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Bulk carriers ballast exchange requirements at sea

Ships ballast tanks allow her to maintain adequate trim, propeller immersion and sufficient stability to proceed safely on a ballast voyage. This is usually between 30 - 45% of the carrier's deadweight carrying capacity.

The nature of their trade usually means that bulk carriers spend half of their life travelling large distances in ballast.

It is estimated that billions of tonnes of water, along with thousands of species of plants, bacteria and othe marine organisms, are transported on ballast voyages each year. Anything that can pass alive through a ship's ballast system can be loaded in the ballast tanks and then transported to another country's territorial waters where that particular organism may not yet exist.

Cape size bulk carrier underway

Ballast water exchange at sea

The practical method to minimize the introduction of unwanted organisms from the discharge of ballast water. The exchange procedure shall be carried out in an “open ocean condition” at least 200 nautical miles from the nearest land and in waters at least 200 metres in depth. It can be accomplished by either the sequential empty-refill method, by flow-through method or by or dilution method whereby tanks are overfilled by pumping in additional water. Due to limited biological efficiency the ballast water exchange at sea is to be regarded as an interim measure.

Flow-through method – This method involves pumping open-ocean water into a full ballast tank. Ballast equal to approximately three times the tank capacity must be pumped through the tank to achieve 95% effectiveness in eliminating aquatic organisms. Applying the flow through method does not alter the stability, stress, and ship attitude.

Sequential method – This method entails emptying ballast tanks completely and refilling with open-ocean water. During ballast water exchange sequences there may be times when, for a transitory period, the criteria for propeller immersion, minimum draught or bridge visibility cannot be met. Emptying of certain tanks may lead to major reduction of stability, higher stresses, high sloshing pressures and increased probability of bow slamming.

Further reading: MSC.Cir. 1145 Precautionary advice to masters when undertaking ballast water exchange operations, ABS Advisory Notes on “Ballast Water Exchange Procedures” – can be downloaded from www.eagle.org

Ballast water exchange standard D1 – Ships performing ballast water exchange shall do so with an efficiency of 95% of ballast water. For ships exchanging ballast water by the flow-through method, pumping through three times the volume of each ballast water tank will be considered to meet the standard described. Pumping through less than three times the volume may be accepted provided the ship could demonstrate that at least 95% exchange is met. Ballast water management – Various measures to prevent, minimize and ultimately eliminate the risk of introduction of harmful marine organisms within ballast water. Ballast water management includes the ballast water exchange at sea as well as the ballast water treatment by mechanical, physical, chemical or biological processes, either singularly or in combination. Compliance with the ballast water performance standard (regulation D-2 of the BWM Convention) seems to be achievable only by use of a Ballast Water Treatment System.

Ballast Water Management Plan – Ships of 400 gross tonnes and above are required to have on board and implement a Ballast Water Management Plan approved by Administration. The BWMP is specific to each ship and includes a detailed description of the actions to be taken to implement the Ballast Water Management requirements and supplemental Ballast Water Management practices. Ships must have a Ballast Water Record Book to record when ballast water is taken on board, circulated or treated for Ballast Management purposes, and discharged into the sea. It should also record when ballast water is discharged to a reception facility and accidental or other exceptional discharges of ballast water.

Further reading: IMO Resolution MEPC 127 (53) Guidelines for Ballast Water Management and Development of Ballast Water Management Plans

Ballast water performance standard D2 – Ships conducting ballast water management must discharge fewer than 10 viable organisms per cubic metre that are greater than or equal to 50 micrometers in minimum dimension and fewer than 10 viable organisms per millilitre that are less than 50 micrometers in minimum dimension and greater than or equal to 10 micrometers in minimum dimension; and discharge of the indicator microbes must not exceed the specified concentrations.

The indicator microbes, as a human health standard, include, but are not limited to: 1. Toxicogenic vibrio cholerae (O1 and O139) with less than 1 colony-forming unit (cfu) per 100 millilitres or less than 1 cfu per 1 gram (wet weight) zooplankton samples. 2. Escherichia coli – less than 250 cfu per 100 milllilitres. 3. Intestinal enterococci – less than 100 cfu per 100 millilitres.

Ballast water treatment – Any method to kill, remove or render infertile, harmful or potentially harmful organisms within ballast water.

Ballast Water Treatment Systems (BWTS) – Ballast Water Treatment System (BWTS) is a system designed to remove and destroy/inactive biological organisms (zooplankton, algae, bacteria) from ballast water. Ballast water treatment is still evolving technology with an ever-growing number of manufacturers. This means that there is limited inservice experience for the systems being offered and there is a general understanding that no single system is suitable for all ship types. See also AQUARIUS ballast water treatment plants.

