The Bulk Carrier & Operations

Q. What is a bulk carrier?
Ans. Bulk carrier is a ship specially designed to transport unpackaged bulk cargo, such as grains, coal, ore, steel coils and cement, in its cargo holds. Actually, bulk carriers are specially designed to maximize capacity, safety and efficiency.

Q. What are the general features of a bulk carrier?
Ans. General features can be explained as follows:

  • The engine room on a bulker is usually near the stern, under the superstructure. The hatch covers are between 45% and 60% of the ship’s breadth. The length of hatch covers is about 60% of the length of the holds.
  • For better efficiency, hatches must be large, but large hatches present structural problems. Hull stress is concentrated around the edges of the hatches, hatch areas are reinforced by locally increasing the scantlings or by adding structural members called stiffeners.
  • These vessels have hydraulically operated metal hatch covers. The ‘Load Line 66’ imposes a requirement that hatch covers must withstand load of 1.74 tons/m² due to sea water and a minimum scantling of 6 mm for the tops of the hatch covers. The International Association of Classification Societies then increased this strength standard, requiring that the pressure due to sea water be calculated as a function of freeboard and speed, especially for hatch covers located in the forward part of the ship.
  • Bulkers have the upper and lower corners of the holds, used to place ballast tanks in addition to the double bottom area. The angle of the upper hopper tanks is kept less than that of the angle of repose of the anticipated grain cargoes, thus making the holds self trimming for grain. 
  • The double bottoms are made high enough to allow the passage of pipes and cables and also are made spacious enough to allow safe access to perform surveys and maintenance.
  • Hulls are made usually of mild steel.
  • High-tensile steel used on newer vessels reduces the light weight. However, the use of high-tensile steel for longitudinal and transverse reinforcements can reduce the hull’s rigidity and resistance to corrosion. 
  • Transverse partitions are normally corrugated bulkheads, reinforced at the bottom and at connections.

Q. How are bulk carriers categorized as per Regions?

Ans. Bulk carriers are often associated with the names of places, indirectly reflecting a few features. Thus, Malaccamax means a ship of ‘length over all’ of 330 m, draft 20 m & dwt 300,000. It limits the size for vessel that can pass through the Straits of Malacca. Similarly, Dunkirkmax means a ship of ‘length over all’ of 289 m, beam 45 m & dwt 175,000. It limits the size for vessel that can enter the eastern harbour lock in the Port of Dunkirk.

Q. How are the bulk carriers categorized according to size?
Ans. The categorization of bulk carriers as per size may be done as follows:

  • Mini-bulkers with a capacity of under 10,000 dwt are generally designed for river transport.
  • Handysize and handymax ships, typically of 150 to 200 m in length and dwt about 40,000 to 55000 are of general purpose in utility.
  • Panamax vessel limited by the Panama canal’s lock chambers, has the limitations of beam 32.31 m, length overall 294.13 m and draft 12.04 m.
  • Capesize ships are too large to traverse the Panama canal & Suez canal.
  • Very Large Bulk Carrier (VLBC) are generally of length over 270m, draft 20m or more & dwt 180,000 and more.

Q. How are the bulk carriers categorized, gear-wise?
Ans. Geared bulk carriers are typically in the handysize to handymax size range. They have cranes, derricks or conveyors  that allow them to load or discharge cargo in ports without shore-based equipment. Gearless carriers on the other hand are bulkers without cranes or conveyors. Self-dischargers are bulkers with conveyors belts,  or with the use of an excavator that is fitted on a traverse running over the vessel’s entire hatch, and that is able to move sideways as well.

Q. What are Lakers?
Ans. Lakers are the bulkers seen on the Great Lakes, often have a forward house which helps in transiting locks. They suffer less corrosion damage and have a much longer lifespan than the conventional ships.

Q. What are the different codes and publications, for assisting you in loading of a bulk carrier?
Ans The most important document is the ‘loading and stability manual’. The important codes being Grain Code, Solid Bulk Code, now called International Maritime Solid Bulk Cargoes Code (IMSBC Code) and Supplements; viz. Bulk Loading and Unloading Code. There might be a separate Grain Loading Manual. The other reference materials are the past loading records of similar cargo, preferably if it is in respect of the same port. ‘Bulk Carrier Practice’, By Capt J. Isbester is an extremely useful publication giving variety of information in detail.

Q. What is the difference between BLU Code and the IMSBC Code?
Ans. The BLU Code, as the name suggests is to provide safety in loading or unloading a bulk carrier. It is intended to rule out an accident, which could result due to communication gap, negligence etc. between the parties involved viz. ‘The Ship’, ‘The Terminal’ and ‘The Charter’.

