Fig: Self unloader components in operation
Under no circumstances should the hatches be left open at night while on passage. A lack of, or improper, ventilation can lead to condensation (also known as sweating), which causes cargo deterioration. There are two types of sweat: Cargo sweat and ships sweat
If ventilation with air which is similar in temperature to or warmer than the loaded temperature of stable cargo is applied, at best it will serve no useful purpose; at worst there will be a risk of wetting damage due to condensation of moisture from the ventilating atmosphere (cargo sweat) on cold cargo surfaces possessing no or low moisture-absorptive capacity in the interiors of stows, or there will be a risk of undesirable absorption of moisture from the ventilating atmosphere by cargoes with substantial moisture absorption properties.
Thermal capacity of large stows
Under no circumstances are any of the high, low and zero moisture content categories of cargoes under consideration to be ventilated when the external air temperature is similar to or higher than the loaded temperature of the cargo. Large stows of these cargoes generally have enormous thermal capacity.
Hence, only peripheral regions of stows will usually warm or cool significantly from the loaded temperature following changes in external temperatures during a voyage. The remaining interiors of stows change in temperature from their loaded temperature much more slowly or often remain at or very close to the loaded temperature throughout a voyage, regardless of changing external air temperatures.
If the cargo has undergone fumigation, which is required to continue through the passage, checks should be made to ensure that the seals remain in position and that the fumigants do not leak due to movement of the vessel in a seaway. Any adverse changes should immediately be recorded in the logbook and precautionary measures taken to avoid any further damage and aggravation of the situation.
Self-heating and spontaneous combustion
Many bulk cargoes have a tendency to heat due to the oxidation process taking place during the voyage, which may lead to fire or explosion if the temperature rises to a level where spontaneous ignition can take place. Cargoes liable to spontaneous combustion include some types of coal, concentrates of lead, oil seed cakes (transported in bulk), fishmeal and scrap metal.
Even where the type of coal is not considered a danger for self- heating, this can still occur if stacks have accumulated over a long period ashore.
Many bulk cargoes are liable to spontaneous combustion or ship or cargo sweat. The only possible way to obtain an early warning of the start of spontaneous combustion is by monitoring the temperature of the cargo holds. Many ships are fitted with `temperature ports', ie pipes that are fitted beside the cargo hold access ladders into which thermometers can be lowered to obtain the hold temperature. The best practice is to leave the thermometers within the ports and withdraw them when a reading is desired. However, if the ship is not fitted with temperature ports, the sounding pipes could also be used to obtain temperatures. Whichever method is used for measuring temperature:
i) The thermometers should be reset before introducing them into the pipes
ii) the thermometers should be left in the pipes for some time (2-3 minutes at least)
iii) the temperature should be measured at least 2-3 height levels within the hold
iv) the temperature should not be measured solely at the surface of cargo as it is likely to be quite different from that at the bottom of the cargo hold.
Modern bulk carriers may be fitted with permanent temperature sensors providing continuous readings. It is important to maintain records of all temperature observations and ensure readings are taken at the same times and at regular intervals. This makes it easy to establish a pattern for any irregularities in the observed behaviour.
Generation of gases
Many bulk cargoes emit combustible gases in large quantities that may present a fire or explosion hazard and can corrode the steel structure of a ship.
Oxidation occurs in many cargoes as a result of chemical reactions taking place within them. This generates carbon dioxide and other gases harmful to human health. Therefore, when entering any space containing cargo, enclosed space entry procedures must be followed. Holds containing cargo should only be entered under exceptional circumstances.
Physical Inspection of Vessel
Hatch covers on a bulk carrier are weathertight, ie they can withstand a certain amount of seawater on deck and resist leakage into cargo holds. Ship's officers must ensure that the deck, including hatch covers, is regularly inspected for any signs of leakage, slackening of hatch cover securing devices and other loose items that may require securing. It is important that drain valves are inspected to ensure they are free and still in position.
