Page 38 - Sayı-08

36 A. M. YASA and H. AKYILDIZ

areas which consists of constant threat to safety of life, environment and property. This
assumptions and assessment have been carried out by five steps.

For generic OSV, following assumptions are applied regarding vessel age.

Fig. 1. Age profile of offshore support vessels [9]

As it can be seen above Fig. 1., approximately 70% of world fleet of OSVs less than 20 years old.
Also considering the distribution of older vessels, it is fair to limit ourselves to 20 years of a
lifespan for OSV accordingly. There is the first assumption; average lifetime assumed as 20 years.
In the world, we can define five major areas doing offshore for and thus in need of offshore
support vessels or work vessels related to this area. These areas are US Gulf of Mexico, Europe
North Sea, Asia Pacific Region, South America and Africa Region. Considering the workload, it
is good assumption to have 330 operational days in a year. So, our average operational days per
year assumed as 330 days.
Marine and as well as offshore industry are operating almost every hour of a day. Offshore
platforms, support vessels, ports and relevant areas are always working. Therefore, operational
number of hours in a day is 24 hours.
This is assumed as 2.5 years (or 30 months) in accordance with international regulations. Ships
are subjected to docking survey every 30 months in connection with SOLAS therefore, 2.5 years’
assumption is very realistic.
At this point, now it is important to define operational phases of an offshore support vessel in
order to define and analyze the risks of a such phase. On this paper, we defined below given
phases and followed accordingly.

1. Design/Construction/Commissioning
2. Port Operations (Berthing, Unberthing, Mooring Operations etc.)
3. Platform Operations (Maneuvering, Mooring, Lifting etc.)
4. Navigation
5. Other Operations (Lifting, Towing etc.)
6. Dry dock Maintenance
7. Decommissioning/Scrapping

However, it is important to adjust some of the operational phases due to low risk. When the
historical records checked and as well as expert opinions asked, it is fair to assume that the 1st and
7th phases are bearing very low risk. Therefore, it is acceptable to omit these two phases. In this
sense, risk assessment of offshore support vessels will have 5 phases accordingly.

GiDB|DERGi Sayı 8, 2017