The cargo should be loadable and compatible with the ship and the ship should be berthed at appropriate wharf, which the charterer must ensure. The ship particulars must be declared correctly to the charterer so that he can do appropriate arrangements. The terminal and the ship must exchange important details such as loading rate, acceptance rate, number of holds, number of loaders, deballasting rate, air draft, position of accommodation, mode of communication, notice required etc. so that safety is maintained during the loading / unloading operations. The BLU Code also provides a sample loading / unloading plan. The purpose of the code is to assist persons, responsible for the safe loading / unloading of bulk carriers, to carry out their functions and to promote the safety of bulk carriers. The code primarily covers the safety of ships loading / unloading solid bulk cargoes and reflects current issues, best practices and legislative requirements. The code deals with the procedures between the ship and terminal prior to cargo handling and even prior to the ship’s arrival. Code is also good guide in respect of loading of cargo and handling of ballast.

IMSBC code on the other hand deals with the dangers associated with the shipment of certain types of cargoes, lists typical products which are shipped in bulk and gives advice on their properties and methods of handling. Code also describes various test procedures, which should be employed to determine the characteristics of cargoes. The code deals with three basic types of cargoes:

1. Those which may liquefy.

2. Materials which possess chemical hazards.

3. The materials which fall in none of these categories but may pose other dangers.

Q. How would you go about making a loading sequence on bulk carrier?
Ans. One of the most useful reference materials would be the recent loading sequence of the ship, preferably for the similar cargo and even more preferably from the same terminal. A sample loading sequence with the worked example is provided in appendix of BLU Code. The two most important factors to consider are,

1. The stresses should be in limit throughout the loading and deballasting.

2. The vessel should be stern trimmed throughout for stripping of the tanks. The loadicator can be used effectively to do the calculations and confirm the status of stresses.

Q. Can you find the SF and BM values if loadicator fails?
Ans. Yes, in all the new ‘loading and stability manuals’, required information and procedure are provided in order to calculate SF and BM values at selected stations, normally the bulkheads. The ship’s officers have to only feed the cargo, ballast, FW and bunker information in the locations provided.

The previous loading plans and the standard load conditions may also be referred if necessary.

Q. What is bulkhead correction?
Ans. The SF and BM values, calculated normally, assume no bulkheads along the length of the vessel. In practice, some of the load caused by cargo in the hold is transferred to the adjacent bulkheads though the DB structure, instead of through side shell. The correction is significant only when alternate loading is done. The bulkhead correction is calculated by comparing the SFs, at adjacent bulkheads on both the sides. This is multiplied by a factor that is available in the loading manual. If the bulkhead correction is ignored, it will be the error on safer side.

Q: What are Harbour / Sea condition of stresses used in loadicator?
Ans. On loadicator there are two setting of stresses viz. ‘Harbour permitted stresses & Sea permitted stresses’. In harbour, while doing the cargo operations alongside at berth, vessel remains in static water. There are no waves; hence the ship is exposed to stresses & bending purely due to the loading. On the other hand, in open sea, with the waves influencing the stresses, the situation is different. One of the worst conditions for the ship’s bending would be by a wave faced longitudinally, which is approximately equal to the ship’s length (wavelength = ship’s length) & has a height or amplitude that is large and is practically possible. Thus, if the ship is generally loaded more in middle will sag in harbour, caused purely due loading. This ship when at sea meets a wave of above kind longitudinally & its trough is amidships with crests at ends then the ship will sag more but even then the total bending moment must not exceed maximum allowable bending moment.

Q. How is it decided whether the permitted stresses are appropriate for a Ship?
Ans. Classification Society, on behalf of the Administration, prepares the ship specific loading & stability manual. Maximum stress or bending a ship can take being already calculated by naval architects.

The various factors which are considered are:

  1. Nature of voyage & cargo expected to carry.
  2. Steel ship/ wooden ship.
  3. Material of steel used.
  4. Dimensions such as width, vertical separation between decks.
  5. Length of vessel.
  6. Thickness of decks & strength members especially the main girder & keel.
  7. Possibility that the data is usable even when the ship gets old, i.e. the lifespan of ship.
  8. The way the loading will be done, i.e. block loading, alternate hold loading, etc.
  9. Torsional stresses, double hull, bulkheads influencing the bending.

Q. What do you mean by Capesize bulk carrier or Handysize bulk carriers?
Ans. Very large bulk/ore carriers of dwt more than 80000t are called Capesize Bulk Carriers. These are too large to traverse the Panama canal & Suez canal Handysize Bulk Carriers have dwt from 10,000t to 35,000t.

