Beitrag 17

Ballast Water Management - Accumulated Experience on Exchange Methods

Lefteris Karaminas
Area Marine Business Manager for East Mediterranean and Black Sea
Product Manager for Ballast Water Management Services
Lloyd's Register of Shipping

  1. Abstract
  2. Introduction
  3. Lloyd's Register Response
  4. ShipRight BWMP descriptive notes
  5. Experience with Safety and Operation
  6. Experience with Ballast Water Management Plans
  7. Experience with Preference on Exchange Methods
  8. Experience with Ship Design and Specification for New Construction
  9. Industry support


Abstract

The present IMO legislation as well as the draft convention do not include specific assessment criteria for the approval of ballast water management plans. Lloyd's Register has filled this legislature gap and has gone beyond the present legal framework by developing the ShipRight Procedure for the Assessment of Ballast Water Management Plans in order to assist shipping companies to understand the risks and protect their assets (ships and crew) and businesses, and the asset of all the environment. This procedure has been applied for new ships under construction as well as ships in service. The procedure has become a useful industry standard and, therefore, experience has been accumulated on a common platform for all ship operators. This paper describes the relevant issues in some detail and unfolds the so far accumulated experience from the perspective of shipping companies.

Keywords

Risks. Assessment. Management. Impact. Options. Solutions. Approval. Certification. Experience.


Introduction

The continual educational efforts of IMO and various Member States have achieved widespread acceptance that introduction of harmful aquatic organisms should be prevented rather than cured afterwards. It is also imperative that the resulting widespread socio-economic problems also receive acceptable techno-economic solutions. We use the term acceptable, because we believe that the industry partners should always work together. Therefore, solutions should not be imposed, but be part of a selection process, which at the end of the day will satisfy the needs of the Administrations and still is safe and practical for the Operators. The PEST framework for ballast water management, shown in Table 1, has been discussed and analysed on several occasions and is considered to be understood by the stakeholders.

   P   
    Political/Legal
  • IMO, port state, quarantine legislation
  • Environmental protection
  • Safety of Life
  • Ship safety

   E   
    Economic
  • Fisheries
  • Clean up costs
  • Energy and treatment costs
  • Economic stability

   S   
    Socio-cultural
  • Country focus
  • Safety and quality culture
  • Cleaner seas
  • Attitude and expectations

   T   
    Technological
  • R&D activities
  • Education system
  • Training and know-how channels
  • Technological solutions

Table 1. PEST framework for ballast water management

It is useful to appreciate the numbers involved before proceeding discussing issues. In that respect, Lloyd's Register has developed a ballast water discharge simulation model based on worldwide trade. The simulation model takes into account the Lloyd's Register Fairplay World RECSO / IMO Joint Seminar on Tanker Ballast Water Management & Technologies Fleet Statistics, for the various ship types and, therefore, has the ability to estimate the amount of discharged ballast water on an annual basis for any given year. Figure 1 shows the results for the period 1996 - 2001.

Figure 1. Estimated Annual Ballast Water Discharge Worldwide

It can be concluded that the average annual ballast water discharge worldwide is nearing the 3 billion tonnes, whilst the annual ballast water discharge worldwide has changed by small increments since 1996. As the world shipping capacity is a mature market, only small fluctuations can be expected. Therefore, the results from the Lloyd's Register ballast water discharge simulation model can establish an annual average discharge figure.

Voluntary guidelines usually expect that ship's masters carrying ballast water into the waters of the country after operating beyond the EEZ employ at least one of a suite of ballast water management practices. These include exchanging ballast water in areas at least 200 miles from any shore and at least 2,000 meters deep, or in an alternative ballast exchange zone approved by the country; retaining ballast water on board; using an acceptable treatment method; or discharging ballast water to an approved reception facility.

Exchange includes flow-through exchange, in which at least three full volumes of open-ocean water are pumped through a ballast tank, and empty-refill exchange (sequential method), in which a ballast tank is emptied completely and then refilled with mid-ocean water. Thus, for exchanged ballast water, full compliance with these voluntary guidelines includes water that has been exchanged 100% (one full tank volume) by sequential method or at least 300% (three full tank volumes) by flow-through method.

Ballast water management is also about sediment removal at periodic intervals. Whilst sediment forms a small very small number when compared with the above, there are practical and safety issues associated. The Administrations have not yet defined what is an acceptable interval, since most operators deem removal of sediments from double bottom tanks impractical for periods other than docking.

The Administrations' inability to multilaterally agree and define clearly the acceptable methods, procedure and criteria for ballast water management indicates that the problem is not an easy one to solve. However, this lack of decision making could have serious implications.


