ASPHALT COMMANDER - Hot-Mix Magazine

(Continued from Page 7)
keep 8 million gallons of liquid
AC at a temperature that was uniformly
manageable. This was not
Sargeant Marine’s first time to be
associated with Heatec.
“We’ve done business with Heatec
for years,” said Stow. “We have
purchased more than 100 liquid-
AC shipping containers from
Heatec and our association has
always been very satisfactory.
There’s a lot of mutual trust there.
We hold them in very high regard.
“But we still shopped this project
around. We met with three different
suppliers and asked all of
them to put packages together
and give us bids. And after some
more pretty intense meetings, we
selected Heatec to do the job.”
How Heatec designed
the thermal-liquid system:
The “job” was more complex
than it might appear on the surface.
There were 14 different containers
built into the cargo hold of
the ship. Each had to be outfitted
with serpentine heating coils at
two levels: high and low. Three
hot-oil heaters had to be installed
on the deck of the ship. Pumps
and control valves had to be
strategically placed to provide an
even supply of hot oil to the coils.
According to Buddy Ledford, the
director of engineering for Heatec,
his company was probably the
only one in the country that could
handle the total job. “We are able
to do something that is pretty
unusual in our industry. We can
provide all of the heating coils, as
well as the heating source. A lot
of companies that make thermalfluid
heaters do not make heating
coils—and those that make coils
do not typically make heaters. We
can handle it all: heaters and
coils. On this job, it was definitely
to the customer’s advantage to
have one company that was
capable of providing both types
of components.”
Ledford said that the three Heatec
heaters were installed on the main
deck of the ship. The large structure
that houses the heaters is
clearly visible in aerial photos on
the aft part of the ship, just behind
the stack and the bridge.
“Each of the heaters is rated at 15
million Btu,” said Ledford. “Each
unit has two circulating pumps,
one of which is a standby in case
the other fails. All three of the
heaters feed into a common
header that goes from one end of
the ship to the other. There is a
minimum bypass valve located in
the bow of the ship. Regardless
of how many of the 14 cargo
compartments are being heated,
if they have a heater turned on,
there is a flow measurement taken
for that heater. That reading
goes into a summing controller
which controls a minimum
bypass valve—and this assures
that each heater maintains an
absolute minimum flow rate. It’s
a pretty complex system—but
the heating requirements on this
job were also pretty complex.”
According to Ledford, the system
requires a total of 45,000 gal.
(170 000 L) of heating oil. “That
includes the oil required in the
heater, the headers, and all of the
heating coils. Each heater has a
minimum flow rate of about 600
gpm (2 300 Lpm). When all three
pumps are working, the flow rate
is about 2,100 gpm (8 000 Lpm).”
A total of 22 miles
of serpentine heating coils
Ledford said that the heating system
uses about 22 miles of the
serpentine heating coils in the 14
separate cargo compartments.
“We fabricated all of the coils,”
said Ledford, “and the shipyard
did the actual installation. Imagine:
22 miles of heating coils.”
The actual heating process itself
is fairly complicated. In a typical
cargo compartment or tank, there
are two levels of heating coils:
one at the bottom of the tank and
another about 5 ft. (1.5 m) higher.
The low coils do not have a very
high heating capacity because
In drydock during its conversion and refitting, the Asphalt Commander towered
over the workers. In this photo, the ship is far in the background (notice
the size of the forklift by the bow) behind Heatec employees Ron Henry (left)
and Gary Yearwood (right) who were installing the on-board heaters.
they are only intended to replace
whatever heat loss there is
between the ship’s hull and the
water. The higher sets of coils do
most of the actual work of heating
the liquid AC in the tanks.
Once the liquid AC at the bottom
of the compartment gets hot
enough, it will move up toward
the surface. Eventually, the liquid
AC will actually roll over and start
a circulating motion that keeps
the contents of the compartment
at an even temperature.
The actual work of refitting the
ship took a little more than seven
months, although the entire project
took about a year as far as
Sargeant Marine was concerned.
“We spent a fair amount of time
finding the ship and purchasing
it,” said Stow. “It was in the
Maritime Administration reserve
fleet, excess to the needs of the
government. It was a product
tanker—originally named the
Falcon Champion—and it was a
resupply vessel for U.S. Navy
tankers. We bought the ship and
towed it to Mobile, Alabama for
conversion and refitting.”
And how did things go after the
ship was refitted and renamed
the Asphalt Commander?
“We had the normal gremlins
you’d expect on the first voyage,”
said Stow. “But the second voyage
was really outstanding! Everyone
who has dealt with the Asphalt
Commander so far has been very
impressed. And that includes
everyone in our company.
“If you think I’m proud of this
ship, you’re right!” ▼▲▼
FOR MORE
INFORMATION
about Heatec
vertical or horizontal
storage tanks and heaters—
for ocean-going vessels or
conventional HMA operations
—call and ask to speak with
Gail McKeehan:
423-821-5200
(FAX: 423-821-7673)
HOT-MIX MAGAZINE 8 VOLUME 1, NUMBER 5