Analysis of casualties to tankers in the Baltic, Gulf of Finland and Gulf of Bothnia in 1960 - 1969

HELSINKI UNIVERSITY OF TECHNOLOGY

SHIP HYDRODYNAMICS LABORATORY

OTANIEMI

FINLAND

Report No. 5

ANALYSIS OF CASUALTIES TO TANKERS IN

THE BALTIC, GULF OF FINLAND AND

GULF OF BOTHNIA IN 1960-1969

by

V. Kostilainen

DD R

OIL TANKER DAMAGES

BALTIC AREA

1960-1969 GROUNDING £ COLLISION EXPLOSION OR FIRE OIL HARBOUR POLAND O

.

o

F i g. 1. Geographical distribution of oil tanker damages in the Baltic area during the years 1960-69.

U.S.S.R.

HELSINKI UNIVERSITY

OF TECHNOLOGY SHIP HVDRODVNAM 105 LABORATORY FIN LAND L-239 O 20 100 ISO KM ft

Introduction

Earlier the safety of life at sea has been the main human problem to be dealt with in shipping and ship-building. Now more and more importance has been attached to the effects man has on the balance of the nature. The Baltic, Gulf of Bothnia and Gulf of Finland form a limited sea water basin, where the change of water is small and the effects of man marked. As the climate is rather cold the balance can be more easily

dis-turbed. Oceanographers have done very valuable work in

following the variation of the sea water composition and biology in the Baltic. Some attempt have also been made to evaluate the effects of sewage discharged from the settled areas and from the factories on the coasts of the Baltic.

One of the worst threats to the sea water is the oil leaked from the ships. This oil gets into the water in

ship casualties or by accidental or deliberate discharge of

spill oil to the sea. The oil amounts leaking into the water are very large in ship accidents if the ship or ships in question are tankers in loaded conditions and tanks

are damaged.

A reliable foundation for the planning and construction

of effective countermeasures is the basic knowledge of

the conditions and causes of accidents. In research on the

causes of the accidents maritime industry has lagged behind the aviation and ground transportation industries. When marine accidents occur there might be some investigations of the separate cases for the purpose of establishing legal responsibility, acts of negligence etc. However there exists no systematic and extensive data

collecting on marine casualties, which is indispensable for statistical analysis and from which meaningful conclusions

may be drawn. IMCO is now making valuable efforts conserning this topic which will result in useful records in due time. The U.S. Coast Guard and some others already have marine casualty records, but they do not cover the Baltic, Gulf of Bothnia or the Gulf of Finland. Also some older records do not include data necessary

for the analysis of oil leakage and human factors.

ANALYSIS OF CASUALTIES TO TANKERS IN THE BALTIC, GULF OF

FINLAND AND GULF OF BOTHNIA IN 1960

- 1969

by V. Kostilainen

Abstract

The problem of limiting the oil pollution of the sea is becoming increasingly important. The collection of dataon

tanker damages in the Baltic, Gulf of Bothnia and Gulf of Finland during the years 1960 - 69 was made in the Helsinki University of Technology last year. The data consisting of a total of 268cases, of which complete data were

available in 102 cases, have been statistically analysed and the results are presented. Some correlationsare discussed.

More efficient international co-operation between Shipbuilders, Shipowners, Classification Societies and

Adminis-trations in collecting and analysing damage data is emphasized.

Data Collection

One of the difficulties in statistical research is choosing

the data to be collected. It would be useful to get as much data as possible, because there is no known scientific criterion for choosing the data relevant to this kind of an analysis. On the other hand if too detailed information is required difficulties might arise in getting answers to the questionnaires at all. Specially the availability of human factors information is poor in

older cases. Finally, the data presented in the "Oil Tanker

Damage Card" of Appendix I was considered to be proper for this study.

