Leaflet for damage stability calculation according to SOLAS 2009

Transcription

1 Hamburg Version 1.2 Leaflet for damage stability calculation according to SOLAS 2009 Table of contents: 1 Background Intention of this paper Formal application Application by early implementation New and amended regulations All type of vessels (dry cargo and passenger vessels) Initial draughts Attained Index for each draught Trim Permeability of cargo spaces Double bottom Wells in double bottom Transverse penetration Cross flooding Opening points Passenger vessels Probability concept Minor damage concept Escape routes and hatches External heeling moments Intermediate stages of flooding Documents to be submitted for examination and approval to Class On-board documentation Contact Persons at Germanischer Lloyd Version date description V Initial version V text update referring to MSC.Res.216(82) / previously referrring to MSC.Res.194(80) update on Reg. 9, base conditions for bottom damage scenarios / wells and sump tanks in DB update on Reg. 7-2, consideration of escape routes Leaflet for damage stability calculation according to SOLAS of 10

2 1 Background In its 80 th session, IMO has revised the SOLAS regulations referring to damage stability calculation. In the so called harmonization of damage stability the concept of a probability assessment will be applied for dry cargo vessels and also for passenger vessels. The philosophy behind the probabilistic concept is that two different ships with the same attained index are of equal safety and, therefore, there is no need for special treatment of specific parts of the ship, even if they are able to survive different damages. The latest edition of regulations are included in MSC.Res.216(82) [afterwards referred to as SOLAS 2009], in addition Explanatory Notes to the SOLAS Chap. II-1 Subdivision and Damage Stability Regulations have been finalised which will be issued as a MSC Resolution in November. The technical content is already available in IMO Paper SLF51/WP.1. 2 Intention of this paper This paper is intended to highlight new and amended regulations in SOLAS 2009 in comparison to the present SOLAS It is the intention to serve customers when designing vessels based on the new regulations, respectively when preparing the required documentation and calculations. This leaflet does not substitute the careful and detailed study of the relevant regulations and continuing this paper is not intended to cover all aspects of the new regulations. 3 Formal application Related regulation: MSC.Res.216(82), Reg The new SOLAS 2009 regulations will apply for dry cargo ships and passenger vessels with a keel laying date on or after respectively for vessels which undergo a major conversion on or after that date. 3.1 Application by early implementation For a series of vessels which are built around that date, it might happen that different regulations apply to different vessels of the series (i.e. SOLAS 2004 for vessels with a keel laying date before 2009, and SOLAS 2009 for vessels with a keel laying date afterwards). In case it is the intention of the shipyard or owner to apply the new regulations for all vessels within the series ( early implementation ), a formal acceptance from the Flag State Administration would be required. In such a case GL offers support to obtain a respective allowance from the responsible Administration. 4 New and amended regulations Several new, respectively amended regulations have been developed in comparison to the present SOLAS 2004 requirements. For instance the formulas within SOLAS 2009 for the subdivision indices A and R and further the probability values p, r, v and survivability factor s are based on latest evaluation of Leaflet for damage stability calculation according to SOLAS of 10

3 statistical data and stability assessments have been adjusted accordingly. Therefore such formulas differ from the phrases contained in SOLAS In general a correct application of such new regulations is crucial for designers to obtain best possible results in short time and to facilitate and speed up the certification process. 4.1 All type of vessels (dry cargo and passenger vessels) Initial draughts Related regulation: MSC.Res.216(82), Reg. 2 and 7 Three (3) initial draughts shall be considered as a basis for the damage stability calculation (in SOLAS 2004 two draughts are considered). The definition of deepest subdivision draught d S, partial subdivision draught d P and light service draught d L is included in Reg. 2. It is noted that the light service draught represents in general a ballast arrival condition for cargo ships, respectively arrival condition with passengers for passenger ships. By this assumption the light service draught is commonly higher than the counterpart in SOLAS 2004 (light ship draught). As a consequence the partial draught for SOLAS 2009 is commonly higher than the partial draught for SOLAS Attained Index for each draught Related regulation: MSC.Res.216(82), Reg. 6 For each of the three considered draughts the calculated partial indices A S, A P and A L shall meet a percentage of the total attained index A. For dry cargo vessels that percentage shall be not less than 0.5R, for passenger vessel 0.9R. This requirement is intended to ensure a level of safety for the entire range of operational draughts Trim Related regulation: MSC.Res.216(82), Reg , 7.2 The damage stability calculation shall be based on a deepest subdivision and partial subdivision draught with level trim and a light service draught with a trim level corresponding to that condition. The validity of such damage stability calculation is restricted to an operational trim of ±0.5% of the ship s length L S. If in any service condition greater trim levels occur, additional damage stability calculations with different trim levels shall be performed. The intervals of trim values should not exceed 1% of L S. Results of such calculation shall be compiled in form of a GM envelop curve covering all relevant trim levels. In the Stability Booklet respective remarks regarding restrictions in operational trim are to be included. Leaflet for damage stability calculation according to SOLAS of 10

