Accidents with Lifeboats and Rescue Boats. Design Failures (1)

On February 10, 2013, when the crew of the cruise ship “Thomson Majesty” was conducting a training exercise with lifeboats in the calm waters of the port of Santa Cruz de La Palma, they added to the long list of accidents and incidents during exercises regulated by SOLAS. On this occasion, the tragedy resulted in five fatalities and three serious injuries. The incident received extensive media coverage worldwide.

Maritime journalist Juan Carlos Díaz Lorenzo, in his blog “Del acontecer marítimo,” reported on the events with a detailed follow-up of the tragedy.

The seriousness of the accident prompted the Maltese government to issue a SAFETY ALERT in the same month of February, initially pointing to the probable cause of the cable break as corrosion deterioration.

The Malta Maritime Authority has published the final report of the accident that occurred on the “Thomson Majesty” (MARINE SAFETY INVESTIGATION REPORT NO. 05/2014). The purpose of publishing such reports is to alert professionals in the sector so that they can draw conclusions that enhance safety in their respective roles aboard ships and on land. The “lesson learned” is of great interest when carefully analyzing the circumstances of the accident and critically and constructively questioning the conclusions drawn.

As part of the aforementioned report, Annexes containing highly relevant information for an objective study of the incident are also published:

Annexes A, B, C, D, E.- Certificates of the cables, including their history. Report on Wire Rope Load Test. Annual inspection certificate according to MSC1206. Certificate of the last five-year inspection. Inspection report from the Classification Society DET NORSKE VERITAS.

Annex F.- Destructive and non-destructive tests to which the broken cable was subjected.

Annexes G, H, I, J, K.- Report on the lubrication used in the cables of the davits. Report issued by the davit manufacturer SCHAT HARDING.

Safety alert issued by the MSIU (Marine Safety Investigation Unit).

Finally, two annexes with details of the cable and general information on use and maintenance, WIRE ROPES AND THEIR USES, are included, where we can find a possible cause that contributed to the cable break. A document of utmost interest that on page 10 “LIFEBOAT WIRES” clearly and precisely outlines the existing risks that can lead to serious accidents.

There have been many accidents in recent years during regular lifeboat drills. In issue number 88 of the magazine “Marina Civil,” an interesting report was published: MARITIME SAFETY: “How to Increase Safety in the Use of Lifeboats.”

On May 26, 2006, the IMO published MSC1206, later revised by MSC.1/Circ.1206/Rev.1 on June 11, 2009. The first paragraph lists seven groups in which accidents with lifeboats and rescue boats fall. Among them, number 7 states, “Design failures different from those related to tension release devices.” It is therefore recognized that properly certified devices can have design failures. On ships, we must pay maximum attention to identify these potential failures.

In the BOE (Ministry of Development), Royal Decree 38/2009, of January 23, is published, regulating the tests to which lifeboats and their launching means are subjected and authorizing their execution by specialized companies. It regulates the weekly and monthly maintenance and inspection to be carried out by the crew, and the annual and five-year inspections corresponding to the manufacturer or authorized companies. In BOE number 15 of January 17, 2013, amendments to the IDS Code were published, adopted through the IMO MSC 320 (89) resolution.

The annex of the mentioned regulation includes the new requirements that must be met by the release mechanisms of survival craft. Prior to this regulation, amendments to Chapter III of SOLAS were published in BOE 292 of December 17, 2012, establishing that this regulation will apply to all ships during the first scheduled dry dock entry after July 1, 2014, but no later than July 1, 2019, all release mechanisms must comply with the requirements established in the amended IDS Code.

In MSC1326 CLARIFICATION OF SOLAS RULE III-19, the IMO agreed to recommend that it should not be required for the assigned crew to be aboard the lifeboat during launching, which is at least alarming, considering that this recommendation stems from the large number of accidents and incidents that have occurred during launching and recovery during mandatory drills, generally in the calm waters of ports or at anchorages in good weather. Despite this recommendation, some lifeboats have been certified as rescue boats.

In the annex of MSC.1-Circ.1327 Guidelines for the Installation and Use of Fall Prevention Devices (FPD), the requirement for tension release devices is justified in the first paragraph. It is strictly prohibited to drill the suspension system to adapt a safety pin unless the Maritime Administration approves such a modification. Cables or chains should also not be used as they would not absorb the impact in the event of premature hook opening. The use of synthetic material strops approved by the Administration and meeting the established Certification requirements is allowed as a fall prevention device.

Ultimately, the IMO openly recognizes the existing problems with the release devices currently installed on certified lifeboats, issuing the Circular of the Maritime Safety Committee MSC1392, dated May 27, 2011, which outlines guidelines for the evaluation and replacement of lifeboat release and recovery systems.

