Class society concerned at trawler stability

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 classification societies in particular. To meet this challenge, PRS is building risk models assessing the probability of ship sinkings due to structural failures.

At the same time, PRS believes that the oft-sidelined issues related to the safety of smaller vessels also require action. Its new Research and 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.

PRS believes that 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 larger 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;

• Inadequate stability criteria and standards, which are based on static stability in calm waters rather than a vessel’s real dynamic behaviour in waves.

Fishing vessels highlighted

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 conditions 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 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.

Water on deck

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 large fleet already in existence needs 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.

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A case of capsizing

A report by the UK’s Marine Accident Investigation Branch (MAIB), published in February this year, highlights some of the stability problems inherent in small fishing vessels.

At about 09:30 on 23rd May 2005, the small fishing vessel Bounty capsized and sank in Lyme Bay, off the UK south coast as a result of the vessel catching her trawl on a seabed obstruction at the time. The two crew onboard found themselves in the water, with lifebuoys, but were able to board the vessel’s liferaft and were rescued about five hours later.

Bounty had departed Brixham, in Devon, earlier that morning for a day of bottom trawling. The weather was initially fine, but deteriorated as the day progressed. The snagging occurred during the first trawl while the vessel was stern to the wind and sea.

Engine power was used to try to free the vessel, but a wave broke over the stern and swamped the working deck. The floodwater was trapped within the vessel’s shelter and did not have time to clear through her freeing ports. The vessel listed to port and then wallowed for about 20 seconds before capsizing.

Crew escape

The crewman, who was at the stern, jumped overboard as the vessel listed to port. The skipper, who was at the forward end of the working deck, thought about retrieving lifejackets from the wheelhouse, but decided there wasn’t time and evacuated through a hatch in the starboard side of the shelter as Bounty was capsizing.

Bounty inverted fully and then sank by the stern. Two lifebuoys floated clear and the crew used these as buoyancy until the liferaft surfaced and inflated. The two survivors boarded the liferaft, and although only about four miles from shore, they had to wait nearly five hours, until 14:28, before they were seen and rescued by the crew of the UK Royal Fleet Auxiliary tanker Black Rover. The survivors were subsequently landed ashore at Portland.

Inadequate freeboard

There are currently no minimum requirements for stability, freeboard and loading of small fishing vessels. Bounty had inadequate freeboard. The lack of freeboard, and consequent lack of buoyancy aft, were contributory in causing the wave to break over the stern. The lack of suitable minimum freeboard requirements has been recognised in numerous accidents previously investigated by the MAIB and, consequently, action is already being taken to improve regulation in this respect.

Bounty had been built at about the time of the introduction of the UK’s Marine and Coastguard Agency’s (MCA) Small Fishing Vessel Code and the Seafish Construction Standards of 2001. The Code required compliance with Seafish standards, but only regarding the construction of the hull. Seafish standards for outfit are only recommendatory.

The freeing ports on Bounty were of inadequate size and did not meet the current Seafish minimum standard. However, freeing ports are considered part of the outfit, and therefore the minimum standard was not compulsory. In any case, the MAIB believes the existing minimum standards for freeing ports are insufficient where an enclosed shelter is fitted, and a recommendation has been directed to Seafish in this respect.

Liferaft benefit

The benefit of carrying a liferaft was graphically demonstrated in this case as it almost certainly saved two lives. The owner/skipper was not obliged to carry one; the fact that he did, showed a good attitude to safety. The value of liferafts on small fishing vessels has already been recognised, and their free issue by various branches of government is currently being arranged. MAIB fully supports these initiatives.

During the investigation, MAIB discovered Bounty had not been inspected by the MCA until more than three years after she had been built, shortly before the vessel was sold on to new owners. MAIB believes it would be beneficial if all new small fishing vessels are inspected before entering service. A recommendation has been made to the MCA in this respect.

Other cases

Three other fishing vessel accidents, which involved poor stability or freeboard standards in small fishing vessels, have been investigated by MAIB recently:

• Charisma, which capsized in January 2002 with the loss of one crew member. A heavy load of mussels was carried on deck and the manual bilge pump was missing with poor sealing of the open overboard discharge pipe. The heavy load submerged the discharge pipe, which led to flooding.

• Kirsteen Anne, which sank in December 2002 with the loss of two lives. Poor stability was caused by modifications made since she was built, including increased weight of fishing gear. Undetected flooding also contributed to her loss.

• Amber, which sank in January 2003 with the loss of the skipper. Her stability was compromised when a rock was caught in her net and by extensive modifications.

Investigation reports for these accidents can be viewed on the MAIB website at www.maib.gov.uk.

These cases led to a recommendation being made to MCA to develop a stability, freeboard and loading standard for small fishing vessels. MCA has commissioned a research project to look at these aspects. After the loss of Bounty, an MAIB database search was carried out. Between January 1991 when MAIB’s database was established, and the capsize of Bounty, 64 UK fishing vessels under 12m in length have capsized resulting in 38 fishermen losing their lives. A significant proportion of these losses related to inadequate stability or freeboard.