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2.8 VOYAGE CARGO ORDERS

Before departing from the loading port, the master will receive orders for the next voyage. If it is a short voyage, both the voyage and cargo orders may be received in one message. If the voyage to the loading port is longer, the first message may contain only the voyage instructions, to be followed by the cargo instructions and bunker instructions at a later date. Cargo instructions may be received either direct from charterer or via owner's office, where the orders will have been reviewed before being passed on the ship. Whatever the origin of the orders received, or the number of prior reviews they have had, it is the responsibility of the master to see that the ship can successfully implement them.
The way in which the voyage instructions are developed into a voyage plan have been discussed in section 2.7 Cargo instructions require a similar careful analysis and planning effort to ensure adequate preparation of the ship's cargo tanks and pipelines for carriage of the cargo. The 'charterer's instructions' for a time chartered tanker may include an extensive set of instructions for tank preparation, cargo loading and cargo custody. The master and chief officer must ensure that all requirements of both owner's and charterer's instructions are complied with as they apply to the next cargo.

Cargo orders should include:

  • Ports of loading and discharge.

  • Limiting drafts and where they apply.

  • Volume of cargo to be loaded.

  • Cargo grade and specific gravity or API gravity.

  • Special care requirements, such as heating or dehumidification.

  • Special properties or safety concerns, such as H2S content.

  • Bunker stem details.

  • Fresh water and/or ballast expected to be carried.
  • Both the charter party under which the vessel is operated, and the bill of lading under which the cargo is shipped require the exercise of due diligence in all aspects of loading and care of the cargo. To protect the owners and charterers against cargo contamination claims, the ship must exercise due diligence to properly prepare for and carry the cargo and document the work such that due diligence can be demonstrated by the routine records alone, without producing additional reports. The routine records will include both the tank cleaning records and the cargo system maintenance records.

    2.8.1 Does the cargo fit the ship?
    When the cargo instructions are first received they are evaluated to see that the nominated cargoes can be properly carried by the ship. The cargo is checked against ship capabilities for:

    Deadweight and draft
    Is the cargo deadweight within the ship's allowance? Is the final draft permissible at the loading port, en route and at the receiving port? The chief officer calculates the cargo deadweight indicated by the loading orders and the equivalent loaded draft. He compares the draft to the vessel's leadline for the loadline zones he will load in and will be sailing through. Then he checks the draft against harbour and dock depths of the loading and discharging ports, including the amount of fresh water allowance that should be applied for each. If these calculations indicate that the ordered quantity is slightly in excess of the allowed deadweight, the lesser quantity is usually acceptable. Cargo order quantities may normally be exceeded or shorted by 5% or 10% and still provide compliance. If a permitted variation is not indicated, the master should inquire what the allowed volume variation is. If a 'maximum' quantity is indicated, it must not be exceeded.

    Segregation
    If the cargo is made up of more than one parcel, can the quantities indicated be arranged in the ship to provide two-valve separation between each cargo grade at all times? Can a loading and discharging sequence be arranged which safeguards each of the cargo parcels from contamination?

    Vapour pressure
    Is the Reid vapour pressure (RVP) of the cargo within the ship's pressure/vacuum relief valve and hull structure capacity? Are the settings of the vessel's pressure/vacuum valves sufficiently high to prevent large vapour losses if the cargo has a high vapour pressure?

    Hull stress
    With the cargo in the ship, are the hull stresses within acceptable limits? The ship will be stressed by 'sagging' when fully loaded. The main deck will be in compression and the keel structure under tension. This stress must be calculated and compared to the allowed stress for the ship. Stresses while loading/discharging must be less than 100% of the allowed harbour stress and the stress throughout the voyage must be less than 100% of the allowed 'at sea' stress.

    Stability
    Will the proposed cargo layout produce acceptable list and trim for the ship loading, discharging and underway?

    Cargo temperature
    Is the ship properly equipped to maintain the required cargo temperature? Is the proposed loading temperature high enough to meet the required discharge temperature? If heating instructions are not provided for a cargo which must be heated, the master must request heating instructions immediately.
    Cargo should never be loaded at temperatures above 60 C except on bitumen carriers and some crude carriers approved to carry cargo at 65 C or higher temperatures.

    Instructions to load cargo above 60 C can only be followed if:

  • The owner is in agreement.

  • The Classification Society is consulted and agrees.

  • The temperature difference between the cargo and the sea is less than 66 C.

  • The handling of the cargo will not increase the hazard level for employees to an unsafe condition.
  • Tank coatings
    Are the cargo tank coatings suitable for the cargo to be loaded? Is the cargo safe for the coating? The chief officer must ensure that a cargo will not damage the tank coating.

    Pumping equipment
    Some cargoes can only be pumped with positive displacement pumps; others require vacuum assist units because of the vapour formed when pumping.

    Cargo system defects
    Are there any defects in the cargo system such as pipeline or bulkhead leaks, defective pressure valves, or leaking heating coils which could cause cargo contamination or losses? Bulkhead leaks are a minor problem between tanks containing the same cargo, but can cause significant cargo damage claims if they occur between tanks on different systems.
    If losses occur and the ship's cargo equipment is found to be defective, then the vessel will be liable for the loss. Cargo system adequacy is part of the duty of 'proper care of the cargo' owed by the owner to the charterer. In any dispute, the burden of proving proper care is upon the vessel's owners.
    The first officer examines all aspects of the loading, carriage and discharge of the proposed cargo. He must think through every step of the cargo handling plan. He prepares a tentative cargo layout plan for the ship and evaluates its effects on draft, list, trim, hull stress, loading and discharging operations and cargo heating. If one of the criteria is outside the permitted limits of ship's capabilities, the plan is changed. With a modern cargo computer a proposed cargo layout can be completed and adjusted in a matter of minutes. If no computer is used, the calculations are more laborious, but no less necessary! When a suitable plan has been developed it is given to the master for his review and comment.
    When the master has reviewed and agreed with the chief officer's cargo plan, the master advises the owner that the cargo can be carried as ordered, or that the instructions cannot be complied with as received. He must clearly indicate why the orders cannot be implemented and propose any changes that would permit the closest compliance to the original orders. When the owner's representative is in agreement with the master, the charterer is informed and, if necessary, an amendment to the cargo orders is requested.

    2.8.2 Maximum cargo orders
    Occasionally a ship will be ordered to load 'maximum cargo'. This may mean either maximum deadweight (as with fuel oil), or maximum cubic capacity (as with condensate or gasoline cargoes). Deadweight cargoes must be distributed in the way which provides the least stress to the hull. Because it is a deadweight cargo, ballast cannot be used to trim the ship and minimum fuel will be carried. The cargo plan alone must trim the ship properly and provide acceptable stress. If it is necessary to shift cargo during the voyage to provide even-keel trim both departing and arriving, charterer must be advised of this requirement and his permission obtained to make the necessary cargo transfer en route.
    Maximum cubic cargoes permit additional fuel and/or ballast to provide the necessary trim (draft restrictions permitting). The critical concern with cubic cargoes is the minimum ullage to allow for any anticipated cargo expansion due to heating by adjacent cargo tanks or by the sea temperature. Generally, cargo tanks should not be filled above their 98% capacity ullage level. If the tanks are fitted with high-level alarms the high-level alarm is typically set at 95% capacity and the 'hi-hi alarm' at 98%. Tank loading should never proceed past the sounding of the 'hi-hi alarm'!

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