Crude Oil or Product Tanker Cargo Calculations

Crude Oil or Product Tanker Calculations

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Requirements References Oil Rig Machinery Find Maps Marine Internet Crude Oil Washing List of Cargoes (lengthy page).

Introduction

We have developed spreadsheet-based files that have customised cargo work calculations for a crude oil and product tankers. Our standalone products are designed for the business of shipping cargo (chemicals, oil or products) via shipping vehicles (tankers) or storing them ashore or in floating storage units (FPSO). We prefer to work with Microsoft Excel (images below are snapshots of Lotus 1-2-3 files). The latest products are standalone with a backend database storing the manual entries for each port of call. The database can be used to produce all kinds of MLI statistical analysis.

Entries by user would be:

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Cargo Ullages and temperatures tank-wise;
Gauge readings/Soundings of ballast tks;
Fuel/FW Tks Qty;
Sp. Gr. of Sea Water;
Interface sounding for free water, if any;
V.E.F.;
OBQ/Slops on board, if any;
API and/or Density;
Tables required (6, 24 or 54 A/B); (selectable by mouse click)
etc.

Make your own spreadsheets or standalone projects. Download the add-in dll(s) with all the functions you need for the tanker industry.

The results are transferred to the following with tabulated and/or chart representations and may be printed at will

Trim/Stability;
stress pages;
Record of V.E.F. for last 10, 20 and 30 voyages;
Charterer's and Owner's forms, viz. Letters of protest for BL discrepancies, delays, free water, port log, Ullage Report, Stowage Plan;
Etc.

Hydrostatic calculation (draft survey) with hog or sag deflection is also included.

Customised menus allow macros to run for:

Online registration of tank volumes where such hardware fitted, (We can undertake turnkey installation of hardware at dry-dock);
New Reports;
Print;
Backsolve to required - Nett MT, Barrels, DWT or Draft;
Change SW density - same cargo/ballast;
A scratchpad for quick conversion from degrees F'ht to C, Ft to M and vice versa with resultant DWT for that Ft or M.

Also included is the extremely powerful and much used (by the Chief Officers), add-in called Solver. Solver provides an optimal solution to various loading/discharging scenarios in a matter of seconds.

Example:
You have a nominated BL Qtty of 630,000 Nett Barrels of Oseberg Blend to load from Sture (Salt water) for discharge at Immingham (brackish). With the given bunker ROBs and load temperatures, draft restrictions, Solver can find a loading distribution to satisfy the given constraints which would be - no list, even keel arrival, volumes <= 98%, minimum stresses, etc.

We offer to write a similar customized spreadsheet for a fee, for any tanker operator/owner who may get in touch with us by e-mail for a sample spreadsheet at:

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Trim & Stability

The following is a picture of the bottom half of the "Trim/Stab" page in the Lotus Workbook. The unseen portion has the data for Provisions, Constant, FW, Ballast, Fuel / Diesel and Cargo.

KG, LCG and Inertia Moments are tabled for each and the results are displayed as seen below.

Results of the "Stress" page are also incorporated.

Trim/Stability Results With GZ-Curve

An attempt is made to reflect the actual draft taking into consideration the deflection due to stresses vis-a-vis the straight girder theoretical results. This is useful in cases of sailing in shallow waters where the additional max. draft due to stresses must be taken into consideration, as too the squat.

Also calculated, is the loss of GM upon touching the blocks during dry-docking.

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Back Solve

BackSolver Dialog Box

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

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.

Solver Dialog Box

In the problem above -

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:

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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Hydrostatic Calculation

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.

Hydrostatic Calculation Comparison Table

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Sample Prints/Wkb Pages

To list of a few -

Make your own spreadsheets or standalone projects. Download the add-in dll(s) with all the functions you need for the tanker industry.

Requirements

Microsoft Excel
Online hardware, if pickup of online data required
Modern PC

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Additional Information

We have undertaken smaller projects too - Ullage reports only for crude and product tankers with results exported to charterer's and owner's standard forms (ship specific data for tank volumes with trim and heel correction, stability, stresses and hydrostatic calculations, etc. not included).