LIFELINE USER MANUAL

As part of the LifeLine system a user manual is provided. The user manual is floater specific and contains information regarding the configuration file set up and guidelines on how to interpret the output messages.

LIFELINE METHODOLOGY

The LifeLine methodology consists of two different but complementary approaches, the short-term approach (STA) and the long-term approach (LTA). The short-term approach employs an event based algorithm to assess the integrity of the mooring system. The algorithm aims to identify a mooring line failure by looking at semi-instantaneous shift in the mean position of the floater. The long-term approach employs a status based algorithm. This algorithm aims to identify a mooring line breakage by comparing the zero-environment equilibrium position of the floater pre and post potential failure. The LTA monitors and updates the equilibrium position of the floater periodically. When a failure occurs the equilibrium position will change and after a sufficient amount of time it will be detected by the LTA. This approach is characterized by a longer detection time but it is not sensitive to data quality and extreme environmental conditions.
MARIN mooring line failure identification

Validation and verification

The LifeLine system was validated using different tools and sources of data including numerical simulations, blind tests and in-service measurements. The validations were done for multiple floaters, both spread moored and turret moored, installed in different regions including West Africa, Australia, NorthSea, Brazil and Gulf of Mexico.

Software input and output

A configuration file is used to define the floater specific input parameters which includes among others, the type of mooring system (turret or spread moored), floater natural period, maximum allowable identification time (LTA), quality threshold (STA and LTA) and minimum and maximum offset caused by a line failure.
The output of the LifeLine system is returned to the customer position monitoring system by two serial NMEA messages. STA serial messages ($LFSTA) are sent every three hours whereas the LTA serial messages ($LFLTA) are returned once a day. Among others the following information is included in the messages:
• The date and time of the event detected (STA)
• The warning level for the mooring line integrity assessment (STA-LTA)
• The offset related to the event detected (STA)
• The offset related to the equilibrium position of the floater (LTA)
• The direction associated to the offset position detected (STA-LTA)
• Error code

LIFELINE JIP and LIFELINE User Group

The LifeLine software was developed in the LifeLine Joint Industry Project from 2018 up to 2020. A user group was initiated in 2021 which is aiming to support the practical application of the LifeLine technology on the field and to support further development needs.