Cargo Cargo Handli Handling ng
Cargo handling is usually divided into four phases:• • • •
Terminal storage Transfer from storage area to apron cargo hook Hook to hold Stowage of cargo
When ordering a new ship the ship owner normally specifies the number, safe working load, position and any special features of the cargo handling derrick to be fitted. Cargo handling can be divided into the following categories: 1. DERRICK RIG SYSTEMS Although gradually gradually being ousted by deck cranes, this system has been the most popular method of handling cargo. a) Fixed Outreach Systems The union purchase system is the most common outreach system.
The system utilizes two derricks and two winches with the derrick in fixed positions. One derrick is arranged over the quayside and the other over the hold. By a combination of hoisting on both winches and hoisting on one winch and Marine Outfittings
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payi g out on the other hold or vice ver sa.
inch it is possible to transfer fr m the quayside to the
This system has the follo ing disadv ntages: •
•
It can o ly be used between a fixed p int on the quayside and a fixed point in the hold; this creates a serious roblem of manhandli g the cargo into its s owed posi ion. Due to the sharing of the load between two derricks, overlo ding of one derrick can occur if the operation is not properly managed and arising fro this many harbor a thorities h ve expressed their c ncern about its use.
b ) Swingin g Derrick
igs
All t ese rigs The e designs winch. Whilst t the asic disa thro gh 360o.
ave been develope to enabl accurate “spotting” of the loa . usually (b t not alw ys) includ a hoistin , topping and slewing ese rigs can perform all the fu ctions of a deck crane they have vantages f being c nfined to one hatch,, i.e. they cannot sle
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2. HEAVY LIFTING SYSTEMS The conventional method of lifting heavy loads is shown in figure and consists of one or two hoisting winches lifting on a multi-fall system. In addition, the topping and slewing motions operate through a multi-part rope system to ensure control of the load all the time.
The introduction of patented heavy lift systems (and the introduction of heavy deck cranes) has created a decline in the heavy lift derrick. A typical patented heavy derrick is shown in figure below (Stülken Derrick). With this system loads up to 300 tonne can be lifted and it has the unique advantage of being able to operate in two holds. It is positioned between two outwardly raked tapering Marine Outfittings
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tubular column . Several winches a e provide for the v rious hoisting, slewing and opping du ies. The c ntrols are all arranged as lever in one co sole, which can be operated by one an. Smaller derricks are also igged fro the tubul r colu ns for no mal cargo ork.
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Special precautions have to be taken when lifting heavy loads to ensure adequate stability of the vessel and correct functioning of equipment as angles of inclination up to 17 o could be encountered. The yo-yo arrangement For loads heavier than the safe working load of a single derrick, two derricks coupled together by a “yo-yo” arrangement may be used. The derrick heads must be kept close together during operation.
3. DECK CRANES This is the most recent method of handling cargo onboard ships. They have the following advantages: •
Rigging time is negligible, i.e. port time is reduced
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•
• • • • • •
The safe working load can range from 25 to 90 tonne and the jib radius from 20 to 35 m. For heavy lift cranes these values could reach 350 tonne and 60 m. Spotting cargo very accurately Readiness for action They require only one operator They provide more usable deck space and greater visibility from the bridge Greater safety is inherent in the crane over conventional cargo gear The crane’s operating gear and controls can be located within a protecting enclosure. This protection reduces maintenance and provides protection for the operator
However, cranes are perhaps less efficient with light loads. For large beam ships if the cranes are positioned on the ship’s centerline, they may require an extremely long jib. Therefore, fixed cranes, one at each end of the hatch, may be placed at opposite corners.
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As shown in figure a typical crane consists of a jib which can be lowered to the horizontal for stowage purposes, and a hoisting unit which can be on a single fall of rope or multi falls depending on the lifting capacity. Facility is provided for slewing the crane through 360 o. The main specifications of a deck crane are the hoisting capacity in tonne, the jib radius in m, and the hoisting speed in m/min. Some of the patented deck cranes are shown below. They are all designed to meet the rules of all classification societies and regulatory bodies. MacGregor Compact and Slim Crane These electro-hydraulic cranes are intended for various duties, particularly where dimensions must be compact and air-draft is limited. These cranes can be equipped with the tools needed for handling various cargoes, such as containers or bulk materials. The standard range covers lifting capacities from 36 to 45 tonnes. Outreaches are between 20-34 m.
MacGregor Container and Multipurpose Cargo Crane These electro-hydraulic cranes are self-contained units with all machinery enclosed in the crane house. This protects it from the weather, corrosion and damage. The standard GL range covers lifting capacities from 25 to 90 tonnes, with outreaches up to 32 m. Hoisting, luffing and slewing motions are
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independent of each other. This means that at their maximum capacity GL cranes can operate at full speed using all three movements at the same time.
MacGregor Heavy Lift and Multipurpose Crane The standard range covers lifting capacities from 120 to 350 tonnes, with outreaches up to 36 m. Like the previous type, hoisting, luffing and slewing motions are independent of each other.
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Liebherr Ar ticul ated Deck Crane This is a double girder container crane especially designed for use in harbour complexes where high turnover and continuous operation are required. The control of the turntable ensures the unchanged position (rotation axis) of the container during loading and unloading. Driver's cabin is positioned on the underside of the container rotating arms allowing unrestricted view of the containers.
Liebherr Heavy Lift Deck Crane This crane is designed for installation on heavy lift vessels a well as multipurpose vessels providing the following advantages: •
Low height allowing for better visibility from the bridge.
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•
Low weight and centre of gravity leading to improved vessel stability and moreover increased cargo capacity.
Liebherr Wire-Luffing Cranes These are designed for bulk and container handling with the following advantages: • • •
Hydraulic control instead of electronic. Jib brackets are directly integrated in jib beam for higher rigidity. Wire sheaves inside beam for better protection.
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Twi Cranes
The consist of two indep ndent cra es of equ l capacity mounted o a common platf rm whic can be rotated i dependently. Each crane can be used individually for ormal car o working, but when a heavy lift is require the jibs ar e slewed parallel to each other and a lifting bea is connected betwe n the cargo hoo s. A variation of the i ea has be n used wi h cranes of unequal apacity.
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