First information on a total of 268 casualties was obtained from the Boards of Navigation in Finland and Sweden and from Lloyd's Weekly Casualty Reports. To complete this information, circulars with Oil Tanker Damage Cards were sent to a total of 130 shipowners of the ships involved in casualties. Answers were obtained from 77 shipowners of which 43 were capable of giving satisfactory data about their ships. 31 of the shipowners gave us the permission to utilize the data on damages

available in the Records of those Classification Societies, where the ships were classified. This was also done and

rel-atively complete information according to Appendix I

was obtained in 102 cases.

How representative this sample is cannot be deter-mined with a high degree of certainty, because of the

variety of data sources. Specially in older accidents some

of the information must be approximate and affect the reliability of the analysed results. No damage informa-tion was obtained from The Soviet Union. In Lloyd's Weekly Casualty Reports only 17 casualties to tankers from The Soviet Union were given. No details on these

casualties were available.

Nature of the Casualties and their Local and Annual Distributions

More than half of the casualties, total 149 (56 %) were groundìngs, 93 (35 %) were collisions and the rest 25

2 50 L'O 30 N 20 N 10 SOUND G R OU ND INGS COLLISIONS

FIRES AND EXPLOSIONS

(9 %) were fires and explosions. In 262 cases the place of the casualty was known and these places are marked in Fig. 1. From this figure it can be seen that the highest casualty densities are found in the Danish Sounds, in the Stockholm approach and in approaches to other oil harbours. Local distributions of the different nature of casualties are presented in Fig. 2. lt should be noted that the number of groundings is twice the number of collisions in approaches to the harbours. In the Sound and Fehmarn Belt the number of collisions is larger than

the number of groundings while in the Great Belt and in the Kalmar Sound the number of groundings is three times or more the number of collisions. Only 6,5 % of the casualties took place at open sea and at open coast. According to T. D. Mora's investigations [9] the Mate on the Watch has a heavy overload in most restricted waters specially when there is no pilot on the bridge. Therefore the use of two mates on the watch during these periods of high workload is to be recommended. This will increase the costs. On the other hand a considerable

increase in safety far outweighs the cost of one-two hours

overtime per port.

The annual distribution of the three main casualty groups is presented in Fig. 3. Three high casualty rates can be observed in the years 1960, 1963 and 1966.

The smoothened casualty rate line shown in this figure is obtained on the least-square basis. lt indicates that the casualty rates are slightly increasing. The main casualty group as percentages of the total number of casualties

over the years can be seen in Fig. 4. Here again the prevailing large frequency of groundings can clearly be seen and its relative magnitude is

at any rate not

diminishing.

For comparison the relative change of casualty

frequen-cy as percentage of the 1968 value is presentedin Fig. 5

F i g. 2. Local distribution of groundings, collisions and fires.

40 35 3D 25 20 N 15

F i g. 3. Rates of groundings, collisions and fires of the tankers in the Baltic, Gulf of Bothnia and Gulf of Finland 1960-69. COLL 151 ONO GROUND IFIGS FIRES AND EXPLOSIONS

i

100 90 BO 70 50 - 50 z LU 4Q 30 20 10 -io

\GROJ

COLL ISI ONS

1060 --63 -64 -65 TEAR ..:«.;.... 4::.:.»:4 -.2 -.3 -.4 TEAR s

F i g. 4. Relation between different groups of casualties

over the years.

GREAT BELT FE HM AR N KALMAR STOCKHOLM APPROACHES TO ALANO WITH OPEN SEA AND

50-50

N

CASUALTY RATE

NUMBER OF SNIPS ARRIVED AT HARBOURS OF THE BALTIC AREA

IN DANMARK, FINLAND AND SWEDEN

OIL PRODUCTS LOADED AND UNLOADED

IN ABOVE-MENTIONED HARBOURS 20

TANKER VOYAGE CHARTER FREIGHT RATE

10

-60 -61 -62 -63 -EN -65 -66 -67 -68 -69

TEAR

F i g. 5. Annual casualty rate 1960-69 as percentage of

casualty rate in 1968 together with the correspond-ing percentages of number of ships, oil products

loaded and unloaded in the Baltic, and tanker

voyage charter freight index.

