201235 Anchor cable rendered in severe gale

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.). The 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.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------
Feedback to MARS 201235
I am afraid that I must take issue with the Editor’s note regarding the above MARS report. I fully agree that the stopper should not be taking the weight but consider it should be engaged.

My reasoning is as follows:
Stopper scantlings appear to be designed to withstand full anchor cable load. The bitter end securing does not. If the stopper is not used then a single failure (of the brake) could lead to loss of the anchor, and potentially the vessel. In such a scenario I think not having the stopper engaged might be extremely prejudicial at subsequent enquiry!

My practice/recommendation is:
Have the brake holding the weight. Have the stopper engaged but not holding the weight. In the event of more cable being required, the stopper can be readily opened to allow more cable to be veered. This will ensure that any brake failure/slippage is ‘caught’ by the stopper, and vessel can schedule early maintenance before it becomes an ‘issue’. I will admit there is a very small chance that brake might slip (transferring load onto stopper) and the vessel might start to drag and vessel might have no power to adjust chain, but this requires a number of adverse factors/failures, so should be unlikely, particularly if the gap between cable and stopper is routinely monitored during anchored periods. Having seen the chain locker damage when a cable has run away without load on it I would never wish to see it happen with load! If stoppers are not meant for use in this way, but merely as a lashing when the anchor is secured, then they appear to be massively overspecified.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Feedback to MARS 201235

I wish to add a further comment:

Classification Societies typically state the following (GL in this case):
The anchoring equipment is intended of temporary mooring of a vessel within a harbour or sheltered area when the vessel is awaiting berth, tide, etc. The equipment is, therefore, not designed to hold a ship off fully exposed coasts in rough weather or to stop a ship which is moving or drifting. In this condition the loads on the anchoring equipment increase to such a degree that its components may be damaged or lost owing to the high energy forces generated, particularly in large ships.
The anchoring equipment is designed to hold a ship in good holding ground in conditions such as to avoid dragging of the anchor. In poor holding ground the holding power of the anchors will be significantly reduced.
The equipment numeral formula for anchoring equipment is based on an assumed current speed of 2.5 m/sec (approx. 5 knots), wind speed of 25 m/sec (approx. 50 knots) and a scope of chain cable between 6 and 10, the scope being the ratio between length of chain paid out and water depth.
It is assumed that under normal circumstances a ship will use only one bow anchor and chain cable at a time.

Readers must not assume that the anchor equipment will hold the vessel without damage in any state of wind and current.