By David S. Wiggins of C.I.I. (Overseas) Limited, Dubai
Throughout the marine industry, over the past few years there have been a large number of accidents with davit-launched totally-enclosed lifeboats. Most of these involve injury to crew members of some nature and, particularly disturbing, death in a significant number of cases. With few exceptions the incidents investigated have involved "on-load release hook mechanisms".
It is important to define which type of lifeboats are being discussed. This article covers totally enclosed lifeboats lowered from davits, the majority of which have on-load release hook mechanisms. These are not free fall lifeboats which are launched from sloping ramps and fall into the sea end on.
Following the investigation of many of these accidents, the necessary actions by ship owners and managers in their loss prevention procedures to minimise them become apparent.
Although there are many variations to the causes of these accidents due to human error and the happening of secondary or tertiary failures, the root causes can be summarised under four headings:
(1) Poor original design of lifeboats and hook release mechanisms.
(2) Poor maintenance, or maintenance unrelated to the specific design of hook release mechanisms.
(3) Little attention paid to lifeboat operations.
(4) Lack of training in the various types of hook release mechanisms. This relates to ships crew and dry-dock staff.
This article refers to details from specific incidents and uses the lessons learned to suggest items to be included in owners and managers loss prevention programmes.
It should be noted that The Safety of Life at Sea Convention (SOLAS) is only a guide to sea-goers providing them an envelope of safe practices within which to work. The responsibility for applying it and detail design is in the hands of the owners, classification societies, and equipment designers.
2. Lifeboat design
Lifeboats are designed, and are tested, to fall from a height of 3 metres with a full complement of crew each having an average weight of 75 kg. Various incidents have shown that:
The boat hull is strengthened in the keel area to withstand the impact forces, assuming the boat falls straight downwards onto the keel. In some cases where the boat has turned during its drop to the water, the areas of the hull near the keel have broken open due to the impact.
The seating in many boats has been provided to meet the basic requirements of SOLAS. This is not considered to be adequate to fully protect the crew when falling from 3 metres.
(1) Some boats only have seats without support for the head and back.
(2) Some lifeboats have a pad for the head but in some of the seats, particularly next to entrance hatches, have no support for the back so that when the boat hits the water the back bends causing spinal injury.
(3) The minority of boats witnessed have been fitted with in-built foam pads to sit on. These pads prevent impact fractures of the spine.
(4) A lap belt is not sufficient to hold crew in place during a load release. If the boat does not hit the water, level, then impact fractures of the wrists can happen if
a safety harness is not fitted to hold the body in an upright position.
3. Hook release mechanisms
The design, operation and maintenance of these mechanisms is the area that has to be addressed in detail by all parties concerned.
Many types of lifeboats have hook release mechanisms that enable the crew to release the falls when the boat is on the water. The objective of on-load hook release mechanisms for totally enclosed lifeboats is to enable the hooks to be released from within the boat in the event that some problem occurs with lowering.
These boats are designed for the complete complement of crew to enter the boat at the embarkation deck, close the hatches, operate the davit brake from within to lower the boat to the water, and then cast off the hooks.
This system is to enable ships crew to leave a burning vessel and protect them from smoke, fumes, and flames while being lowered to the water and moving away from the ship.
If the lowering of the lifeboat is interrupted by external influences and it is no longer under the coxswains control, he has the option of releasing the hook mechanisms and letting the boat fall to the water.
It should be noted that the majority of incidents happen when the boats are being lowered to the water during lifeboat drills. These are normally carried out when a tanker is waiting for cargo and therefore is ballasted when the height of the lifeboat above the water is much more than when the tanker is fully loaded. In many incidents the lifeboats have been released when higher than 3 metres above the water (SOLAS requires a lifeboat to be designed to fall from this height).
There are many variations in design of hook release mechanisms which cannot be discussed in detail in this article. Nevertheless some of the causes of incidents are listed below.
(1) In order to prevent flame entering the boat and compressed air from leaking, out some hook mechanisms are totally enclosed. This prevents visual inspection and maintenance to being carried out.
(2) In many cases it is not possible to clearly obtain good visual or body access to these mechanisms to enable proper maintenance, resetting of the hooks before recovering the boat. Whether the mechanisms are operated by rod or cable it is difficult to adjust them at the adjustment point, and see the positions of the hook release pawls. It is essential that when the mechanism is operated both hooks release at exactly the same time, and that when the hooks are reset the pawls lock at the same time.
(3) Many of the hooks, pivot pins, and locking pawls are made from carbon steels so that corrosion plays a big part in preventing release of the hook mechanisms. This can also cause one hook to release before the other. They should either be made from stainless steel (316L), or galvanised.
