Question on Stowage Factor and Ballast Arrangements

Professional Mariner Forum
1

Hey Folks,

Recently ventured into the shipping industry, so please excuse my rudimentary questions:

  1. Can anyone explain / give a rough overview of how carrying different types of ores in different holds of a single general purpose bulk carrier will affect ballast arrangements? (e.g. some holds carrying Iron Ore. others carrying coal).

and

  1. Also, Is it right to say that the higher the stowage factor, the more space is needed to store 1 metric tonne of a cargo. As such, if coal’s Storage Factor is 1.40 and iron ore’s is 0.40 m3/MT, for every tonne of coal placed into a hold, I could actually have 3.5 Tonnnes of Iron Ore?

and

  1. Also, what does having a “strengthened bulkhead” have to do with allowing a vessel to carry a much wider range of bulk cargoes?

Appreciate your patience and many thanks in advance!

2

[QUOTE=Imperium;148019]Hey Folks,

Recently ventured into the shipping industry, so please excuse my rudimentary questions:

  1. Can anyone explain / give a rough overview of how carrying different types of ores in different holds of a single general purpose bulk carrier will affect ballast arrangements? (e.g. some holds carrying Iron Ore. others carrying coal).

and

  1. Also, Is it right to say that the higher the stowage factor, the more space is needed to store 1 metric tonne of a cargo. As such, if coal’s Storage Factor is 1.40 and iron ore’s is 0.40 m3/MT, for every tonne of coal placed into a hold, I could actually have 3.5 Tonnnes of Iron Ore?

and

  1. Also, what does having a “strengthened bulkhead” have to do with allowing a vessel to carry a much wider range of bulk cargoes?

Appreciate your patience and many thanks in advance![/QUOTE]

  1. Don’t know, I would think hull stress might be an issue.

2.Given those SF numbers 1 ton of coal would take up the same cubic metes as 3.5 tons of Ore. Basically it’s the reciprocal of density.

  1. Don’t know.
3

an ore strengthened bulk carrier will be classed as such, where alternate holds may be left empty to raise the center of gravity of the heavy ore cargo due to the low angle of repose (less then 35 degrees), as to improve the stability of the vessel at sea and give a level trim, where steep angles could be unsafe and cause the cargo to shift with sudden force, IMO has specific guidelines for loading iron ores in the IMBC code as well as the IMO BLU (bulk loading guide) which are available for purchase in print and digital in the IMO’s online bookstore

iron ore your talking 15-20 cuft/lt where as coal 41-44 cut/lt depending on grade, green delayed petcoke is 46-48’ cuft/lt coking coal 50-55 cuft/lt, where wheat may be 42.5-45 cut/lt, corn 49-51 cuft/lt, HSS 48cuft/lt

conversion m3/mt to cuft/lt is one m3/mt is equal to 35.87 cuft/lt, often shippers give stowage factors on cuft/mt which is not correct, but only a slight adjustment

so yes, heavier and more dense the cargo, the less space utilized which is a ‘deadweight cargo’ so would typically load to load line marks and/or disport, or load port draft, where a lighter cargo like soft grains may “cube out” where all available cubic capacity has been utilized, or the perfect case of a “full and down” vessel would be all cubics and load line draft utilized

you should always refer the the vessels classification and statutory cargo certificates when planning a lift, as well as the IMBC code and the vessels load line certificates and loadlines zones the vessel will transit on her voyage

as for ballast arrangements, that would depend on the vessel, trim and stability, draft loading to, etc…thats a technical issue specific to the vessel, but sure, with alternate holds empty, even with iron ore, she may have some aft or forepeak, wing tanks or double bottoms requiring ballasting, the ships stability books/program would guide the mate in planning ballast required

hope this helps

4

Based on my short time on Great Lakes self unloading bulk carriers: 1. Split cargo loads of stone and sand are somewhat common on the lakes also split loads of coal where some of the cargo holds are emptied and ballasted in order to go to the next port and offload the remaining cargo onboard. When dealing with ballast tonnage out vs cargo going in you need to pay attention to stress on the hull. Using a loading software allows you to see the computed hull stresses. 2. While yes 3.5 tons of ore could fit in the space of 1 ton of coal roughly, you’ve got to consider the TPI of the vessel and it’s maximum draft you can load to. On the lakes it is pretty common to have most of the cargo holds full of coal up to the hatch coaming while with ore it looks like a little pile in the bottom. Looking in the hold you would think, damn let’s haul some more, however look at the drafts. If you filled the holds up with ore on a Great Lakes freighter she would be sitting on the bottom and well past the load line. So while it seems based on stowage factor only you could haul 3.5 times the amount of ore vs coal, remember the ship can still only haul a given tonnage at a max draft, wether the cargo holds are full or not. 3. Reinforced bulkheads, imagine putting a bunch of heavy stone against a transverse bulkhead and having nothing on the other side. If it is weak you have the potential to buckle the bulkhead. With a reinforced bulkhead you could load a hold with out having to worry about the empty hold or a hold filled with a less dense cargo like coal. On many of the very old “lakers” the bulkheads are very thin and it is common to bank some cargo on both sides of the bulkhead prior to filling the hatches to prevent the bulkheads from potentially giving out by only loading one hold only. Hope this helps out.

5

Regarding strengthened bulkheads, quite often you see e.g. a five-hold bulk carrier with additional class notation “holds 2 and 4 may be empty”.