- Customised Solutions For The Tanker Industry

Crude Oil or Product Tanker Calculations

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Back Solve

Facility is provided to compute the weight of the cargo on board by hydrostatic calculations from the draft gauges as well as from the observed drafts at the draft marks.

BackSolver Dialog Box


You may select an item from the list above to backsolve.

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 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.

Solver Dialog Box

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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