8
Cargo Work for Maritime Operations
Fig. 1.1 The conventional ‘general cargo’ vessel ‘Sunny Jane’ lies port side to, alongside in the Port of Amsterdam.The vessel is fitted with conventional derricks, supported by bi-pod mast structures.
Derrick rigs – Union Purchase Method The Union Purchase Method of rigging derricks is perhaps the most common with conventional derrick rigs (Figure 1.2). With this operation, one of two derricks plumbs the hatch and the other derrick plumbs overside. The two runner falls of the two derricks are joined together at the cargo ‘Union Hook’ (this is a triple swivel hook arrangement sometimes referred to as a ‘Seattle Hook’). The load is lifted by the fall which plumbs the load, when the load has been lifted above the height of the bulwark or ship’s rail, or hatch coaming, the load is gradually transferred to the fall from the second derrick (Figure 1.3). Cargo movement is achieved by heaving on one derrick runner and slacking on the other. The safe working angle between the runners is 90° and should never be allowed to exceed 120°. There is a danger from overstressing the gear if unskilled winch drivers are employed or if winch drivers do not have an unobstructed view of the lifting/lowering operation. In the latter case, signallers and hatch foremen should always be employed within line of sight of winch operators. The CSWP for Merchant Seaman provides a code of hand signals for use in such cargo operations. Single swinging derricks The conventional derrick was initially evolved as a single hoist operation for the loading and discharging of weights. It was the basic concept as an aid which became popular when combined within a ‘Union Rig’. However,