As we see, the issue of safety in the launching and recovery of lifeboats is quite complex. However, not only have release devices been the cause of serious accidents and countless unreported incidents known in the sector: Breakage of suspension cables, generally attributed to corrosion deterioration due to lack of maintenance, including inadequate lubrication.

The same problem noted can be observed in many of the davits for launching and recovering rescue boats and fast rescue boats. The accident that occurred on the “Tombarra” may be another case where the final conclusions attribute the cause of the cable break to factors other than shear cutting of the sheave.

For rescue boats, lifeboats, or life rafts, a key and fundamental part of the equipment is the devices for launching and recovery: The davits.

Davits can be found in the sector from very different manufacturers and types. However, a common element among all is the sheaves and blocks configured as a simple pulley rig in most of the different models where double strips of steel cables (wire fall) are used.

In a pulley system, an important risk is that the cable skips some of the sheaves that direct the cables. Namely, a cable can skip the sheave while rotating for various reasons, the main one being misalignment:

- which may originate from the cable getting caught on the edge of the sheave and coming off.

- due to the “whip effect”: this phenomenon occurs when a violent movement (sticking of translation wheels or three-dimensional accelerations of the ship) induced to the cable causes it to sway in such a way that it can get caught on the edge of the sheave.

The above should not have major consequences when analyzed statically, that is, with the sheave not rotating. Things get complicated and the risk of cable fracture increases extraordinarily when the cable skips the sheave while continuing to rotate.

Once the cable has skipped, at this point we could still admit a controlled risk: The cable skips the sheave and gets trapped on the axis of the sheave if it is from the inside, or stops performing its function if it is from the outside. If the operator notices and stops operating the winch, the damage can be limited to the deterioration of the cable, generally requiring its replacement.

In any case, the most likely scenario for a cable in good condition is that the safety devices of the motors automatically stop the winch operation, reducing the possibility of cable breakage due to tension.

The extreme danger occurs when the sheaves are protected in their working area by a guard, beam, pins, etc., generally mounted to prevent the cable from skipping the sheave. This adjustment with the edge of the sheave must be less than the diameter of the cables used. Misaligned cable and following the forced rotation to pass under the protection of the sheave, we have activated a perfect shear, with the result that we can easily imagine.

Analysis of the Problems in Conventional Davits

The rigging generally used for gravity davits is a simple pulley system on each arm. This system consists of one end of the anchored steel cable passing through a series of sheaves conveniently distributed over the structure and arms of the davits, as well as through the block, which serves to connect the rigging to the boat's release device. The other end of the cable runs symmetrically along the arm of the davit so that its pull is even and balanced, ending at the winch drum.

We may encounter systems formed by a variable number of sheaves on each davit arm, symmetrically distributed on each side of the arm to guide the cable to the winch drum, passing through the sheave of the block. The most common installation consists of a single winch with two drums. For lowering, only the force of gravity is required. For hoisting, it is generally powered by an electric motor, synchronized and adjusted so that when hoisting for recovery, the boat is moved evenly, and as the blocks reach the ends of the davit arms, both are moved synchronously to the stowage and securing position of the boat.

The system has an end-of-travel device that stops the winch operation when the davit arms reach their stowage position. On the other hand, it should be considered that both hydraulic and electric drives do not have sufficient power to hoist the boat with its full complement of people. They are designed to launch them by gravity and not to hoist them fully loaded. This criterion gives us a wide safety margin regarding the resistance of a cable diminished by poor conditions, for example, due to corrosion.

Let us consider that SOLAS requires the renewal of cables every five years if the ends have been reversed, or every four without splicing, and in any case when deterioration is detected during inspection. Undoubtedly a wide margin of use for the worst conditions in which ships can operate. Of course, we must take into account the quality of the cables as well as relieve tension in them when at rest. Good practices, along with efficient lubrication, are essential.

For a system such as the one described, we can analyze how the cable can skip the sheaves. This can happen, either during monthly maintenance tasks where the cables are left slack when the boat is suspended from its system using the cables arranged for this purpose (not the cables for the maneuver of approaching the boarding place, tricing pennant), or if it is misaligned more than necessary to dock the boat alongside, at the boarding place, leaving the suspension cables slack, a bad practice.

As previously mentioned, in both cases the cable, when left slack, especially at the anchored part, where the sheaves do not rotate until the davit arm begins to pivot inward, can become misaligned. When releasing the tension of the maintenance cable or the approach cable, and then reapplying tension to the suspension cable, the cable can misalign and mount on the edge of the sheave at the end of the davit, becoming trapped between the edge of the sheave and the cable guard. Just at the moment when the block joins the davit arm and begins to pivot inward, the sheave that had the cable trapped begins to rotate, shearing the cable.

The cable can also skip out of the sheave due to misalignment caused by whip effects originating from violent and irregular movements of the davit arms due to sticking of the wheels that guide the arms along the track. The effect is the same as described above: Misaligned cable and mounted on the leading edge of the sheave, if it encounters a sufficiently strong cable guard, we already have the perfect shear. If we add to this that the cable has some corrosion or lack of grease, the result is catastrophic.

The solution to this failure could be to equip sheaves with lateral protection as installed on crane peaks, or on the blocks themselves for the hoisting of lifeboats: The sheaves mounted on the blocks are fully protected laterally to prevent the cable from skipping when misaligned. Each of the sheaves, especially those at the end of the davits, should have the same type of protection to prevent the cable from skipping out of the sheave's throat. This is not the case in most davits designed for merchant ships. Generally, simple sheaves are used on a pivot axis with a plate or pins for protection to prevent the cable from coming out of the sheave, which, as we have explained, forms a shear.

It should be noted that in most cases of cable breakage, the weight supported by them was much lower than the weight with the total complement of people (8 people instead of 150 in the accident of the “Thomson Majesty”). Similarly, generally, both suspension cables do not break at the same time, and the second cable usually holds in such a way that it either pulls the suspension hook from its location or opens it. Given that the cables are of the same quality and have the same usage time, we should question the fact that one breaks and the other does not.

In accidents caused by cable breakage, the most general conclusion is to determine corrosion as the cause, due to defective maintenance, with the loss of original characteristics. The solution, obviously, involves replacing all cables that are in the same conditions, making the investment manageable and the ship's downtime minimal. Responsibilities become diluted. In the end, all involved are left with the idea that inadequate lubrication was the cause of the deterioration that led to the cable break in question: “Deficient maintenance of cables by the crew is the easiest conclusion, but not always the most accurate.”

References

https://delacontecerportuario.wordpress.com/tag/thomson-majesty/ Blog by Juan Carlos Díaz Lorenzo, DEL ACONTECER MARITIMO “A routine maneuver on the Thomson Majesty ends in tragedy.

February 10, 2013. - MSIU SAFETY ALERT 01/2013. Failure on lifeboat wire fall due to corrosion that resulted in five fatalities on the Maltese registered passenger vessel THOMSON MAJESTY.

MARINE SAFETY INVESTIGATION REPORT NO. 05/2014. Safety investigation into the failure of a lifeboat wire rope fall on board the Maltese registered passenger ship THOMSON MAJESTY. 201302/008. Annexes from A to K.

MARINA CIVIL magazine issue 88. DGMM “How to increase safety in the use of lifeboats.”

MSC.1/Circ.1206/Rev.1. June 11, 2009. MEASURES TO PREVENT ACCIDENTS CAUSED BY LIFeboats.

BOE No. 40 February 16, 2009. Royal Decree 38/2009, of January 23, regulating the tests to which lifeboats and their launching means are subjected and authorizing their execution by specialized companies.

In BOE No. 15 of January 17, 2013. Amendments of 2011 to the International Code of Lifesaving Appliances (IDS Code) adopted in London on May 20, 2011, by Resolution MSC.320(89).

BOE 292 of December 17, 2012. Amendments of 2011 to the International Convention for the Safety of Life at Sea, 1974, as amended, adopted in London on May 20, 2011, by Resolution MSC 317(89).

MSC.1/Circ.1326. June 11, 2009. CLARIFICATION OF SOLAS RULE III/19.

MSC.1/Circ.1327. June 11, 2009. GUIDELINES FOR THE INSTALLATION AND USE OF FALL PREVENTION DEVICES (FPD) - MSC.1/Circ.1392. May 27, 2011. GUIDELINES FOR THE EVALUATION AND REPLACEMENT OF LIFeboat RELEASE AND RECOVERY SYSTEMS.

Interim Factual Report. Marine Inquiry 11-201. Passenger vessel VOLENDAM, lifeboat fatality, port of Lyttelton, New Zealand, January 8, 2011. Approved for publication: February 2011.

User manual for cables. UNION. A brand of WireCo® WorldGroup. www.wirecoworldgroup.com.

MAIB. REPORT NO 19A/2012 July 2012. UK. Report on the investigation of the fatality of a rescue boat crewman on board TOMBARRA at Berth 3, Royal Portbury Docks, February 7, 2011.