Optimization Speed and Consumption

The purpose of present task is to find out basis information about actual performance of the ship (as contained in AMI reports and results of bunkers surveys) what is the optimum mode (actual RPM or speed/consumption in the C/P description with Owners), which will produce lowest total costs (hire+bunkers) for fixed voyage distance and with expenses basis vessel's actual performance and then to choose RPM or C/P speed which will produce lowest expenses for the voyage.


Separate calculations are done for ballast and for laden leg. At the start of the calculations user should be prompted will voyage be laden or ballast (imperative choice). Then user will be given an option to enter actual voyage draft (for ballast condition it will be rarely done in practice); if not entered [Summer draft] should be used for laden condition and [Default ballast draft] - for ballast condition.
In the tab "Ship's particulars" data should be downloaded from the program database or entered into manually by operations manager except [Default ballast draft] which is always calculated automatically.
In the tab "Actual performance calculations" data in blue cells should be downloaded from database of AMI report but figures of consumption for each voyage should be corrected basis information about bunker survey reports stored in the program. Data in green cells is assigned default values unless changed manually by operations manager. Results of calculations in that tab are summarized in the table "Weighted average forecasted performance for selected voyages".
In the next three tabs "Optimum speed selection", "Speed mid voyage analysis", "Speed end voyage analysis" similar calculations are performed. The essence of these calculations is to compare estimated expenses for the voyage of the same length on all C/P speeds (as guaranteed by the Owners i.e. -0.5 knots on speed & +5% on consumption) with expenses basis vessel's actual performance and then to choose RPM or C/P speed which will produce lowest expenses for the voyage.
In the tab "Optimum speed selection" there are several "IF" which it will be necessary to check - type of C/P speed/consumption warranty (e.g. if C/P speed/consumption produce lowest expenses for the voyage but this warranty is on "WOG" basis then it is of no value and optimum speed/consumption basis actual performance is to be used), is there guaranteed C/P speed/consumption with difference in voyage expenses from non-guaranteed speed/consumption not more than 0.5% (there is no point to switch to non-guaranteed speed/consumption unless we expect sensible savings from such action), is there C/P speed/consumption with difference in consumption not more than 5% from optimum mode (small changes of RPM have very little practical effect on voyage costs so it make sense to send the vessel on guaranteed C/P speed/consumption on which actual voyage expenses should be very close to voyage expenses on optimum speed/consumption even if we would not otherwise choose such guaranteed speed/consumption).
After start of the voyage, when information from several noon reports is available (in the future the program should recognize Date, Time since last report, RPM, IFO+MGO consumption but on the first stage manual entering of the data would do) in the tab "Speed mid voyage analysis", we are attempting to get preliminary answer on the question "Fine, we have calculated basis past performance of the vessel how the vessel should theoretically perform in the optimum mode. What is actually happening - what RPM does she maintain, what is her consumption and how actually reported figures affect out previous calculations about optimum mode?". For example the master may ignore instructions to maintain 70 RPM and continue running the ship at 75 RPM, or she may switch to 70 RPM but report consumption 27 mt instead of expected 24.4 mt. The latter problem is most common and, in theory, the ship should be accumulating excess of bunkers on board which will be found in the next port during bunkers survey and thus returned to Charter. In practice excess bunkers may be used to set-off previously existing shortage of bunkers on board or may be sold by the crew during bunkering (if it takes place before bunkers survey) by way of signing bunkers delivered receipt for higher quantity than actually delivered by the barge to the ship. Speed from noon reports is not taken into account as it is impossible to quantify effects of weather on speed without AMI report.
During later part of the voyage (when AMI mid-voyage report is received) or after completion of the voyage (when AMI end-voyage report is received) we perform calculations in the tab "Speed end voyage analysis". These calculations may take into account results of bunkers survey made after the voyage. The questions we will be looking to answer at this stage will be:
-Was decision about selection of speed/consumption justified by events?
- Estimated savings for the voyage compared to maintaining C/P speed/consumption corresponding to minimum of costs.
- May decision to switch to non-guaranteed optimum speed be justified in the future?
- Expected excess or shortage of bunkers on board, mt.
Normally after completion of the voyage 1st calculations are made after receipt of AMI end-voyage report and figure of expected excess or shortage of BROB is communicated to the bunkers surveyor. After bunkers survey results are known, 2nd calculations are made and final verdict about decision made before commencement of the voyage is made.
The program should store in the memory figures " Estimated savings for the voyage compared to maintaining C/P speed/consumption corresponding to minimum of costs". If bunkers survey has been performed - then figure is to be calculated basis AMI end-voyage report & bunkers survey; otherwise the figure is to be calculated basis AMI end-voyage report only. Upon request for user-defined period of time (e.g. last year) sum of these figures for the whole fleet or for segment of the ships (capesize, panamax, supramax, handysize) should be calculated. This will answer the question "Is operation on optimum actual speed/consumption produce actual savings compared to what would have been achieved in case of operation on best guaranteed C/P speed?".
The program should store in the memory figures of difference "Expected excess or shortage of BROB" vs " IFO+MGO excess/shortage found during bunkers survey" for voyages, after which bunkers survey has been performed. Upon request for user-defined period of time (e.g. last year) sum of these figures for the fleet or for segment of the ships (capesize, panamax, supramax, handysize) should be calculated. This will answer the question is crew able to steal saved but not reported bunkers or same are inevitably found during bunkers surveys. The answer on that question will help us to answer on another question "What are we doing if the ship is maintaining instructed RPM but is reporting bunkers consumption higher than theoretical - shall we continue the voyage in the theoretical optimum mode expecting to find excess of bunkers in the next port during bunkers survey?".