4 4.1.4 Permeability of cargo spaces Related regulation: MSC.Res.216(82), Reg. 7-3 Variable permeabilities for cargo spaces are newly implemented (in SOLAS 2004 fixed permeabilities are stipulated). The permeabilities depend on the considered draught (deepest subdivision / partial subdivision / light service) and on the type of cargo space (dry cargo / container / ro-ro / liquid cargo). In addition in the Explanatory Notes permeabilities for timber and wood cargo are included. space permeability subdivison draft partial draft light service draft Dry cargo spaces 0,70 0,80 0,95 Container spaces 0,70 0,80 0,95 Ro-ro spaces 0,90 0,90 0,95 Cargo liquids 0,70 0,80 0,95 Timber cargo in holds 0,35 0,70 0, Double bottom Related regulation: MSC.Res.216(82), Reg. 9 SOLAS 2009 specifies in detail requirements for fitting a double bottom. In case parts of a double bottom are not arranged, an equivalent level of safety is to be proved by a separate set of calculation. Generally a double bottom is to be fitted extending from the collision bulkhead to the afterpeak bulkhead which shall be continued out to the ship s sides. Under certain circumstances a double bottom needs not to be fitted respectively an unusual arrangement would be acceptable in accordance with Reg. 9.1, Reg. 9.4 or Reg This includes if it is not practicable or not compatible with the design and proper working of the ship or in way of watertight tanks, including dry tanks of moderate size, provided the safety of the ship is not impaired in the event of bottom or side damage. Furthermore, according to the Explanatory Notes it is considered an unusual bottom arrangement, if the inner bottom reaches the side shell above the partial draught d P. In such a case, if a double bottom is not fitted or an unusual arrangement is applicable, a sufficient level of safety is to be shown by a separate calculation for bottom damage scenarios according to Reg As base conditions for the bottom damage scenarios, the three initial cases (d S, d P, d L ) from the damage stability calculation shall be used. In figure 1 examples for missing / unusual double bottom arrangements are shown. Leaflet for damage stability calculation according to SOLAS of 10

5 Partial Subdivision Draught Figure 1 B/20 Keel Line It is to be noted that this regulation is a deterministic element (distinctive damage extensions in longitudinal, transverse and vertical direction) within the probabilistic concept of SOLAS For the calculations the position of the damages should be assumed anywhere at that parts of the vessel which are not fitted with a double bottom or fitted with an unusual bottom arrangement, however, including bordering parts within the reach of the damage (see figure 2). Area where no double bottom is fitted Possible damage locations Figure 2 Proof of compliance with Reg. 9.8 can be regarded of equivalent safety where a double bottom does not comply with the requirements of this regulation. Leaflet for damage stability calculation according to SOLAS of 10

