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Table 3 - Asset register RAM modeling
The model construction in Optimise© involved
the equipment configuration, as assumed by the
RBD and reliability data, as assumed by the asset
register. The Bureau Veritas software Optimise©
has also been used to model a number of more
complex scenarios using a modeling artefact called
“conditional logic”. Conditional logic, defined by
simple Boolean logic has been used to model:
• gradual subsea / plant restarts following
failures;
• delayed repair for some particular equipment;
• interconnected / common equipment (e.g.
for instance if two sets of heat exchangers
are sharing a common spare, once the spare
is used a subsequent failure will result in a
complete interruption in production);
• equipment / system bypasses (e.g. due to non
critical or partially critical equipment);
• voting, 2 out of 3 (2oo3) (e.g. in a dehydration
system where one of three dehydrator
columns is in regeneration duty at any one
time, failure of one of the units will cause a improvement performed on this unit will impact in
reduced throughput capacity to 50%);
• impact of cyclones / metocean on the
production system and offloading system;
• impact of planned and preventative
maintenance (specially for gas turbines,
compressors and dehydration & mercury bed).
RAM results
In order to establish average results and confidence electric motors instead of gas turbine or additional
levels, the RAM model was run for 1,000 individual
lifecycles considering 25 years as the system life.
The following presents and discusses some of
the outputs of the study based on the previous
Table 4 - FLNG FSC
summary results
assumptions.
The full supply chain (FSC) model base case main
outputs are summarizing in table 4:
From this first set of results, it can be concluded that
over the 25 years, in average, the unit will be able
to produce for about 90% of the time. Each year,
the unit will stop its production for a bit less than 36
days because of unplanned shutdowns (random
failure of equipment), preventative maintenance,
time to restart after a shutdown and spurious trips
of safety systems. This general information will help
to operator to develop its pricing strategy based on
the potential income the unit will generate as well
as to have an appreciation of the productivity of its
installation.
Following that, the operator needs to know what
are the most critical systems in order to understand
which modifications in the design or in its IMR
strategy will impact the most the availability of the
unit in a positive manner. Figure 8 identifies the
top 5 systems or events that contribute the most
to overall production losses:
As presented in figure 8, the liquefaction unit is the
main contributor to FLNG project downtime. Based
on this information, operator knows now that any
an effective manner the availability of the whole
project.
For instance, as the losses in production within
liquefaction system are mainly driven by gas
turbines and compressors failures, modification in
the design can be studied in a separate sensitivity
case in order to assess impact on availability
but also to understand cost associated with the
implementation of the new components (i.e.
turbo compressors for a higher redundancy).
Inspection strategy for the topsides induces
Impiantistica Italiana - Maggio-Giugno 2015 97