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 BASICS/THE COMMON CORE - Module 9 |
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BASICS/THE COMMON CORE - Module 9 |
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Masts on general cargo ships may fulfil a number of functions but their prime use is to carry and support the derricks. Single masts are usually fitted but many ships have various forms of bipod masts. Samson posts, which are very strong masts,are also popular.
Various forms of derrick rig may be used. The commonest use of the single derrick is a single swinging derrick with a safe working load between 10 to 80 tonnes.
Adjacent derrick booms may be used as in union purchase. Cargo is lifted from the hatch and swung overboard by the operator controlling the winch.
The patent Stülcken derrick in the very heavy lift range, can serve two hatches and has a safe working load of between 80 to 300 tonnes.
On modern cargo ships deck cranes replace the derricks. They usually are an alternative to the union purchase rig. They can rapidly pick up and land loads anywhere within their working radius.
The safe working load is generally between 10 and 15 tonnes but larger cranes can lift from 30 to 40 tonnes.
Dockside cranes are of different types, perform different jobs and are named in different ways, e.g. straddle carriers or gantry cranes, transtainers and portainers depending on their build and use.
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