A ship may not be laden to her full available draft at the port of loading due to the restricted loading zones en route to the port of discharge. A ship cannot enter a winter line when loaded to summer marks and thereby submerging winter free-board. In voyage estimation form, cargo calculations section leaves a margin for:
- load-line considerations
- deductions (bunkers and constant weights)
In shipping business, it is crucial to know the load-line zones.
Knowing the cargo quantity as well as the loading/discharging rates per day of the proposed cargo, it is now possible to deduce port time with some accuracy, to enter the information in the appropriate boxes of the voyage estimation form and to calculate port bunker consumption.
In dry-cargo shipping, weekends and holidays frequently not count as laytime. In reality, dry-cargo ships are often left idle and not worked during weekends and holidays. Furthermore, there may be weather delays, the effect of which it may be reasonable to anticipate and to allow for by an adjustment in expected port time.
For example: MV DARIA is to load 50,000 mtons of bulk cargo, charterparty loading rate is 5,000 mtons per weather working day of 24 consecutive hours, Saturdays, Sundays and Holidays Excepted (SSHEX). By dividing 50,000 by 5,000 we find out that the loading time allowed to charterers is 10 days on the basis of SSHEX terms.