Our vessel let go her starboard anchor at an exposed roadstead at night in a near gale (30-33 knot wind), awaiting delivery on a new charter. The next morning, the wind increased to a severe gale, with gusts of 40-45 knots, and waves 3-4 metres high. After a day with the cable paid out to this scope, the attending superintendent suggested the paying out of a few links in order to ‘freshen the nip’ of the cable at stress points (e.g. gypsy whelps, guide roller, chain stopper and hawse pipe etc.).
he Master agreed and this operation was successfully executed by the anchor team under the supervision of the C/O at about 0900 hrs, after which the crew re-tightened the brake and re-engaged the bow chain stopper. At about 1315 hrs, the Bosun, who was working on the forecastle deck, heard a loud noise and noticed the chain stopper lifting and the anchor brake rendering slowly under heavy tension. He immediately tightened the brake further and reported the event to the duty officer, who, in turn, informed the Master and superintendent.
Results of investigation
1. Chain stopper support brackets were found deformed;
2. Securing pin of chain stopper bar found displaced and deformed;
3. Stopper bar also found deformed and not aligning with guillotine recess;
Root cause/contributory factors
1. Prevailing severe weather conditions;
2. Possible insufficient tightening of the brake after adjusting scope;
3. Ineffective design of the securing arrangement on the chain stopper bar – comprising oval holes only on the counterweight side, which permitted large play in the engaged position, allowing the cable to slip from under the stopper bar.
Immediate corrective actions
1. Near miss report sent to office;
2. Chain stopper support brackets and stopper pin temporarily faired;
3. Anchor watch and deck crew instructed to continuously monitor status of anchor cable to ensure avoidance of overstressing.
Further planned corrective/preventive actions
1. Incident to be discussed at next safety meeting;
2. Chain stopper to be modified to include additional securing pin arrangement on the ‘gravity’ side of stopper bar;
3. Securing pins to be renewed with stronger material;
4. Pin’s securing points/holes to be changed from oval to round;
5. Consider fitting additional chain stopper device designed to engage on a vertically-oriented link of the cable (e.g. devil’s claw).
Editor’s note: The engaging of a ‘guillotine’ type bow stopper whilst at anchor is not advised, as this may prevent the emergency release of the anchor cable. As a good practice, the brake mechanism should be properly maintained and adjusted so that it begins to render at its designed safe holding power.
Source: Mars/Nautical Institute