Cargo transportation is one of the key tasks of shipping equipment. There are various configurations and methods for the technical implementation of the cargo infrastructure, but in most cases it focuses on the possibility of autonomous crew maintenance without support from the coastline. However, this does not at all preclude the possibility of interaction between the ship’s cargo devices and land lifting manipulators.
Overview of Marine Cargo Infrastructure
Ship lifting and unloading equipment is a complex of devices and appliances. These include arrows, cranes, gripping and transporting mechanisms that are directly responsible for the movement of cargo flows - both on the ship’s site and beyond. As for the devices, they are responsible for the mechanical support of the main cargo mechanisms. A description of the general structure of ships in terms of cargo infrastructure and without elements of in-hold mechanization will not be dispensed with. The path from horizontal cargo handling involves passing several stages of transportation from the berth to the deck, followed by moving to sections of storages and container blocks. The organization of this movement is carried out using wheel and rail equipment on the deck. The distribution of technical equipment is carried out by ramps (inclined paths) with the connection of elevator mechanisms and ramps.
Features of the cargo device of the vessel
The main distinguishing feature of the marine cargo infrastructure can be called stringent conditions for the arrangement of lifting and transporting mechanisms. Since the requirements for the technical support of the vessel impose severe restrictions on the installation of large-format autonomous devices, engineers have to design optimized multi-functional systems, moreover, closely connected with marine executive bodies, units and assemblies. A typical component of the cargo device of a vessel of this kind is a winch, presented in different versions. It performs the functions of a transitional load-lifting mechanism, linking several areas served - again, from the pier to the deck and hold, depending on the installation site. Universal cargo devices that perform several tasks include the topenant stopper, guy wires, pulleys, swing platforms, drum mechanisms and drive units in the form of generators and electric motors.
Main and auxiliary devices
This is the basic classification of equipment on ships, which fundamentally separates the elements of cargo infrastructure. It’s worth starting with a review of the main units directly involved in lifting and moving cargo. Such mechanisms include:
- Arrows with devices for mounting and rigging.
- Masts or columns supporting the boom.
- Winch mechanisms.
- The premises containing the cargo are holds and twins. In this case, not so much the left-luggage office is interesting as the equipment for their maintenance with loading mechanisms and hatches.
Auxiliary types of cargo devices on ships are divided by the nature of the tasks performed. The simplest elements serve to support the main equipment - they perform the functions of clamps, regulating mechanisms, stoppers and calibrators. More responsible devices of this group are involved in servicing engine rooms, support receiving channels in the process of pumping liquid cargo, are involved in moving ship supply and food, and also perform small business operations.
Devices of periodic and continuous action
By the nature of the operation, equipment for servicing cargoes on ships is divided into direct and continuous use. In the first case, we are talking about winches and arrows, which work with the support of columns and masts, providing regulatory operations. Also in this category are cranes and hybrid (mixed) devices that are used continuously on passenger ships. The composition of the continuous cargo device is formed by elevators and conveyors. Such systems provide functional equipment on self-unloading vessels.
Cargo cranes
The lifting rod of this unit, depending on the type of construction, can range from 1 to 25 tons. Cranes can be rotary, retractable and stationary - belonging to one of these classes determines the functionality of the device. The advantages of this kind of manipulators include maneuverability, high speed and at the same time small size. Unlike heavy booms, the crane has a limited carrying capacity, not to mention the high sensitivity to rolls. Crane cargo devices on ships are installed with the support of the foundation. Only mobile structures do without a supporting platform, but they have a reliable rail track. For almost all cranes, equipment is provided in the form of supporting columns and counterweights.
Cargo masts
The lifting function as such for such devices is not primary, but secondary. Usually, with the help of masts, they perform installation works, organize communication lines for signaling and communication. Sometimes they are used for high-altitude placement of lights and antennas. In the composition of the cargo equipment of the vessel, if there is a sufficiently strong supporting structure, the mast can be used in one-time lifting and lifting activities. The complexity of its application on a regular basis lies precisely in the need to carry out special training. For power actions, the mast is additionally reinforced with cables leading to the sides. In the front of it, rods support it, and backstops are sent.
