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We know that the main purpose of most types of ships is to carry cargo or passengers from one place to another. Of course there are other special-purpose vessels such as research ships or icebreakers but in this article we will concentrate on cargo carrying ships only. Please note that when I use the word cargo in context of this article, it refers to any type of cargo carrying ship such as bulkers, tankers, reefers, OBOs and so forth.
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Cargo Ship Plans
Even an average sized ship can carry thousands of tons of cargo, and this cargo cannot be simply dumped on board the vessel in a haphazard manner but needs to be stowed in an orderly fashion. This is necessary due to several reasons such as the following.
Ship Stability: The safety of the ship's crew as well as the ship itself is of foremost importance as unplanned stowage of cargo could lead to the ship capsizing on being unstable in the rough seas. We have learnt about how a ship floats on seawater but thats a case of simple stationery ship and dynamics of loaded ship in rough sea can be different and dangerous. This is certainly to be avoided at all costs and there are some basic rules to be followed depending on the type of cargo. For example in case of solid cargo such as containers it is important to store heavy objects towards the bottom while the lighter ones on top just as you would do when stowing luggage on top of your car. Similarly in case of liquid cargoes it should be ensured that the cargo is compartmentalized in such a manner so as to reduce or minimize the free surface effect of the cargo which could lead to instability during the voyage. For example just see the picture of a small ship which was overloaded and what happened to it. Of course this just shows a small ship which is near the harbour but just image the case it this were to happen in the open sea.
- Structural Safety: Apart from stability, another factor to be kept in mind for safety reasons is to remain within the prescribed working loads for the ship structure parts such as the decks and so forth. Care should be taken not to exceed the load density of the decks.
- Safety Codes: There are safety codes available for all types of dangerous cargoes such as chemicals and gases and these rules have been laid down by classification societies and/or regulatory bodies such as the International Maritime Organisation. These codes must be adhered to under all conditions so as to ensure safety of the ship staff who handles such cargoes.
Economy: since the main purpose of the ship is to maximize profit for the owners and operators, it can be achieved by carrying or transporting the maximum amount of cargo in a single voyage. Hence a proper cargo plan ensures that the available cargo space is utilized to the maximum possible efficiency. Of course this is subject the previously described norms of safety and one cannot overload a ship for maximizing profit while it jeopardizes the safety of the ship, staff and the very cargo it is carrying.
Intermixing: when more than one type of cargo is being carried, it is quite possible that some or all of these cargoes may not be compatible with each other in the sense that they could either get damaged on getting in contact with each other, or could produce some unwanted chemical reactions and so forth.
Having taken a look at the usefulness of preparing a cargo plan, we will proceed to take a look at how to go about preparation of a cargo plan as well as an actual cargo plan on a typical cargo mix. But before we get on to that final stage, it is also necessary to take a look at some of the typical properties of most commonly transported cargoes in the shipping trade in our next article and will also discuss about a real cargo plan after that.