Lloyd's Register Response

With concern for safety and a plethora of requests by owners and operators to assist them understand the risks and protect their assets (ships and crew) and businesses, and the asset of all the environment, Lloyd's Register has so far:
  • Conducted an investigation on 26 ships and passed the results to the industry.
  • Defined criteria and procedures for the assessment of ballast water management plans.
  • Developed a review, approval and certification service for ballast water management plans.
  • Developed the ShipRight BWMP descriptive note, which indicates to port states, flag administrations, charterers, insurers and prospective buyers that a Company has a documented procedure in place.
  • Devised and conducted 19 exclusive ballast water management practical workshops with over 400 attendees in 8 locations around the world.
  • Attended and contributed to a series of international conferences.
  • Developed the new Lloyd's Register Model Ballast Water Management Plan, which assists in the efficient preparation of the plan. The Model Plan is provided complimentary in electronic format to those who request the Lloyd's Register Ballast Water Management Services.
  • Developed specifications for new construction projects to ensure that the owners understand the issues and get the best deal for bulk carriers, tankers and container ships.
  • Developed the operational envelope concept and defined the acceptable sea state, which is a risk management approach solution, based on self-regulation.
  • Developed a training service for companies who wish to find out the latest regulatory requirements, understand the operational risks involved and help them prepare a practical ballast water management plan.
  • and more...


ShipRight BWMP descriptive notes

LR has developed the ShipRight BWMP descriptive note which identifies that a ship's operational procedures follow the current IMO guidelines with respect to treatment process, flowthrough exchange or sequential exchange, confirming that strength, trim and stability considerations have been taken into account as necessary.

It is recommended to approve the ship's ballast water management plan according to the ShipRight Procedure "Assessment of Ballast Water Management Plans".

The ShipRight BWMP (T, F, S) descriptive notes, which are recorded in column 6 of the Register Book, provide a means to indicate to port states, charterers and insurers that a ballast water management plan is in place. The suffice to the descriptive note - T (treatment), F (flow-through) and S (sequential) - indicates which method of ballast management is employed, as some administrations may not accept all methods.

Ships which intend to utilise one or both exchange methods, i.e. sequential and/or flow-through, could be eligible to one of the following descriptive notes:

  • ShipRight BWMP(S) indicates that the ship should be utilising the sequential method stand alone.
  • ShipRight BWMP(F) indicates that the ship should be utilising the flow-through method stand alone.
  • ShipRight BWMP(S+F) indicates that the ship should be utilising the sequential and the flowthrough methods combined.
  • ShipRight BWMP(S,F) indicates that the ship should be utilising the sequential method stand alone or the flow-through method stand alone.
  • ShipRight BWMP(S,S+F) indicates that the ship should be utilising the sequential method stand alone or the sequential and the flow-through methods combined.
  • ShipRight BWMP(F,S+F) indicates that the ship should be utilising the flow-through method stand alone or the sequential and the flow-through methods combined.
  • ShipRight BWMP(S,F,S+F) indicates that the ship should be utilising the sequential method stand alone or the flow-through method stand alone or the sequential and the flow-through methods combined.


Experience with Safety and Operation

IMO Resolution A.868(20) Guidelines for the Control and Management of Ships' Ballast Water to minimise the Transfer of Harmful Aquatic Organisms and Pathogens, published in November, 1997, includes guidance on safety aspects of ballast water exchange at sea. Lloyd's Register papers on ballast water management, which identify additional risks and available options, should be read in conjunction with IMO Resolution A.868(20), for training purposes.

The exchange of ballast water in open sea is a relatively new practice and has to be distinguished from any ballast operation carried out in ports or in sheltered waters. Practices therefore which are well established in a normal ballast operation should be applied with great care in case of ballast exchange at sea.

Taking into consideration that adverse weather and sea conditions can be established in a short time while under way in an open sea, ballast water exchange has to be well pre-planned.

The safety points outlined below simply emphasise the fact that an error at sea can have more serious consequences than those emanating from the same error in port.

  • Hull girder damage due to insufficient longitudinal strength as a result of unsuitable ballast exchange steps.
  • Reduction in ship's stability due to free surface effects resulting in a reduction of ship's GM or increase in heeling angle while emptying ballast water tanks or holds originally in a filled or partially filled condition in order to achieve exchange.
  • Structural damage to ship bottom forward caused by insufficient forward draught, as a result of emptying forward ballast water tanks or holds originally in a filled condition or filling partially filled aft water ballast tanks in order to achieve exchange.
  • Reduction of manoeuvrability and/or ability to make headway; caused by insufficient after draught, as a result of emptying after ballast water tanks or holds originally in a filled condition or filling partially filled forward water ballast tanks in order to achieve exchange.
  • Reduction of bridge visibility forward caused by insufficient forward draught, as a result of emptying forward ballast water tanks or holds originally in a filled condition or filling partially filled aft water ballast tanks in order to achieve exchange.
  • Structural damage to topside and hopper side tanks caused by inertia loading, as a result of full ballast hold with empty adjacent wing tanks.
  • Structural damage to partially filled ballast water tanks or holds caused by sloshing as a result of resonance with ship motion.
  • Over pressurisation damage of ballast water tanks when filling empty or partially filled tanks caused by blockages in air pipes or using excessive pumping capacity relative to the design of the ballast system. Blockages may result from lack of proper maintenance, ball failure, freezing, sabotage, or unintended closure.
  • Under pressurisation damage of ballast water tanks when deballasting tanks by gravity to an empty or partially filled condition caused by blockages of air pipes or insufficient design.

