transportation systems are allocated each ‘Failure mode’, the
contribution to these figures are also demonstrated by the associated
‘Transportation type’. The ‘Manual reset’ and ‘Minor’ failures
are required to be repaired by the O&M technicians allocated by
either CTVs or helicopter. In this respect, ‘Shift’ and ‘Weather’ have
the highest 2 proportions in the total ‘Manual resets’ and ‘Minor’
failure downtime by 48% and 38% (on average), respectively. Due
to the fact that these transportation systems (CTV and helicopter)
are utilised only in day shift, the failures during night can only be
Fig. 5. Distribution of transportation system associated costs
Fig. 6. Distribution of total O&M cost
Table 10
Designated values for the variables.
Value Variable name Unit
1 Shift start h
2 OAV charter length days
3 Jack-up vessel charter type N=A
A Fix on fail
B Purchase
4 Jack-up vessel charter length days
5 Helicopter contract hour h
6 Preventive maintenance start month N=A
7 O&M technician allocation order N=A
A Corrective maintenance or preventive maintenance
Preventive maintenance after corrective maintenance
Preventive maintenance only after corrective maintenance
N=A
B N=A
C N=A
8 Power based availability %
9 Total O&M cost d=MWh
Y. Dalgic et al. / Ocean Engineering 101 (2015) 211–226 221
attended in the first following day shift. In addition, these
transportation systems have relatively lower operability and
accessibility limitations than other transportation types; therefore,
the O&M activities cannot be performed due to rough ‘Weather’ by
38%. The remaining 14% of the failure downtime is shared by the
‘Travel’, ‘Repairs’, ‘Resource’. It is important to highlight the fact
that ‘Repairs’ account for only 3% of the total ‘Manual reset’ and
‘Minor’ failure downtime, so actual O&M activity has a very minor
contribution to the total turbine downtime.