Carriage of Emulsified Oils

7/31/2019 Carriage of Emulsified Oils

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Regulation 13F: Applicable to new tankers as defined by paragraph 1 of the regulation

2.1.2 The cargo areas of tankers of 600 DWT or above are to be protected by double bottom

tanks and each cargo tank capacity is limited to 700 m3 unless its sides are also protected.

Additionally, if the tanker is 5000 DWT or above, double sides must be provided, thereby

constituting a complete double hull. These spaces, which protect the cargo oil spaces, areprohibited from carrying fuel oil bunkers.

Regulation 13G: Applicable to existing oil tankers, as defined by regulation 13G(1)(a)

2.1.3 Currently, regulation 13G requires product carriers of 30,000 DWT and above and crude

oil tankers of 20, 000 DWT and above to be phased out at 25 years of age unless steps are taken

to mitigate the outflow of oil in the event of collision or grounding by operating HBL or by

protecting the cargo tanks with ballast tanks or void spaces in which case the tanker can operate

to 30 years of age.

2.1.4 The IMO amended regulation 13G in 1999, such that product tankers carrying fuel oil,heavy diesel oil or lubricating oil as cargo would be subject to regulation 13G for tankers of

20,000 DWT and above. This is due to come into effect on 1 January 2003. However, in view of

the revised regulation 13G agreed at MEPC 46 in 2001, the above amendment is superseded.

Regulation 14: No fuel oil tank should however be located forward of the collision bulkhead.

2.2 SOLAS Convention

2.2.1 The provisions of SOLAS regulation II-2/15.2.3 with respect to the location of the oil fuel

tanks reads as follows:

As far as practicable, oil fuel tanks shall be part of the ship's structure and shall belocated outside machinery spaces of category A. Where oil fuel tanks, other than double

bottom tanks, are necessarily located adjacent to or within machinery spaces of category

A, at least one of their vertical sides shall be contiguous to the machinery spaceboundaries, and shall preferably have a common boundary with the double bottom tanks,

and the area of the tank boundary common with the machinery spaces shall be kept to aminimum ..

2.2.2 The intent of this regulation is to minimize the exposed area of fuel oil (FO) tanks within

the machinery space and thereby reduce the risk of breaching an internal boundary. ProtectingFO tanks from hull damage will have little or no impact on increasing the FO tanks exposed area.

2.2.3 SOLAS regulation II-2/15.2.4 further states:

No oil fuel tank shall be situated where spillage or leakage therefrom can constitute a

hazard by falling on heated surfaces.

2.2.4 The fitting of side protection to FO tanks may have an impact of the location of the tank

relative to heated surfaces given the limited space available in machinery spaces.

2.3 Classification rules

IACS Members have integrated requirements similar to SOLAS requirements in their own

Classification Rules.


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2.3.1 Amounts which may be carried unprotected

2.3.1.1 Large amounts of fuel oil can be carried in ships as bunkers. Most of today's oil

tankers, bulk carriers and container ships can carry more fuel oil as bunkers than the amounts of

cargo oil which drive the requirements of Annex I for an oil tanker carrying fuel oil as cargo, as

shown hereunder.

2.3.1.2 Fuel oil can be carried in bunker tanks located in the ER and in bunker tanks

distributed throughout the ship's length including in way of the double bottom, except for tankers.

2.3.1.3 The general issue of size and location of bunker tanks should be considered with

respect to protectively locating the bunker tanks.

2.3.1.4 The various oil quantities referred to in MARPOL Annex I which are used to

determine when and how the regulations apply could be considered as a base line if considering a

requirement for the protective location of fuel oil tanks.

2.3.2 Bunker tanks located in the engine room

2.3.2.1 The engine room being usually located aft of the cargo area, is less vulnerable to

damage in a collision or grounding than more forward spaces. Locating the bunker tanks in this

area would thus seem appropriate for the purpose of protecting the environment.

2.3.2.2 The space available in the engine room area is more limited than in any other location,

particularly in smaller ships. Double bottom tanks are normally used to store fuel oil in the

engine room area owing to the hazards inherent to the carriage of fuel in the engine room. (If they

are not located in double tanks, further requirements apply as to their location, which makes the

limitation of space even more crucial).

