National Technical University of Athens School of Naval Architecture and Marine Engineering
Laboratory for Maritime Transport
Analysis of Probabilistic Oil Outflow from Tankers: Quantities & Costs
Panagiοtis Sοtiralis Identifying the Problem
Main Problem
Oil Outflow Cost
Effects
Risk-based design methods were applied to optimize the arrangement of crude oil tanker cargo holds with respect to reducing environmental risk for collision and grounding cases where a tanker is involved.
Greek Section of SNAME Previous efforts
Recent Literature Review
Sirkar White & Ventikos Hamann Papanikolaou et al. Molloy et al. & Loer et al. ) (1997) (2003 (2009) (2010) (2010)
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Etkin Yamada Psarros Kontovas (1999) (2009) et al. et al. (2010) (2010)
Greek Section of SNAME Outline
Sections
•Tankers : Design, Accidents and Regulations 1
•Statistical Analysis of the Database 2
•Regulations 19 And 23 of MARPOL in the Context of Simulation 3
•Simulation Model of Probabilistic Oil Outflows: Description and 4 Presentation of the Results
•Cost Models of Probabilistic Oil Outflow 5
•Regulation 23 of MARPOL at the Programming Environment of Fortran 6
•Conclusions and Suggestions for Additional Future Work 7
Greek Section of SNAME 1. Tankers : Design, Accidents and Regulations Accidents and Regulations
Presentation of the Most Important Accidents and Regulations
Significant Accidents
• Amoco Cadiz
• Exxon Valdez
• Erika
• Prestige
Significant Regulations
• 1978 Protocol of MARPOL,
• ΟΡΑ 90,
• Revision of MARPOL 73/78 (Reg. 13G),
• ERIKA I and ERIKA II.
Greek Section of SNAME 1. Tankers : Design, Accidents and Regulations Design of Tankers
Presentation of the Global Fleet of Tankers
Development of tanker world fleet (ship years) between 1980 and 2008 broken down into size categories as well as types SH and DH.
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Features
1. Use of the IHS SeaWeb database which has registered the global fleet;
2. Development of a dedicated database for each category of oil tankers;
3. Double hull tankers: no tankers (i) with single skin construction; (ii) with only double sides; and (iii) with only double bottom design;
4. Removal of the extreme outliers with regards to the main particulars of the ships (L, B, D, T);
5. Acceptance of the mild outliers with regards to the main particulars of the ships (L, B, D, T).
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Outlier Analysis (Boxplot)
• No 5: Aframax tanker (210 m of length) extreme outlier (omitted from the rest of the analysis); • No 4: Aframax tanker of (220 m of length) mild outlier (it was integrated into our analysis).
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Finalization of Database (Population)
CATEGORY DWT (TONNES) RECORDS PRODUCT TANKER 10,000 – 60,000 660 PANAMAX 60,000 – 80,000 406 AFRAMAX 80,000 – 120,000 960 SUEZMAX 120,000 – 200,000 521 VLCC 200,000 – 320,000 642 ULCC 320,000 – ………… 40
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Typical Cargo Tank Configurations
CATEGORY CARGO TANK CONFIGURATIONS PRODUCT TANKER 5Χ2 6Χ2 7Χ2 PANAMAX 5Χ2 6Χ2 7Χ2 AFRAMAX 5Χ2 6Χ2 7Χ2 SUEZMAX 5Χ2 5Χ3 6Χ2 7Χ2 VLCC 5Χ3 5Χ4 5Χ5 6Χ3 ULCC 5Χ3 5Χ4 5Χ5 6Χ3
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Typical Cargo Tank Configurations
A 6x2 cargo tank arrangement (6 tanks long by 2 tanks wide).
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Typical Cargo Tank Configurations
Midship sections for tankers.
