Kristiansen Svein. Maritime Transportation: Safety Management and Risk Analysis
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7. Double sides and hydrostatic dr iven passive vacuum (DS/H D PV)
This design configuration (DS/HDPV) is a combination of both double sides (DS) and
hydrostatic driven passive vacuum (HDPV). See Figures 9.12 and 9.14.
8. Double hull and hydrostatic driven passive vacuum (D H/H D PV)
This design configuration (DH/HDPV) is a combination of both double hull (DH) and
hydrostatic driven passive vacuum (HDPV). See Figures 9.13 and 9.14.
The eight design alternatives presented above are different with respect to the foll owing
costs:
. Capital cost: The deadweight of the alternative designs is equal. However, the cost of
design and construction will vary because of different complexity.
. Maintenance and repair costs: Some designs require more maintenance and repair
because of higher exposure to salt wat er, resulting in more corrosion, increasing need
for inspections, and higher steel replacement costs. In addition, some designs are more
exposed to cracking damage, resulting in the same types of costs.
. Insurance costs: Insurance will vary slightly between the design alternatives in that hull
and machinery insurance is proportional to capital cost. In addition, less risk for
serious spill accidents may reduce insurance costs.
. Fuel consumption: Higher tanker lightweight will increase fuel consumption.
The alternative designs were analysed relative to a MARPOL tanker with protective
location of segregated ballast tanks (PL/SBT). The volume of oil spills averted by
implementing the different design configurations was estimated through an analysis of
38 large spill accidents, and the spill volume averted is considered as the benefit of the
implementation. The tons of spill averted are presented in Table 9.13, and as can be seen it
is distinguished between a typical and a major spil l year as well as between small and large
Ta b l e 9. 1 3 . Tons of oil spill averted for the different design alternatives
Design
alternatives
Typical spill year
performance
Major spill year
performance
Small
tanker (tons)
Large
tanker (tons)
Small
tanker (tons)
Large
tanker (tons)
Double bottom 2,600 4,500 13,600 24,000
Double sides None None None None
Double hull 3,300 5,300 17,600 28,400
HDPV 4,300 3,700 22,800 19,600
Smaller tanks 2,100 2,700 11,200 14,400
IOTD 4,000 5,400 21,200 28,800
DS/HDPV 3,800 5,500 17,200 29,200
DH/HDPV 3,800 5,600 20,000 29,600
276 CHAPTER 9 COST -BENE FIT ANALYS IS
tankers. The analysed accident s showed that the economic claims clustered around USD
28,000 per ton of oil spilled (1990). However, some claims could reach up to USD 90,000
per ton (i.e. Exxon Valdez). Because of this variation the tons of oil spill averted is not
transferred into economic figures in Table 9.13.
The increased transport costs as a result of the design alternatives were calculated
through a realistic weighting of three typical (and realistic) transport scenarios. All the
alternative designs had higher trans port costs than the base transport cost of a MARPOL
tanker with PL/SBT. On the basis of 600 million tons of oil carried per year, which
approximated the total US seaborne oil transport, the increased transport cost associated
with each design alternative was established. The results of this analysis are presented
in Table 9.14.
The cost-effectiveness of the different tanker design alternatives can be found by
dividing the incremental transport costs for each design alternatives by the amount of
oil each design prevents from being spilled, shown in Table 9.13. The results are presented
in Table 9.15.
Ta b l e 9. 1 4 . Incremental transport costs for the design alternatives
Design alternative Incremental cost
(USD 10
6
per year)
Double bottom 462
Double sides 339
Double hull 712
HDPV 1080
Smaller tanks 430
IOTD 872
DS/HDPV 1102
DH/HDPV 2047
Ta b l e 9. 1 5 . Added transport cost per ton of oil saved
Design
alternatives
Typical spill year
performance
Major spill year
performance
Small tanker
(10
3
USD/ton)
Large tanker
(10
3
USD/ton)
Small tanker
(10
3
USD/ton)
Large tanker
(10
3
USD/ton)
Double bottom 178 103 34 19
Double sides No oil saved No oil saved No oil saved No oil saved
Double hull 216 134 40 25
HDPV 251 292 55 47
Smaller tanks 205 159 38 30
IOTD 218 161 41 30
DS/HDPV 344 200 64 38
DH/HDPV 539 366 102 69
9.5 CBA OF OIL SPILL PREVENTION MEASURES FOR TANKERS 277
Based on Table 9.15, the most expensive ways to prevent oil spill are double sides (DS),
which does not prevent any oil spill, and double hull with hydrostatic driven passive
vacuum (DH/HDPV). Two of the design alternatives could be described as medium cost,
namely the double sides with hydrostatic driven passive vacuum (DS/HDPV) alternative
and MARPOL ships with HDPV. The most cost-effective alternatives are double bottom,
double hulls, smaller tanks, and interior oil-tight deck (IODT).
Assuming that the costs of oil spills vary from USD 28,000 to 90,000 per ton of oil
spilled, none of the design alternatives are cost-effective in a typical year. However, in
major spill years all the design alternatives can be cost-effective. Other cost-effectiveness
studies carried out on the implementation of double hull tankers have, however, shown
that this measure is not cost-effective. A study performed by the Transportation Centre of
Northwestern University (Brown and Savage, 1996) showed that the expected (i.e. most
likely) benefits of double hulls on tankers were only about 18% of the costs expected.
278 CHAPTER 9 COST-BENE FIT ANALYS IS
REFERENCES
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Management, Vol. 23(2), 167–175.
HSE, 1992, The Tolerability of Risk from Nuclear Power Stations. Health and Safety Executive, UK.
McCormick, N. J., 1981, Reliability and Risk analysis: Methods of Nuclear Power Applications.
Academic Press, San Diego.
O’Rathaille, M. and Wiedemann, P., 1980, The social costs of marine accidents and marine traffic
systems. Journal of Navigation, Vol. 33(1), 30–39.
Roland, H. E. and Moriarty, B., 1990, System Safety Engineering and Management. John Wiley,
New York.
Sexsmith, R. G., 1983, Bridge Risk Assessment and Protective Design for Ship Collisions. IABSE
Colloquium ‘Ship Collision with Bridges and Offshore Structures’, Copenhagen.
Skjong, R. and Ronold, K., 1998, Social Indicators of Risk Acceptance. OMAE 98, Det Norske
Veritas, Høvik, Norway.
279
10
FORM A L SAFETYASSESSME N T
The degree to which you overreact to information will be in
inverse proportion to its accuracy.
(‘‘Weatherwan’s Postulate’’)
10. 1 I NTR O D UCTI ON
The use of qualitative methods has a long history within the maritime industry. More
recently, however, the use of quantitative methods has opened up an opportunity to
compare different concepts and safety measures on a common scale. In the previous
chapters several techniques, both quantitative and qualitative, have been described for
analyses of event probabilities and consequences. In addition to these techniques, the cost-
benefit analysis (CBA) described in the previous chapter makes it possible to compare and
implement the results of the risk analysis in terms of costs. Hence, by applying a sequence of
all these methods, decisions can be made about which concepts to choose and which safety
measures to implement based on a simple assessment of the costs involved. The validity of
comparing different concepts or safety measures on a common scale is, however, not only
related to the scale itself but also to the analysis process. Different approaches to the
problem and different assessment of details may contribute to different results. As a result
of this situation a need for standardization and generalization of the analysis approach/
process was brought to the surface. One proposed standard analysis approach that has
gained wide recognition is the so-cal led Formal Safety Assessment (FSA) approach.
Formal Safety Assessment (FSA) is a designation used in a number of different contexts
and industries (e.g. the nuclear industry) in order to descri be a rational and systematic risk-
based approach for safety assessment. In the maritime world the expression Formal Safety
Assessment (FSA) is now being used by the International Maritime Organization (IMO)
and its members to describe an important part of the rule-making process for internati onal
shipping. It is this maritime type of FSA that will be reviewed in this chapter. FSA is
sometimes referred to as the safety case concept, which was first developed in the nuclear
industry and has been used in other industries, such as in offshore.
