stability requirements l.
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  1. STABILITY REQUIREMENTS Rob Gehling Principal Adviser – Technical Marine Standards Maritime Safety & Environmental Strategy AMSA, Canberra

  2. YOUR TASK • Presumed to be to design your vessel with intact stability characteristics to meet the appropriate statutory criteria - and ultimately prepare trim & stability booklet as would be required for submission to a regulatory authority

  3. YOUR AIM! • If under AMSA jurisdiction, to provide the Master with “such information satisfactory to the Administration as is necessary to enable him by rapid and simple processes to obtain accurate guidance as to the stability of the ship under varying conditions of service” • Refer SOLAS II-1/22.1 • Load Lines Protocol (1988) reg. 10(2)(b) similar • Appendix 2 of Marine Orders Part 12 defines what is “satisfactory” to AMSA • Other jurisdictions (eg. State, Military) have similar, if sometimes less stringent requirements

  4. MY BACKGROUND • 3 years as Naval Architect in Drawing Office of large shipyard, preparing and gaining approval for stability booklets • 12 years in AMSA and its predecessors, assessing and approving stability booklets • Australian delegate to IMO’s Sub-Committee on Stability, Load Lines and Fishing Vessels Safety (SLF) since 1988, taking specific interest in operational intact stability issues • Recently elected as Vice-Chairman of SLF

  5. JURISDICTION • Determined by ship type and trading pattern • Military – DoD’s own rules but are often guided by commercial rules which they may make mandatory (ref. s.3, Navigation Act 1912) • Trading ship (ref. s.2(a), Navigation Act) - State requirements (USL Code) for intra-state voyages incl charter boats, but AMSA (Marine Orders/SOLAS) for inter-state and international service • Fishing vessel or fishing fleet support vessel (ref. s.2(b)/(ba), Navigation Act) – State requirements (USL Code) unless on international voyages, then AMSA • Pleasure craft (ref. s.2(d), Navigation Act) - State Boating laws re equipment but refer AYF and relevant parts of AS.1799 re design and construction

  6. DEFINITIONS • Passenger ship (SOLAS) is ship which carries more than 12 passengers • Cargo ship (SOLAS) is any ship which is not a passenger ship • Special purpose ship (Special Purpose Ship Code) is a mechanically self-propelled ship which by reason of its function carries more than 12 special personnel (persons who are not passengers or crew and who are in board in connection with the special purpose of the ship or special work being carried out aboard the ship, number includes any passengers)

  7. CODES • Offshore Supply Vessel (OSV) Guidelines • Intact and damage stability requirements • Mobile Offshore Drilling Unit (MODU) Code • Includes intact & damage stability • High-Speed Craft Code (2000) • Alternative to SOLAS construction/equipment /certification requirements, includes intact & damage stability criteria • Special Purpose Ship Code • Modifies SOLAS for SPSs, includes intact & damage stability criteria • Uniform Shipping Laws (USL) Code • Used by State/NT authorities, stability mainly intact

  8. IMO INTACT STABILITY CODE • Adopted in November 1993 through res. A.749(18) and has since been amended by res. MSC.75(69) • Intended to be a consolidation of requirements and guidance information adopted by IMO (eg. res. A.167(ES.IV), A.168(ES.IV), A.206(VII), A.268(VIII) & Codes for specific vessel types) • Non-mandatory but now under review again with view to some parts being made mandatory • Useful reference but not implemented by Australia (refer Marine Orders Part 12) because of problems with weather criterion among other things

  9. TYPICAL TRIM & STABILITY BOOKLET AS PER MO.12 • General stability-related info • vessel particulars, draft mark diagram, immersion angle & heeling lever diagrams • Info for Master and officers • Instructions & stability criteria • Worked example of stability condition calculation • Calculations for typical / “worst” loading conditions • Supporting data/tables/graphs • Tank plan & table, tank calibrations, hydrostatic tables, KN tables, nomenclature, inclining report NOTE – Actual required content varies with ship type

  10. STABILITY CRITERIA –LANDING CRAFT • Statutory Authority is Dept of Defence, so following info relates to hypothetical (?) application of commercial criteria • Criteria are at 6.2.2 and 6.2.3 of Appendix 2 to Marine Orders Part 12, most likely using 6.2.3(k), or 8.C.16 of USL Code • Allows for maximum GZ to occur at angles between 15deg. and 25deg, but requires higher area under GZ curve to 30deg. than normal IMO criteria • Note that criteria not to vary between load conditions

  11. STABILITY CRITERIA –MBD DAY SAILER/RACER • As “pleasure craft” no statutory stability requirements apply • But refer AYF stability requirements(?) • Refer yacht stability requirements(?) of AS.1799 Small Pleasure Boats Code • Not mandatory but have effect under consumer protection and trade practices law • Statutory stability requirements could apply if vessel put into survey for commercial operations (eg. harbour sailing) • USL Code section 8.C.12 implemented by State authorities and also called up by Marine Orders Part 12 (not AMSA jurisdiction!)

