Anti-roll tanks

[ombugge]

Anti-roll tanks are nothing new on OSVs and Fishing vessel among others, but use of anti-roll tanks on Mega Container Carriers is not yet common:

Joint project launched to expand ART application to large container ships ‣...

Consideration for ART installation on large container ships is growing as this solution is expected to improve container loading efficiency by reducing roll motion and preventing parametric roll, which is regarded as one of the causes of container collapse accidents.

Parametric roll is a resonance phenomenon in which the roll of a ship is rapidly amplified when the roll period of the ship and the encounter period of waves are in a certain relationship. When a ship encounters parametric rolling it is almost impossible to take any action.

[spowiednick]

In 1983 on this class or ro-ro we had Old Flume design .There were 4 sister ships .Pictured one is Gdansk II . was there as 3rd mate on WE- EC AUS run via Suez canal . Later they shifted to route via Cape to Aus and it was then when this system proved very effective as captains were going from Cape to Aus following as far as possible (depending on the weather) great cirle
Good old times

Now I read from time to time thre are systems with compressed air which are capable of shifting almost instantaneously huge amounts of ballast water from tank to tank. Marvelous!!!

[spowiednick]

@ombugge

Parametric roll is a resonance phenomenon in which the roll of a ship is rapidly amplified when the roll period of the ship and the encounter period of waves are in a certain relationship. When a ship encounters parametric rolling it is almost impossible to take any action.

Check this out pls. Definition above applies to sunchronous resonance rols.

Parametric roll is another kind of relation between the changes of vsl GM and the wave period .AFAIK it is 1/2, 1, 2 … or sth like that. Different sources sometime give different definitions and it is a bit complicated although digestable .

• Parametric rolling will not occur on ships with a high GM – False

Parametric rolling occurs because of the fine hull
form of large post-Panamax container ships. The
large bow flare and wide transom increase the
effect. The phenomenon occurs because of changes
in the waterplane area, which can cause large
changes in GM as waves pass. A large initial GM
will provide large righting levers that can lead to
violent rolling

SOURCE:

[Chief_Seadog]

I sailed on an ex-Farrell/US Lines ship that had Flume Tanks. SeaLand (which got it after US Lines went under) opted not to repair the Flume Tanks. They instead had them redesignated as void spaces. Without those anti-roll tanks along with no bilge keels that ship would roll in a bathtub. Without a doubt one of the worse riding ships I was ever on. Securing for sea took on a whole new meaning.

[jimrr]

they were ok if you had FW in them!! (never happened) but they usually worked fine till the seas got weird then you could list quite a ways but one of the newer NOAA ships , (Dyson class) has them 3 decks up!, jeez … I heard it had a explosive to dump them (in case the water froze or something) but i’m not sure. in either event, i never did like having tons and tons of water sloshing around that high up, yes, it was effective but in the Northern oceans I’d probably rather had them emptied !!

[ombugge]

There are two general types of passive anti-roll tanks: the free-surface tank and U-tube tank.
Free surface anti-roll tanks works best and requires the least fluid the higher they are above the CG:
https://www.researchgate.net/publication/286553750_Reducing_Roll_Motion_by_Passive_Free_Surface_Tanks

U-tube anti-roll tanks utilize double bottom tanks and generally require more liquid to obtain the same effect:
https://www.sciencedirect.com/science/article/abs/pii/S0141029619316864

This longliner has passive free surface anti-roll tanks placed just under the wheelhouse, reaching from side to side of the vessel. She is operating in the Southern Ocean:

BalticShipping.com

https://soviet-trawler.narod.ru/pages/ussr/kapitan_kartashov.html

[spowiednick]

huge container vessels are rather having problem with HUGE GM especialy doing coastal legs or on mty evacuation ocean runs . The ocean legs are managable in some ways ( ALTHOUGH NOT ALWAYS) but coastal re not . Example : MSC ZOE

So having a system like described will not be a bad idea when one can not influence much cargo plans fully controlled from shore.