Successful test yields DUNE steel beam a mile underground

Teams from the Fermi National Accelerator Laboratory and the Sanford Underground Research Facility have successfully completed the first test lift and lowering of a six-ton ​​L-shaped steel beam for construction of the Deep Underground Neutrino Experiment in Lead, South Dakota.

Transporting a large, irregularly shaped steel part through a narrow mine shaft to a cave a mile underground at SURF is no easy task due to the size and weight of the beam and the elevator-like loading space that is about the size of a storage room in the backyard. The successful test is an important step forward, allowing engineers and crews to anticipate future challenges.

DUNE is an international collaboration and the steel components are an in-kind contribution to CERN’s experiment. The first overseas shipment of beams earlier this year is just the start of the 2,100 structural elements that will be delivered to SURF early next year.

“Our entire team was excited to see the sample arrive in South Dakota for testing,” said Jolie Macier, remote detector and cryogenics project manager at Fermilab. “I am grateful to everyone at SURF who helped with this year-long planning process, as well as our partners at CERN. This is truly a collaborative effort.”

The first two beams, delivered in January, are part of the external structure for DUNE’s massive cryogenic ships at the Long-Baseline Neutrino Facility. Once assembled with the remaining 2,500 tons of steel, they will help form a structure 66 meters long, 20 meters wide and 20 meters high.

After the internal insulation material is installed, the integrated structure will support and house a particle detector that will be filled with 17,000 tons of liquid argon, cooled to -186°C. Scientists will use these detector modules in their quest to understand neutrinos – ghostly particles that are incredibly difficult to detect.

No surprises

Months of careful planning among LBNF/DUNE’s international partners paved the way for this initial success.

“We don’t want any surprises when we lift heavy steel objects into the shaft,” says Jeff Barthel, rigging supervisor at SURF. “You learn things while testing and this testing has helped identify steps that can be taken to make this a safe and repeatable task when the time comes to scale down the large numbers of cryostat components required for the Far Site Detectors. “

This test involved one of the many steel L-shaped beams that will form the corners of the structure. Because of their size, shape, and center of gravity, L-beams present some unique constraints. The initial L-beam lowered in this test is approximately 18 feet long and 11 feet wide and weighs 12,000 pounds.

“The most critical thing for the L-beam is the tilt angle, because the tilt should not be more than five degrees,” says Sanmitra Pingulkar, a mechanical engineer at Fermilab. “The beam had to fit within the footprint of the car and shaft, and the crew also had to keep in mind that the weight of the total load could not exceed 13,500 pounds. 90% of the weight for this particular lift was the L-beam itself.”

When the beam reached the bottom of the elevator shaft after descending at a rate of 100 feet per minute, nearly a mile underground, the crews were rewarded for their diligent planning.

“In the end, the L-beam was stable and stayed within one degree. It was a success,” said Pingulkar.

“And the success of this test is due to the joint effort of everyone involved during the past planning year,” said Charles Maupin, mechanical engineer at SURF. “This learning experience is the first of many pieces of cryostat steel that we will transport 1,450 meters underground at SURF.

Perfecting procedures

In preparation for the test hoisting of a steel beam, the SURF teams first made a full-size wooden replica of an L-beam last spring. Although much lighter than the actual steel part, the mockup’s shape and center of gravity helped create a better understanding of how crews could most effectively interact with the steel structures.

To date, SURF has carried out 350 lifts for the LBNF/DUNE project alone. This work includes analyzing the load dynamics and limitations of the lifting equipment, as well as minimizing the risk of unexpected events, such as a sudden stop of the cage in the shaft.

“You have to quantify everything,” Barthel said. “If something happens, activities could be shut down for a long time. It could have enormous consequences that could cost the project months. You can’t take any risks with that.”

“There are a lot of people who put a lot of effort and thought into these lifts,” Barthel added. “The professionalism and teamwork our crew members demonstrated during the test lift was a testament to their training and skills.”

In late 2022, CERN, in collaboration with Fermilab and SURF, successfully conducted a similar test for large, vulnerable DUNE particle detector components known as anode plane assemblies.

International partnership

Members of CERN were on site at SURF during the execution of the lift. Olga Beltramello, mechanical engineer at CERN, was one of the observers present at SURF during the lowering test.

“This test was an important learning opportunity,” Beltramello said. “It is very important for CERN not only that we check that everything works, but also that the timing of the equipment lowering is compatible with the rest of the installation schedule for the CERN-supplied cryostat.”

“Our partnership with CERN is an important part of the LBNF/DUNE project,” said Macier. “Their commitment to the success of this partnership is critical and greatly appreciated.”

One step closer

The successful test for lowering the heavy steel components brings the international cooperation an important step closer to the start of the DUNE detector installation. Once operational, a beam of neutrinos sent from Fermilab’s campus near Chicago will travel 800 miles through the Earth to DUNE’s massive underground detectors at SURF.

Scientists expect DUNE will provide a clearer picture of how neutrinos behave and change into different states, and even provide clues to the origins of matter in the universe.

More than 1,400 scientists and engineers in more than 35 countries are contributing to the experiment.