How are steel coils loaded onto ships?
It’s no secret that steel is a cornerstone of the global economy. This commonly used iron alloy is one of the most widely produced, manufactured, transported, and consumed materials in today’s supply chain.
Steel has a wide range of uses, encompassing everything from industry and agriculture to homes, cities, infrastructure, and various products.
According to reports, global steel production has increased more than 10 times in the past 70 years and is expected to reach astronomical figures in the future.
This is due to a surging population, globalization, booming infrastructure construction, growing production, diversified supply chains, and, of course, growing demand from all walks of life. Steel and its various products are a vital part of global trade, playing a crucial role in the economic growth of any country.
Transporting Raw Steel
After the hot steel is removed from the blast furnace, it must be cold-annealed and further processed to enhance its strength, quality, and surface and internal properties.
The steel is then formed into slabs, ingots, plates, bars, and other shapes for subsequent use. This process is also called steel casting.
The steel processed into these shapes is transported to steel mills or other production facilities. The steel is then formed into plates, bars, beams, profiles, channels, tubes, and other shapes according to commercial standards.
After the initial stage of steel production, there are two rolling processes in the rolling mill. The steel is cast into various shapes in raw or semi-finished form after annealing:
Hot rolling/Cold rolling
During hot rolling, the steel is heated to extremely high temperatures (until it is red hot) and then rolled. During cold rolling, the steel is cooled rapidly and processed at a lower temperature to improve its surface and mechanical properties.
After cold rolling, the steel is ready for use. After partial processing of bulk steel, following hot rolling or full processing of steel after cold rolling, the steel is typically rolled into large coils for easy transportation and storage.
Steel Coil Loading Pattern
Steel coils made from hot-rolled or semi-processed steel coils are called hot rolled coils, which require further processing and cold rolling before they can be put into use. Hot rolled steel coils are usually rolled after annealing. Similarly, steel coils made from quenched and cold-rolled or fully processed steel coils are called cold-rolled coils.
These steel coils possess excellent surface and mechanical properties, and are ready for the market after being properly formed into various customized products. These steel coils can be uncoiled and then processed or cold rolled (for hot-rolled coils) or made into various products or parts (for cold-rolled coils).
For ease of transportation, most of these steel products are transported in the form of steel coils through cargo ships. The transportation of such steel products plays a crucial role in the freight market of the commercial supply chain.
We are also familiar with these large cylindrical steel coils, which are loaded and unloaded at cargo terminals and transported by road in trucks and trailers.
However, specific regulations and guidelines govern the bulk storage and transportation of these steel coils on ships.
Loading of Steel Coils on Ships
These steel coils are usually transported in bulk and stored accordingly in designated cargo holds of ships. The weight of these steel coils ranges between 40 and 50 tons. Therefore, before loading on ships, the following must be ensured:
The cargo holds must be swept clean, washed with fresh water, and thoroughly dried. All remaining deposits, such as rust, chips, swarf, and other contaminants, must be removed. Any residual gases in the cargo hold must also be removed before loading. According to regulations, after the cargo hold is cleaned, a “cleanliness certificate” must be obtained from a third party.
Inspection of the steel coils before loading is essential.
Assess the integrity of the cargo hold and its watertightness, openings and hatches, ventilation system, and the integrity of the loading crane.
Inspect the cargo hold thoroughly and accurately mark any sharp edges or corners that may be present.
Ensure that loading and securing guidelines are prepared as well as an appropriate loading plan. Although for practical purposes and in accordance with Regulation VI of the Safety of Life at Sea Convention, securing guidelines are required for all types of cargo, steel coils are not subject to any specific framework. It is therefore the responsibility of the operator and cargo management personnel to ensure that the steel coils are safely and adequately stowed, maximizing the available space.
Loading and unloading procedures
Whether on board a ship, at a freight terminal or in a port, loading is performed with extreme precision using cranes and booms. The coils are usually lifted from their geometric center, with the attachment point usually being a braided wire or rope. Avoid using chains to prevent damage to the steel surface.
Extreme care is taken to ensure that the coils are intact (especially for cold-rolled and finished coils). When handling these coils with forklifts, round or circular lifting forks are used in addition to the traditional rectangular forks with sharp edges, which can damage the steel surface or deform the center of the coil.
The coils are always placed axially in the longitudinal direction of the ship; that is, their circular center of gravity is always facing the bow and stern of the ship.
The coils are permanently fixed transversely to the bottom of the ship to prevent rolling and damage. To prevent damage to the steel surface and to ensure sufficient friction to prevent rolling, the coils are usually placed on transversely arranged wooden boards (called “shims”).
Coil Loading
These coils are usually 25 to 30 mm thick and act as an intermediate layer between the coils and the hull. Additionally, they absorb most of the structural loads from the coils before distributing them evenly throughout the hull.
These fillers are carefully dried beforehand to ensure that they contain no moisture, which may cause rust and corrosion to the coils. The piles are bolted to prevent any movement of the coils during the voyage and transfer the resulting dynamic loads to the hull.
For practical purposes, cargo coils are always placed in designated holds and not anywhere on the deck or above the stiffened deck. The loading pattern should be reasonable to ensure optimal space utilization and prevent abnormal or irregular loading of the coils.
In addition, the packing position is carefully designed to ensure that the weight of the coils is not transferred to the unstiffened parts of the hull (which may generate static, dynamic and local stress loads), but is transferred as a whole to the lower hull or inner lower hull (in double-bottom ships) in the form of linear distributed loads, with the highest loads often falling on the stiffeners and overhanging members.
On the other hand, this can also be problematic as it can result in the entire shipload not complying with the loading information specified in the Cargo Information Booklet and the Instruction Manual. However, in practice, steel coils are usually transported using large bulk carriers or other multipurpose cargo ships that are well reinforced and have a high design load rating.
Similarly, during unloading, the piles and ties need to be carefully removed and the steel coils lifted one by one by a crane starting from the top deck, just like cargo.
Storage and stabilization
After the steel coils are loaded, storage and stabilization are another important step. Steel coils vary in size and weight. Therefore, from the outset, their storage method is similar to that of any other type of cargo. To accommodate more of this type of oil, the oil is stored in the lower cargo hold and loaded from the bottom up.
To keep the center of gravity free from vertical restrictions, the heaviest oil coils are loaded first and stored at the bottom, and the lighter or smaller oil coils are placed on the top. Suitable fasteners are used between the oil coils and secured with belts or strapping.
Steel Coils
To accommodate more coils, the coils are placed horizontally and in multiple layers. The coils are secured with strapping between two consecutive layers. To store multiple rows of coils, a gap of at least 10 to 15 cm must be left between the coils to avoid contact forces and damage during loading and unloading.
The central coil (also called the master coil) is placed horizontally and vertically in the center with the steel straps facing the adjacent coils and the coil below.
The strapping is made of strong, taut metal and is usually pneumatic in modern systems. Any key coils that are located on the lower coils should be strapped and secured.
The lower edge of the diameter should be located below the upper end of the lower coil, and its position should not be less than one-third of the geometric diameter of the lower coil; but it should not exceed 60% of the diameter of the upper coil or main coil.