According to IMO, FSA is a rational and systematic process for assessing the risks
associated with any sphere of activit y, and for evaluating the costs and benefits of different
options for reducing those risks. It therefore enables an objective assessment to be made of
the need for, and content of, safety regulations (see IMO’s web site).
281
10 .1.1 Historic al Ba ckground
Large-scale maritime accidents, in particular the accidents with Herald of Free Enterprise
(1987) and Exxon Valdez (1989), prompted a re-evaluation of the current prescriptive (i.e.
rule-based) regime for marine safety. The regime was regarded unfavourably compared to
the safety regimes used in other industries, which were based on more scientific methods
such as risk and cost-benefit analyses. Especially within the UK, work was carried out in
order to establish a more rational approach to rule development. In 1993 the UK Marine
Safety Agency, renamed the Marine Coastal Agency in 1998, proposed a five-step
procedure for safety analysis, named Formal Safety Assessment (FSA), to the
International Maritime Organization (IMO). The main purpose of the FSA methodology
was to provide a more systematic and proactive basis for the IMO rule-making process.
In 1997 IMO adopted ‘Interim Guidel ines for the Application of Formal Safety
Assessment (FSA) to the IMO Rule-Making Process’ and has since been evaluating trial
applications of the technique. The use of the FSA methodology on helicopter landing
areas on cruise/passenger ships in 1997 was influential in IMO’s decisio n to abandon this
risk reduction measure because the implied cost of averting a fatality (ICAF) was found to
be far from cost-effective. The main principles for Formal Safety Assessment now seem to
be widely accepted within the IMO.
10.1 .2 The Intentions of FSA
FSA is a tool designed to assist maritime regulators in the process of improving and
deriving new rules an d regulation. The main intention behind the development of the FSA
methodology for maritime activities was that it should be used in a generic way for
shipping in general. The methodology was initially derived with two potential users
in mind:
. IMO committees: The application of the FSA methodology can provide helpful
inputs into the review process of existing regulations and into the evaluation process
of proposed new regulations.
. Individual maritime admi nistrations: Application of the FSA methodol ogy can be
used in the process of evaluating/assessing proposed amendments to IM O regulations.
It can also be used in order to evaluate whether additional regulations, which exceed
the IMO requirements, should be introduced.
It is anticipated that FSA should be relied upon where proposals may have far-
reaching implications in terms of safety, cost and legislative burden. The application of
FSA will enable the benefits of proposed changes to be properly established and will
therefore give decision-makers a clearer perception of the scope of the proposals and an
improved basis on whi ch to take decisions.
At the present time the classification societies seem to recognize that the FSA
methodology also can be used in the process of impro ving and developing classification
rules. This should in principle not be fundamentally different from using the methodology
on the IMO rules. The phrase Formal Safety Assessment has also been applied to the
282 CHAPTER 10 FORMAL SA FETYASSESSMENT
safety assessment of individ ual ships. Although the general methodology is the same in
these cases, the specific aspects have been adjusted to the particulars and characteristics of
the ship under consideration.
10.2 T H E FSA A PPR OA CH
The FSA approach/methodology is a standardized holistic approach to risk assessment.
The approach involves several standard elements, which can be illustrated by the five-step
process shown in Figure 10.1. Each step involves the use of specific methods and tasks,
many of them described in detail in earlier chapters.
The interactions between the five steps of the FSA methodology are in reality not as
simple as shown in Figure 10.1, which serves more as an overview of the sequential nature
of the FSA methodology. The results and findings in one step are often used as feedback
and input into several other steps. For example, the generation of safety measures, also
known as risk control options, in step 3 of the methodology is based on both the most
important hazards identified in the risk assessment step (i.e. step 2), as well as the more
qualitative background and understanding of the hazards established in the step 1. These
mutual interactions between the five steps of the methodology means that the FSA
approach in reality looks more like the flow chart given in Figure 10.2.
