Dec 10, 2001

Filters Help Preserve 17th Century Shipwreck

To most people, water clarity is important, but the nautical
archaeologists at Texas A&M University know that to rebuild a 300-year-old
ship, it is essential. They needed filtration equipment that was up to the

Rene Robert Cavelier, Sieur de La Salle, was a French trader
and explorer who also started the first European colony in Texas. In 1682, he
had traveled the length of the Mississippi River and claimed the territory for
France. This land ultimately was the subject of the Louisiana Purchase in 1803.
La Salle left France again in 1684, and returned to the New World with four
ships. One of his ships, a small 17th Century French frigate named the Belle,
ran aground and sank in the Gulf of Mexico in 1686.

The Belle was discovered in July 1995 in Matagorda Bay,
Texas, in 12 feet of water. Approximately one-third of the ship had survived.
The Texas Historical Commission constructed a cofferdam around the ship and
pumped out the water to expose the Belle. They spent about eight months taking
the ship apart, rather than risk damaging it by removing it in a single piece.

In 1997, they brought the remains in more than 400 pieces to
the Texas A&M University Conservation Research Laboratory for conservation,
as well as to reassemble the ship and preserve several thousand artifacts. The
reconstruction task was aided by numbers carved into the ship's 381 original
components by its original builders. Experts believe La Salle had intended to
ship the vessel in pieces to America and assemble it upon arrival. But the
amount of cargo necessary for his mission to establish a permanent settlement
in the territory required the Belle to become part of La Salle's fleet.

The delicate nature of the waterlogged wood meant it could
not be allowed to dry out. For two years archaeologists carefully pieced the
remains of the ship back together in a concrete tank measuring 60-ft long by
20-ft wide by 12-ft deep, and containing more than 100,000 gallons of water.

They built an elevator platform to allow the ship to be
reconstructed in and/or out of the water as necessary and to keep the ship
submerged when it was not being worked on.

When it was time to plan the water treatment, several
factors came under consideration, including the staff’s safety within the
water and the wood’s preservation. It would be critical for the water to
be kept free of particulate to allow for maximum penetration of polyethylene
glycol (the conservation solution) into the wood. The water also would need to
remain free of algae and bacteria growth, which would cause a permanent
discoloration of the wood and interrupt the preservation process. And because
the labora-tory staff was required to be in the water with the ship, only mild
sanitizing agents with low mammalian toxicity could be added to inhibit
bacterial and fungal growth.

This is when Harmsco Industries, a filter manufacturer and
filtration engineering company located in Florida, was brought in on the
project. The company provided four Harmsco Hurricane 170 filters, 5- and
20-micron cartridges, and several hours of technical support. With the ability
to filter 175 gpm, the laboratory’s pumps now cycle all the water in the
vat through the filters twice during a 24-hour period.

These filters combine three filtration technologies into a
single, compact design. As a separator/cartridge filter, it provides optimum
performance separating dense solids prior to cartridge filtration. This means
extended filter life, increased dirt holding capacity, and reduced maintenance
costs. Components include an outer chamber for particle separation, an inner
chamber for cartridge filtration, and built-in drain for purge.

Hurricane’s patented cartridges are made with deep,
angled pleats to direct the flow into the pleated area for increased solids
removal. Centrifugal separation occurs in the filter’s outer chamber by
rotational flow and centrifugal force. Heavy solids, which accumulate at the
bottom of the filter, may be purged manually or automatically. Liquid flows
from the outer chamber into an inner chamber and through a single cartridge
where the liquid is filtered and subsequently leaves through the standpipe and
outlet fitting.

In the end, the Harmsco equipment made it possible to obtain
the maximum performance from the system during the entire delicate process.

shipwreck is spectacular and to see her underwater with this much clarity, we
couldn’t be happier,” notes Kim Jobling, project manager and
research associate at Texas A&M University. “We are excited that
Harmsco was able to join the team and provide its filtration engineering and
technology experience.”

The preserved hull eventually will be partially disassembled
and shipped to a museum where it will be displayed.           

About the author

This article was contributed by Harmsco Filtration