordinated is about 60 m. This length is judged to be sufficient for the Verification Tests.
Composite Tendons – The project has been expanded to include limited tests of composite tendons at no additional costs to participants. The tests will include both testing of stands (components of the tendon) and a damaged tendon.
· Strand Tests – ConocoPhillips will furnish two 15-meter composite terminated strands for testing at Stress Engineering Services, Houston, TX. These strands are components of the full-scale tendon. Each strand contains 85-6mm carbon composite rods and has a load capacity of 3200kN (320 tonne). Discussions between Stress, ConocoPhillips, and DNV on terminations and interfaces have been completed, and equipment is being designed and fabricated. The strand tests are expected to be completed in August.
· Tendon Test - ConocoPhillips is arranging to test complete tendon sample on DNV’s 2500 tonne test facility. It is expected that the tether test will start with an intact tendon, and then progressively damage the tendon (damage simulated by cutting strands) until it fails. That test is scheduled for August 21 at DNV, Bergen, Norway.
ConocoPhillips will also provide results from other static, fatigue and creep tests in both air and seawater (atmospheric and high pressure), and document these in a report that will be available to the MMS and Industry Participants.A meeting between MMS, Industry Participants, and Contractors was held at Stress Engineering on May 9 to review progress and plans
Date: December 2002
Project Name: Damaged Polyester Ropes – Large Scale Experiments
Project Number: 32558-5888Y Task Order: 18201
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2003
Project Description:
Polyester ropes will be tested to determine the impact of damage of the strength of polyester mooring lines. Small-scale ropes of various lengths will be tested to examine the effect (if any) of rope sample length on the break strength of damaged rope. Full-scale ropes will be tested to determine the break strength of damaged rope. These data and other results will be available to develop API guidelines for deciding how best to handle polyester mooring lines damaged during installation or service. The project is being sponsored by the MMS and the industry through a JIP.
Progress:
Agreements were prepared and sent to the following contractors:
Polyester fiber for all rope samples – Honeywell Performance Fibers
Rope Samples – Bexco, Whitehill, CSL, Marlow
Rope Testing – Stress Engineering Services, Tension Technologies Inc, CSL
Certification Services for Testing – ABS
Some contacts have been completed and others are being negotiated.
Industry support was solicited at a meeting in September. Agreements were prepared and sent to two classes of potential participants – firms whose principal business is developing and producing oil and gas, and firms whose principal business is providing services to oil ad gas companies. To date, several companies have joined the JIP and negotiations are continuing with others. We expect sufficient funding will be available to complete the program as planned.Preparations for obtaining rope samples and testing at TTI and Stress have been initiated.
Reports & Publications:
The paper “Characterizing Polyester Rope Mooring Installation Damage” by R.R. Ayers, C.E. Smith, and E.G. Ward was prepared and presented at the 2002 Deep Oil Technology Conference in New Orleans, LA in December.
Date: June 2002
Project Name: Damaged Polyester Rope – Large Scale Experiments
Task Order: 18201 Project Number: 5888Y
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2003
Project Description: Full-scale polyester ropes (~700 T break strength) will be tested to determine the impact of damage on the strength of the polyester mooring lines. These data and other results from related projects will be used by the MMS and the industry to develop API guidelines for mitigating damage that could occur to polyester rope mooring lines during installation or during their service life. The data will also be used to validate the computer model being developed in Project 58878, which will allow the extension of these results and guidelines to other rope constructions. This project will be sponsored by the MMS and the industry through JIP funding.
Progress: The Technical Plan for the project has been completed. Ropes from four manufacturers will be tested (Bexco, Whitehill, CSL., and Marlow). The ropes will represent rope product lines that are commercially available, and will be furnished with commercially available splices. The project will conduct three series of tests on damaged polyester rope samples.
· Length Effect Tests - The purpose of these tests is to qualitatively examine the potential for length effect to impact tests of damaged polyester ropes. Model scale ropes will be used for these tests.
· Damaged Full-Scale Rope Tests – The purpose of these tests is to quantify the impact of damage on full-scale ropes. These test are the main focus of this project.
· Verification Tests - The purpose of these tests is to verify the results of the Damaged Full-Scale Rope Tests with a limited number of tests on longer length samples.
Important test parameters are summarized in Table 1.The L/D ratios
Test
Break Strength (T)
Diameter
Length
(m)
L/D
Total # Tests
Test Facilities
Length Effect
35
36 mm (1.5 in)
2
60
8
Lloyds Beal, UK
35
36 mm (1.5 in)
23
560
12
35
36 mm (1.5 in)
35
1000
4
Damaged Full-Scale
700
178 mm (7 in)
10
60
26
Stress Engr, Houston
CSL, Brazil
Verification
700
178 mm (7 in)
100
560
4
Holloway, Houston
Lowrey, New Orleans
44
Agreements and contracts are being finalized, and industry support for this JIP will be solicited in July 2002.
Date: January 23, 2002
Project Name: Damaged Polyester Rope – Large Scale Experiments
Task Order: 18201 Project Number: 5888Y
Principal Investigators: E.G. Ward
Estimated Completion Date: August 2003
Project Description: Full-scale polyester ropes (~700 T break strength) will be tested to determine the impact of damage on the strength of the polyester mooring lines. These data and other results from related projects will be used by the MMS and the industry to develop API guidelines for mitigating damage that could occur to polyester rope mooring lines during installation or during their service life. The data will also be used to validate the computer model being developed in Project 58878, which will allow the extension of these results and guidelines to other rope constructions.
Progress: Following the MMS-sponsored Polyester Workshop conducted by OTRC (Project 5888H), we have been developing a Technical Plan for this project. This project will be sponsored by the MMS and the industry through JIP funding. We have involved industry stakeholders as we have developed the Technical Plan to understand their interests and needs, and to obtain their input.
The basic plan is to test rope from three different rope manufacturers. Eight 15-m long samples of ~ 700 T break strength rope would be tested: 2 samples undamaged, 3 samples damaged at Level 1, and 3 samples damaged at Level 2.
The MMS supported BP tests on damaged ropes conducted in 2001, and made those results available to OTRC. In those tests, the failures often involved the splices, and were difficult to understand and interpret. A central issue is whether the short length of these test samples contributed to the splice failures, i.e. the so-called “length effect”.
Due to the concerns raised by the BP tests, we retained Steve Banfield of Tension Technologies Inc for consultation and advice on to avoid or manage such difficulties in our planned test program. We will likely supplement the large rope tests with smaller rope tests that are scaled to investigate the potential for length effect impacts on our test plan. Consideration of these issues has resulted in a delayed start of the large scale tests, but is expected to result in more meaningful and useful results.
Reports & Publications: several drafts of the project’s Technical Plan