Each of the steps in Figures 10.1 and 10.2 is given a more detailed description in the
following text. The FSA methodology is quite complex because it involves the use of
a wide range of different techniques, some which are described in earlier chapters. As a
result, only the most important aspects are described and discussed here, and where
appropriate references to other chapters are made.
Figure 10.1. The five-step process of Formal Safety Assessment (FSA).
10 .2 TH E FSA APPR OA CH 283
10.2. 1 The Generic Ship
As mentioned in the introductory part of this chapter, FSA is a tool designed to assist
maritime regulators in the process of developing rules and regulations. Rules and
regulations must apply to ships on a general basis, and an important element of the
FSA approach/methodology is therefore the use of generic ships. A generic ship should
represent all the ships that are affected by the rules/regulations under consideration in the
FSA process, and it should therefore have those functions, features, characteristics and
attributes that are common to the vast majority of the ships relevant to the problem under
concern. Hence, a generic ship model does not normally include characteristics
such as cargo and detailed design features, which often vary greatly between ships. The
construction of a generic ship generally means establishing a common starting point for
the FSA process, and in addition it results in analytical consistency and efficiency.
FSA can, for example, be used to develop safety measures (or risk control options),
such as rules and regulations, which will apply to all ships of a particular type. When
performing an FSA, the generic ship will be a hypothetical vessel with characteristics that
are typical or average for the ship type in question. As much effort as possible should be
made in order to develop a generic ship that is representative of as many of the ships in the
fleet as possible. The first efforts to establish a generic ship model aimed at creating one
that would account for nearly all (merchant) ships. In later years the development has
gone more in the direction of different generic models for different ship types, for example
different generic ship models for oil tankers, chemical tankers, gas tankers, etc. No matter
Figure 10.2. Flow chart of the FSA approach/ methodology.
284 CHAPTER 10 FORMAL SA FETYASSESSMENT
what method is used, it is of crucial importance that the generic ship model applied in the
FSA methodology is applicable to the problem examined.
With reference to MSA (1995), a description of a generic ship, meant to cover most
ships in international trade, is outlined below:
The generic ship is a vessel, of monohull construction, over 500 GT, manned by com-
petent persons, having the propelling and primary power generation machinery and
associated systems located in machinery spaces within the hull. The accommodation,
containing the cabins, communal areas, galley and refrigerated stores, is situated at
a level above the machinery space, the upper reaches of which may be surrounded by
accommodation.
The primary control position, the Navigation Bridge, is situated at the forward
upper area of the accommodation. A control position for machinery is located within
the main machinery space. Emergency power is provided from a self-contained unit
located within the emergency generator room, which is located external to the main
machinery, but with a dedicated access. Emergency protection devices, such as fuel valve
trips, ventilation fan stops, oil service pump stops and machinery space fire supervision
systems, would also be located at a space remote from the main machinery.
Mooring equipment is located at the bow and stern. Anchors are provided with the
means to be deployed and recovered using windlass machinery provided at the bow.
In addition to this description, the generic ship inhabits a set of generic systems and
functions, which enable it to operate and trade safely. The system categories and functions
are listed alphabetically in Table 10.1.
The transport operation is characterized as a sequence of distinct phases where each
phase requires the use of different functions. Hence, the need for the various functions
given in Table 10.1 will vary according to a specific ship’s operational cycle. The
Ta b l e 1 0 .1 . S yste ms and functions of a generic ship
Systems Functions
Accommodation and hotel service Anchoring
Communications Carriage of payload
Control Communications
Electrical Emergency response and control
Human Habitable environment
Lifting Manoeuvrability
Machinery Mooring
Management systems Navigation
Navigation Pollution prevention
Piping and pumping Power and propulsion
Pressure plant Bunkering as storing
Safety Stability
Structure
10 .2 TH E FSA APPR OA CH 285