Mermaid considers not only the accessibility of the site, i.e., the available weather window, but also
the severity of the metocean conditions and their impact on the working efficiency of a vessel and its
crew.
Weather windows and response to downtime
Acceptable weather window identification is based on tolerable metocean conditions occurring at
site – tidal current velocity, significant wave height, mean wind speed and daylight. These conditions
are compared to work limiting parameters requiring user input:
Task limits which relate to the capability of a vessel and crew to make progress on a specific task of
the project (g0.5 if work can be carried out at 50% efficiency, and g0 for no progress at all);
Vessel station keeping limits (gv), which dictate the vessel capability of staying at site.
The operation being undertaken at each time-step is considered inoperable as soon as any one of
the metocean conditions exceeds the acceptable limit.
In this way, two different sets of downtimes are determined. Firstly, Mermaid has the capacity of
looking forward at the future metocean conditions and can consequently determine periods of time
for which vessel station keeping limits will result in storm, or calm, events. These storm events can
be extended due to the ability of a given vessel to hook up at site (i.e. moor and make safe to work).
As a result the calm periods are reduced in length.
Mermaid considers not only the accessibility of the site, i.e., the available weather window, but also
the severity of the metocean conditions and their impact on the working efficiency of a vessel and its
crew.
Weather windows and response to downtime
Acceptable weather window identification is based on tolerable metocean conditions occurring at
site – tidal current velocity, significant wave height, mean wind speed and daylight. These conditions
are compared to work limiting parameters requiring user input:
Task limits which relate to the capability of a vessel and crew to make progress on a specific task of
the project (g0.5 if work can be carried out at 50% efficiency, and g0 for no progress at all);
Vessel station keeping limits (gv), which dictate the vessel capability of staying at site.
The operation being undertaken at each time-step is considered inoperable as soon as any one of
the metocean conditions exceeds the acceptable limit.
In this way, two different sets of downtimes are determined. Firstly, Mermaid has the capacity of
looking forward at the future metocean conditions and can consequently determine periods of time
for which vessel station keeping limits will result in storm, or calm, events. These storm events can
be extended due to the ability of a given vessel to hook up at site (i.e. moor and make safe to work).
As a result the calm periods are reduced in length.
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