30-20 10_ Fig. 6. 5 6 7 8 ₉ 10 11 12 MONTH

Seasonal distribution of damages.

30

I \\I

I \\1

G ROUND ING S

COLLISIONS

FIRES AND EXPLOSIONS

F i g. 8. Distribution of ship lengths.

3

together with the relative change in the number of ships, transported oil products and tanker voyage charter freight rates. The general tendency in casualty rates seems to be the same as in the total number of ships

sailing in the area.

The seasonal distribution of casualties is presented in Fig. 6. According to this the accident frequency in December and January is more than twice that of June and July. The seasonal distribution of the three casualty groups as percentage of the total number of casualties each month is shown in Fig. 7. This figure indicates that the relative rate of groundings is highest during the autumn, the darkest season of the year, probably due to busy traffic before the winter. On the other hand the rate of collisions does not increase. The increased traffic and the dark season increase the burden of work of pilots taking the ships in and out. The heavy burden increases

the probability of human errors. Thus the rate of

casualties in the autumn could probably be reduced by

increasing the number of pilots on duty during this season. Size, Age and Loading Conditions of Tankers Involved

Two tanker sizes are used very much in the Baltic area,

the small coastal tanker with length below 60 m and the handy size tanker with length between 140m and 180m.

Correspondingly 32 % of the tankers involved in

casual-ties had a length below 60 m and 37 % had a length between 140 m and 180 m. From Fig. 8 it can be seen

that groundings were twice as frequent as collisions in the

first group and in the second group the number of

groundings and the number of collisions are approximate-ly equal.

II

.R.

60 Ea 100 120 150 160 180 2 0 220

SHIP LENGTH IN METRES

5 6 7 10

MONTH

F i g. 7. Seasonal relation between different groups of

N 4 20 30-20_ io 10-j

SHIP LENGTH 8ELOW 100 m

SH P LENGTH FROM 100 m TO 200 m

SHIP LENGTH OVER 200 n

-so -si 62 -63 -00 -65 -66 -67 -60 -69

YEAR

F i g. 9. Annual casualty rates devided according to the

length of ships involved.

In Fig. 9 all ships involved in casualties are divided according to their length into three groups, length below loo m, between 100 m and 200 m and over 200

m. Distributions of casualties over the years in each group

are presented. These histograms show that two of the three high casualty rates which were noticed already in Fig. 3, namely casualties in 1963 and 1966, concern the ships of the medium size tanker group having a length between 100 m and 200 m. This is also the size group

where occasionally over-aged tonnage is chartered.

The age of ships involved in casualties varied a great

deal. The age distribution of ships is presented in Fig. 10.

The age distribution of all tankers sailing in this area the was not known. Distribution in percentageof age groups

of ships involved in accidents in periods of two years is presented in Fig. 11. No clear tendencies can be seen from this figure though the structure of the last group (1968-69) seems to indicate a slight decrease of

casual-ties to new ships.

Information on loading conditions was obtained in 125

cases. 59 % of these were fully loaded and 24 % in ballast

conditions. According to this, the probability of casualty in loaded condition is roughly twice of that in ballast condition! This agrees with the great relativenumber of groundings in general.

Dimensions and Location of Damages

The number of cases where damage location and

dimensions could be discovered was 104. This sample sizel is far too small for a detailed analysis.

N 50 So 30 N 20

F i g. 10. Ages of the ships involved in groundings, collisions

and other casualties.

z 20 25 20 15 10 30 \ \ 10 5-9 10-14 15-19 20 SHIP ASE 1960-61 - - 1962-63 1965-65 1966-67 -I' 1968-69 D-4 s-s io-is is-ig 20-24 25-29 SHIP ASE G ROUND ING S COLLISIONS

FIRES ANO EXPLOSION

30 AND OVER

20 30 40 50 60 70 80 90 100

STERN CENTER OF HULL DAMAGE IN ROW PERCENTAGE OF LENGTH

F i g. 12. Distribution of centers of damages of all casualties.