Greek Section of SNAME 2. Statistical Analysis of the Database Elaboration of the Database
Distribution Fitting (through Goodness of Fit Tests)
Normal(13917,90; 818,59) Logistic(14846,55; 198,63)
9 2,5
8
2,0 7
6 1,5 5
4 1,0
3
2 0,5
1
0 0,0
11 12 13 14 15 16 17 18 19 20 21
13,5 14,0 14,5 15,0 15,5 16,0 16,5
Fitting the Draught (T) to Normal distribution Fitting the Draught (T) to Logistic distribution for the examined fleet of Panamax tankers. for the examined fleet of Aframax tankers.
Greek Section of SNAME Regulations 19 And 23 of MARPOL 3. in the Context of Simulation Monte Carlo Method
Characteristics
• The Monte Carlo method uses a pseudo-random number generator which produces values that pass tests for randomness;
• The number of repetitions of the experiment is sufficiently large to ensure accuracy of results;
• The decision-maker has a comprehensive view of the range of possible outcomes and their probabilities.
Greek Section of SNAME Regulations 19 And 23 of MARPOL 3. in the Context of Simulation Theoretical Background
MARPOL Regulations of Interest
Regulation 19 : Double hull and double bottom requirements for oil tankers
• Wing tanks or spaces : w = min {0.5 + DWT/20000; 2.0 m} > 1.0 m
• Double bottom tanks or spaces : h = min {B/15; 2.0 m} > 1.0 m
Regulation 23 : The mean oil outflow is calculated independently for side damage and for bottom damage and then combined into the non-dimensional oil outflow
parameter OM
• The Mean Outflow Parameter : OΜ = (0.4 OMS + 0.6 OMB) / C
3 OMS = mean outflow for side damage, in m ;
3 OMB = mean outflow for bottom damage, in m ;
C = total volume of cargo oil, in m3, at 98% tank filling.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Inputs
• The distribution of the length (L) of each category of tanker;
• The distribution of the breadth (B) of each category of tanker;
• The distribution of the depth (D) of each category of tanker;
• The distribution of the draught (T) of each category of tanker;
• The distribution of the double bottom (HDB) of each category of tanker;
• The distribution of the wing tanks of each category of tanker;
• The distribution of the length of the engine room (LER);
• The distribution of the position of the collision bulkhead;
• The distribution of the position of the engine room bulkhead.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Assumptions
• The HDB and the wing tanks follow uniform distribution. The lower limit of the range was chosen so as to satisfy the requirements of regulation 19 of Marpol while the upper limit derived from the database;
• The location of the collision bulkhead follows uniform distribution within the range: 0.05 x L < L.f.p. < 0.05 x L + 3.05;
• The location of engine room bulkhead follows uniform distribution within the following range: 0.75 x L.f.p. < L.a.p. <1.25 x L.f.p. This range was extracted from the records of the elaborated database;
• The length of engine room follows uniform distribution within the following
range: 0.18 x LB.P. ≤ LE.R. ≤ 0.22 x LB.P.. The range came up from our database;
• A nominal density of cargo of 0,84 ton/m3 was assumed.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Range of the Double Bottom and the Wing Tanks against Tanker Size
CATEGORY DWT (TONNES) HDB W
PRODUCT 10,000 – 60,000 1.0-2.5 m 1.0-2.5 m TANKER PANAMAX 60,000 – 80,000 2-3 m 2-3 m
AFRAMAX 80,000 – 120,000 2-3 m 2-3 m
SUEZMAX 120,000 – 200,000 2-3 m 2-3 m
VLCC/ULCC 200,000 – ………… 2-4 m 2.5-4 m
The range of uniform distribution of the double bottom and the wing.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Constraints
CATEGORY L/B B/T L/D D/T PRODUCT 5.1-8.55 2-4 8.7-14.48 1.2-1.8 TANKER PANAMAX 4.3-7.21 2.17-3.4 9.77-15.1 1.3-1.75 AFRAMAX 5.1-6.8 2-4 10.1-13.8 1.2-1.83 SUEZMAX 5-6.2 2.45-3.4 9.7-12.6 1.3-1.6 VLCC/ULCC 4.5-5.9 2.48-3.7 9.9-12.6 1.2-1.57
Acceptable ratios of the main particulars for each category of oil tankers.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Accident Scenarios
The user can choose among a cargo tank, multiple cargo tanks, or even all onboard cargo tanks for calculating the probability distribution of total oil outflow. The results of the simulation model were based on the following accident scenarios:
• Damage to a single tank from grounding;
• Two damaged tanks from grounding;
• Damage to a single tank from collision;
• Damage to all cargo tanks from grounding;
• Damage to all cargo tanks from collision;
• Damage to all cargo tanks from grounding and collision.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Presentation of the Probability Distributions of Oil Outflow
Distribution of total oil outflow (m3) from Aframax tanker of 6x2 cargo tank configuration.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Presentation of the Probability Distributions of Oil Outflow
Distribution of total oil outflow (m3) from Aframax tanker of 7x2 cargo tank configuration.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Presentation of the Probability Distributions of Oil Outflow
Overlay of computed oil outflows (m3) from grounding of Aframax tanker of various cargo tank configurations (2 tanks damaged).
