Data used in Case Study 1
Table 4. Properties of different repair types.
Repair
time (h)
Manual
reset
Grease topup
Minor
repair
Medium
repair
High
priority
repair
Annual
service
Technicians
required
Value
Cost
Weight of Probability of
(£ ,000) (£ ,000) spares (kg) correct diagnosis
2
2
100
0
0
1
3
2
80
0.5
20
1
4
3
100
1
100
0.8
6
3
100
18.5
400
0.9
5
3
120
25
500
0.95
6
2
80
18.5
300
1
Table 5. Shape and scale parameters of the gamma distribution function.
Mean (h)
Shape
Gamma
parameter
distribution
Scale
Parameter
2
2
Expected repair length (h)
3
4
5
3
4
5
6
6
4
6
8
10
12
0.5
0.5
0.5
0.5
0.5
Table 6. Properties of vessels used in Case Study 1.
Vessel
number
1
2
3
4
5
Crew
capacity
12
12
12
12
12
Speed
(km/h)
50
50
40
40
40
Fuel consumption Hire cost
(£'000/km)
(£'000/day)
0.01
0
0.01
20
0.006
0
0.006
0
0.006
10
Load capacity
(kg)
2000
2000
1200
1200
1200
Table 7. Probability of transfer given wave height and type of vessel.
Vessel
1
2
3
4
5
Probability of successful crew transfer in a given wave height
Hs<1.4m
1.4 ≤ Hs < 1.6m
1.6 ≤ Hs < 1.8m
1.8 ≤ Hs < 2m
1
1
0.75
0.5
1
1
0.75
0.5
1
0.8
0.5
0
1
0.8
0.5
0
1
0.8
0.5
0
Figure 7. Proposed policy for Case 2 in Case Study 1.
Figure 8. Proposed policy for Case 4 in Case Study 1.
Figure 9. Proposed policy for Case 5 in Case Study 1.
Table 8. Order of turbine visits for cases 2, 4 and 8.
Case 2
Case 4
Case 5
Vessel 1
Vessel 2
Vessel 3
Vessel 4
Vessel 5
Vessel 1
Vessel 2
Vessel 3
Vessel 4
Vessel 5
Vessel 1
Vessel 2
Vessel 3
Vessel 4
Vessel 5
Probability
9.3%
60.1%
65.6%
9.7%
12.2%
69.3%
54.3%
44.8%
9.7%
27.3%
54.3%
60%
31.9%
44.8%
65.4%
T95
T54
T60
T20
T52
T60
T89
T16
T20
T77
T89
T12
T77
T16
T43
T77
T90
T85
T29
T43
T12
T90
T24
T29
T43
T90
T19
T67
T24
T54
Order of visits
T89 T16 T77 T89
T54 T99 T90 T99
T60 T33 T85 T33
T19 T67 T19 T67
T24 T12 T12 T24
T60 T54 T12 T54
T99 T99 T90 T89
T33 T33 T24 T16
T19 T67 T19 T67
T85 T85 T77 T43
T99 T99 T90 T89
T12 T60 T19 T60
T85 T85 T67 T77
T33 T33 T24 T16
T54 T43
Figure 10. Gantt Chart for Vessel 3 in Case 1.
T95 T16
T20 T29
T43 T52
T20 T29
Data used in Case Study 2
Table 9. Repair properties for Case Study 2.
Half day
repair
Full day repair
High priority
repair
Low priority
action
Repair Time
(h)
Technicians
Required
Value
Cost
Load
(£ ,000) (£ ,000) (kg)
2.5
2
100
1
100
Probability of
correct
diagnosis
1
6
6.1
3
3
100
120
1
1
100
100
1
1
5.9
2
80
1
100
1
Table 10. Properties of vessels used in Case Study 2.
Vessel
number
1
2
3
4
Crew
capacity
12
12
12
12
Speed
(km/h)
36
36
36
36
Fuel consumption Hire cost
(£'000/km)
(£'000/day)
0.006
0
0.006
0
0.006
0
0.006
0
Table 11. Case Study 2 inputs.
Technicians available
Time to transfer crew from vessel to turbine (min)
Time window (h)
Speed correction factor (for turbine-turbine journeys
33
15
11.5
0.667
Load capacity
(kg)
1200
1200
1200
1200