When it comes to spellbinding structures, the Gateway Arch in St. Louis, Missouri, holds its own among icons ranging from the Statue of Liberty to the Eiffel Tower.
The bold vision of Finnish-American architect Eero Saarinen, the arch stretches 630 feet into the sky and draws more than one million visitors every year. Its signature curve pays tribute to a city that opened the door to the westward expansion of the United States.
Built between 1961 and 1965, the arch is constructed of triangular, double-walled stainless-steel sections. Saarinen chose stainless steel for its strength and visual appeal. Radiographic, or x-ray, testing (RT) would play a critical role in ensuring the safety, stability, and longevity of this monument-in-the-making.
RT: A Breakthrough in Non-Destructive Evaluation
Radiographic testing (RT) and other non-destructive testing (NDT) methods allow for internal inspection, without altering or damaging the material or item being tested. Without non-destructive testing tools like radiography, defects could go undetected and lead to dangerous conditions or failures.
RT is a highly accurate method to detect internal defects not apparent on the surface of the part. Then and now, radiography is a safe, effective, fast and affordable testing technique to ensure that welds are safe and sound.
With roots that date back to 1929, Industrial Inspection & Analysis’s (IIA’s) St. Louis lab — known at the time as St. Louis Testing Laboratories — was brought on board the Gateway Arch project in the early 1960s. Our St. Louis lab was tasked with using radiography to perform field weld inspections, as well as inspecting and analyzing the field welding process for the arch project.
Intrepid Inspections
During construction of the arch, our highly skilled inspectors safely completed more than 4,300 radiographs to ensure the structural integrity of the arch’s stainless steel welded joints. Committed to the safety of the project, our team performed the x-ray testing in the evenings and on weekends to streamline the work flow and minimize radiation exposure.
According to the February ’66 issue of Welding Design & Fabrication:
“The films were processed overnight and delivered to the site the following morning. For a while, St. Louis Testing even had a darkroom trailer parked at the job site. If there were no rejects, and there were very few, Pittsburgh-Des Moines [the steel fabricator] moved its scaffolds to start adding a new section. When inspectors found rejects, the discontinuity was removed, repaired, and radiographed again.”
Ultimately, radiographic testing helped to ensure the safety and success of the Gateway Arch project.
View from the Top
Today, radiographic testing remains a core service at IIA’s St. Louis lab, where new generations of inspectors work tirelessly to make the world a safer place. In doing so, they follow in the footsteps of the late Clarence Cherry, an intrepid inspector on the Gateway Arch project.
In a 2015 interview with St. Louis Public Radio, Cherry reminisced about his experience on the arch project.
“As each section was x-rayed, you got higher and higher and higher. The wind would blow from 35 to 70 miles an hour down on the river. So, we had to be like mountain climbers. We tied ourself on so we wouldn’t be blown off the Arch.”
During his interview, Cherry predicted the iconic Gateway Arch would be safe, sound, and soaring for many years to come.
“The Arch to me stands as a triumph of men working at that height at that time,” said Cherry.
IIA is proud to have played a role in St. Louis’s iconic arch, which stands strong today as a marvel of engineering and a testament to the power of non-destructive testing.