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Presentation of the Probability Distributions of Oil Outflow
Overlay of computed oil outflows (m3) from collision of Aframax tanker of various cargo tank configurations (one tank damaged).
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Presentation of the Probability Distributions of Oil Outflow
Total mean oil outflow (m3) Product Configuration Panamax Aframax Suezmax VLCC/ULCC tanker 5x2 340-1,013 667-1,234 1,289-2,172 1,929-3,394 - 6x2 330-904 573-1,075 1,162-1,998 1,723-3,023 - 7x2 310-848 542-1,024 1,099-1,808 1,592-2,806 - 5x3 - - - 1,164-2,029 2,122-4,824 6x3 - - - - 1,926-4,427 5x4 - - - - 2,744-4,256 5x5 - - - - 2,570-3,687
The results are in line with the findings presented in Hamann & Loer (2010), e.g. the types of oil spill distributions (beta, gamma and lognormal)
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Minimization of the Oil Outflow through the Optimum Position of the Longitudinal Bulkhead The starboard longitudinal bulkhead moves The port longitudinal bulkhead moves from from Β/2 to CL: -Β/2 to CL:
• Β/2 ≤ x1 (position of longitudinal • -Β/2 ≤ x2 (position of longitudinal bulkhead starboard) ≤ 0 (Center Line) bulkhead port) ≤ 0 (Center Line)
VLCC DWT = 320000 tn L 320 m B 60 m C.L. D 30,5 m T 22,22 m w 4 m
HBD 3 m
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Minimization of the Oil Outflow through the Optimum Position of the Longitudinal Bulkhead
At the tank configuration 5x4 an additional longitudinal bulkhead is placed at the center line
VLCC DWT = 320000 tn L 320 m B 60 m D 30,5 m T 22,22 m w 4 m
HBD 3 m
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Sensitivity Analysis
Sensitivity analysis for oil outflow Sensitivity analysis for oil outflow from grounding. from collision.
Greek Section of SNAME 4. Simulation Model of Probabilistic Oil Outflows Description and Presentation of the Results
Comparison of the Theoretical and Actual Oil Outflow
Quantity Probability Ship-years Quantity per ship-year (tons) Actual mean oil 13451 - 17713 0.786 tons/ship year outflow Theoretical mean outflow (quantity with 3330 10% 17713 0.188 tons/ship year the highest probability)
Theoretical mean outflow 4841 3% 17713 0.273 tons/ship year (largest quantity)
Comparison of the theoretical and actual oil outflow
Greek Section of SNAME 5. Cost Models of Probabilistic Oil Outflow Presentation of Spill Cost Models
Features of the Cost Models
• A constant value of 60,000 USD per ton of oil. This value was derived by work done in SAFEDOR and it reflects the threshold value of CATS (Cost of Averting one Tonne of Spilled Oil);
• The submission from Japan (IMO, 2009a) proposed the spill total cost evaluation using a spill size dependent approach. In this outline, the total spill costs are calculated as shown below:
0.66 CSPILL (W) = 38.735 USD * W
• Following the same rationale Greece (IMO, 2009b) proposed a different formula as this is given:
0.728 CSPILL (W) = 51.432 USD * W
• The proposal from Norway (IMO, 2009c) follows a similar approach:
0.647 CSPILL (W) = 60.515 USD * W
W = spill size in tonnes; C = total cost (USD $, 2009).
