Submarines, Shipwrecks, Air Knives, and Corrosion

Monday was a notable day in naval warfare history. On February 17th, 1864, the H.L. Hunley sank the USS Housatonic, a Union sloop that was blockading the harbor in Charleston, South Carolina, during the American Civil War. In doing so, the Hunley became the first combat submarine to sink a warship in battle. Unfortunately, they never returned.

Treasure hunters and archaeologists searched for the sunken vessel in the years following the war. Despite grand efforts, one even spurred by a $100,000 reward offer from legendary showman P.T. Barnum, the ship and crew were lost to history until 1995. So many people had mistakenly thought they’d found the wreckage that when underwater archaeologist Harry Pecorelli actually did find it, he radioed to his boat, “I don’t know what it is, but it is definitely not the Hunley.” Because of this, the preservation group, Friends Of The Hunley, have affectionately dubbed him “the first person to have never found the Hunley.”

In 2000, the intact ship was raised and placed in a specially built tank, where the conservation team immediately went to work. Because of her iron construction and age, this turned out to be an engineering (mechanical and chemical) feat like no other. Over the next four years, precision excavation efforts allowed the team to exhume the remains of the crew, and they were buried with full military honors in the spring of 2004. They still haven’t proven conclusively why the Hunley sank, but as restoration work continues, she may give up her final secrets yet, as long as they can keep corrosion at bay.

hunley in tank

The prevalent use of aggressive chemicals in certain manufacturing processes today can likewise take their toll on equipment made from materials that aren’t compatible for use in these environments. As advances have been made in the development of these chemicals, metallurgists and materials engineers have kept pace in the field of corrosion resistance. EXAIR has taken full advantage of these innovations by offering our Super Air Knives in a variety of materials that can stand up to just about whatever you can throw at them:

Two grades of Stainless Steel are available: Type 303 is well suited to mildly corrosive environments. Type 316 offers even better corrosion resistance, and is often specified in the food, pharmaceutical, and surgical product industries. Both are also good to 800°F (427°C).

PVDF (Polyvinylidene Fluoride) Super Air Knives are resistant to harsh conditions where UV light, inorganic chemicals, solvents, ozone, weather, fungi, chlorinated hydrocarbons, strong acids, and/or salts are present. They are equipped with PTFE shims, 316SS pipe plugs, and Hastelloy C-276 hardware for superior performance in the most aggressive environments.  These are rated for temperatures up to 275°F (135°C).

Of course, if your application doesn’t concern any of these, our Super Air Knives in aircraft grade aluminum construction are perfect for general purpose applications in standard conditions. Just about wherever you need to install it, though, EXAIR has a Super Air Knife that is up to the task. Try us.

Russ Bowman
RussBowman@EXAIR.com
@EXAIR_RB

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