97011 Over Loaded and Over Stressed Bulk Carrier

Over Loaded and Over Stressed Bulk Carrier
Report No. 97011

An 80,000 dwt bulk carrier was loading iron ore in a port with limited wateralongside and a restricted air draft. The load rate was 3,000/4,000 tphand the cargo was to be loaded in #1, 3, 5, 7 & 9 holds. The 2/O and3/O worked watch and watch about and the C/O was always on call handlingde-ballasting. At about 1145, the vessel was one quarter loaded and about45 minutes into the second of four 4,000 mt runs into #1 hold. De-ballastingof #1 db tank was scheduled to run simultaneously to the loading but wasdelayed by a faulty valve. The C/O went to assist the C/E with the valvein the pipe tunnel. About 30 minutes later, having released the valve,they emerged from the pipe tunnel to find, unexpectedly, that cargo wasstill being loaded into #1 hold.

Enquiries revealed that the loading gauge had ceased working and theshore did not know how much they had loaded. Loading was immediately stopped. A rough draft survey found the vessel considerably further by the headthan had been planned and with about 2,000 tonnes excess cargo in #1 hold. The loader was ordered to #9 but, because of the air draft, could onlyreach #7. Excessive negative trim prevented discharge of forward doublebottom tanks. The fore peak tank and TWTs were already empty. Loadingcontinued at #7 and the aft tanks were ballasted. The loader moved to #9as soon as the air draft allowed.

The next day, with all the cargo on board and the vessel on an even keel,the calculated "at sea" bending moments were 104% of allowable. The additional weight in #1, the counter balancing cargo in #9 and thereduced loads in #3, #5 and #7 resulting in a severe hog. Centre doublebottoms and wing tanks were ballasted as the vessel cleared the berth. This brought the stresses to just within the sea limits but submerged thetropical marks. This condition remained until de-ballasting of #4 wingtank and double bottom in the English Channel. The difficult decision ofwhether to be over stressed or over loaded in bad weather fortunately wasunnecessary as the weather remained favourable throughout the voyage.

Some factors that precipitated this incident are:

• The late report from the engineers that the valve was stuck was exacerbated by the inability to reach the OOW or C/O by telephone
• The OOW and the C/O failed to halt the loading once the problem had been reported to them.
• The C/O did not adequately brief the OOW regarding the draft, trim and expected completion time of the run. In this case the interruption to de-ballasting complicated the issue.
• The Stability Calculator was in the C/O's cabin and not available to the OOW.
• The C/|O allowed himself to become involved with freeing the valve instead of re-calculating the draft and trim for the end of the run with the ballast still in.
• The implications of the jammed valve may not have been made clear when the OOW handed over the watch at noon.
• The fact that the ballast controls were in the Engine Room complicated the communication and control.
• The remote draft read outs were inoperative and, reportedly had been for several years.
• The Terminal failed to stop the loading when their equipment failed. This should be standard operating procedure.

Actions Taken to Avoid Similar Occurrences in the future.

1. Standard Operational Procedure set so that the OOW would stop loading if draft or trim varied from predictions by 5cm and 10cm respectively.
2. Stability calculator was moved from the C/O's cabin to the cargo office to allow the OOW to update predictions in case of ballast problems.
3. The Engineers were lent a radio to aid communication. This was only partially successful due to the ship's structure. UHF radios were not available.
4. Deballasting of double bottoms was scheduled first, allowing fall back on TWTs for stress and trim control. It is seldom that TWTs cannot be pumped out.
5. Further unsuccessful attempts were made to have the remote draft indicators repaired.

Design faults which contributed to the incident:

• Unreliable pneumatic butterfly valves on the ballast system.
• C/O had to use his cabin, which had no forward facing windows as his office. The Chief Steward, on the other hand, had a large office. Perhaps this was an indication of the priorities of the French owner.
• The view forward from the cargo office on the main deck was blocked by the hatch coaming which was situated one metre from the scuttle.

Some Other Thoughts which come to mind:

• Why not mount a large shore tonnage display on every loader? The expense of this would be recouped quickly by the improved loading efficiency and the avoidance of delays such as those which occurred in this incident.
• Bulk carriers need proper cargo control rooms with ballast controls and a clear view over the deck. The height of modern coamings require these to be at least one deck above the main deck.
• Access to the shore for draft reading is often difficult. A gangway should be provided from the loading structure.
• All bulk carriers should have reliable remote draft indicators.
• At the very least, they should have fore and aft deck lines similar to amidships so that freeboards can be easily taken.