The procedures for managing ballast water have to be specifically designed to address the hazards mentioned above. It is therefore imperative that the procedures contained in a ballast water management plan are followed when conducting ballast water exchange at sea.

The use of the pumps should be clearly stated in ballast exchange plans. It is recommended that a statement is exhibited in the ship's Control Room to the effect that two pumps must not be employed together for one ballast tank due to risk of over pressurisation.

Where a Port State has designated areas for ballast exchange or has accepted or imposed other ballast water management options or contingency measures, the operation should be planned and conducted accordingly.

The ship's position, sea state, weather forecast, equipment performance, hull condition and degree of crew fatigue should be considered before proceeding with ballast exchange. If any factors are considered unfavourable, the ballast exchange operation should not commence or should be suspended. Within the limitations imposed by overall safety and operational constraints, efforts should be made as follows:

  • Where practicable, ballast exchange should be conducted in deep water, in open ocean and as far as possible from shore. Where this is not possible, requirements developed within regional agreements may be in operation, particularly in areas within 200 nautical miles from shore.
  • Where the flow-through method is employed by pumping ballast water into the tank or hold and allowing the water to overflow, at least three times the tank volume should be pumped through the tank.
  • When the sequential method is employed, all of the ballast water should be discharged until suction is lost, and stripping pumps or eductors should be used if possible.
  • Where practicable, routine cleaning of the ballast tank to remove sediments should be carried out in mid-ocean or under controlled arrangements in port or dry dock.
  • Sediment resulting from tank or hold cleaning or stripping should not be disposed in Port State territorial waters.
  • Where one or more of the recommended approaches for ballast water discharge has been followed, and loose sediment which is likely to be discharged in an initial flush, (e.g. in the bridge well of a hold space), such sediment should be drawn off by a suitable means (e.g. an initial "suck" to flush out any sediment that may have accumulated in hat boxes or suction bays during the voyage), the discharge from this operation should be placed into a holding tank or by carrying our initial release into an approved discharge area, or at sea outside territorial limits, before full discharge overboard takes place.
  • The uptake of ballast water should be minimized or, where practicable, avoided in areas and situations such as:
    • areas with outbreaks, infestations or known populations of harmful organisms and pathogens;
    • areas with current phytoplankton blooms (algal blooms, such as red tides);
    • nearby sewage outfalls;
    • nearby dredging operations;
    • when a tidal stream is known to be the more turbid; and areas where tidal flushing is known to be poor;
    • in darkness when bottom-dwelling organisms may rise up in the water column;
    • in very shallow water; or
    • where propellers may stir up sediment.
  • If it is necessary to take on and discharge ballast water in the same port to facilitate safe cargo operations, care should be taken to avoid unnecessary discharge of ballast water that has been taken up in another port.
  • Minimise departure and arrival ballast quantities but always within the constraints of safe navigation.
  • Take additional good house keeping measures to minimise the risk, such as rinse anchors and anchor chain when retrieving to remove organisms and sediment at their place of origin, remove fouling organisms from hull, piping and tanks on a regular basis.

Ballast Water exchange at sea should not be undertaken in any weather condition that would jeopardise the safety of crew operating equipment on the upper deck. As a guide, ballast exchange at sea should not be carried out or, if under progress, interrupted under the following conditions:

  • When wind strength exceeds Beaufort 4 and sea state exceeds moderate.
  • When there is indication that weather and sea conditions will deteriorate prior to completing ballast exchange program or a step thereof, adequate time margin should always be included in such cases.
  • When sailing in areas which are known to be seasonally affected by cyclones, typhoons, hurricanes, or heavy icing condition.
  • When any part of the power or ballast system (generators, pumps, level indicators, etc.) is inoperative or gives sign of under-performance.
  • When sub-zero temperatures are encountered. Sub-zero weather, where weather decks are icing, is generally considered to be unsuitable for ballast water exchange operations. If deemed absolutely necessary, particular attention should be paid to hazards associated with the freezing of overboard discharge arrangements, air pipes, ballast system valves (together with their means of control and the accretion of ice on deck.
  • When due to other important duties on board not enough trained officers and crew are available to perform the ballast exchange safely.
  • When abnormal vibrations of the vessel's hull or equipment are experienced while progressing on a certain step of the ballast exchange.
  • When other abnormal conditions are observed which, to the judgement to the Master, endanger the vessel's or the crew's safety.

