Conventional general cargo handling
Cargo gear
Derricks, cranes and winches, together with their associated fittings should
be regularly overhauled and inspected under a planned maintenance
schedule, appropriate to the ship. Winch guards should always be in place
throughout winching operations and operators should conform to the
Code of Safe Working Practice (CSWP) (Figure 1.1).
Only certificated tested wires, blocks and shackles should be used for
cargo handling and lifting operations.
General principles of the handling, stowage and carriage of cargoes 7
Note:Wire ropes which have broken wires in strands should be replaced. Whenever 10%
of wires are broken in any eight (8) diameters length, the wire should be condemned. Guy
pennants, blocks and tackles should be kept in good condition.
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,
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.
Fig. 1.2 Union purchase. Derrick rig.
Fig. 1.3 The conventional derrick rig. Modern general cargo vessel rigged
with conventional 5 tonne SWL derricks and steel hatch covers. The derricks
can be rigged to operate as single swinging derricks or rigged in ‘Union Purchase’
SWL (U) _ 1.6 tonnes. Such vessels are in decline because of the growth in unit
load ‘Container and Ro-Ro, Traffic’.
improved materials and better designs have created sophisticated, single
derricks in the form of the ‘Hallen’, the ‘Velle’ and the more popular speed
cranes. All of which now dominate the reduced activities of general cargo
ships (Figure 1.4).
Where the single swinging derrick concept has been retained is in the
arena of the heavy-lift operation. Here conventional ‘Jumbo Derricks’, of
the single swinging variety, are still employed amongst specialist rigs as
‘Stuelckens’ and heavy-lift ships.
Specialized derrick rigs
The many changes which have occurred in cargo-handling methods have
brought about extensive developments in specialized lifting gear. These
developments have aimed at efficient and cost-effective cargo handling
and modern vessels will be equipped with some type of specialist rig for
operation within the medium to heavy-lift range.
The ‘Hallen derrick’
This is a single swinging derrick which is fast in operation and can
work against a list of up to 15°. They are usually manufactured in the 25–40
tonne SWL range and, when engaged, operate under a single-man control
(Figure 1.5).
Joystick control for luffing and slewing is achieved by the Port and
Starboard slewing guys being incorporated into the topping lift arrangement.
Use of the outriggers from a ‘Y’ mast structure provides clear
leads even when the derrick is working at 90° to the ships fore and aft line.
A second hoist control can be operated simultaneously with the derrick
movement.
As a one-man operation, it is labour saving over and above the use of
conventional derricks, while at the same time keeps the deck area clear of
guy ropes and preventors. Should heavy loads be involved only the cargo
hoist would need to be changed to satisfy different load requirements.
The ‘Hallen Derrick’ has a similar concept to the ‘Velle’, in that the topping
lift arrangement and the slewing wires are incorporated together and secured
aloft, clear of the lower deck. The outreach and slew are wide achieved by the
‘T’ yoke on the Velle Derrick and by outriggers with the Hallen.
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