Dead Slow Ahead!!

March 14th, 2009 by JCB
Posted in Articles, Technical and Training | 1 Comment »

 

Further to reports of high Dead Slow Ahead speeds here is one daunting copy of a pilot cord received from IMPA.

The DSA on this 2007 built, 246.80 LOA ship is 12.5 Kts in ballast!  One aspect to note is that in the comments box below it does state that the minimum RPM is 28 which is less than the DSA RPM but would probably still result in a speead of 8 – 9 kts which is the maximum safe speed for tug handling.

 

There is an increasing trend for these container ships to be designed with high DSA speed but this may not be the minimum speed that the vessel can run at. I have come across several ships with high DSA speeds and when advising the Master that we would need to stop the engine in order to reduce speed to make tugs fast he has advised me of the possibility of having a minimum speed. So without any consultation, the naval architects have introduced a new speed, which of course doesn’t have a designated slot on the engine telegraph and we pilots are obviously expected to be clairvoyant and know that the DSA may no longer be the slowest speed available. So, during the MPEX process, pilots should now check with the Captain whether the DSA speed declared is actually the minimum speed available. All very confusing but it is an extremely important factor to be aware of prior to manoeuvring the vessel. Of course if starting from stopped, the engine will run up to the designated DSA revs prior to the Master bringing them back to minimum and this obviously has serious implications for adjusting the final positioning when alongside, especially if mooring lines have already been passed to the shore. A serious accident as a result of such design speeds is almost inevitable.

JCB