433
Table 21. Stability parameters
_______________________________________________
Maximum righting arm (max. GZ) 0.19 m
Heel angle at maximum righting arm 11.3 deg
Range of the GZ curve 16.6 deg
_______________________________________________
Table 22. Critical openings distance to the waterline
_______________________________________________
Frame Distance Reduction of distance
No. to the to the waterline
waterline per degree of heel
_______________________________________________
Stern door - 6 2.21 m 0.08 m
Door 3 rd. Deck 50 2.87 m 0.21 m
Bow door 197 1.87 m 0.07 m
_______________________________________________
The ship in state of reduced DWT has a good
stability, and will float in equilibrium position. The
stability complies with the criteria of SOLAS ’90.
6 CONCLUSIONS
Results of the damage stability calculations, presented
in this paper are getting knowledge of risk in practice
of Ro-Ro/ Passenger ship’s exploitation. This type of
ships, with open un-subdivided cargo decks, is losing
the stability in case of damage very easy.
The damage stability calculations, presented
above, are giving a clear image of risk when some of
the ship’s compartments have been damaged.
It should be noted very clear, that in case of
damage the Ro-Ro/Passenger ship in state of reduced
DWT, and Minor penetration, has much better chance
for float in equilibrium position with a small stability
margin, than in case when the ship is fully loaded ,
with maximum DWT, having the same damaged
compartments.
The Major penetration in case of damage of the Ro-
Ro/Passenger ship resulting always as the stability
loss.
If the ship’s floating condition and stability are
calculated, a question arises if the damaged condition
is sufficiently safe. In some cases the answer is simple:
if a ship sinks, it is no longer safe. When staying
afloat, the amount of submersion or list, and the
residual freeboard has to be stated.
The results of the calculations witch has been
presented above, are giving the proof of the
significance of simplified stability information for the
Master and tools for fast verification: if the Ro-Ro /
Passenger ship sinks, or staying afloat.
Stating that in state of reduced DWT the Ro-
Ro/Passenger ship has much better chance to survive
in case of damage than the ship in state of maximum
DWT , the important advise should be noted.
When the extremely bad weather, and sea state
conditions are predicted for the sea passage of the Ro-
Ro/Passenger ship, it is better to have this ship in state
of reduced DWT than in state of maximum DWT. The
above is in connection with the accelerations, which
are extremely high in fore and after part of the Ro-
Ro/Passenger ship, and may cause the damage of
cargo lashing, and shifting of vehicles during the bad
weather. As the effect of the above, the ship is missing
the stability. Due to the above, there is a practical
advice to reduce the number of vehicles loaded in fore
and after part of main deck and on higher deck, in
order to reduce destructive effect of the high value
acceleration, and to get the partly loaded conditions of
the ship.
The process of the development of safety
regulations pertains the construction of bulkheads,
watertight doors in lower deck, watertight of
ventilation channels, construction of longitudinal
bulkheads, installation of monitoring systems for
critical openings, systems of monitoring for leakage in
cargo decks, systems of fast drainage of lower vehicle
decks.
Damage stability calculations are made during the
ship’s design phase, but they are limited to a number
of cargo conditions. In the design phase it is
impossible to predict all load variations that occur
throughout the exploitation of the ship. By law, a ship
in all conditions must satisfy the damage stability
requirements. This means, that the loading conditions
may not be exactly as it was in the design calculations.
In practice there are two solutions:
1 1. Every ship has a table or diagram of maximum
allowable KG in damage conditions.
2 2. A specialized computer software provides
instructions for captain in every imaginable or real
situation .
The results presented in this paper were
performed by using the certified vessel’s software for
loading and stability calculations according to SOLAS
2009 and STOCKHOLM Agreement (1996), taking
into account the imaginable reduced value of DWT or
fully loaded Ro-Ro / Passenger ship, with maximum
DWT.
REFERENCES
1. Loading Manual of Ro-Ro / passenger ship:
unpublished.
2. Resolution MSC.267 (85): Adoption of the
International Code on Intact Stability. (2008).
3. Simopoulos, G., Konovessis, D., Vassalos, D.:
Sensitivity analysis of the probabilistic damage
stability regulations for RoPax vessels. Journal of
Marine Science and Technology. 13, 2, 164–177
(2008). https://doi.org/10.1007/s00773-007-0261-x.
4. Szymoński, M.: Some Notes on Risk and Safety
Evaluation of Ro-Ro Passenger Ships Exploitation.
In: European Navigation Conference (ENC). IEEE,
Warsaw, Poland (2019).
https://doi.org/10.1109/EURONAV.2019.8714157.
5. Vassalos, D., Papanikolaou, A.: Stockholm
Agreement—Past, Present, Future (Part 2). Society
of Naval Architects. 39, 3, 137–158 (2002).