A total of 104 cases.

F i g. 11. Age groups of ships involved in accidents during the periods of two years.

2D

11

F i g. 13. Distribution of centers of damages in collisions and in groundings.

G ROU ND INES

_ __

F i g. 14. Distribution of damage length in collisions (29 cases) and in groundings (72 cases).

5, 60 7 80 90 iDO 110 120

DAMAGE LENGTH III METRES

3D

20 -

10

-Distribution of the center of the damages of groundings

and collisions is presented in Fig. 12. According to this distribution, 72 % of the damages locate forward of the 1/2 L. The frequency function of this sample as a

poiy-nomial of fourth degree is

f(E) = 166.1 - 301.7

+ 192.4 E2 41.70

+ 7.86

E = x/L, x is distance of the center of damage from the AP and L is the length of the ship. This distribution

differs from the distribution obtained e.g. by Wendel [6] and Riepe [7]. On the other hand Aleksandrov [8] obtains a somewhat similar distribution. 1f distributions are taken

separately for groundings and collisions they differ in

character as can be seen from Fig. 13.

The distribution of damage length is given separately for groundings and for collisions in Fig. 14. They differ a great deal from each other, median value of the former is 19 m and the latter 3 m. Distributions of penetration

in groundings and in collisions are presented in Fig. 15.

Penetration in groundings was less than 10 % of the

ship's depth in4O cases which corresponds to 75 % of the total number of cases where depth penetration was given.

This indicates that the fitting of a double bottom

construction to tankers does not by any means totally prevent oil outflow in groundings. Also one should take

LOLL IS IONS

N

F i g. 15. Distribution of penetration as percentage of ship depth in groundings (53cases) and as percentage of ship breadth in collisions (41 cases).

2 31 '

'5

60I 70 I PENETRATION IN PERCENTAGE OF SHIP BREADTH 5 20 G RO UND INES 75 CASES io LOLL 151005 29 CASES 30 '.0 50 60 7 80 90 100 1 20 10 20 30 10 20 30 40 50 60 70 80 90 100

STERN CENTER OF HULL DAMAGE IN BOW PERCENTAGE OF LENGTH '.0 - 20-GROUNOINGS N 20 30 PENETRAI ON IN PERCENTAGE OF SHIP DEPTH

6

into account the fact that the fitting of double bottoms to tankers might increase the draught of the ship and thus increase the probability of grounding. On the other hand the double bottom changes the rigity arid strength properties of the bottom and affect the whole grounding

process at least in high-energy groundings. A comparative

statistical study of the grounding damages of the dry-cargo ships and tankers might bring insight into this problem.

The fitting of the tanker by means for closing the

breather valves as proposed by Japan in IMCO [2] would

be a more efficient and immediately applicable counter-measure to oil outflow in groundings in the Baltic area. Generally the freeboard of the tankers sailing in this area is small and thus the underpressures due to closing of breather valves are small and the strengthening of decks

might not be necessary.

Visibility and Weather Conditions

Information on visibility at time of casualty could be obtained in 196 cases. In 93 cases (48 %) the visibility was good. In Fig. 16 visibility conditions are divided

according to the nature of the casualty. Weather distribu-tion in a total of 194 cases is presented in Fig. 17. This distribution corresponds roughly the weather

distribu-tion in the area. In 114 cases (59 %) weather was good at

the time of the casualty. In 30 % of the casualties both visibilit,' and weather conditions were good. This leads to the conclusion that human factors are affecting the casualty rates. In bad weather and in poor visibility conditions there are generally more men on the bridge and they are more on the alert and the probability of

human error in decision making is less.

