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IMOS - Max Lift Calculations

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IMOS - Max Lift Calculations

 This is a Key Topic, with high value for all users.

Max Lift is the maximum quantity a vessel can lift in the port in the voyage that has the most restrictive deadweight and draft limits. This amount can be calculated based on the density of the cargo, the vessel's deadweight, and the weight of bunkers and everything on the vessel.

  1. On the Voyage Estimate menu, click Auto Calculate by Max Lift Qty. The following information is used:

    • From the Vessel form:

      • Capacity fields vary with Type Code, for example:

        • Type Code T (Tanker): Capacity M3 or Capacity Bbl

        • Type Code B (Bulk): Capacity (Bale) or Capacity (Grain)

      • Vessel DWT (taking into account the season and the salinity of the berth)

      • Constants and Safety Margins

    • Bunkers ROB

    • Cargo Name

      • Cargo Class Dry or Unspecified: Stowage Factor (M3/MT or Ft3/MT)

      • Cargo Class Liquid: Density (API/Specific Gravity)

      • Cargo Class Dry: The Capacity Basis default is Grain, but you can change it on the Cargo Name form.

  2. Quantities appear in Voyage Estimate Details view:

    • On the Draft/Restrictions tab, in the Cargo and L/D Qty fields.

    • In the Cargoes grid, in the CP Qty field, depending on configuration flags.

  3. You can override the calculated lift value.
    To recalculate, clear the field and then press Enter. The new value appears blue.

To see the inputs to the calculation, on the Draft/Restrictions tab, hover over the value in the Max Lift field.

Max Lift Calculation

In determining the Max Lift, three possibly restricting quantities are calculated:

The Max Lift is taken as the most restrictive of these values.

You can see which restriction is in effect on the Itinerary Details form.

Max Lift = Capacity divided by Stowage Factor

Max Available Deadweight = DWT minus Bunkers ROB on Arrival minus Constants and Margins

If the result from the Max Lift calculation is higher than the Max Available Deadweight, then the Max Lift is the Deadweight itself (the maximum the ship can lift).

Max Available Deadweight

Max Available Deadweight = Vessel Deadweight − Bunkers and Constants

Vessel Deadweight

The deadweight comes from the baseline chosen for calculations:

  • Vessel DWT, SW Summer Draft, and TPC/TPI on the Vessel form.

  • Information entered on the bottom half of the Vessel DWT/Draft tab.

If an exact baseline does not exist (meaning Deadweight, Draft, or TPC is missing) backups are used depending on the relevant loadline:

  • Tropical Fresh Water -> Tropical Salt Water -> Summer Salt Water

  • Winter Fresh Water -> Winter Salt Water -> Summer Salt Water
    Note: Winter Fresh Water is not an available line, so a backup is always used.

  • Summer Fresh Water -> Summer Salt Water

When Summer Salt Water is used as a backup for Winter/Tropical loadlines, the draft and the deadweight are adjusted as follows:

  • Tropical SW Draft = Summer SW Draft + 1/48 * Summer SW Draft

    Tropical SW DWT = Summer SW DWT + (Tropical SW Draft − Summer SW Draft) * TPC *100 CM/M


  • Winter SW Draft = Summer SW Draft − 1/48 * Summer SW Draft

    Winter SW DWT = Summer SW DWT − (Summer SW Draft − Winter SW Draft) * TPC * 100 CM/M

Bunkers and Constants

Bunkers and Constants = Sea Constants + Fresh Water + Other Constants + Bunker Margins + Arrival ROB Bunkers + Bunkers Received

Sea Constants, Fresh Water, Other Constants, and Bunker Margins come from the Vessel Consumption tab:

  • In the In Port Consumption Table (Per Day) grid, the Margin column.

  • Under Variables and Safety Margins, Constants Sea, Fresh Water, and Others fields.

ROB Bunkers and Bunkers Received come from the Voyage/Estimate.

Example

Let’s consider the calculation of the Max Available Deadweight for the vessel seen in the screenshots below:

Suppose we are sailing to Bergen in winter, so our loadline is Winter Salt. We arrive at Bergen with 200 MT IFO and 150 MT MGO. We also buy 150 MT IFO and 100 MT MDO at the port. Because we do not have information on the Winter Line, we will need to use the summer line. Therefore, our calculation will look as follows:

Adjusted Vessel Draft = 15 M − 1/48 * 15 M = 14.6875 M

Adjusted Vessel DWT = 80,000 MT − (15M − 14.6875 M) * 70 MT / CM * 100CM / M = 77,812.5 MT

Bunkers and Constants = 20 MT (Sea Constants) + 30 MT (Fresh Water) + 40 MT (Other Constants) + 110 MT (IFO and MDO Bunker Margins) + 350 MT (IFO and MDO Arrival ROB Bunkers) + 250 MT (Bunkers Received) = 800 MT

So, we get: