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You may select
an item from the list above to backsolve.
Example:
You may need to know, with the given the cargo API/Density and
temperatures (which would be entered in the "Ull Rep" page and the
Constant / Fuel / FW / Ballast conditions (entered in the "C Fuel FW B"
page), and the OBQ ("Wedge" page) and Slops onboard ("SlopCert" page),
what the cargo loadable would be for a "Mean-Draft" of 12.192 M Sea
Water?
Backsolver would
obtain results for you in a matter of seconds.
The distribution
of the cargo tank-wise with the resultant drafts, trim and list would
not usually be satisfactory. For a satisfactory distribution, the user
would need to use the "Solver" facility.
Nevertheless,
Backsolver serves the important purpose of a quickfire answer to
quickfire questions that are posed ever so often to the vessel by the
charterers / brokers. The distribution (stowage plan) may be obtained
more leisurely by using the Solver facility.
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Solver
Solver is an
add-in feature that comes free with Excel (Tools menu).
Solver is an Add-in for Lotus 123 and licenced by Frontline Systems. We
provide this add-in.
In the problem -
The set cell is
"AVG-ALL STRESS", which is a cell in the spreadsheet that represents
the average of all the BM and Shear Forces. The demand is to "MINIMISE"
the stresses.
The Changeable
(Variable) cells are "CARGO GAUGES", which are the MMC Ullages in the
table. Additional variable cells may be added, viz. Ballast Tank
Gauges.
The constraints
are many - (up to 100 constraints may be included in this part of the
dialog box). The constraints not seen in the picture above are:
Click on Image To Magnify It
-
Volumes of each
of the other cargo tanks <=98%
-
Heel Moments = 0
-
Deadweight
<=96,510 (Summer DWT)
-
Nett Barrels =
631,890 (B/L nomination 630,000 * clean VEF of 1.003)
Solver should be
able to come up with an optimal solution in a matter of minutes, if not
in seconds.
In the example
above, the results (solution), will provide a possible loading pattern
keeping to the SetCell demand for a minimised average of all stresses,
a cargo quantity of 631,890 Nett Barrels, No List, aft trim=0.2M, etc.
Any Chief
Officer would be delighted to use this add-in and it would be redundant
to point out that the cost of the add-in is well worth the time saved
in this aspect of loading/discharging operations.
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