Cargo arrows
The base of the boom is a metal pipe with the presence of reinforcing additions in the central part. To ensure the connection (articulated) with the mast, a special shoe is installed. It is attached to a single mast at an altitude of about 2.5 m. The support of the knock is realized by the topant, the adjustment of which allows you to adjust the lift of the boom itself. Steel cables, a locking mechanism and a winch are also involved in the infrastructure of the system. Depending on the tasks set, different control schemes for the switch cargo device of the vessel can be implemented. A ship with a properly organized system of guy wires allows you to precisely control the removal of cargo with subsequent fastening. In systems with paired boom configurations, one mechanism must be carried overboard (the nock is located above the berth), and the second (bilge) is mounted above the hatch so that its nock rises above the lumen of the hold hatch.
Hatch covers
In order to facilitate unloading operations, special cutouts are arranged on decks and in holds. The hatches obtained are then enclosed by a vertical barrier - coaming, the height of which is 50-60 cm. The closing mechanism can be folding, sliding, removable and even wound. The simplest designs require a removable hatch in the form of a steel cover. They are conveniently used in service systems for lighter carriers and container ships. A multi-sectional version of the cargo device of the vessel is also used, in which the hatch is interfaced with coaming and itself consists of several parts. The connection nodes are made through hinges, and a hydraulic drive is used to control the mechanics. Each part of the hatch receives driving rollers and one centering guide. As an addition, damping, blocking and stabilization accessories can be used.
Mooring and towing devices
On the approach of the vessel to the berth, special mooring equipment is being prepared, the basis of which is mooring cables. At the end of such a cable a loop is fastened, worn on a berth. Also, the mooring system includes deck devices like a bollard, bitten or duck (cable fasteners). They also participate in the process of securing the ship's hull. The dimensions and number of mooring elements are determined by the characteristics of the vessel. During operation, the same equipment can be involved in fixing the anchor and tow rope. To eliminate the risk of fraying ropes and cables, bale strips and cleats are used.
On small vessels, cargo mooring and towing devices represent the same power infrastructure. On large ships, this functionality is divided due to an increase in the power responsibility of mechanisms due to increased loads. In this case, towing operations are performed by a special rope, which is attached in the diametrical plane to the bow platform. In the stern part of the cable clamps can be located on different sides along the sides. In this case, a loop is installed, from which the tow rope will already leave in the center. Fastening the tug itself directly to the sides is prohibited.
Cargo handling requirements
Lifting operations on sea vessels pose serious risks both for the cargo itself and for the crew. Therefore, standards are regularly improved and updated, in accordance with which it is possible to perform maintenance of such devices:
- Persons who are planned to be involved in cargo operations must complete a full safety briefing by the time they begin work.
- Zones with the passage of cables and ropes should be fenced and marked with special inscriptions.
- Hatches and enclosures that are in an upright position must be locked. Permission to work with open hatches is given by the watch assistant to the captain or head of the lifting operations.
- Crane operators and winches operate only on orders given by the signalman. Exceptions include the emergency stop signal.
Also, when servicing crane and winch mechanisms of a ship’s cargo device, it is prohibited to:
- Correct slings with load attached.
- Allow uneven tension on different sides when using multi-loop slings.
- Rock the load with a view to laying it outside the radius of the crane or boom.
- Spread the load before it fits securely onto the gaskets.
Conclusion
The vessel is equipped with a specific set of cargo mechanisms with specific structures and characteristics performed by specialists on a previously prepared project. But even before direct installation, the equipment is subjected to a thorough inspection. To initially eliminate the risks of accidents and increase the efficiency of the operation of mechanics, the cargo device of the vessel undergoes a survey. This is a kind of audit, during which a visual inspection and a series of technical tests are carried out. Based on the results of such an inspection, a decision may be made on the replacement of equipment, repair work or the continuation of current operation.