It is noted that these conditions are guidelines only. It is the responsibility of the ship's Master to ensure the safety of crew and passengers is not jeopardised.

Additionally, operational limits defined for specific ballast exchange conditions must be adhered to during operation. Therefore, it is considered imperative to plan for and find the appropriate weather window to conduct safe sequential ballast exchange operations.

Ballast exchange operations are complex procedures and may last from several hours to days. All personnel engaged in ballast exchange should be well trained to respond to routine and emergency procedures.

It should always be considered that while performing a ballast exchange at sea, failure of power system or any part of ballast pumping and piping system can take place. Such incidents should be brought immediately to the attention of the Company's Safety Officer and emergency procedures should be activated to bring the ship back to her ballast seagoing condition as soon as possible. Such emergency procedures could be ballasting by gravity and even utilisation of the general service pump. Ships enrolled with the Ship Emergency Response Service (SERS) could, if necessary, activate the service.

Where a Port State Authority requires that specific ballast water procedures and/or treatment option(s) be undertaken, and due to weather, sea conditions or operational impracticability such action cannot be taken, the ship's Master should report this fact to the Port State Authority as soon as possible and, where appropriate, prior to entering seas under its jurisdiction. IMO requires that Port States should not require any action of the Master which imperils the lives of those on board or the safety of the ship.

Ships' Masters have frequently provided one of the following reasons for not exchanging ballast water:

  • clean ballast on board
  • treated on board
  • on board retention
  • discharge to reception facility
  • time-restricted route
  • location-restricted route
  • ship's design and equipment
  • ship's safety


Experience with Ballast Water Management Plans

IMO introduced the concept of a ballast water management plan (BWMP), specific to each ship, which is to contain information and guidance intended to provide safe and effective procedures for ballast water management.

In the case of exchange methods, a ballast water management plan will include Ballast Exchange Plan(s) prepared specifically for the ship.

The procedure shown in Figure 2 could be followed for the preparation of a ballast exchange plan, identifying which method is used for various ballast tanks and ballast conditions. At the planning phase the user defines the criteria for compliance. Then, the user follows several paths until a ballast exchange plan acceptable to all parties concerned is prepared.

A Ballast Exchange Plan (BEP) contains step by step instructions for the safe exchange of ship's ballast water. A BEP indicates the status of the ballast tank with relevant assessment criteria.

BEP is prepared on the basis of ship's capabilities and occasionally contains specific advice and limitations which need to be observed and adhered to.

A BEP is intended for typical ballast conditions. It is at the discretion of the ship's master to follow one of the prepared BEPs or to prepare a new BEP for the ship's specific condition, taking into account the relevant assessment criteria. If in doubt the Master should seek assistance by shore management.

Where a new BEP is to be introduced in the ship's ballast water management plan, the shore management should be advised, who in turn need to submit the new BEP to Lloyd's Register for review and approval, as necessary.

A BEP is to be followed with a great degree of thoroughness. Pre-planning and familiarisation is essential in order to ensure the safety of the ship and those on board.

Figure 2. Flow chart for BEP

In the meantime, some operators in an attempt to comply in the best possible way have developed -either themselves or with the assistance of consultants- ballast water management plans on the basis of the exchange methods (sequential and/or flow-through), without an independent vetting by a Recognised Organisation against specific assessment criteria.

Until November 2002, the following undesirable practices have been experienced:

  • Some companies have perceived that BEP and BWMP are the same documents
  • Many companies have prepared a BEP with a loading instrument not approved from stability aspects and without any cross-check with the approved loading manual
  • Some companies have prepared a BWMP by inserting the ship's details on the first pages but leaving the rest of the model plan empty!
  • Many companies have prepared a BWMP on the basis of a model plan, without tailoring it to ship's capabilities
  • Many companies have prepared a BWMP without taking into account the relevant risks
  • Many company managers have instructed their ships' Masters to prepare a BWMP without appreciation of the knowledge required
  • Many company managers have supplied their ships' Masters with a BWMP and asked them to train the crew but with negligible training supporting material
  • Many model plans having omissions with serious safety consequences have been sold to shipping companies for further use
  • Some companies have downloaded free model plans, having omissions with serious safety consequences, from the internet for further use
  • Many companies have refused to approve the BWMP due to lack of international implementation and enforcement
  • Some companies have perceived the approval process as an unnecessary added expense of no added value!
  • Some companies have commissioned BWMPs with only one BEP, despite ship's capability for an alternative BEP, in order to keep development costs to minimum
  • Many consultants with insufficient knowledge have prepared BWMPs of unacceptable quality with serious safety consequences, just for the sake of satisfying the needed paperwork
  • Some consultants with sufficient knowledge have prepared BWMPs of unacceptable quality with serious consequences, after competing at very low margins!
  • Some consultants have advertised that they are authorised to prepare and approve BWMPs on behalf of a Flag Administration!
  • Some BWMPs have been approved with serious omissions by a Flag Administration, thus endangering ship's safety and the life of those on board!