Greek Section of SNAME 5. Cost Models of Probabilistic Oil Outflow Presentation of Spill Cost Models
Cost of Oil Outflow
Total spill costs for Aframax tankers (of 7x2 cargo tank configuration, total oil outflow) calculated with different cost formulas.
Greek Section of SNAME 5. Cost Models of Probabilistic Oil Outflow Presentation of Spill Cost Models
Distribution of the Cost of Oil Outflow
Distribution of spill costs for Aframax tankers (of 6x2 cargo tank configuration, collision, tank 4STB damaged) calculated according to the cost model from Greece.
Greek Section of SNAME 5. Cost Models of Probabilistic Oil Outflow Presentation of Spill Cost Models
Distribution of the Cost of Oil Outflow
Distribution of spill costs for Aframax tankers (of 6x2 cargo tank configuration, collision, tank 4STB damaged) calculated according to the cost model from SAFEDOR.
Greek Section of SNAME Regulation 23 of Marpol at the Programming 6. Environment of Fortran Fortran
Objectives and Benefits from the Development of the Programming Code
The development of a handy tool for the fulfillment of regulation 23.
The programming of the entire simulation model.
The response of the simulation model through a programming code is more rapid compared with the use of software.
Greek Section of SNAME Conclusions and Suggestions for Additional 7. Future Work Conclusions
• The regulation of MARPOL focuses on the design of tankers and do not converge to the actual outflow;
• The probability distributions represent the global tanker fleet (per size category) supplying probabilities for specific amounts of oil outflows (MARPOL, Annex I);
• The cost evaluation either with the proposed constant value, or the spill size dependent cost models is based on the results of the implemented model;
• The spill costs derived by the SAFEDOR approach are substantially higher than the respective costs arisen from the application of the rest of the implemented cost models.
• The optimum position of the longitudinal bulkheads leads to a reduction of the theoretical oil outflow of 7%;
• When the oil outflow is from grounding, the theoretical outflow reaches in some cases the 4% of the total capacity of the tank, whereas when comes from collision the percentage is increased and reaches up to 9%.
Greek Section of SNAME Conclusions and Suggestions for Additional 7. Future Work Tasks for Future Work
• The evaluation more tank configurations such as the 5x3 tank configuration in Aframax using the existing simulation model;
• A probabilistic assessment of the oil outflow by using probabilities from more recent accidents in the context of risk analysis challenging the existing regulation;
• The evaluation of the tank configurations not only from the aspect of the oil outflow but taking into consideration and other parameters such as the payload, economic criteria (e.g. maintenance costs), the reduction of the air emissions and the fuel consumption, by assessing spherical the design of oil tankers;
• The convergence between quantities and costs. The quantities which are derived from Regulation 23 must converge to the limit of the non linear cost model.
Greek Section of SNAME
National Technical University of Athens School of Naval Architecture and Marine Engineering Laboratory for Maritime Transport
End of presentation
Analysis of Probabilistic Oil Outflow from Tankers: Quantities & Costs
Publications:
Ventikos N.P., Sοtiralis P. (2011), "Probabilistic Oil Outflow: the Tanker Fleet in the Context of Risk Analysis", European Conference on Shipping Intermodalism & Ports (ECONSHIP 2011), June 22-24, Chios, Greece
Ventikos N.P., Sοtiralis P. (2011), "The global fleet of tankers in the context of probabilistic oil outflow analysis", International Journal of Shipping, Transport and Logistics (IJSTL) , (upon final approval)
Panagiοtis Sοtiralis