(4) These lifeboats are designed so that they can be lowered to the water immediately the crew are on board. As a result the weight of the boat is hanging on the davits all the time. This means that the only time the hooks can be properly maintained or completely overhauled is when the vessel is at anchor or at the dry-dock, the boat has been lowered to the water, and the hooks released.
(5) Some mechanisms, due to wear of their parts or fastening methods of operating rods or cables, have lost motion when operating them. This once again is a cause of one hook being released before the other, and the cause of difficulty in resetting them.
(6) Injury has also been caused due to the coxswain having to remove his safety harness so that he could move his body to operate the hook release mechanism. In this case the boat was above water level and the coxswains seat was so poorly constructed it broke when the boat hit the water.
(7) In many cases the designers or manufacturers of the lifeboats do not give sufficiently detailed information on the construction of the mechanisms and the maintenance of them.
Many maintenance problems are due to poor design as mentioned above, but there are others that are due to poor practices.
(1) SOLAS states that the falls shall be turned end for end not more than every 30 months and replaced at intervals of not more than five years. "The falls" refers to the wire ropes. There is no legislation for the replacement of the other components that form part of the davit systems. Incidents have happened where the bottle screws at one end of the falls and the chain connecting the other end of them to the boat hooks have failed due to corrosion, and lack of NDT inspection during dry-dock periods.
(2) Depending on the capability or attitude of the crew, and owners or managers procedures, the maintenance of some boat hook mechanisms have been neglected by one crew and when found to be corroded by the following crew they have been partially greased and then hit with a hammer until free. In these cases the mechanisms should have been completely stripped down, repaired properly and then reset.
(3) Lack of maintenance training has caused some incidents. Starting with poor maintenance manuals from the manufacturer and then lack of specific training by the owners/managers in the maintenance and setting of hook mechanisms. This also applies to dry dock companies who are responsible for overhauling the lifeboats during the four year dry dock.
In a number of cases incidents happen and injuries to crew can be made worse due to lifeboat operations.
(1) In a surprising number of cases incidents have been caused, or made worse, by lifeboat painters having been fastened off too short or caught on something while the boat was being lowered during lifeboat drill. This is due to lack of fore thought or attention being paid to such an important function as safety drills.
(2) When a lifeboat is being lowered with crew on board during a safety drill it is important to emulate a real situation. This means that the lifeboat hatches should be closed, the lifeboat lowered by the coxswain from within the boat, and the hook release mechanisms operated when the boat is on the water.
(3) The traditional method for the crew to enter the lifeboat has been that they muster, put on their lifejackets and enter the boat. With totally enclosed lifeboats this is not good practice for, when using the permanent buoyancy type of lifejacket, it is difficult or impossible to fasten the safety harness. SOLAS refers to this.
Ship owners and managers should review their loss prevention procedures in light of lessons learned from these incidents.
(1) Hook release mechanisms must be kept maintained and adjusted so that boats can be lowered to the sea at the five minutes notice required in SOLAS. Lifeboats should be able to be recovered, the hook mechanisms locked and the boat hoisted back to the embarkation deck; This is without crew members being injured.
(2) In some cases hook release mechanisms should be completely replaced by those similar in design to the TOR or MILLS systems. (The TOR hook arrangement follows). These give prevention of unplanned release by having a hydrostatic operating lever release, plus two other operations necessary to release the hook mechanism. In a dire emergency the hydrostatic release can be by-passed. This type of system also has a pendant link that can be attached to the davit to take the weight of the lifeboat during on board maintenance.
(3) No system is 100 per cent fool proof. Therefore it is necessary to protect crew members in the event of the boat falling after the on-load release mechanism has been activated. This means that each seating position should have a head rest support for the lumbar region of the back, plus a padded seat. Harnesses should be used as opposed to a lap belt, and crew should not wear permanent buoyancy lifejackets when entering the lifeboat.
(4) Detailed manuals regarding construction, operation and maintenance should be obtained from lifeboat or release mechanism manufacturers, and detailed training given to crew by owners and managers on hook release mechanisms and lifeboat operations.
(5) It is also believed that classification societies should become more deeply involved in the whole aspect of loss prevention related to ship safety equipment and particularly on-load release mechanisms.
David Wiggins is the director of C.I.I. (Overseas) Limited which operates out of Dubai in the United Arab Emirates. C.I.I. (Overseas) Limited offers specialist engineering services to the marine and petroleum industries. Part of these services includes the investigation of equipment and plant failures for insurance purposes. Over the past three years David Wiggins has investigated a number of incidents involving injury and death as the result of lifeboat equipment failure.