The industry is moving towards a convention, which will be requiring approval of the ballast water management plans. Such approvals need to be based on clear assessment criteria and not only by reference to IMO Resolution A.868(20). Supported by the so far experience this is without doubt a very dangerous situation and, therefore, Lloyd's Register feels obliged to warn the industry once again.

In turn, Flag Administrations should accept approval of a BWMP by a Recognised Organisation only when the latter has documented assessment criteria from research and service experience. Only then the shipping companies can have confidence that the relevant risks can be properly managed thus safeguarding life, ship and environment, whilst controlling the business impact.


Experience with Preference on Exchange Methods

At present, the majority of the operators of deadweight and freight carriers are selecting between the sequential or the flow-through method or a combination of these, provided ship is capable. The typical reasons behind such preferences are shown in Table 2.

Reason for selecting an exchange methodUsual preference
Increased scantlings for new constructionSequential
Ship and crew suffer less in-serviceFlow-through
Short route timeSequential
Promotion of company to charterers, port states, underwriters and prospective buyersFlow-through, sequential and their combination via certification
Avoidance of penalties and black listing as a result of samplingNeither method can guarantee 100% effectiveness, with the sequential method perceived to be the better of the two

Table 2. Reason for selecting an exchange method


Experience with Ship Design and Specification for New Construction

One primary aim of a company is to have a workable and approved ballast water management plan. The ballast water management plan includes the ballast exchange plan(s) which are based on the flow-through and sequential methods or a combination of these. Relevant issues are summarised.

Flow-through issues:

  • The company needs to ensure that the double bottom and side tanks will be connected. The aim is to ensure that the tank scantlings will be sufficient with a head to the top of the tank.
  • The next step should be to ensure good overflow. This can be done either by specifying the overflow design (see figures) and/or by requesting pipe overflow to inlet total sectional area ratio greater than 2,0. A larger discharge pipe is to be located in a remote position opposite from the filling pipe and a smaller discharge pipe is to be located in a closer position to the filling pipe.
  • Whilst it is expected to have two exclusive ballast pumps, it is beneficial to check that the capacity will be sufficient. Comparison with other designs should only be done to establish a minimum requirement.
  • The company should request the designer to disclose the pressure loss calculations in order to confirm that the overpressure risks have been mitigated, i.e. pressure drop characteristics are to be determined and matched to the ballast pump operating curve data.

Air pipes on ballast tanks are intended to allow air to escape, or enter, a tank during ballast operations and are usually of flat disc type or ball float (see Figure 3). They are not meant to be capable of handling large-scale discharge of ballast water, which can result from continuous ballast pumping as experienced in flow-through systems.

The anticipated high maintenance to the ball float and spindles could lead to the designs shown in Figures 4 and 5.

Figure 3. Air vent head with broken ball float

Ballast water should not be discharged from an air pipe head with float type closing appliance, unless a blank flange with a short distance piece is fitted below the air pipe head, which should be removed during the flow-through operation (see Figure 4).

Figure 4. Overflow/Air pipe for double bottom ballast tank

Manholes on upper deck should not be used as overflow discharge, unless the blank flange with a seat are fitted to the manhole cover so that a portable type plastic overflow pipe with 900 elbow can be connected during the flow-through operation (see Figure 5).

Figure 5. Portable plastic overflow pipe on manhole and deck for deep tank or topside tank

Portable type overflow discharge pipes, which are properly connected to manholes, may be utilised in order to reduce the amount of water on deck during water ballast exchange operations. However such systems are to be properly designed.

If the portable type overflow discharge pipes are at the same height as the air vent, then the situation shown in Figure 6 will arise. This situation is not advisable.

If the portable type overflow discharge pipes are aligned in the fore-aft direction, then water on deck is expected to accumulate fast, (see Figure 6). This situation is not advisable.