The present tendency to try to prevent the casualties by new instruments which facilitate the navication in

poor visibility conditions is thus one-sided. Attention should also be paid to the human factors.

Oil (,utflow

Information on oil outflow was obtained in only 9

cases. The total sum of thesereported amounts of leaked oil was 769 tons. In 81 cases oil leakage was reported to be O and in 178 cases there was no information atall

available.

That this sample is very small and non-representativeis

apparently a consequence of the fact that some five or six years ago practically no attention at all was paid to

the oil

leakages. Now this attention is excessive and

influences the information given.

The Japanese have computed the amounts of oil, which probably would leak out in tankercasualties [5]. According to this research the probable ratiobetween the

volume of oil outflow and the total

transported oil capacity in tanks in Japan is 0,07 in the case of a fully

loaded tanker. The total of the deadweights

of the

tankers involved in casualties in the Baltic area in loaded

conditions was 844 000 tons. The ratio between the

N 50

30

0-3.5

F i g. 16. Visibility distribution at the time of casualty.

Sample size 169.

GROUND INGS COLLISIONS FIRES AND EXPLOSIONS

A-5.5 6-7.S

BEAUFORT SCALO

5-1 2

F i g. 17. Weather conditions at the time of casualty. Sample

size 194.

cargo tank volume in cub. metres and deadweight in tons can be taken as 1,25 and the total tank volume of these tankers is thus approx. 1055000m3. According to

this the probable amount of leaked oil should be

74000 m3 = 66000 tons and the mean value is then 6600 tons/year. This figure is probably overestimated because of the fact that the conditions in Japanese tanker transportations are different, tankers are larger in size

and the risk of total loss is bigger.

Conclusions

In all fields the cause of accidents has been shown to depend on the interaction of many factors. In this study

the selection of random variables and the sample size are

far too small and the information on human factors diminutive so that it is not possible to get a reliable

50

-N

30

N 20

coherent picture about the tanker accidents in the

Baltic, Gulf of Bothnia and Gulf of Finland. Et is to be regretted, that no data was obtained on the casualtiesto

the tankers from The Soviet Union. This will restrict the validity of the results of this research as a regional

research. However some intermediate conclusions can be drawn:

The dominating casualty group in the Baltic area is

groundings; the distribution is groundings 56 %,

colli-sions 35 % and fires and explocolli-sions 9 %. In harbour approaches the number of groundings is twice the

number of collisions.

The highest casualty rates are found in The Danish

Sounds 41 % and in approaches to the harbours 42 %.

Only 6,5 % of the casualties took place at open sea or

coast.

The total number of casualties is slightly increasing with time in relation to the total number of ships sailing in this area. The relation between the different groups of casualties is approximately constant in long

time intervals. Seasonal distribution indicates the highest rate of casualties in December and January and lowest

in June and July. The frequency of

groundings is highest during the autumn.

The probability of casualty is twice as great in loaded

condition as in ballast.

In 25 % of the groundings, where damage penetration

was given, this penetration was higher than 10 % of the ship depth.

More than half of the casualties took place in good visibility conditions. Thus human factors are strongly

affecting the rate of casualties.

if the international co-operation of maritime organisa-tions is extended to include also this data collection.

Acknowledgement

This investigation was carried out in the Ship Hydro-dynamics Laboratory of the Helsinki University of Technology. I would like to express my gratitude to Mr. H. Lindroos, Mr. V. Novitsky and others who contributed to this research. The kind co-operation of the Finnish and Swedish Maritime Administrations,

numerous Shipowners and major Classification Societies

made the collection of necessary data possible. This investigation has been financially supported by the Wihuri-Foundation and the Finnish Commitee of

Tech-nical Sciencies. References

A Consideration on the Relationship between Subdivision Arrangement of a Tanker and the Volume of Oil Outflow. IMCO, DE 1/12 Jan.

1968.

Construction of the Tanker Aimed at Limiting the Volume of Oil Outflow When Grounded. IMCO, DE 1/13 Jan. 1968.

