At anchor, just as when underway, it is important to maintain close monitoring of the ship's position and of the vessels in the vicinity. A shifting tidal stream or changing weather can easily result in a collision.
A recent Mars Report discusses a close call when a vessel started swinging at anchor and the lessons that can be learned from this incident.
Shifting Tidal Stream
When another large tanker anchored about 0.3 nm away at the same anchorage. Some time later, the vessels began to swing about their respective anchors due to the shifting tidal stream, but the effects on each ship were slightly different. The vessel’s sterns began to approach one another.
Engine Brought Online
Concerned about a possible collision, the OOW on vessel A repeatedly attempted to communicate with vessel B, but received no response. The master was called to the bridge. With the vessel still receiving no response on VHF from vessel B, the anchor party was made ready and the main engine brought on line for manoeuvring.
Only 25 minutes had transpired since the vessels began to swing from their initial positions, but they were now less than 0.15 nm apart. Dead slow ahead was ordered and the anchor was heaved up simultaneously, increasing the distance between the vessels.
Lessons Learned
- When going to anchor, place your vessel in a position that allows for a 360° swing on the anchor chain and still provides a safety margin with other anchored vessels that may also swing 360°.
- Even at anchor it is important to maintain close monitoring of the ship's position and of other vessels in the area.
- If you have concerns about traffic, weather, et cetera, while at anchorage, keep your main engine available at short notice to help prevent any risk of collision.
Mars Reports
This is one of the April Mars Reports, originally published as Mars 201927, that are part of Report Number 318. A selection of this Report has also been published in SWZ|Maritime’s May issue.
Submit a Mars Report
More reports are needed to keep the scheme interesting and informative. All reports are read only by the Mars coordinator and are treated in the strictest confidence. To submit a report, please use the Mars report form and send it to mars@nautinst.org.
