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NDT.net Issue - 2013-05 - NEWS
NDT.net Issue: 2013-05
Publication: e-Journal of Nondestructive Testing (NDT) ISSN 1435-4934 (NDT.net Journal)

TÜV Rheinland’s Computed Radiography Expertise Benefits Historic Site

TÜV Rheinland13, Cologne, Germany

Fort Pitt Block House in Pittsburgh, Penn., Kicks Off Preservation Work With X-Ray Exam To Determine Structural Integrity of 18th Century Timbers.

Two original gun access holes are visible in the featured section of the first-tier gun loop at the Fort Pitt Block House. One loophole is covered with a red imaging plate, called the cassette, and another can be seen farther down the wall above the ladder.

Aaron Drake, Radiographer, is feeding an imaging plate from a previous exposure of the gun loop into the computer processing unit, which converts the plate to a digital file.

Radiographic crew members Jake Fetchin, Assistant Radiographer, (left) and Phil Martin, Radiographer, (right) are performing a radiation survey of the equipment to ensure the radioactive material is returned to its safe and shielded position.

Phil Martin, Radiographer, is setting up the imaging plates for the next exposure during the radiographic inspection of the gun loops at the Fort Pitt Block House.
Aliquippa, Penn., April 18, 2013 – TÜV Rheinland Industrial Solutions (TRIS), a full-service inspection, testing and certification company, has completed its first computed radiographic inspection of a national historic landmark, the Fort Pitt Block House in Pittsburgh, Penn. The X-ray examination kicked off the Fort Pitt Society’s preservation and restoration efforts for the structure dating back to 1764.

The Block House is all that remains of Fort Pitt, the largest and most elaborate British fort in North America built in the last days of the French and Indian War. Given to the Fort Pitt Society of the Daughters of the American Revolution of Allegheny County in 1894, the Block House has remained free and open to visitors from around the nation and the world for over a century. The current preservation project will get the structure in top shape for its 250th anniversary next year.

The two-story redoubt features mostly original stone foundation, bricks and timbers. Both floors have a tier of wooden gun loopholes going around the building. The loopholes provided a 360-degree view for the soldiers stationed in the Block House to defend the Fort Pitt; the soldiers could fire their muskets through the gun loops at enemies trying to attack.

The Society intended to preserve the gun loop timbers and needed to know their structural condition to determine the scope of restoration work. It contracted with TRIS to conduct the radiographic inspection of the original wood in the Block House.

“After evaluating the local firms capable of performing the necessary radiographic work at the Fort Pitt Block House, I recommended going with TUV Rheinland/TRIS because I felt they had the most experience in this specific area and their product samples had the highest quality,” said Dirk Taylor, of Taylor Structural Engineers, Inc., the structural engineer overseeing the Block House restoration project.

Unlike conventional, or film, radiography, computed radiography is a digital X-ray process that offers a more precise imaging with a greater picture enhancement. It does not require film and development chemicals and produces longer lasting records than film, which can degrade over time and became illegible.

“We take a radioactive material source that passes through the wood, from inside to outside, and is transferred to the imaging plate on the other side,” explained TRIS Radiation Safety Director Chris Dugan. “Then we take the exposures, pick them up, and take them over to the mobile unit, where they appear on a video screen.”

The video screen shows a picture-like image representing density variations in the wood; a lighter area would show a “healthy” material while a darker area would indicate decay, insect damage, rot and other potential impairs.

“The technicians from TRIS were very professional and easy to work with,” Taylor said. “We appreciated their sensitivity to the unique needs of this project and the delicate nature of the materials being studied.”

The X-ray exam showed that the gun loops did not have any significant internal wood deterioration and did not require complicated internal structural repairs. Rather, wood deterioration worked its way from the exterior surfaces inward, requiring only relatively simple repairs applied to the surface. In addition to the structural repairs, the preservation experts specified treating the wood with a borate-based preservative for future protection against water and insect damage.

“Working to help preserve an important national landmark was very rewarding,” said Dugan. “It’s good to know that modern technology and expert knowledge can save the 18th-century timbers for the future generations.”

The preservation work, which also includes masonry restoration, French drain repairs, and interior repairs, is planned to be finished by the end of October 2013. The Block House will remain open to the public as much as possible during the restoration.

For more information about the Fort Pitt Block House, contact Maureen Mahoney Hill at 412-780-4708 or at mmahoneycfre@gmail.com. For more information about TRIS services, visit www.tuvris.com.

About the Fort Pitt Block House
The Fort Pitt Society is a supporting organization of the Pittsburgh Chapter of the National Society of the Daughters of the American Revolution. The Fort Pitt Society owns, operates and maintains the Fort Pitt Block House and the surrounding grounds as a historical site and museum, and promotes preservation, education, and public awareness of Pittsburgh's role in early American history. Located in Point State Park, the Fort Pitt Block House is free and open to the public Friday through Sunday between 10:30 a.m. and 4:30 p.m. during the winter months. Summer hours begin April 1st, Call 412-471-1764 for more information or to schedule a tour.

About TÜV Rheinland Industrial Solutions
TÜV Rheinland Industrial Solutions, Inc. is a full-service inspection, testing and certification company providing both field and laboratory inspection services, including all NDT methods, QC/QA functions, and material testing. A subsidiary of TUV Rheinland North America, TÜV Rheinland Industrial Solutions, Inc. laboratory and field services are ISO 17025 accredited, and its mechanical laboratory services are both Nadcap and ISO accredited. For more information, visit www.tuvris.com.

About TÜV Rheinland
Founded in 1872, TÜV Rheinland is a global leader in independent testing, inspection, and certification services, ensuring quality and safety for people, the environment and technology in nearly all aspects of life. The company maintains a presence in 500 locations spanning 65 countries, employs 17,000 people and has an annual revenue of $2 billion (€1.5 billion). TÜV Rheinland inspects technical equipment, products and services, oversees projects and helps to shape processes for a wide variety of companies through its worldwide network of approved labs, testing facilities and education centers. Since 2006, the company has been a member of the United Nations Global Compact to promote sustainability and combat corruption. For more information, visit www.tuv.com/us.

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