Descriptions of numerous treatment systems can be found in the ABS notice “Ballast Water Treatment Advisory” The IMO adopted the International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention)8 in February 2004. According to this Convention, maritime nations are required to take joint measures to ensure prevention, reduction or elimination of transportation of harmful marine organisms by appropriate management of ships' ballast water and sediments. These measures include rules for the design, control and construction of:

In addition, the following guidelines are also given in the Convention:

While the BWM Convention is not fully implemented, countries such as the USA, Australia, Ukraine and Brazil already have similar requirements for ships to exchange ballast by either the flow through, sequential or dilution method.

It is recommended that approval of a procedure for exchanging ballast water at sea be obtained from the ship's classification society.

A major hazard when carrying out ballast exchange at sea is the sloshing of seawater in ballast tanks and holds. The variability of the sea and swell conditions in a short period of time is an important factor in deciding whether to exchange ballast water at sea. Responsibility for deciding on whether to exchange ballast at sea must rest with the ship's Master, taking into account the permissible limits in respect of structural strength and stability and the sea and weather conditions prevailing at the time.

Where the exchange of ballast water at sea is to be carried out, that the following guidelines be followed;

a) The ship's Master must ensure that the necessary calculations are carried out at each intermediate step so that:

i) Adequate intact transverse stability is maintained.

ii) The permissible seagoing SWSF and SWBM are not exceeded.

iii) For each cargo hold and block of cargo hold(s), the combined weight of the cargo in the hold(s) and the water ballast in the double bottom and hopper wing ballast tanks directly in way of that hold(s) does not exceed the allowable Seagoing limits for all intermediate draught conditions.

iv) The present and forecast sea and swell conditions must be favourable to ensure that significant sloshing loads, which could cause structural damage to holds or tanks, cannot be generated.

b) If the ship has been provided with a ballast exchange sequence and procedure approved by the classification society, it should always be used and followed.

c) To minimise the risk of structural damage, the exchange of water ballast at sea should always be carried out in calm weather conditions. All available weather forecasting should be utilised to determine that the weather condition is likely to stay calm within the 'weather window' of the ballast water exchange operation. This 'weather window' should be determined based upon the ballast water exchange sequence and the achievable ballasting/deballasting rates. A sufficient time margin should always be included to allow for any unexpected circumstances such as the breakdown of ballast pumps.

d) Ballasting and deballasting of each pair of symmetrical port and starboard wing and double bottom ballast tanks should always be carried out simultaneously, such that the amount of water ballast carried in each tank is always the same, to avoid the introduction of twisting and torsional loads into the hull girder.

e) The progress of the ballast/deballast operation and the weather and sea condition should be closely monitored throughout the ballast exchange operation.

f) The practice of continuously pumping in new ballast water from the sea and allowing the old ballast water in the tank to overflow through the tank's ventilation pipes may be considered. However, caution should be exercised as over pressurisation of the ballast tank could result if one or more of the vent lines are obstructed and lead to structural damage.

g) If there is any difficulty in establishing a safe ballast exchange sequence, or if there is any doubt in the interpretation of an approved procedure or the stress limits imposed on the ship, no attempt should be made to exchange water ballast at sea.

Ballast Water Discharge Requirements

1. Ballast Water Convention, 2004 -The International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004. The convention calls for ships greater than 400GT to conduct ballast water exchange or treatment in accordance with IMO regulations.

2. USCG Ballast Water Program – Rules and regulations for the management of ballast water in United States Waters, with a discharge standard in-line with IMO Ballast Water Conventions, 2004. Ballast Water Management Systems are to be tested and approved by the USCG for use on vessels transiting US Waters. Detailed information can be found at USCG Homeport, and regulation CFR 33 Part 151.

3. USCG Alternate Management System (AMS) – An interim ballast water management system recognition program, whilst systems are tested and Type Approved under the USCG regulations. Accepted AMS are Type Approved by a foreign administration pursuant to the standards set forth in the International Maritime Organization’s International Ballast Water Convention, 2004, and meeting all applicable requirements of U.S. law, and which is used in lieu of ballast water exchange. The list of AMS accepted BWMS can be found at USCG Homeport.

4. US EPA Vessel General Permit (VGP 2013) – Part of the Nation Pollution Discharge Elimination System (NPDES) program under the Clean Water Act (CWA) containing rules and regulations for the management of ballast water in United States Waters.

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  3. Loading of high density cargo and water ballast distribution for bulk carriers

  4. Regulation of pumping system of bulk carriers

  5. Risk of partially filled ballast tanks

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  12. Handling water ingress problems in bulk carrier, investigation and countermeasures

  13. Survival and safety procedure for bulk carriers

  14. Procedure for exchanging ballast at sea

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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.
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