6 4.1.6 Wells in double bottom Related regulation: MSC.Res.216(82), Reg SOLAS 2009 specifies that small wells shall not extend downward further than necessary. Wells are permitted if the protection given by a regular double bottom is still achieved. Other wells (e.g. lubricating oil tanks under main engines) shall in no case extend downward further than 500mm above baseline. Small wells Engine Room Cargo Hold ME-LO-Sump Tank min. 500mm Figure Transverse penetration Related regulation: MSC.Res.216(82), Reg. 7.5 and 7-1 A maximum transverse penetration depth of half of the breadth of the vessel shall be assumed. As a consequence, in the forward and aft ends of the ship where the sectional breadth is less than the ship s breadth B the transverse damage penetration can extend beyond the centreline bulkhead. The methodology of transverse damage penetration is based on a normalized damage statistics with the full ship s breadth B rather with the actual breadth along the ship s length. For calculation of the probability values p, the maximum penetration b is limited to B/2 measured inboard from the ship s side, at right angle to the centreline at the level of the deepest subdivision draught Cross flooding Related regulation: MSC.Res.216(82), Reg and Explanatory Notes --- Cross-flooding devices, which are intended to correct large heeling angles, shall be self-acting (as far as practicable). In case where controls to equalization devices are provided they shall be operable from above the bulkhead deck. Respective information regarding the use of such cross-flooding devices shall be included in the on-board documentation for the master (Damage Control Plan, Damage Control Booklet and Stability Booklet). The time for equalization by cross-flooding shall not exceed 10 min (in SOLAS 2004 for passenger vessels 15 min). The calculation of the cross-flooding time shall be performed according to IMO.Res.A.266(VIII), whereby this regulation is presently under revision by IMO. Leaflet for damage stability calculation according to SOLAS of 10

7 4.1.9 Opening points Related regulation: --- Explanatory Notes referring to Reg. 7-2 and 15-1 The correct consideration of position and level of tightness of opening points is crucial for the calculation of damage stability. In the Explanatory Notes it is stated that openings are the most critical factor to prevent an inaccurate A index; therefore all opening points need to be considered. This includes weathertight and unprotected openings such as airpipes, vents, hatches, doors etc. With respect to the level of tightness, the Explanatory Notes further clarify that airpipes should be regarded as weathertight (not watertight). 4.2 Passenger vessels Probability concept For passenger vessels the concept of a probabilistic damage stability calculation is implemented on a mandatory basis (previously in SOLAS 2004 a deterministic concept was considered, alternatively a probabilistic approach according to IMO.Res.A.265 could be applied). This could have major influence on the design of such ships as the principles for assessing the level of safety by means of a damage stability calculation are fundamentally changed Minor damage concept Related regulation: MSC.Res.216(82), Reg. 8 For passenger vessels intended to carry 36 or more persons additional calculations for minor damage scenarios are to be performed. The concept is based on a deterministic approach with distinctive damage extensions in longitudinal, transverse and vertical direction depended on the main data of the vessel and number of persons on board (see table 1). For all considered damage scenarios at least a survivability factor s of not less than 0.9 is to be achieved (damages on both sides of the vessel, incl. possible cross-flooding, incl. moments acc. to Reg , lesser extent acc. to Reg. 7.6). N Pers l dam b dam v dam position of damage 36 max (0.015L s, 3m) max (0.05B, 0.75m) at any position between transverse 36 < x < 400 linerar interpolation d s m watertight bulkheads 400 max (0.03L s, 3m) max (0.1B, 0.75m) at any position along the side shell Table 1 For passenger vessels intended to carry 400 or more persons an additional damage scenario involving all compartments within 0.08L measured from the forward perpendicular is to be calculated, whereby a survivability factor of s=1 is to be achieved. The calculation shall be performed for all three basic draughts (deepest subdivision draught, partial subdivision draught and light service draught). Leaflet for damage stability calculation according to SOLAS of 10