Structures of Tankers Restricting the Volume of Oil Outflow in the Case of Collision. IMCO, DE II/lo Sept. 1968.

Construction and Equipment of Ships Carrying Oil or Other Hazardows Cargoes from the Point of

of View of Preventing Pollution of the Sea by Such Cargoes. IMCO, DE 11/12 Oct. 1968.

Studies on the Construction and Equipment of Ships with a View to Avoiding or Limiting the

Escape of Oil

in

the Event of Collision or

Stranding. IMCO, DE 111/25 April 1969.

K. Wendel: Die Wahrscheinlichkeit desÙberstehen

von Verletzungen. Schiffstechnik Bd. 7. 1960 Heft 36.

W. Riepe: Statistische Untersuchungen über

Leck-grössen bei Schiffsunfällen. Hansa Bd. 103. 1966

Nr. 18.

M. Aleksandrov: Probabilistic Approach_{to the}

Ef-fectiveness of Ship Systems. SNAME, Nov. 1970.

Paper no 10.

Thomas D. Mara: Human Factors in ShipControl.

Volume I. Analysis of Ship Operations, Operator Capabilities and Recommended Bridge

Arrange-ments. General Dynamics Corporation. Groton. January 1968.

7

This study is too one-sided for the planning of effective

counter measures against the tanker casualties in the Baltic area. Specially the human factor forms an un-known element of risk should be studied by experts.

Furthermore, in collisions there are two parties so not [5]

only the tankers but the whole maritime traffic in the Baltic area should be considered. For reasons presented in this paper at least the following measures should be taken under consideration:

Passages to oil harbours should be improved. New [6] harbours should be located at open coast.

In approaches to the harbours and in the Danish Sounds and the Kalmar Sound the use of two mates on the watch should be considered, if there is no [7] pilot on the bridge.

The number of pilots on duty should be increased in the autumn season.

The possibility of closing the breather valves of the [8]

cargo tanks in case of groundings should be studied.

After work lasting one year only 102 of the 268 cases were satisfactorily declared. This is a poor result and one

arrives at the conclusion that a great deal of irreplace- E9]

able information is continuously wasted by time. This can be avoided

in the future by a systematic and

continuous data collection of all maritime accidents immediately after the occurence. This can easily be done

TECHNIC A L

U N IVE R SIT Y

SHIP HYDRODYNAMICS LABORATORY, OTANIEMI, FINLAND

OIL TANKER DAMAGE CARD

Date and place of casualty

Nature of casualty (collision,stranding,etc.)

Name (or number) of damaged ship

Length between perpendiculars L

m. Moulded breadth B

..m

Moulded depth D

m.

Draught before damage:

amidships d

m (or fore

m and aft

m)

Number of cargo tanks

, number of ballast tanks in cargo

tank area

SIDE DAMAGED

APPEND I

containing before the casualty total

tons of oil

Approx. amount of oil leaked into the sea

due to damage

Additional data to be supplied if available

1. Wind and sea (Beaufort scale) at time of casualty

XI

BOTTOM OR BILGE

DAMAGED

Dimensions and location of damage (see sketch

above):

Distance from AP to centre of damage X

m

Location: side I bottom / bilge

Distance from base line to the lower point

of damage Z

.... m

Length of 1

z

m. Height of h

m. Penetration b

z

... m

If damage is located in the bottom, give also

the distance of the

center of damage from the center

line of the ship y z

.... m

Loading condition: 100 per cent load /

per cent load/ballast

Number of oil tanks in damage area

,

of these tanks were

tons

Speed at time of impact,

damaged ship v

z

(in knots)

second ship V2 z

.

(in case of collision)

Visibility at time of casualty

4 Radar in operation yes / no

Manual / Autopilot steering

Pilot on the bridge /

no pilot

Casualty took place in the open sea

I

meters (depth) passage