Figure 6. Example of an adverse overflow situation

An example of a successfully designed and tested arrangement, which could avoid the adverse situations described above, is the following:

  • Size of ballast water filling pipe is for instance 250 mm nominal bore
  • Size of overflow discharge pipes (at least two) on upper deck is at least 250 mm nominal bore each
  • Portable type plastic pipe (GRP) or fixed steel type 900 elbow with blank flange
  • Size of air vent pipes (two pipes) is 200 mm nominal bore each
  • Distance of height between centre of overflow pipe and centre of air vent pipe is not less than 600 mm
  • Actual distance between bottom of air vent pipe and top of overflow discharge pipe is minimum 375 mm
  • Direction of the outlet of the overflow discharge pipe is transverse outwards and not longitudinal
  • Actual total sectional area of overflow discharge pipes on upper deck is not less than 2 times the sectional area of the ballast filling pipe for the ballast tank

Pressure loss calculations within the ship's ballast water supply and air vent system should be requested in order to establish as to whether it is likely ballast water tanks to be over-pressurised during ballast water handling operation; including ballast water exchange.

The specification should identify that such verification needs to be provided with the ballast pump with the greatest pump capacity is used when over-flowing individual ballast tanks (e.g. one tank only); including peak tanks, i.e. not only for combined ballast tanks. Typical factors affecting the final outcome are considered to be the pipe length, routing, inner surface finish, aging, and the type of closing appliances. The flow capacity curves should be provided for the closing appliances.

Present rules require that the total cross-sectional area of the air pipes is to be not less than 25 per cent greater than the effective are of the respective filling pipe. However, for tanks where this requirement cannot be met, the rules require the fitting of overflow pipes. An example of such case is shown in Figure 7.

In the design shown in Figure 7 the ballast tanks are protected from a vacuum by two air pipes 100A. Protection from over pressure is safeguarded by the two air pipes 100A and an overflow line 400A.

This arrangement provides better protection when compared to an arrangement which has just a filling line and air pipes of 1.25 times the filling size. This is because such a system would not allow the tank to overflow through the air vent head.

It can be seen that this arrangement meets Lloyd's Register rules in respect of over pressurisation and vacuum protection of the ballast tanks, however, in case of ballast exchange by flow-through the system would not be effective, unless modifications are carried out.

The absence of a ship-side valve from the overflow system is a notable drawback and it is recommended this arrangement to be opposed.

Figure 7. Example of a ballast system based on rule alternatives

Sequential issues:

  • It is recommended BEPs to be developed with half consumables and to comply with the Lloyd's Register assessment criteria without the need to impose limitations or restrictions or define acceptable sea states, unless agreed by the company or instructed otherwise by the company.
  • Some companies are requesting that bridge visibility, propeller immersion and inclination angles of machinery to comply during all steps.
  • Aim to develop sequences where the longitudinal strength results do not exceed 85% of the class assigned permissible SWBM and SWSF, in order to account for small deviations in service, so that the Master and the Appointed Ballast Water Management Officer can have confidence in following the proposed sequences.
  • Stability to be investigated with the combination of maximum free surface effects from all ballast tanks, irrespective if ballast tanks are shown full or empty.
  • In addition, it is proposed that at the start and end of a step there will be no partially filled ballast tank. If sequences with specified partial fill levels cannot be avoided, then -since it is practically difficult to match the specified partial fill level whilst ship motions are experienced the sequences should be further assessed at ±10% of the partial fill level against the criteria.
  • Ballast hold(s) to be equipped with pressure/vacuum valves (applicable primarily for bulk carriers) in order to mitigate the risk of a large drop in pressure, due to the rapid change in the contents of the tank during ballast discharge by gravity.

For sequential systems alternative options are summarised in Table 3.

Where the global and local strength criteria are not satisfied, the following options, or a combination of these, would be available:
  • to find a new sequence
  • to define the acceptable sea state
  • to enhance the structure
  • to implement the flow-through method
  • to re-design
Where the intact stability criteria are not satisfied, the following options would be available:
  • to find a new sequence
  • to implement the flow-through method
  • to re-design
Where the propeller immersion is not sufficient, the following options would be available:
  • to find a new sequence
  • to implement the flow-through method
  • to re-design
Where the bridge visibility forward is not sufficient, the following options would be available:
  • to find a new sequence
  • to install a CCTV forward, acceptable to the Flag
  • Administration
  • to implement the flow-through method
  • to re-design

Table 3. Alternative options for sequential systems

Ship type additional issues:

Table 4 includes a selection of additional notes for sequential (S) and flow-though (F) systems, for bulk carrier (B), double hull tanker (T) and container ship (C) companies intending new construction.

