The safety of small vessels at sea is a problem that rarely hits the headlines. Rather, it is the dramatic casualties of larger ships that spark public interest and concern and safety initiatives developed by the maritime industry tend to focus on large seagoing vessels such as tankers and bulk carriers.

The development of safety criteria for big ships (eg bulk carriers and tankers) is being progressed by IMO, which has recognised the need to base this development on the safety level approach. This is a challenge for the maritime industry as a whole and particularly for classification societies. To meet the challenge, Polski Rejestr Statków (PRS) is building risk models assessing the probability of ship sinkings due to structural failures. The risk models assume various scenarios of progressing structural failure, as well as mathematical models enabling the determination of structural failure probability in the sequence of events of a given scenario. This approach may lead to more rational safety criteria.

PRS believes that the oft-sidelined issues related to the safety of smaller vessels also require action. Its new Research & Development Division, established in 2006 and led by Dr Stefan Grochowalski, is redressing the balance by progressing research into the area of small vessel survivability in severe weather conditions.

Depending on individual ship type and size, different aspects affect safety. In the case of large bulk carriers or tankers, the strength of the ship structure is the decisive factor, while in the case of smaller vessels, dynamic stability is the predominant factor.

Existing stability regulations governing small vessels are not sufficient. This is reflected in accident statistics, which indicate that annual casualties are several times more likely to involve smaller vessels than they are large ships.

The main reasons for stability problems in smaller vessels and issues affecting stability standardisation include:

• an unfavourable relation between stability capability and the magnitude of external heeling moments (waves, wind);
• weight shifts that cause more significant changes in the centre of mass, thus creating dramatic changes in stability;
• a large variety of types, designs, operational procedures, stability features, etc, which make it difficult to develop a unified approach to capsize prevention; and
• inadequate stability criteria and standards, which are based on static stability in calm waters rather than a vessel’s real dynamic behaviour in waves.

Particularly alarming is the safety of fishing vessels, which constitutes the most acute and urgent problem. Small vessels, especially fishing vessels, often lack technical documentation, are subjected to hull conversions and equipment alterations without the appropriate supervision, demonstrate poor technical condition due to a shortage of financial resources for technical improvements and, in some cases, are manned by insufficiently skilled crews.

There is an urgent need for new rational criteria and standards based on vessels’ real behaviour in extreme waves and not on static considerations.

The overall objective of the PRS project is to increase the safety of vessel operations in extreme weather conditions and significantly reduce the number of accidents through the development of:

• new survivability standards and regulations based on vessel dynamics in extreme weather conditions (breaking waves, freak waves, wind, etc) which will provide safety against capsizing and foundering. These will form the basis for improvement in ship design so that intact stability will be better assessed, thus reducing the risk of capsizing;
• operational guidelines for individual types of ships to enhance and supplement the their inherent stability;
• on-board decision support systems;
• instruction and training courses to educate crews about the basics of stability safety and to demonstrate how they can avoid critical mistakes.

The initiated development of criteria and standards preventing capsizing and foundering in extreme waves involves:

• theoretical analyses of physical phenomena;
• development of mathematical models and computer software;
• model tests;
• systematic numerical simulations;
• statistical analyses of real accidents versus “safe” vessels;
• development of rational criteria preventing capsize; and
• development of safety standards and regulations.

Criteria and standards, once developed, require support in the form of practical tools for the verification of ship geometry characteristics and the examination of their actual safety levels. Such tools will significantly reduce smaller vessels’ risk of capsizing and foundering in extreme weather conditions, thus minimising the loss of human life and material goods in marine operations and reducing marine environmental pollution.

One such tool is a program designed by PRS to measure small vessels’ dynamic stability by simulating vessel movement with green water on deck. The theory and algorithm developed on the basis of R&D studies initiated by PRS last year have resulted in computer software that enables the simulation of small vessel motion in irregular waves (and with water on deck) – right up to the point of capsize.

PRS is confident that the criteria and standards being developed, along with the tools for their implementation, should improve the safety of newbuildings in the small vessel sector. However, the problem of the large fleet already in existence is also waiting for a readily acceptable solution.

The safety of existing small vessels needs to be evaluated. To do that, methods enabling the reconstruction of the ships’ body lines and simple methods for measuring the vessels’ centres of mass also need to be developed – activities in which PRS is already engaged.

It must be remembered that the small vessel sector is governed by certain peculiarities. For example, in the case of fishing vessels operations are based largely on tradition rather than on vocational education. Such ships are also very often family property and so owners can be either reluctant or simply unable to put substantial investment into safety improvement. The sector as a whole also forms a significant lobby group that strongly resists what it often sees as unnecessary and costly methods for improving safety. Therefore, the method for improving the safety of small vessels must be straightforward and easy to implement. It will be a challenging task for maritime administrations, classification societies and the small vessel sector itself, but a challenge that urgently needs facing.

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For further information contact: Anna Stajewska, Polski Rejestr Statków
Tel: +48 58 341 17 64, Email: mailbox@prs.pl, Website: www.prs.pl

Issued by: Sharon Cunningham, Dunelm Public Relations

Tel: +44 20 7480 0600, Email: info@dunelmpr.co.uk, Website: www.dunelmpr.co.uk