Site hosted by Angelfire.com: Build your free website today!

Crude Oil or Product Tanker Cargo Calculations

Contents

Go to Dedicated Site.

Documentation for NavionFormsBGTA.xls.

 

We've developed spreadsheet-based files that have customised cargo work calculations for a crude oil and product tankers. We prefer to work with Microsoft Excel.

Entries by user would be:

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

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

Customised menus allow macros to run for:

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 spreadsheet for a fee, for any tanker operator/owner who may get in touch with us by e-mail for a sample spreadsheet at: sales@cargocal.com

 

Go to Top of Page

 

 

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.

 

 

An attempt is made to reflect the actual draft taking into consideration the deflection due to stresses vis-à-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.

Top of Page

Return

 

Back Solve

 

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.

Top of Page

Return

Solver

Solver is an add-in that comes with Excel (Tools menu).

 

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.

Top of Page

Return

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.

 

Top of Page

Return

 

We have included a facility to search from the master database, details of all previous cargoes. The user may search and output to screen, data as selected from the following criteria.

  • Cargo Grade
  • Load Port
  • Heating Cargo

    The output fields include: Voyage Number, B/L Date, TCV & B/L volumes, type of load port (Pier/SBM/STS or Part), whether heating or not, avg. load temp and API.

    Sample Prints/Wkb Pages

    Requirements

    • Microsoft Excel
    • Online hardware, if online updating required
    • Modern notebook / desktop PC.

    Top Of Page


    Subscribe to Tanker Cargo Calculations
    cargoa2z archive Hosted by eGroups.com

    Copyright 2000 : Sovereign New Zealand