2.3.2.3 More stringent requirements for the carriage of emulsified oil or high-density oil

within the engine room area could encourage the carriage of these fuel oils in areas which are

more vulnerable to collision and grounding.

2.3.2.4 This aspect should however be weighted against what could be considered an

acceptable risk.

2.3.2.5 MARPOL Annex I regulation I/2(2) uses 200 m3 as the maximum amount of cargo oil

which can be carried by a ship other than an oil tanker without being submitted to additionalrequirements. Above this amount, the ship is required to comply with certain oil tankers

requirements of Annex I, in particular, the length of its cargo tanks is limited.

2.3.2.6 The use of 200 m could constitute a compromise starting point with respect to the

carriage of emulsified or high-density fuel oil in unprotected bunker tanks located within the

engine room.

2.3.3 Bunker tanks located throughout the ships cargo length

2.3.3.1 As noted above, these areas are more vulnerable to collision and grounding. Any

pollution has become unacceptable to the public, whatever the origin (bunker oil or cargo oil),and by inference there is clearly a demand for the ships designers, builders and for the legislator

to take all necessary measures to prevent risks of oil pollution incidents. Therefore, the public

and environmental bodies may expect bunker tanks to be protectively located, in a similar way to


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an oil tankers cargo oil tanks. Even more so in the case of critical fuels such as emulsified and

high-density fuel oils.

2.3.3.2 Owing to the amount of fuel oils being carried on ships, there would be a rationale for

considering the same quantities as for cargo oil tanks when discussing the requirements which

could be advisable to apply to fuel oil tanks. These amounts mentioned here, are those whichregulatory bodies may take into account:-

600 DWT (i.e. around 600 m3)

2.3.3.3 This is the deadweight above which a double bottom is required to be fitted to protect

cargo oil tanks of new tankers against stranding. The capacity of cargo oil tanks is further limited

to 700 m3 if the sides are not protected (Reference: MARPOL regulation I/13F)).

200 and 1000 m3.

2.3.3.4 These are the quantities of cargo oil above which ships other than tankers carryingcargo oil are applied further requirements of Annex I otherwise applicable to oil tankers

(Reference: MARPOL regulation I/2(2)).

700 m3

2.3.3.5 Oil tankers less than 5000 DWT having cargo oil tanks with individual capacities less

than 700 m3 are not required to be protectively located with wing tanks (reference: MARPOL

regulation I/13F.7(b)).

5000 DWT(thus around 5000 m3).

2.3.3.6 This is the deadweight above which new oil tankers are required to be fitted with

double sides, thereby constituting a complete double hull (reference: MARPOL regulation

I/13F)).

3 OTHER CONSIDERATIONS IN THE CARRIAGE OF EMULSIFIED OILS AND HIGH-DENSITY

OILS

3.1 High corrosion rate

3.1.1 One concern with the carriage of emulsified fuel oils, would be the risk ofMicrobial/Sulphur Reducing Bacteria (SRB) attack on the steel. The collection of water/sludge

in a tank would need to be kept to a minimum or at risk areas suitably protected, to avoid the risk

of microbial/SRB attack. Micro-organisms are prolific in the temperature range of 15-35C.

3.1.2 A double hull arrangement could be more at risk than single hull, due to its insulating

potential, this may lead to storage temperatures within the 15-35C range. Single hulls benefit

from the cooling effect of seawater in contact with the hull of single skins and, therefore, lower

temperatures.

3.2 Need for protective coating

If fuel oil tanks are protected by a 'double hull', the surrounding cellular spaces will need

to be protected to a high specification to prevent the inevitably high corrosion rates (all corrosion

not just microbial/SRB) that would ensue if they are void spaces, corrosion rates would increase


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if used as ballast tanks. In particular, there may also be a need for special requirements for anti-

bacterial coating of such bunker tanks.

3.3 Re-evaluation of survey regime

3.3.1 In view of the possibility of increased corrosion in these spaces, the question arises as towhat would be needed for current non-ESP ships in terms of inspection regimes?

3.3.2 The shape and structural configuration of the aft end of a ship in way of the ER may cause

design and structural problems in installing a double side to protect fuel oil tanks in these areas.

In addition there is likely to be problems of access to and survey of the double side spaces for

fuel oil tanks greater than those posed by double hulls in protecting cargo spaces.