NoSelected additional notesSFBTC
1If a Company wants a stand alone sequential for a BEP for a normal ballast condition, where obviously the ballast hold is not used, then provided longitudinal strength and stability are satisfied there are two remaining strength aspects:
(a) Minimum draught forward, which may not be complied. For this case, the options are:
  • to define the acceptable sea state by 0,75 x draught forward
  • to enhance the structure
  • to implement flow-through method
(b) Sloshing aspects in topside tanks, where the risk is expected in the fill range 70%-95%. For this case, the options are:
  • to insert moderate sea state note in the BEP (feasible for short duration just to avoid critical fill range)
  • to enhance the structure
  • to implement flow-through method
x x  
2If a Company wants a stand alone sequential for a BEP for a heavy ballast condition, then provided longitudinal strength and stability are satisfied we have the three remaining strength aspects:
    (a) Minimum draught forward. For this case, the options are:
  • to define the acceptable sea state by 0,75 x draught forward
  • to enhance the structure
  • to implement flow-through method
    (b) Ballast inertia, i.e. full ballast hold with empty topside and/or hopper tanks. Experience indicates that existing designs are unlikely to pass the ballast inertia assessment if typical in-service corrosion margins are deducted. For this case, the options are:
  • to define the acceptable sea state as moderate sea
  • to enhance the structure of the adjacent tanks in question (sloped bulkhead plating and/or
  • longitudinal stiffeners and/or web and/or web stiffeners and/or lugs, as necessary)
  • to implement flow-through method for the adjacent tanks in question
    (c) Sloshing aspects in ballast hold. From experience, ballast holds are not designed to withstand sloshing loads. Structural enhancement is also very difficult. For this case, therefore, the options can be:
  • to implement flow-through method
  • to insert zero sea state note in the BEP (rarely found in open seas). The zero sea state note in the manual may be fictional. From experience, some operators have opted to have this note in their manual in order to gain the "S" character of the BWMP descriptive note. For such cases, operators usually opt for flow-through.
x x  
3If a Company wants a stand alone sequential for a BEP for the ballast condition(s), then provided longitudinal strength and stability are satisfied there is one remaining strength aspect:
    Minimum draught forward, which may not be complied. For this case, the options are:
  • to define the acceptable sea state by 0,75 x draught forward
  • to enhance the structure
  • to implement flow-through method
x  xx
4It is common on bulk carriers to discharge by gravity that part of the ballast above the load waterline through an overboard valve, which gives rise to a potential high vacuum due to the rapid rate of discharge. Unfortunately, air pipes alone do not have the capability of handling such large changes in pressure as those which occur due to discharge by gravity and, unless hold ventilators are open prior to discharge, then serious damage could occur due to under-pressure. It is anticipated that for sequential systems this kind of operation will be performed in open seas, probably far away from safe haven, which makes the effect even more undesirable.x x  
5Ballast holds are normally provided with adequate ventilators, which should ensure that the hold would not be subjected to excessive pressure or vacuum. For sequential systems, it is recommended that the bilge suctions are blanked, the blanks removed from the water ballast connections and the ventilator covers are kept open whenever the floodable hold is being used for the carriage of ballast and during ballasting and deballasting. Similarly, before the hold reverts to the carriage of dry cargo the above blanking and unblanking process must be reversed.x x  
6Ballast holds and large ballast tanks should be equipped with pressure/vacuum valves, in order to mitigate the risk of a large drop in pressure, due to the rapid change in the contents of the tank during ballast discharge by gravity. These valves, if fitted, would need to be main-tained in good working order, as a chocked pressure/vacuum valve could result in hatch cover damage.x x  
7Container ships are prone to bow flare slamming, due to the fore end flare angle and frequent operation at high speed. In that respect, masters should be advised to reduce speed and/or change course accordingly.x   x
8Propeller immersion and bridge visibility criteria are expected to comply at least at the start and end of the ballast exchange operation.x xxx
9During the intermediate steps/stages, the machinery's operating design characteristics (angles of inclination) are not to be exceeded.x xxx
10Where two ballast pumps are used for filling purposes, when the fill level reaches 80% - 90%, then one of the pumps is to be deployed, in order to mitigate the risk of over-pressurisation.x xxx
11Where operational limits are specified (acceptable sea state), at least two independent pumps should be fitted. These should be arranged such that, if one pump fails, then the stand-by pump is immediately available for operation. It has been reported that most ships are equipped with two exclusive service pumps and, therefore, this recommendation may not have design ramifications for most ships in service.x xxx
12Avoid sequences with specified partial fill level. Where at the end of a sequence a tank remains partially filled, conditions at ±10% of the partial fill level should also be assessed, since it is practically difficult to match the specified partial fill level whilst ship motions are experienced.x xxx
13Aim to develop sequences where the longitudinal strength results do not exceed 85% of the permissible values, in order to account for small deviations in service, so that the Master and the Appointed Ballast Water Management Officer can have confidence in following the proposed sequences.x xxx
14For sequential systems, the fore peak tank should be fitted with a centreline wash bulkhead or a centreline ring structure or horizontal ring structures.x xxx
15If side/topside and bottom/hopper tanks are not interconnected by design, then the bottom/hopper tank should not be exchanged by flow-through, unless the tank boundary structure is checked and found satisfactory or any necessary structural enhancements are carried out. xxxx
16For flow-through systems, consider maintenance to the ball float and spindles. xxxx
17For flow-though systems, consider fitting one tank access hatch per topside tank, similar to those fitted to ballast tanks on tankers. xx  
18If flow-through is selected as the preferred method, then consideration should be given to the additional fuel consumption and possible design ramifications on fuel tanks. xxxx
19For flow-through systems, in order to improve circulation:
  • Inlet and outlet piping connections should be located as far apart as practicable.
  • A larger discharge pipe should be located in a remote position opposite from the filling pipe and a smaller discharge pipe should be located in a closer position to the filling pipe.
  • The double bottom and peak tanks may need additional pipework, if deemed necessary.
 xxxx
20For flow-through systems, the total sectional area of the ballast water discharge pipes should be not less than two times the sectional area of the filling pipe, in order to mitigate the risk of overpressure. xxxx
21For flow-through systems, avoid the use of two ballast pumps simultaneously due to the risk of overpressure, unless the system is designed for the simultaneous use. xxxx
22For flow-through systems, distribute one ballast pump to several tanks, in order to mitigate the risk of overpressure. xxxx
23For flow-through systems, to avoid water on deck, portable FRP pipes and portable FRP elbows can be considered as part of the ballast water management arrangements. xxxx
24Where overflow pipes are fitted to hatch coamings, it is recommended to fit them to the side coaming with a closing plate hinge arrangement and it should be arranged to discharge downward. To avoid water on deck, portable FRP pipes can be considered as part of the ballast water exchange arrangements. xx  
25Manholes on upper deck should not be used as overflow discharge, unless the blank flange with a seat are fitted to the manhole cover so that a portable type plastic overflow pipe with 900 elbow can be connected during the flow-through operation. xxxx
26Ballast water should not be discharged from an air pipe head with float type closing appliance, unless a blank flange with a short distance piece is fitted below the air pipe head, which should be removed during the flow-through operation. xxxx
27Distance between overflow discharge pipe and air vent pipe is to be considered. xxxx
28Direction of the outlet of the overflow discharge pipe should be transverse and not longitudinal. xxxx

