Causes And Countermeasures of Deformation in The Cargo Hold Area of Bulk Carrier

Bulk carrier are ships used to carry unpackaged bulk cargoes such as coal, ore, timber, livestock, grain, etc. Structurally, bulk carriers are divided into single-hulled bulk carrier and double-hulled bulk carrier. A major feature of the bulk carrier is that the ship's cargo hold has a tall hatch enclosure, the interior with inclined side boards connected to the side and the inner floor, the deck below the two sides of the hatch with an inclined top side of the hatch in order to limit the movement of goods, so that can reduce the work of the cabin, but also to facilitate the concentration of goods to the center of the cargo hold. The cargo hold is also equipped with triangular cabinets at its four corners, which can be used as ballast water tanks for adjusting the draught and stability height. In this paper, we will introduce the causes of deformation and preventive measures in the cargo hold area of bulk carrier.

Analysis of the Causes of Hull Deformation in Bulk Carrier

1. Hull Corrosion

Due to the frequent loading and unloading of various kinds of goods in the cargo hold of bulk carrier, it is inevitable that corrosive goods, such as sulfur, salt, coal, etc., will be encountered, and at the same time, under the dual action of water vapor and humid environment, the coating on the side wall of the cargo hold is very easy to be damaged, resulting in the bottom plate of the hull and the wall of the cargo hold being directly exposed to the environment, which greatly accelerates the corrosion rate, and it is very easy to deform or even break the hull in the case of stress concentration, and it will bring a serious potential risk to the safety of the bulk carrier.

2. Unreasonable Loading of Cargo

Overloading of the local strength of the hull will increase the stress and torsion on the bulk carrier, thus causing deformation of the hull and damage to the hull structure and strength. For example, when the bulk carrier is carrying high-density cargo, the unreasonable distribution of cargo in the cargo hold is very likely to have excessive local load, which in turn affects the structural strength of the hull.

3. Structural Defects Throughout the Ship

Usually, shipowners choose irregular shipyards to manufacture ships in order to save manufacturing funds, and use insufficient materials in the manufacturing process, such as small hull size, corresponding transverse beams, longitudinal bone and other structures do not meet the design dimensions and so on. This kind of ship is very easy to produce deformation after being put into operation.

4. Overloading of Ships

Bulk carrier will be approved draft in the design, only to ensure that sailing under the approved draft in order to make the bulk carrier will not be subjected to stresses exceeding the stresses that the materials used can withstand; on the contrary, if the ship is overloaded and the draft is increased, in the case of the ship's structure has not been changed, the actual stresses will be more than the permissible stresses, so that the ship's hull will be deformed, and even lead to bow and stern upward or downward.

5. Damage from Loading and Unloading

The topside compartments and side structures of bulk carrier are very vulnerable to damage, deformation or cracks when loading and unloading cargoes. In the loading and unloading ports of coal and ore, the use of grabs to grab cargoes will cause greater damage to the double-deck bottom plate, and bulk carrier may also use bulldozers, pneumatic hammers and other mechanical equipment when loading and unloading cargoes, which will cause great damage to the double-deck bottom, the bottom side compartments, the ribs and other cargo hold structures.

Countermeasures to Prevent Hull Deformation of Bulk Carrier

1.Good Anti-corrosion Measures

One is to use anticorrosive coating materials in the cargo hold area of the bulk carrier to avoid direct contact between the cargo and the bulkhead, and the other is to take measures to prepare the hold according to the nature of the cargo before loading the cargo, such as cleaning the bulkheads, refinishing and so on, and at the same time, it is possible to strengthen the ventilation of the hold, so as to avoid part of the cargo from heating up and damaging the ship's hull in the process of carrying the cargo.

2. Enhancing Crew Training

The company should strengthen the professional skills training for the crew, implement good safety operation measures, supervise the ship to do a good job of self-checking items before sailing, especially to strengthen the management of cargo loading and unloading, and strictly implement the operating procedures for cargo loading and unloading to prevent similar accidents from occurring. The crew should strengthen the maintenance of the ship, find out the corrosion or deformation affecting the structure as early as possible and take measures in time. Meanwhile, the crew should be familiar with and proficient in the job requirements, business knowledge and professional skills, and carry out the training of skills in dealing with emergency accidents on a regular basis, so as to be able to take measures correctly in case of emergency and minimize the loss.

3. Strengthening Structural Inspections of Ships

Classification societies and maritime departments need to strengthen structural inspections, find structural defects early and take remedial measures, such as increasing the deck thickness in time after the private lengthening and widening of the cargo hatch of bulk carrier, and increasing the support at the mid-point of the cargo hold perimeter plate, etc., so as to make the stresses borne by the structure of the cargo hatch area within the permissible range. When the strength of the cargo hold opening enclosure plate is not up to standard, the enclosure plate can be strengthened by adding reinforcement, increasing the thickness and width of the folding plate, and when the enclosure plate does not form an effective connection with the forward and aft bulkheads and the side of the ship, it can be used to add elbow boards and bulkhead reinforcing material, to prevent deformation of bulkheads due to stress concentration. When the poor welding quality of the ship is found, the shipyard should be asked to make up the welding to meet the standard requirements of welding, so that the ship components can form a whole.

Conclude

Qinhai Shipyardhas been strengthening quality control in the shipbuilding process, and shipowners also need to take precautionary measures in the use of the ship, and find that the hull structure is deformed, and take timely remedial measures to ensure the safe operation of bulk carrier.