The Marine Sulphur Queen was originally a 1944 built T2, the Esso New Haven.
She was converted to a molten sulphur carrier
by Marine Transport Lines in 1961.
The sulphur needed to be kept at a temperature of about 270F.
The conversion involved cutting out just about all the transverse bulkheads
and installing a 306 ft long, 30.5 ft wide by 33 ft high,
free standing tank which could expand longitudinally.
The tank was divided into four holds.
The Marine Sulphur Queen was a double hull,
albeit a rather unusual one.
The MSQ was loaded from Beaumont to Norfolk, VA.
The last word from the ship was at 0125 local on 19630204.
She failed to respond to radio contacts at 1123 on the 4th.
At the time she was probably about 100 miles west of Key West.
The weather was 25 knot winds from the north, gusting to 45.
Extensive search founds only a few lifejackets
and bits of debris.
There was no sign of explosion;
but the life jackets showed signs of shark attack.
The USCG MBOI investigation revealed that
The ship was routinely overloaded by a very slight amount
resulting in sag numerals slightly higher than
the recommended max of 100.
At the time of the sinking, the sag numeral was 101.
The MBOI concluded -- correctly in CTX's opinion --
that this amount of over-loading had little effect on the casualty.
However, the courts gave this illegality a lot of weight.
The conversion resulted in the cargo being
concentrated near the center of roll.
The reduction in roll radius of gyration
resulted in a roll period of about 8 seconds,
which could have been synchronized
with the period of the beam seas
resulting in a capsize,
despite plenty of initial stability.
The MBOI, without apparently much analysis,
treats this as a low probability scenario.
[CTX agrees, however, rapid rolling would
have increased dynamic stresses in the hull.]
The conversion resulted in a reduction of racking strength,
which may have been a factor in the sinking.
In terms of design section modulus, the conversion
actually ended up slightly higher than original,
and replaced a great deal of presumably wasted steel
with new steel.
[At the time the designers
had both no experience with such an unusal structure
nor the analytical capability of estimating the
resulting stress distribution.]
The ship had a history of sulfur leaks,
especially in way of Hold 4 at the aft end of tanks.
This sulfur leaked into the wing tanks,
impregnating the insulation,
which routinely caught fire.
(Nobody knows why, maybe some reaction between
the cargo and something in the insulation.)
The crew treated these very low intensity fires
as almost commonplace events
putting them out with steam smothering or water spray.
Solidified sulfur built up in the bilges of the wing tanks
The MBOI had a number of tests done,
which while not conclusive indicated it was unlikely
that a sulfur-based explosion happened,
and, if it did happen,
would have been very unlikely to sink the ship,
let alone quickly sink it.
This conclusion is also supported
by the condition of the debris.]
Both USCG and ABS did a mid-period survey in February 1962.
But the MBOI report says almost nothing about
these inspections, other than the ship passed.
Without giving any details,
it does say in passing that the USCG inspectors
treated the ships as if she was a normal tanker.
The MBOI ends up by saying we don't know what happened
but we need to be a lot more careful
in approving this sort of conversion in the future.
The CTX finds the MBOI report very disappointing.
There is absolutely nothing on the condition
of the 17 year old hull steel,
despite the fact that the USCG and ABS had done
a biennial survey a year earlier.
Both the USCG and ABS survey reports
must have commented on the steel condition.
If they did not, this would be malfeasance of the first rank.
MTL was not an owner that was known for maintaining steel.
The Time article was accurate in at least that regard.
See Marine Electric.
Were the wing tanks (strangely called void spaces by the MBOI) coated?
The report does not say.
Almost certainly not;
but now all the wing tanks were being used
for ballast every trip without any chance
of getting an oil coating.
They needed to do this to get the ship deep into the water
at the loading terminal.
On top of that we are regularly leaking sulfur
into this space and then extinguishing
the resuslting fires with water, generating a build up
of sulphuric acid in the double bottom.
It is hard to imagine a more corrosive environment.
Apparently, no witnesses were asked
to testify about this issue.
Finally, if the wing tanks had flooded from a shell failure,
there was now only one watertight bulkhead (at frame 59)
in the whole double bottom/double side cargo section.
A normal T2 would have eight watertight bulkheads.
Would flooding of half the void space sink the ship.
CTX guesses to would have.
In any event, this weakness should have been
an obvious focus of the MBOI.
CTX does not know why the MBOI
so carefully stayed away from these issues.
But CTX strongly suspects that the shell steel
was in bad condition, failed in the heavy weather,
whereupon the lack of compartmentation
quickly sank the ship.