Table 4. Ship type additional notes

Container ships rarely operate in ballast only conditions, since containers could be loaded and off-loaded at each port. Ballast systems could be developed to permit easy allocation during the course of the voyage to accommodate changes in the distribution of cargo and consumables.

Passenger ships rarely operate in ballast only conditions, given that their limited ballast capacity is used to compensate usage of consumables. Ballast systems could be developed to permit easy allocation during the course of the voyage to accommodate changes in the distribution of cargo and consumables. Passenger ships could retain the ballast on-board and re-distribute it internally or exchange it during or at the end of the return voyage, if navigating outside the Exclusive Economic Zone (EEZ).

Tankers utilising the concept of Hydrostatic Balance Loading have restrictions on changing their draught and trim. In certain cargo loading conditions, where ballast is taken in, the ballast would have to remain on-board and be exchanged during the ballast leg of the voyage.


Industry support

What is happening at present should not be seen as a lasting solution acceptable by all Administrations. Indeed, many Administrations view the exchange methods as a temporary measure until the introduction of effective treatment systems. Without specific internationally agreed criteria, what is acceptable to one Administration may not be acceptable to another now or in future.

In the meantime, shipping companies, operators and shipyards are supporting Lloyd's Register's efforts by mutual exploration of issues and ideas at our email address bwmp@lr.org.

We take this opportunity to thank all those who take time and effort to contribute, with a view to understand how to manage the relevant risks.

In return Lloyd's Register groups, evaluates and circulates all feedback back to the industry through frequent updates with a view to support the industry needs.

The objectives of Lloyd's Register are to assist people understand the risks associated with the ballast water management operation, find feasible solutions to satisfy regulations and still safeguard their assets (see Figure 8).

Figure 8. The objectives of Lloyd's Register Ballast Water Management Services

Until November 2002, LR has signed contracts to offer ballast water management services and has already issued certificates for many ships worldwide. 41% of the ships where the Lloyd's Register Ballast Water Management Services have been contracted are classed elsewhere. This indicates a high regard of the quality service offered. The following benefits can be realised by shipping companies:

  • Management of risks during ballast water operations helps protect a company's business and assets.
  • Helps prevent loss of hull integrity resulting from unplanned loads during ballast water transfer.
  • Enables a company to demonstrate its vision for health, safety, quality and environmental issues.
  • Allows 'business as normal' without compromising recognised environmental regulations, such as those issued by individual port states and the IMO.
  • Reduces possible business interruption due to visits on board by port state officers for ballast water management audits.
  • Helps demonstrate to flag states that responsible actions have been taken.
  • Provides evidence of duty of care to underwriters.
  • Demonstrates a ship's ballast water management capability to charterers.
  • Helps to differentiate a company from competition.