Filters Help Preserve 17th Century Shipwreck

Dec. 10, 2001

About the author: This article was contributed by Harmsco Filtration

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 task.

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.

 “This 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.           

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