DSK wrote:
Scout wrote:


Doug,
I had a friend who told me they use sea water as ballast on bigger ships in
the navy, possibly CG.


All Navy ships have the capability of ballasting with sea water, not just
"bigger ships."

In fact the newer gas turbine powered combatants *have* to be ballasted because
there is no heavy boiler mounted down low in the hull. Their fuel storage tanks
have a system that lets in seawater to the bottom of the tank as the fuel is
sucked from the top.

G Guess I need to clarify my statements.
For Navy combatants, see DSK's above.
For the majority of commercial, salt water ballast is kept separate from
fuel tanks, so that any water in the fuel tanks comes about the same way
as water in a small boats tanks. The fuel (#6, HFO, Bunker C ... all
names for the same BASIC stuff) is transferred from storage tanks to
settler tanks, then run through purifers/filters and pumped to day tanks
(been awhile, so the engineers can correct my errors). DFO/MDO (diesel)
is handled in much the same way.
On most newer ships, these tanks will never be used for sal****er ballast.
In the past, commercial ships used their double bottoms for fuel (always
got a kick outa this, after everyone started hollerin for DB's on
tankers cause freighters had them) and ballast, once the fuel had been
pumped out.
Where this practice was/is done, the tanks are "decanted" of water to a
level close to, but not at, the oil/water interface, prior to filling
with fuel again.
As you can imagine, this can lead to pumping amounts of oil overboard if
things don't go exactly right. Now, this might be acceptable for the
Navy, due to their operating parameters, but it will get a commercial
ship in a world of hurt .... and not being active Navy, I can't speak
for how well they do and how well their systems are designed to handle this.
The biggest problem with 6 oil when doing this, is that it is very close
to the weight of sal****er and the oil/water interface is not always
well defined.

otn