How are steel water tanks connected to floors

[ldigas]

(is "Boat Design" the right part of this forum for asking this, or should it go somewhere else? "Class Societies" maybe?)

Fresh water, inox steel (I suppose, can't check), rectangular tanks, - relatively wide in comparison to height. When putting them on floors, how are they usually connected/welded? Just an L profile welded to the floor, and then the tank on them? Or do they require special considerations?

I'm trying to clear up some construction details, and although the boat in question exists, I cannot get into that particular compartment to check it out in person.

[michael pierzga]

Is this a metal hulled vessel ?

[ldigas]

Originally Posted by michael pierzga

Is this a metal hulled vessel ?

Yes, steel.

[Ad Hoc]

When you say "floors"...do you mean a sole (deck), or do you mean a frame?

Tanks can be fixed how you like, it is up to you. But, you need to ensure that the seatings for the tank are strong/stiff enough. So, your calculations will dictate whether riveting, gluing, welded, or how ever you wish;shall be suitable.

[ldigas]

Originally Posted by Ad Hoc

When you say "floors"...do you mean a sole (deck), or do you mean a frame?

Tanks can be fixed how you like, it is up to you. But, you need to ensure that the seatings for the tank are strong/stiff enough. So, your calculations will dictate whether riveting, gluing, welded, or how ever you wish;shall be suitable.

"floors" - as in frames, yes, only "below". In the nomenclature I'm accustomed to using frames are transverse elements which stiffen the side, while floors stiffen the bottom. They're both in the same plane.

I'm working on some documentation, and from the description of the owner, I know that there is a tank in the front compartment. He doesn't know if there is a floor (this time, as in deck <- yes, I see your dillema in here) - just knows there is a tank.
The tank is already there, that part of the boat will not be touched at all, in the reconstruction. But I need to represent it in a drawing nevertheless, and that's why I'm curious as to how tanks are usually fixed.

The original documentation is missing some drawings, and those saved are incorrect in many places.

[Ad Hoc]

FWIW

I have never used the nomenclature "floor". This is usually for very large ships, like Bulk Carriers etc and Americans. Americans use this terminology to mean frame, generally.

I design smaller (up to 50-60m ) vessels, and never use the term 'floor'. Except when our boats were built under licence to an American yard (confused me to start with). A frame, a deck, a stringer or longitudinal. But never a 'floor'. Hence i request clarification to which definition you were using, as you rightly noted.

Simply, the mass of the fluid that is in the tank. Then working out the accelerations from the max roll, pitch and heave, and this is applied to the weight of the fluid. This gives you a force, and you design the seatings to transfer this load from the tank, via the seatings, into the surrounding structure; whether frames or decks or both.

[gonzo]

In American floors are the connecting members between frame heels. They may be bolted to the keel or keelson

[michael pierzga]

Its a steel boat so why aren't the tanks Integral ?

Separate tanks are bad boat building practise on metal boats because they create inaccessible spaces inside the hull preventing inspection and maintenance of the inner hull skin. It will be a corrosion problem. Has this installation been specified by a naval architect ?

Additionally SS tanks are always suspect. Poly tanks are a better choice for non integral tanks.

[CDK]

On a steel surface the tank will be supported by stainless profiles around the circumference, with cross members if the size requires additional bottom support.
The profiles may be welded or bolted to the steel structure, the tank is kept in place by its own weight. A tall tank would be placed in a cage, a small tank can have L-profiles welded to the 4 corners and stand on its own feet, bolted to the steel structure underneath.

[powerabout]

most megayachts the tanks are all double bottom
so "kiss"

[ldigas]

Originally Posted by michael pierzga

Its a steel boat so why aren't the tanks Integral ?

Separate tanks are bad boat building practise on metal boats because they create inaccessible spaces inside the hull preventing inspection and maintenance of the inner hull skin. It will be a corrosion problem. Has this installation been specified by a naval architect ?

Additionally SS tanks are always suspect. Poly tanks are a better choice for non integral tanks.

As I said, I'm unsure to anything about that front tank, and due to some circumstances, it is still inaccessible (the stern of the boat is undergoing reconstruction, and the workers have filled the front with everything they could find (stuff ... the reconstruction is in a marina, and there is very little space around the boat, meaning no container) - now unwilling to move it again, "just so that guy can take a peek inside")

I know the two diesel tanks are structural (from what I could see), and that the middle tank is made out of stainless, and then somehow bolted to the floors. The openings were too small for me to get inside for a better look.
As to the front one, this sketch and drawing of the two frames are all I have of that area (the 1400L tank in front). Based on this what would be your opinion its design and fixation?

Just a flooring (as in deck on some transversals and the tank bolted to it or ...?

I'm sorry to be bothering you with such trifle details, but sometimes a mere advice from experienced coleagues is more accurate and better than all of the drawings one has (expecially incorrect and missing ones).

[michael pierzga]

Yes..your tanks will rest on "Floors" . these athwart ship floors will be welded to the frames and then a BOX of 90 degree angle stock will seat on these floors and form the tank support base.

Do everything possible to allow air space between the bottom of the tank and the steel hull. This area is prone to corrosion and will be inspected by a surveyor.

Well worth investigating poly tanks

This is a US link,

http://www.oceanlinkinc.com/tanks/faqs.asp

I lost my European link. It was Italian and had every tank dimension imaginable in its catalogue for supply to the Italian Marine industry. .


Also 2500 liters of water is alot of water for a small craft. What about waste holding tanks ?

[daiquiri]

Originally Posted by michael pierzga

I lost my European link. It was Italian and had every tank dimension imaginable in its catalogue for supply to the Italian Marine industry...

Osculati, perhaps. They have nearly everything you need in their catalogue.
Fuel tanks: http://www.osculati.com/cat/Serieweb.aspx?id=21319&op=y
Water tanks: http://www.osculati.com/cat/Serieweb.aspx?id=21322&op=y

Then there is this company, Merin, which makes bladder-type tanks for automotive, aerospace and naval use: http://www.merin.it/en/serbatoi_usonautico_gasolio.php They can be tailored to fit right between frames and girders, as shown in this pic: http://www.merin.it/images/Depl_nautica.jpg . Unfortunately, the page about naval tanks is in Italian (all the rest can be viewed in English though).

Cheers