8 4.2.3 Escape routes and hatches Related regulation: MSC.Res.216(82), Reg , Reg These paragraphs apply to horizontal evacuation vertical escape routes on the bulkhead deck. Special attention is to be paid to possible immersion of escape routes when calculating the survivability factor s (in SOLAS 2004 a margin line was considered). In case of immersion of escape routes the s- factor is to be taken equals zero. Both types, horizontal and vertical evacuation routs, can be treated the same way with the exemption that the immersion of horizontal evacuation routs is only relevant in the final stage of flooding while vertical escape riutes may not become immersed in any intermediate stage or in the final stage. The definition of the term bulkhead deck acc. to Reg is as follows: Bulkhead deck in a passenger ship means the uppermost deck at any point in the subdivision length (L s ) to which the main bulkheads and the ship s shell are carried watertight and the lowermost deck from which passenger and crew evacuation will not be impeded by water in any stage of flooding for damage cases defined in regulation 8 and in part B-2 of this chapter. The bulkhead deck may be a stepped deck. In a cargo ship the freeboard deck may be taken as the bulkhead deck External heeling moments Related regulation: MSC.Res.216(82), Reg For passenger vessels an additional survivability factor s mom is to be calculated for each case. By this calculation external heeling moments due to passenger movement, wind pressure and launching of survival crafts are considered. For the calculation of s mom the intact displacement is to be taken at the subdivision draught. In calculating the heeling moment due to launching of survival craft M Survivalcraft the lever arm of the empty boats is between the stowage position and the position fully swung out, while the lever arm for the persons is from centre line of the ship to the centre line of the rescue boat in the position fully swung out. Because the lever arm of the boats increases with heel and with the height of the guide roller above the water, these quantities have to be included in the calculation of M Survivalcraft. The heel angle to be assumed is 15 deg as this is the limit for s > 0. For calculation the curves of righting arms the heeling levers can be assumed as constant over the whole range of heel Intermediate stages of flooding Related regulation: MSC.Res.216(82), Reg , Reg For passenger vessels an additional survivability factor s intermediate is to be calculated for each case where intermediate stages of flooding occur. By this calculation the effect of cross-flooding devices respectively the effect of progressive flooding is taken into consideration. Such calculation for Leaflet for damage stability calculation according to SOLAS of 10

9 intermediate stages should be performed wherever equalization is not instantaneous, i.e. equalization is of duration greater than 60 sec. In the Explanatory Notes samples for flooding boundaries which could restrict the flow of water are listed. Where calculation of intermediate stages is required, each stage should comprise of at least two intermediate filling phases in addition to the full phase per flooded space. 5 Documents to be submitted for examination and approval to Class Related regulation: --- Appendix, Reg. 2 Clear guidance is given in the Explanatory Notes what is the required scope of documentation to be submitted. In general the documentation shall be comprehensive and complete to allow the examination body (i.e. classification society or Flag State Administration) to verify all input data and calculated results in detail. For checking the input data of the calculation the following is needed: lines plan, hydrostatic data, cross curves, sub-compartments (including centres of gravity and permeability), watertight integrity plan (with all internal and external opening points), subdivision limits, draught data, opening points (with their level of tightness); watertight door location with pressure calculation, wind profile, cross and down flooding devices and the time calculations. As initial data for the calculation the following is needed: subdivision length, initial draughts with corresponding GM values, R index, A index with summary tables. For checking the calculated data detailed results for each damages cases that contributes to the A index is to be given such as: draught, trim, heel, GM, dimension of damage with probabilistic values, p, v and r, righting lever curve with survivability factor s, critical opening point (weathertight and unprotected). Emphasis is laid on a Watertight Integrity Plan (Reg ) which describes the assumption for the damage stability calculation in form of a drawing by showing the watertight subdivision of the vessel and openings therein. Further it is to be noted that a detailed presentation of results for each damage case (Reg ) including full righting lever curve data for each case contributing to the attained index is required. 6 On-board documentation Related regulation: MSC.Res.216(82), Reg and 19 Appendix Reg. 1.2 The ship s master shall be provided with clear intact stability requirements which are to be included in the Stability Booklet. In general this is achieved by determining GM/KG-limit curves, containing the admissible stability values for the draught and trim range to be covered. For the on-board documentation Damage Control Plans and Damage Control Booklets are to be prepared. These documents are intended to provide the ship's officer in charge with clear information on the ship's watertight compartmentation and equipment related to maintaining the boundaries and effectiveness of the compartmentation so that, in the event of damage to the ship, proper precautions Leaflet for damage stability calculation according to SOLAS of 10

10 can be taken to prevent progressive flooding through openings therein and effective action can be taken to quickly mitigate and, where possible, recover the ship's loss of stability. Newly implemented is the requirement as stated in the Explanatory Notes, that a Damage Control Plan and Damage Control Booklet is also to be provided for tank vessels. 7 Contact Persons at Germanischer Lloyd Headoffice: Christoph Peickert [email protected] +49 (0) (deputy head of stability department) Korea: Jan Schreiber [email protected] +82 (0) China: Hanno Fimmen [email protected] +86 (0) Leaflet for damage stability calculation according to SOLAS of 10