Effects of Fiber Rope - Seabed Contact on Subsequent Rope Integrity

10121-4406-01

Primary Performer
Stress Engineering Services, Inc. (SES)

Additional Participants
To Be Determined

Abstract
Researchers at Stress Engineering will determine the effects of contact of polyester mooring rope segments with the seafloor prior to installation as part of a mooring system in deep water. It is possible for soil particles to bypass the particle filter, become embedded in the rope core, and intensify normal fretting wear damage as the installed ropes respond to cyclic loads resulting from extreme weather forces (such as hurricanes).

Objectives of this program include (1) to develop a fundamental technical understanding of the effects of fiber-rope/seabed contact, whether accidental or planned, to ensure safe production when seabed contact occurs, (2) to better understand the primary cyclic-wear process that reduces the strength of fiber ropes so that risks and unsafe conditions can be identified and avoided, and (3) to assemble a testing plan and reach agreement between project industry participants and the US regulatory agencies for qualifying polyester mooring ropes for incidental seabed contact and seabed pre-installation.

The proposed program will develop a plan and perform experiments for (1) particle ingression and migration, and soil particle impact on cyclic wear and include hypothesis of mechanisms and full tests, (2) exposing rope segments to the offshore seabed, then performing bench-type subrope soil ingression sampling and full-scale subrope cyclic wear testing to determine the impact of seabed soil contact on long-term performance of mooring systems.

Potential soil ingress into rope due to accidental contact with the seabed may affect the long-term integrity of mooring systems for floating facilities, thereby increasing the risk of mooring line failure. This, in turn, places nearby subsea and surface infrastructure at risk. In addition, qualifying mooring rope for pre-installation on the seabed greatly reduces risk by reducing the time required to hook up mooring lines to the floating facility, thus reducing time to reach a safely moored condition before arrival of severe weather. The project expects to pre-qualify certain rope products as safe to use with intentional or accidental seabed contact.

Principal Investigators: Cesar Del Vecchio

Project Cost:
DOE share: $1,902,210
Recipient share: $573,000

Project Duration: 2 years