Exhaust Systems Minimize Noise/Vibration at U. Oregon Integrative Science Complex

A view of the new campus quad on top of ISC 1 with the fans on top of the brick elevator tower.

Some of the most carefully planned laboratory experiments have been waylaid by unwanted vibration from unexpected sources. At the new, two-building Integrative Science Complex (ISC) Phase 1 - Lorry I. Lokey Laboratories (ISC 1) at the University of Oregon, where nanotechnology research is being pursued with high-performance scanning electron microscopes (SEM), vibration is viewed as a form of contamination to be minimized if not eliminated. For that reason, the choice of a laboratory workstation exhaust system for the new facility, as well as its placement, represented a critical step in ensuring the ultimate success of the facility.

The University of Oregon's ISC brings together scientists and researchers with different specialties for cross-discipline research. By combining different areas of expertise, including energy, environmental science, geology, machinery, materials science, medicine, nanotechnology, and semiconductor research, in an environment that fosters an open exchange of information, it is thought that the "blending of brainpower" will lead to innovative solutions and technology developments. To create that environment, high-performance tools, such as SEMs, had to be able to operate at their best. Because of the nature of semiconductor and nanotechnology research, vibration had to be minimized at all costs, including from laboratory exhaust systems.

Minimizing noise was another important consideration for the ISC facility, as that would create a workplace conducive to creativity and problem solving. The ISC building layout was designed to encourage interaction among scientists, but the open layout also posed challenges in controlling noise levels.

In locating the SEMs for materials science and nanotechnology research, stringent requirements were established for noise and vibration. At the same time, the laboratory workstations required venting to the atmosphere in a way that would introduce minimal noise and vibration to the new facility or the existing buildings around it. The shared space at the ISC facility would be used not only by the science departments, but also by the anthropology, art history and geology departments.

With so much hope invested in the facility, the choice of a laboratory exhaust system was obviously not a trivial assignment, but one that fell to Fred Tepfer, planning associate at the University of Oregon and the project planner responsible for the design of the two-building ISC facility. Because of the rapid pace of technology advances, even in fume exhaust technology, Tepfer knew that he would need help in sorting through available exhaust system choices. That help came in the person of Dave Knighton, PE, LEED^® AP, who was the mechanical engineer on the ISC design project.

Knighton, an associate/project engineer at Balzhiser & Hubbard Engineers in Eugene, Oregon, had been previously involved in several construction projects there and had experience with several different types of fume exhaust systems, include mixed-flow systems. Tepfer placed a great deal of confidence in Knighton's knowledge of the facility's requirements for noise and vibration and the possible exhaust system solutions: "He had done a lot of work for us and had actually been describing mixed-flow impeller exhaust fan technology in comparison to other technologies. He explained the advantages and disadvantages of each system."

Although the University of Oregon's ISC employs large-volume mixed-flow exhaust fans mounted on an adjoining roof, the noise and vibration within the ISC facility and surrounding buildings are minimal.

In order to better appreciate a comparison of exhaust-system technologies, Tepfer and members of the ISC design project team visited a local R&D firm to evaluate a fume exhaust system based on conventional belt-driven centrifugal exhaust fan technology. They felt this system and approach were too noisy for their state-of-the-art research facility and ruled against the centrifugal exhaust fan approach in favor of mixed-flow impeller systems from Strobic Air Corporation, Harleysville, PA.

While low vibration was critical to the performance of sensitive research instruments within the ISC's buildings, low noise was as important to the surrounding environment. In particular, the first of the two buildings for the research center would be located underground, between two existing research buildings, with noise and vibration directly affecting these surrounding buildings. Because the new building would be below grade, the exhaust plume would have to reach that much higher to clear the boundary layers of the other buildings. The below-grade architecture was driven by the requirement for a stable environment for the sensitive scientific instruments, but it represented a tremendous challenge in the design of the exhaust systems. Knighton explained, "The only available location was the adjacent Department of Neuroscience building. Originally, we were going to locate the exhaust fans directly on the roof of that building, adjacent to a penthouse."

Knighton offered that it was a number of professors from the Department of Neuroscience who pointed out the need for a noise-free and vibration-free environment, especially with the sensitive SEMs located just below the roof of the building. "One professor took me by the arm and walked me through each of the six scanning electron microscope laboratories located on the third floor, just below the roof," said Knighton. In addition to the SEMs, the research facilities also house sensitive photolithography equipment for forming the fine-featured masks of semiconductor devices.

A view of the screen around the fans on the top of Huestis Hall.

Knighton noted, "We ended up locating the fans straddling the top of the stair penthouse and the elevator penthouse." A spare shaft for the elevator was used to run the main 44" diameter stainless-steel exhaust duct for the new facility. The stainless-steel duct runs from the roof down through the elevator shaft to the basement ceiling, and then turns and runs adjacent to the building's main entryway stairs.

The design team had some initial concern that vibration from the large roof-mounted fans might make its way through the concrete in the Neuroscience building to the laboratories on the third floor. Knighton says that there have been no problems with vibration. "You can stand up there next to the fans and put your hand on them and there's no vibration."

Initial concerns about noise were also unfounded, including for those surrounding buildings. As Knighton explains, "We have a science building that is maybe 50 to 60 feet away, and there are places where they hold the graduate ceremonies with direct line of sight to the fans. Any noise from these fans would disrupt users in the surrounding buildings and those ceremonies, so it would have been a disaster."

Even with the massive airflow produced by the mixed-flow impellers during initial testing, the noise is at a minimum. As Tepfer notes, "No one knew when the fan was being tested at its anticipated operating speed. It was that quiet. There was no vibration that anyone noticed. Most people probably never even knew when the fan went on."

The exhaust system is based on two low-profile mixed-flow impeller systems. The large-capacity system extends into 15 laboratories and equipment galleys, serving a combination of disciplines, including a semiconductor laboratory, a bioprep lab, a photolithography lab and a nanofabrication facility.

The fans, which are positioned on the roof of the building adjacent to the underground ISC building, are not visible from the property line. To ensure low visibility, Tepfer notes, "the fans were already partly concealed and then we built a metal screen around them." The metal screen helped with concealment as well as with any additional sound containment that was needed. "We just wanted to make sure that the sound was contained and sent upward and not down to adjacent campus areas," Tepfer added.

The ISC project is ongoing, explains Tepfer, with work concluding on building construction before research instruments, such as the SEMs, can be moved in. "We are in the process of getting these high-end instruments away from individual researchers and into the shared space. These are expensive instruments that you don't just wheel in, plug in, and turn on," he says. He notes that the design team is now hard at work redesigning the HVAC system in one laboratory in order to accommodate a pair of "Titan" SEMs, each valued at about $4 million. It is the presence of such research tools and the talent to use them that is expected to transform the University of Oregon's ISC into a true world-class nanotechnology research center.