Fuel Tank Design

[jimmymc90]

I was wondering if anyone would be able to help me out with my college marine engineering project. I am currently redesigning the fuel tanks of an Ferry so that it complies with MARPOL regulation 12a.
I have calculated my tank sizes but I do not know how I would go about working out the number of stiffeners I would need and also if I would need transverse stiffeners as well as longitudinal.

The ship is 140m in length and there are 6 tanks located midships. The dimensions are 8m x 5.6m x 3.3m. I know the information given is limited but I just need someone to point me in the right direction.

thanks,
James

[jimmymc90]

Thanks for your reply. The ship is framed at 800mm intervals. Its mostly the stiffeners I am having issues with. I know I will need longitudinal stiffening however I dont know how these are spaced and if I would need transverse stiffeners also

[Dean Smith]

Originally Posted by jimmymc90

Thanks for your reply. The ship is framed at 800mm intervals. Its mostly the stiffeners I am having issues with. I know I will need longitudinal stiffening however I dont know how these are spaced and if I would need transverse stiffeners also

Absolutely you need athwartships BAFFLES , they are called, imagine fuel running fore and aft 8m?
would have a baffle at every frame then , so as it would pick up the frame strucure inline, I would fold it say 150 deep in corrogated pattern. then use INTERCOSTAL fore and aft baffles a metre centres
This is what I would do, and run this past your surveyer
No doubt someone will, come along and correct me
look here some good stuff
http://www.google.com/search?client=...tank%20baffles

[daiquiri]

Dean Smith is right, baffles are necessary because they give both the structural strength and increase the safety. Fuel sloshing in the tank of this size can bring considerable hydrodynamic loads on the tank walls, is detrimental for ship stability in high seas, and increases the possibility of sucking air instead of fuel (when the fuel level is low).

If you foresee that this ship might run with few degrees of trim, then I'd suggest you one thing which comes from the experience of the grey-haired guys who've been in the business for much more time than I am:
- put the sender towards the forward part of the tank
- put the intake pipe (fuel feed pipe) near the rear wall of the tank.
This layout ensure that the gauge will show somewhat lower fuel level than it actually is, giving some safety margin. The intake placed at the rear will work in the zone where fuel tends to settle when the boat/ship is running with trim (bow up).

Cheers!

[viking north]

What Daiquiri--in the boating buisness and no grey hairs yet--????? what's your secret, Grecian Formulia ---Geo

[daiquiri]

No secrets, unfortunately... I do have quite a few gray hairs, damn!

[Ad Hoc]

Originally Posted by jimmymc90

... I have calculated my tank sizes but I do not know how I would go about working out the number of stiffeners ....

The ship is 140m in length and there are 6 tanks located midships...

James

A vessel of this size shall be (I assume) built to Class rules. Therefore, Class rule shall be a suffinciet guide for you in calculatings scantlings.

[boomski7]

Would it be possible to point me in the direction of these specific class rules (Lloyd's if possible).
I have been reading through the class rules but I am not sure specifically which kind of scantlings would apply to these tanks. I have a similar problem but the fuel tanks are located as wing tanks at port and starboard of the engine room (aft) which are integrating a new cofferdam to comply with regulation 12a.

The construction of new stifferners/scantlings/baffles inside the fuel tanks is where I am stuck at the moment.

Thanks in advance.