Precautions against heavy weather and safety of personnel
In extreme weather, when damage is more likely to occur, the safety of personnel involved in the inspection of the vessel should be given priority. In bad weather personnel should only be allowed on deck in an emergency and during daylight. The comparatively smaller freeboard of bulk carriers means added precautions should be taken when an inspection is required:
Fig: Bulk carrier during heavy weather
CARGO LOSS PREVENTION
- Organise the team for inspection. Ideally, the Master should be on the bridge, with the chief mate in charge of the operation on deck and additional crew available as required
- if the vessel is shipping heavy seas, the ship should `heave to' to reduce heavy pitching, rolling and excess water on deck
- communications between the bridge and the deck teams should be established by using portable VHF/UHF equipment
- the engine room should be kept informed about the operation. They may wish to take the opportunity to inspect the fuel tank or other deck machinery and possibly obtain soundings of fuel tanks
- lifelines should be rigged on both sides of the vessel when sailing where bad weather is expected
- each member of the inspection team should be properly equipped with the appropriate PPE
- ideally, the inspection should take place in daylight. Otherwise, sufficient safety lights should be used
- tools necessary to tighten lashings, re-secure hatch covers and for any other anticipated task should be readily available
- the final orders to proceed on deck should always be given by the Master
- it is helpful to have a deck plan to mark the items checked, any observations regarding damage or the repairs that may be required
- on completion of inspection, proper entries should be made in the logbook.
There is an obligation on the Master and crew to exercise due diligence in the loading, carriage and discharge of cargo to ensure that it is carried safely. The major causes of cargo claims are wet damage, contamination, shortage, loss overboard, theft and physical damage.
However, should a cargo claim arise, a defence may be "inherent vice". For example, bulk grain cargoes are accompanied by a moisture certificate prepared while the commodity is in the silos and it is almost impossible for a duty officer to detect a small amount with excessive moisture coming on board as loading continues 24 hours a day and holds are enveloped in clouds of dust. However, provided the holds have been properly washed, are clean and dry, and there is no trace of previous cargoes or taint, it should be possible to provide a robust defence to any claim.
The Master and his officers must be vigilant in recording any abnormality or deviation from the description of the cargo and it is essential that the Mate's Receipt reflects, as far as practicable, the true condition. These observations should be reflected in the Bill of Lading. Thus, the Master's Letter of Authority to agents to issue Bills of Lading on his behalf must be explicit in the requirement for Bills to be issued in conformity with the Mate's Receipt.
P&I clubs and insurers are pro-active in identifying areas where claims arise and notifying members and clients. This may, for example, be in the form of a circular warning of problems with rice cargoes from the Far East, notifying a draught problem at a particular port or any of the many problems affecting the safe and efficient operation of the ship.
On board, proper records and reports must be kept of cargo damage and how it occurred. Most ships now carry digital cameras and photographic evidence to back up damage reports can be invaluable in protecting the interests of the ship. Deck logs, ventilation logs, records of inspection, maintenance records, letters of protest, draught surveys, should also be available if required.
Our detail pages illustrated many safety aspects of Bulk carrier
Home page |||Bulk carrier types ||| Handling of bulk coal |||Cargo planning ||| Carriage of grain |||Risk of iron ores |||Self unloading bulk carriers |||Care of cargo & vessel |||Cargoes that may liquefy |||Suitability of ships |||Terminal guideline |||Hold cleaning |||Cargo cranes |||Ballast handling procedure |||Bulk carrier safety |||Fire fighting systems |||Bulk carrier General arrangement
Bulk carrier voyage agreement - Function of bill of lading
Signing a bill of lading & relevant guideline
- Classification of various dry bulk commodities
- Cargo sweat and ships sweat & recommended ventilation methods
- Risk of ship sweat and how to minimise
- Ventilation requirement for various cargo
- Requirement of bilge monitoring at sea
- How to categorise ship generated garbage and management onboard ?
- What is ship sweat and cargo sweat during loaded passage - how to take preventive measures against cargo damage
Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please Contact us
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