Time at port for loading and discharging operations: Time at port for loading and discharging can be estimated either by reference to the stipulated time allowed for such operations or by calculating the lay time for the ship based on loading and discharging rates.
If, for example, the tonnage of cargo to be carried is known as well as the loading and discharging rate, then one can easily calculate the lay time that, taking into account some allowances, will represent the time in port.
For instance, for a cargo of sixty thousand tons at a rate of loading of ten thousand tons per day gives six days laytime for loading. The time for discharging can be calculated in a similar way.
If terms such as SHEX (Sundays and Holidays Excluded) exist, then estimations must be made to take those into account-in this case, the days in port will be greater than the time required for loading/discharging operations since the ship will be idle during Sundays and holidays.
In this case of SHEX circumstances, a coefficient of 1.4 is multiplied to the calculated laydays to estimate total time in port. At port, ships will use more diesel oil than fuel oil. The consumption of diesel oil for auxiliary engines when in port will be provided in the vessel description.