UK MAIB Incident: No longer fit towline pennant causes injury - SAFETY4SEA - Safety4Sea

UK MAIB published its study connected the nonaccomplishment of a towline pennant and wounded to the unit connected committee the tug Svitzer Mercurius successful Southampton, England connected 22 December 2019.

The incident

On 22 December 2019, Svitzer Mercurius, on with the tugs Svitzer Ferriby and Svitzer Eston, was tasked to assistance the ultra-large1 instrumentality vessel CMA CGM Marco Polo up Southampton Water and connected to its berth astatine Southampton Container Terminal (SCT); Svitzer Mercurius was allocated the relation of stern tug.

At astir 1100, the master, main serviceman and main technologist from the tug Svitzer Alma, who had been appointed to the caller tug for the day, boarded Svitzer Mercurius astatine Ocean Dock, berth 45. At astir 1115, Svitzer Mercurius’s Dutch maestro unberthed the tug and handed implicit the helm to Svitzer Alma’s master. Under the Dutch master’s supervision, Svitzer Alma’s maestro began manoeuvring evolutions to summation an appreciation of the tug’s capabilities. This included mooring it alongside connected some larboard and starboard sides. Once complete, Svitzer Mercurius headed down Southampton Water to rendezvous with the inbound instrumentality ship.

As Svitzer Mercurius proceeded down Southampton Water, its maestro gave Svitzer Alma’s maestro support to thrust the tug during the towing operation. The Dutch maestro was alert of the section master’s acquisition and had seen him grip the tug.

At 1146, Svitzer Mercurius met CMA CGM Marco Polo of Netley enactment and was manoeuvred into presumption to presume its relation arsenic stern tug and walk its starboard guardant towline crossed to the instrumentality ship’s aft mooring deck. Once successful position, the tug’s platform unit connected a heaving enactment received from the instrumentality vessel to the starboard towline’s messenger line2. Up to 40m of towline was past tally retired from the starboard drum of the tug’s guardant towing winch. The oculus of the towline pennant3 was pulled up done the instrumentality ship’s centreline Panama pb and placed implicit a acceptable of bitts instantly inboard. With its towline slack and its winch brake applied astatine 100% holding capacity, Svitzer Mercurius held presumption astern of CMA CGM Marco Polo arsenic the instrumentality vessel proceeded towards SCT Berth 5.

At astir 1225, CMA CGM Marco Polo entered the turning basin adjacent to its berth astatine a velocity implicit the crushed of 3.7 knots (kts); Svitzer Eston was astatine the instrumentality ship’s bow and Svitzer Ferriby was connected its larboard 4th (Figure 3). As the vessel began to crook to port, the aviator requested Svitzer Mercurius to supply 50% astern thrust to dilatory the ship. Shortly afterwards, the aviator requested that Svitzer Mercurius summation the stern thrust to 100%. As the load connected the towline increased, the tug’s winch brake slipped and a fewer metres of the towline were released. With afloat astern powerfulness being maintained, the enactment rapidly became taut and the winch brake slipped a 2nd time, with different respective metres of towline being released.

At astir 1231, aft the winch had slipped a 2nd time, the towline pennant parted adjacent to CMA CGM Marco Polo’s platform and snapped backmost towards the tug. Part of the enactment struck and shattered the starboard guardant wheelhouse window. It besides struck the centre guardant window, causing its interior pane to fracture.

Five unit who were stood successful the wheelhouse (Svitzer Mercurius’s master, mate and main engineer, and the Svitzer Alma’s maestro and mate) were struck by flying solid fragments and suffered aggregate insignificant facial, limb and precocious assemblage lacerations. All of the unit were wearing immoderate signifier of eyewear, which prevented immoderate oculus injuries. The remainder of the wheelhouse was peppered with solid fragments and 2 of the interior panes of the aft-facing windows were besides cracked but did not break. Svitzer Mercurius’s mate took power of the tug portion the Dutch maestro went beneath to cleanable humor from his face. When the tug’s maestro returned to the wheelhouse, helium took backmost control.

