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发表于 2006-3-21 10:18:32
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来自 江苏无锡
Re:[讨论]油船燃油舱双壳形式
关于油船双壳的问题，是MARPOL 13F 13G的相应要求，在没有新的要求出来前，船级社仍然按IMO现行要求进行法定检验。
目前只有对油舱货舱区域的双壳要求，也就是从艏防撞舱壁至机舱前舱壁这一区域内要求设双壳，对于机舱区域是没有要求的。
但是，目前还有些国家对HFO舱提出了一些看法，认为那些大船的HFO甚至可能比小船的货油还要多，事故造成的危害比小船要大的多，因此对于HFO舱提出是否也要加双壳，但好象这个还没有由IMO正式颁布，所以我认为目前还是没有对HFO双壳的强制要求吧。
INTERNATIONAL MARITIME ORGANIZATION
IMO
E
SUB-COMMITTEE ON SHIP DESIGN AND
EQUIPMENT
47th session
Agenda item 6
DE 47/6/3
22 December 2003
Original: ENGLISH
PROTECTION OF FUEL TANKS
Double hull formulation
Submitted by Germany
SUMMARY
Executive summary:
This document includes a proposal for relevant criteria for the
protection of fuel oil tanks based on the on the principles of the
probabilistic oil outflow methodology (revised MARPOL Annex I,
regulation 21).
Action to be taken:
Paragraph 10
Related documents:
DE 46/29; DE 46/INF.4; and MEPC 49/16/6
Background
1 Large commercial ships often carry quantities of fuel that are greater than the lower limit of MARPOL 73/78, Annex I, regulation 13F or 13G requirements for the protection of cargo
tanks of oil tankers. Germany therefore agrees and supports that practicable and reasonable measures should be identified and implemented for the protection of fuel tanks against collision and stranding. In the aftermath of the Erika in 2001 the matter was taken up by the MSC and included in the work programme of the DE Sub-Committee.
2 In order to promote a discussion on this issue, a document had been submitted by the Netherlands to DE 46 for relevant new MARPOL requirements in respect of double hull protecting larger bunker tanks. The Netherlands’ proposal (DE 46/29) is based on the formulae used in MARPOL Annex I, regulation 13F and calculates the minimum width of double hull at ship’s sides as a function of the deadweight of the vessel.
3 Germany strongly supports the need for this kind of measure to ensure marine environmental protection from the spillage of oil by fuel tanks. The formulation of such requirement, however, should be made based on a more sophisticated formulation than the earlier proposal to allow for a more sophisticated approach covering all kinds of ship types rather than only oil tankers. This can be achieved by making use of the hypothetical oil outflow parameter as recently developed for the revised MARPOL Annex I.DE 47/6/3 Problem
4 As mentioned above, Germany supports the proposed measure. Any formulation based on deadweight, however, in defining a required width of a double hull for bunker tanks is considered problematic for a number of reasons. Some of these are mentioned in the following to illustrate the problems with the recently proposed formula:
.1 Deadweight is significantly depending on ship types. Any bulk carrier with 20,000 dwt, 600 m³ bunker fuel tanks and a speed of 14 knots may have more or less the same main dimensions as a passenger ferry with only 5,000 dwt, but a speed of 25 knots and 2,000 m³ bunker fuel tanks. With a double hull requirement based solely on deadweight, the bunker fuel tanks of the bulker would have to be protected to a greater extent than the larger ones of the ferry. This does not seem feasible.
.2 Any conversion of a built vessel would become rather difficult. For example, the lengthening of a vessel, the removal of unused cargo equipment (cranes), the construction of so-called “ducktails” and several other nowadays typical conversions leading to a possibly substantial alteration in deadweight (in most cases this is the task of such conversions) would become more or less impracticable, due to limitations of deadweight by the built width of the fitted double shell of bunker fuel tanks. If deadweight were to govern the size of the double shell width, this would significantly impair the conversion market. Additionally, this would also apply in cases of mere draught increases.
.3 Identical sister ships may differ in the lightship weight by more than one percent, due to changes in design of supplied equipment, tolerances in steel plate thickness and a lot of other reasons outside the responsibility of the yard. If deadweight were to govern the size of the double shell width, it will cause problems in ship designs.
.4 Basing fuel oil tank protection requirements on deadweight would generally reduce the flexibility in design within a series of ships. Within a series of ships some sister vessels might be built with a higher ice class standards, others without. Some vessels will be equipped with cargo gears, others not, etc. All these rather small differences will have impact on deadweight and they sum up. Today this is common procedure to built and employ such sister ships. In future such small changes to the construction, equipment or operation of any vessel may necessitate additional changes of the interior design of a vessel, if bunker fuel tank protection requirements were to be based on deadweight.
.5 In design stages there is also the problem of the accuracy of light ship weight estimation. When building a new first vessel, the design (workshop drawings, especially for equipment and machinery) and the construction of the first vessel is going more or less parallel. Due to this the yard is making a weight estimation of the whole vessel at the beginning of the project. This estimation is more or less accurate and will be amended through its construction. Some times the light ship weight will be overestimated. Today, this would result in additional deadweight, and the vessel will be considered a more efficient design due to its higher earning capacity. If fuel oil tank protection requirements were based on deadweight it would create a problem in this respect.
5 Any double hull requirement for very small oil tanks [<30 m³] is considered to be problematic as well. A lot of small operationally required tanks must be fitted in the double bottom of engine-room at the lowest point of a system (for example lubrication oil circulation tanks, drain tanks, etc.). If double hull will be required for this kind of very small oil tanks, the design of engine-rooms must be changed significantly, engine-rooms would become
inadequately larger.
Worked example
6 On a German ship yard a number of ships, admittedly the sample consist of different sizes of tankers, have already been built with fuel tank protection even though there is not yet any requirement in place for fuel tanks on tankers not located within the cargo tank length. In the annex details of built ships are presented as an example.
Proposal
7 MEPC 42 has approved guidelines that describe the procedures for obtaining approval of alternative tanker designs to double hull standards on the basis of probabilistic outflow performance standards. MEPC 49 has also approved a simplified outflow analysis approach to replace the current hypothetical outflow regulations 22 to 24 of MARPOL Annex I.
8 Adopting a performance-based criterion such as the proposed approach based on the principles of the probabilistic oil outflow methodology gives the designer and future operator the freedom to optimise the fuel tank arrangement with regard to requirements of design and operational considerations, while assuring an environmentally sound standard taking into account
the specific tank sizes and their location relating to the overall risk.
9 Germany therefore proposes that a performance-based standard be developed based on an approach as described in the two related MARPOL requirements, i.e. the guidelines developed for MARPOL Annex I, regulation 13(7) and the revised hypothetical outflow regulations 22 to 24 of MARPOL Annex I.
Action requested of the Sub-Committee
10 The Sub-Committee is invited to note the above information and take action as considered appropriate.
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