Q. What is the difference between Handysize & Handymax bulk carriers?
Ans. Handy max bulk carriers are bigger than handysize with DWT between 35,000t & 55,000t.

Q. What are self discharging bulk carriers?
Ans. A self discharging bulk carrier is the bulker with conveyor belt, or with the use of an excavator that is fitted on a traverse running over the vessel’s entire hatch and that is able to move sideways as well. This allows the discharge of cargo, quickly and efficiently.

Q. W.r.t. Bulk carriers, what is ‘ship shore check list’?
Ans. Ship shore list means the checklist having the format contained in relevant appendix of the BLU code. The idea being the better preparedness of the ship and shore wrt each other. Thus, the cargo operation can run smoothly. E.g. if the terminal does not know the air draft of ship at load draft and the ship does not know the loading rate, etc., the things can become very complicated and cause undue delays.

Q. How is the topping up done in bulk carriers at completion of loading?
Ans. Depending on the size of the bulk carrier, the last 500t to 5000t of cargo is kept in hand for trimming. The actual quantity to load may be slightly different from the one provided by stevedore, owing to the inaccuracy of counter reading. End holds are left for trimming so that the effect due loading in these holds is maximum. When the last part is still to go, vessel is more or less on even keel. The bulk carrier must finish with required leveling in each hold. Ship must sail upright & normally on even keel when loaded fully. Suppose the ship has forward trim of 30cm, when the last bit is yet to be loaded, there are 4 ways in which the sailing trim can be achieved. Thus, the required cargo distribution figure for the balance cargo maybe found:

  1. By loadicator or computer: Distribute the quantity to load in end holds (trial & error), in order to arrive at even keel.
  2. By trim tables: This again is trial and error method. Trim tables give change of forward & aft draft for the quantity loaded in any hold.
  3. By LCB-LCG calculations: For the vessel to be on even keel, tabled LCB must be equal to final LCG. To achieve this LCG the quantity to load in each compartment can be found. The calculations are done by taking the weight moments about aft perpendicular.
  4. By taking moments about COF: Moments are taken about the COF. Forward loading will cause forward trimming moments & aft loading will cause aft trimming moments. The difference of these moments must equal trim change in cm × MCTC.

Q. What precautions must be taken by the Master prior to and during Loading or Unloading Operations? 
Ans. Prior to and during loading / unloading operations the Master must ensure that:

  1. Compliance to port regulations particularly in respect of ballast water management must be ensured.
  2. The Loading or unloading of cargo must strictly be done under the control of the OOD and supervision of the chief officer.
  3. The drafts and trim are monitored throughout the loading or unloading process, to ensure that the ship’s structure is not over stressed. If necessary, the cargo operations are suspended for an intermediate assessment.
  4. The ship should be kept upright or, if a list is required for operational reasons, it must be kept as small as possible, for limited period, with all the precautions.
  5. Mooring lines are continuously monitored taking due account of local weather conditions and forecasts. Sufficient officers and crew are retained onboard to attend to the adjustments of the mooring lines or for any normal or emergency situation.
  6. The Terminal Representative is notified about the requirement of cargo trimming.
  7. The local and international regulations regarding ballast water management are complied with, keeping in mind the stability and stress of ship. The Terminal Representative is made aware of the requirement for harmonisation between any ballast operation; cargo loading; unloading; etc. Any deviation from the pre decided plan is also discussed.
  8. Terminal Representative must be given the periods during which loading may need to be suspended and the duration of such suspensions. 
  9. A plan is agreed with the Terminal Representative about the actions to be taken in the event of rain or any emergency.
  10. Close supervision of the loading or unloading operation, especially during final stages of the loading or unloading is ensured.
  11. The Terminal Representative is informed immediately of any damage caused during loading / unloading.
  12. The Terminal Representative is advised in advance, of the final trimming, in order to allow for the conveyor system operators to be cautioned in time.

Q. In view of the restrictions posed by Ballast Water Management System, what precautions are taken?
Ans. Ballast operations should be planned in advance by the ship’s officers. Any such operation is duly entered in the Cargo Loading and Discharge Plan. Before start of cargo operations, Master should approve the plan. Officers must be able to show an appropriate plan for a complete change of ballast. Latest Port Guide and relevant information must be referred in respect of ballast water sediment discharge procedures. Rules applied by the State authorities must be found out. Thus, articular operations at a port may be; no permission to release any ballast water; release and exchange in acceptable areas; restriction applied so as to minimise the uptake of contaminated water; discharge of ballast water into shore-facilities; etc.

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