3.4 Other consequences of the physical characteristics

Because the oils in question have a density close to (or possibly above) that of sea water

the advantages in connection with a lower hydraulic pressure inside the tank than in the seaoutside the tank could be lost or at least reduced. A rupture in the tank bottom will/may cause

that the oil sinks out just due to gravity. This will make use of double bottom tanks for fuel oil

much more hazardous. It will also imply that the basic theory (hydrostatic balance) behind the

draft new regulation 21 of Annex I (damage assumptions) might have to be revisited as the

balance would be modified and the oil outflow would become bigger in the case of emulsified or

high-density fuel oils.

3.5 An alternative approach

3.5.1 The basis of protectively located bunker tanks is to mitigate oil outflow in the event of

damage which causes a breach of the ship's bottom or side shell. The performance-basedprobabilistic methodology currently being developed by the BLG Sub-Committee for the new

draft MARPOL regulation I/[22] could be similarly applied to the protection requirements for

fuel oil tanks. A rationale that provides for design flexibility and takes into account the

probabilities of outflow amounts due to size and location of bunker tanks could be one which

embraces the performance-based approach used in the new draft MARPOL regulation I/[22].

3.5.2 However, a suitable criteria for maximum outflow would need to be developed based on

an adjusted/weighted criteria taking into account the type of oil and its impact on the environment

may be appropriate when considering ships carrying emulsified or high-density oils as cargo or as

fuel oil.

3.5.3 Some studies are becoming available, which show the impracticalities of protectively

located double bottom bunker tanks, particularly with respect to container ships.

4 OTHER ISSUES INDUCED BY THE CARRIAGE OF EMULSIFIED OR HIGH-DENSITY FUEL

OILS.

Most of the equipment in use today in the treatment of fuel sludge/residues is based on

gravitation. The lesser the density, the more efficient the equipment. With emulsified and high-

density fuels, these gravimetric-based equipment prove to be inefficient. Alternative systems

exist, based on technology such as hyper-filtration or floccation, the current standards for typeapproval of separation and monitoring equipment would need to be revised to allow the provision

of such equipment on board ships which use high-density fuel oils.


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5 ALTERNATIVE OR EQUIVALENT MEASURES ON EXISTING SHIPS

5.1 In the case of oil tankers, regulation I/13G provides for an accelerated phasing-out of

existing single hull tankers.

5.2 The alternative measures provided by Annex I, are unlikely to provide adequateprotection for emulsified fuels and high-density oils, and carriage in single hull/bottom tankers

may not be acceptable. Double hull tankers might thus be necessary, but this should be

investigated against accidental oil outflow performance in view of actual density, amounts being

carried, etc.

5.3 With regard to the protection of bunker tanks, the current belief is that alternative

measures could be aimed only at mitigating the effect of a bunker tank rupture. These could

consist of:

.1 reinforcing the bottom and side areas of the tanks designed for the carriage of

emulsified fuel or high-density oil; or

.2 subdividing the bunker tanks so as to limit the length/capacity and potential

outflow of the tanks.

6 IMPACT ANALYSIS IN THE LIGHT OF AMENDED REGULATION 13G OF ANNEX I TO

MARPOL 73/78

6.1 Most of the tankers subject to phase out belong to Category 3 as defined in the new

regulation 13G adopted at MEPC 46. Single-hull tankers of this category will be phased-out

according to the time scale in the new regulation 13G extending from 2003 up to 2015.

6.2 An IMO informal group of experts numbered the category 3 tankers at around 4,000 with

a total capacity of 18.7 million DWT, of these, about 300 tankers only are provided with a double

hull. This would indicate a considerable newbuilding demand for replacements for the category 3

tankers leading up to 2015. Similar studies have not been made with respect to numbers existing

cargo ships carrying large amounts of fuel oil in unprotected tanks. There are no statistics

available indicating how many ships worldwide use emulsified or high-density fuel oil and there

are no indicators of what could be the expected trend in the next few years.

6.3 However, owing to the effect of the amended regulation 13G on the oil tanker building

capacity, careful consideration of any further impact on the shipbuilding industry with respect toall types of ships is needed when considering measures for the protectively located transportation

of emulsified or high-density fuel oils.

7 ACTION REQUESTED OF THE SUB-COMMITTEE

The Sub-Committee is invited to note the foregoing.

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Carriage of Emulsified Oils