  12. STABILITY CRITERIA –NWBS DAY TRIP BOAT • Apply relevant criteria from section 8.C.1 of USL Code • Assuming vessel is under State jurisdiction (not AMSA) • Could use criteria of 2.3 to 2.5 of 2000 HSC Code • Call-up standards of Annexes 7 and 8 of Code, depending on whether craft is monohull or multihull • Note that 1.1 of Annex 8 to the 2000 HSC Code calls up the “Severe wind and rolling criterion” from the IMO Intact Stability Code • Absence of adjustments to tabulated factors to apply to HSC renders such application difficult

  13. STABILITY CRITERIA –NWBS DAY TRIP BOAT (CONT) • Note that Table 2.3.4 of 2000 HSC Code provides for some inter-changeability between the requirements of Annexes 7 and 8 • Eg. trimarans’ stability is similar to monohulls but amahs of can be tailored to meet the specified stability criteria • CFD may soon enable compliance with 2.4 to be verified by calculation but trials required for now • Intact stability criteria currently being researched as major part of review of 2000 HSC Code

  14. AUSTAL MONOHULL CREW/SUPPLY VESSEL • Mexican flag and high service speed would normally pose questions • But these are answered by specification of IMO Code on Intact Stability (IS Code) • Severe Weather Criterion NOT required • Note 2000 HSC Code could not be applied as HSC Code requires high-speed criterion to be met at displacement of maximum operational weight • Consider using 4.5.6 of IS Code in place of 3.1.2 • Offshore cargo handling probably precludes fitting passenger cabin above cargo deck

  15. DAMAGE STABILITY (Not part of brief for this presentation but generally results in relevant operational information being included in Trim & Stability Booklet)


  17. DAMAGE STABILITY – SOLAS & MARPOL • SOLAS Ch. II-1 Part B provides deterministic requirements for subdivision of passenger ships, Res. A.265(VIII) is probabilistic alternative • SOLAS reg.II-1/8-1 covers probabilistic subdivision and damage stability of ro-ro passenger ships • SOLAS Ch.II-1 Part B-1 provides for probabilistic subdivision & damage stability for dry cargo ships of L>80m unless covered by deterministic criteria • MARPOL Annex I specifies oil tanker subdivision & damage stability requirements incl. double-hulls

  18. DAMAGE STABILITY – SOLAS/MARPOL-RELATED CODES • International Bulk Chemical (IBC) Code gives requirements for chemical carriers • note that where a chemical carrier can carry petroleum grades in addition to noxious liquid substances in bulk, MARPOL Annex I also applies • International Gas Carrier (IGC)Code gives requirements for liquefied gas carriers • Other Codes cover existing ships – unnecessary to list here

  19. NOTE RE PROBABILISTIC DAMAGE STABILITY • Res. A.265 (IX) (1973) is probabilistic alternative to SOLAS Ch.II-1 damage stability requirements • now applied to ro-ro passenger ships through SOLAS reg. II-1/8-1 • Amendments to SOLAS Ch. II-1 scheduled for adoption in May to “harmonise” probabilistic method for passenger & cargo ships (flood length) • Probabilistic principles likely to be extended to Load Line and MARPOL Conventions’ damage stability • MARPOL Annex I oil outflow and guidelines for double-hull equivalence are already probabilistic

  20. INTACT STABILITY DATA -DAMAGE STABILITY LINK • A given ship at a given displacement and trim will have a limiting intact KG at which it meets any damage stability criterion • Tracking this data over a range of intact displacements and trims gives a series of limiting KG curves within which the ship must be operated to maintain compliance with the criterion • Such curves are most useful to the Master when integrated into the intact stability booklet • preferably on the same page as similar limiting KG information for intact stability criteria


  22. SHIPS FOR DRY BULK CARGOES • The most important criterion for such ships is in relation to ships which may carry grain, which must comply with the International Grain Code which is given mandatory effect in SOLAS reg. VI/9 • Most bulk carriers are designed to comply with this Code even if they are intended to engage in the iron ore and coal trades – commercially important in terms of both resale features and being able to accept grain cargoes when they arise • Involves provision of Grain Stability Data • For specialised bulk cargoes, Bulk Cargoes Code should be checked for any extra requirements • Eg. transportable moisture limits, extra watertight integrity / bilge requirements, gas sniffing (coal)

  23. TIMBER CARGOES • Many Handy-size bulk carriers are arranged for carriage of timber on deck (clear side-decks, stanchions) • 1966 Load Line Convention Annex I, Ch. IV provides for assignment of “lumber” load lines • stability requirements are as per 4.1 of Intact Stability Code which in turn calls up the Code of Safe Practice for Ships Carrying Timber Deck Cargoes

  24. SUMMARY • It is essential to establish the jurisdiction and regulatory environment in which the ship will operate at the outset • This varies between your selected projects • AMSA intact stability requirements generally build on basic IMO stability criteria, HSC is exception • Looking beyond intact stability, relevant intact stability criteria related to cargoes and the operational linkage between intact and damage stability should not be overlooked