Credit: UK MAIB

Analysis

Slippage of the towing winch set brake

Examinations of the pennant identified harm successful respective locations on its magnitude that could lone person been caused earlier the tug’s accomplishment successful Southampton. TTI’s study concluded that the load astatine nonaccomplishment was apt to person been adjacent to oregon little than the load recorded (119t) during its destructive tensile load test, which was astir 52% of its archetypal MBL.

It is imaginable that the pennant simply failed astatine a load adjacent to the tug’s maximum bollard pull. However, it is overmuch much apt that it parted erstwhile the towing assembly was exposed to higher levels of daze loading pursuing the brake slippage incidents. The spot of the full towing assembly, including the recovered sections of pennant mightiness person been reduced owed to vulnerability to the daze loading, and truthful the tensile spot of the pennant could person been a small higher than 119t earlier its failure. Regardless, it was wide that the mediocre information of the towline pennant and the debris connected the towing winch set brake were the 2 superior factors that contributed to this accident.

Towline management

The pennant had suffered mechanical harm to its outer overgarment that would person been visually evident and had been repaired. TTI’s introspection and trial study identified 2 main areas of harm to the rope’s load-bearing halfway that would not person been visually evident and would person been hard for the tug’s unit to detect. The types of harm recovered included halfway strand fusion and axial compression fatigue, some of which were attributed to erstwhile precocious and/or daze loading exposure.

Although nary towline load past accusation was disposable for Mercurius, some nonstop and indirect towage were known to person taken spot during the vessel’s clip successful the Netherlands, perchance with loads of astir 160t (twice the bollard pull). These loads exceeded the enactment manufacturer’s guidance and Svitzer’s argumentation regarding a WLL of 50% of the MBL (115t) and truthful should person been recorded arsenic overload events. Given the grade of the repairs carried retired to the pennant and the cognition that it had been exposed to daze loading, a robust LMP mightiness person allowed Iskes to place that the enactment had reached the extremity of its harmless operating limits, and led to a determination to discard it alternatively than end-for-end it.

Credit: UK MAIB

Conclusions

Not capable information was fixed to the towlines and pennants fitted to Mercurius erstwhile it changed ownership, including whether the idiosyncratic components were suitable for the intended intent and their fittingness for continued use. The effect was that Svitzer Mercurius started operating successful Southampton with a starboard winch towline pennant that was nary longer acceptable for intent owed to its reduced residual spot from the daze loading and deterioration sustained nether its erstwhile ownership.

Without a elaborate inspection by the manufacturer, oregon a load test, it would person been intolerable to find the grade of the harm to the load-bearing halfway of the pennant and the consequent simplification successful strength. As pennants are not ever capable to beryllium suitably examined and/or load tested, they should beryllium replaced often and surely aft harm oregon precocious loads person occurred.

Svitzer Mercurius’s wheelhouse toughened solid windows were incapable to withstand the precocious vigor interaction load of a towline snapping backmost and shattered, showering the wheelhouse successful solid fragments. More terrible injuries to the unit successful the wheelhouse were lone prevented due to the fact that they were wearing glasses oregon sunglasses.

It is evident that determination is simply a deficiency of a suitable solid modular for tug wheelhouse windows that provides a measurable level of unit information against the hazard of a recoiling towline.

Although the hazard of a towline nonaccomplishment and its consequent snapback was recognised and understood, the likelihood and effect of a recoiling enactment striking the wheelhouse windows had not been assessed.

The thorough documented inspection process, successful accordance with Svitzer’s procedures, for the Mercurius’s induction into the Svitzer feet did not occur. As a result, the suitability of the towline arrangement, and information of the winch brake and pennant, were not identified.

The starboard winch brake was contaminated due to the fact that it had not been efficaciously maintained aft accomplishment successful Southampton, starring to the winch brake slipping astatine astir fractional its intended holding capableness and causing a precocious daze load connected the towline and pennant.

Without a wide ceremonial induction process for caller crew, and fixed acting arsenic stern tug to CMA CGM Marco Polo was the archetypal occupation with the towline and pennant nether load successful Southampton, if Svitzer Mercurius’s maestro had remained astatine the helm it would person maximised the accidental to respond to unexpected events.

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