Keeping Things Quiet at the University of Oregon

Major colleges, especially those with strong science departments, are often involved in a variety of research projects in cooperation with government and industry partners. The University of Oregon (www.uoregon.edu) is no exception, conducting groundbreaking research in a wide range of areas including energy, materials science, medicine, nanotechnology, and semiconductor design. To bring together scientists and researchers with different specialties and disciplines to assist with research and technology problem solving, the school constructed its new Integrative Science Complex Phase One–Lorry I. Lokey Laboratories (ISC 1). By housing such an eclectic group of researchers under a common roof, the university’s goal was to encourage intellectual interactions. However, there were many problems to solve when planning such a unique facility, including selecting the right laboratory workstation fume exhaust system to help encourage interdepartmental interactions.

The ISC was designed to provide a common space for all of the different scientific disciplines, with enough room to house scientists’ laboratories and research tools — including such vibration-sensitive equipment as scanning electron microscopes (SEMs) used in nanotechnology research. Having such sensitive (and expensive) equipment in one location placed demanding requirements on the building itself and its ventilation systems in terms of noise and vibration. In addition to providing quiet surroundings, the ISC would also feature a building layout that would encourage interactions among scientists from the University’s many different disciplines.

The Challenges of Diversity

The diversity of activities planned for the ISC represented many challenges. Each laboratory workstation required venting to the atmosphere without introducing unwanted noise and vibration within the new facility or to the surrounding buildings. Because of the use of the SEMs by researchers involved in nanotechnology, not only did the building require an extremely stable foundation, but also laboratory exhaust systems that minimized noise and vibration within the facility. In addition to the science departments, shared space at the ISC would be used by such departments as Anthropology, Art History, and Geology.

Fred Tepfer, planning associate for the University of Oregon’s Planning Office, has been with the University as a facilities and laboratory planner since 1984; he is the project planner in charge of the design of the two-building ISC facility. Along with guiding the engineering and architectural teams, Tepfer handled critical decisions for the facility.

Tepfer, a licensed architect, worked closely with many others on the ISC project, including Associate/Project Engineer David Knighton, who handled the mechanical engineering for the ISC design project. Knighton, a Professional Engineer (P.E.) from Balzhiser and Hubbard Engineers of Eugene, OR, has been a project engineer on a number of laboratory projects at the University of Oregon and at Oregon State University. Tepfer drew on Knighton’s knowledge of laboratory workstation fume exhaust technology when it came time to equip the ISC’s different laboratories. Knighton’s experience extended to many different types of laboratory fume exhaust systems, including mixed-flow systems.

Mixed-Flow Systems
A mixed-flow system dilutes contaminated exhaust air with unconditioned outside ambient air. The system employs direct-drive impellers to accelerate the air flow, along with a discharge nozzle where a greater amount of fresh air is entrained into the exhaust plume before it leaves the fan assembly. The combination of added mass and high discharge velocity minimizes the risk of contaminated exhaust being re-entrained into building fresh air intakes, doors, windows, or other openings.

Tepfer and members of his ISC design project team visited nearby facilities, including a local research & development (R&D) company, to check on the noise levels of different fume exhaust systems. The system at the R&D company, which was based on conventional belt-driven centrifugal exhaust fan technology, was found to be excessively noisy. Tepfer noted that the visit made them realize they would need to take great care with noise when selecting the fume exhaust system for the ISC facility.

Taking It Underground
The first of the two buildings comprising the Integrated Science Complex would be located underground, between two existing research buildings. Because the new building would be below grade, the exhaust plume would need to reach that much higher to clear the boundary layers of the other buildings. In addition, noise and vibration from the exhaust system would need to be unnoticeable by scientists in the other two buildings. According to Knighton, the below-grade architecture “was driven by the requirement for a highly stable environment for the sensitive scientific instruments.” In particular, the nanotechnology laboratories had to be kept noise- and vibration-free. Because of the below-grade building, the location of the laboratory workstation fume hood exhaust fans was particularly problematic. A decision was made to locate the exhaust system on the roof of an adjacent building.

The adjacent building was home to sensitive photolithographic equipment for patterning semiconductor devices. It also housed a University department that cherished quiet — the Department of Neuroscience. One of the Neuroscience professors made a lasting impression on Knighton as to the importance of maintaining a low-noise, low-vibration environment.

Knighton and his team selected a mixed-flow impeller system for its low-noise characteristics, locating the fans on the building adjacent to the ISC facility, between two rooftop penthouses. One of those provided access to a spare elevator shaft used to run the main 44-in.-diameter stainless-steel exhaust duct for the new ISC facility. Because of the size of the two fans, there was major concern on the part of the design team that fan vibration would be transmitted through the concrete in the Neuroscience building and to the laboratories on the third floor. But, according to Knighton, the mixed-flow impellers are extremely quiet, in spite of their size. “You can stand up there next to the fans and put your hand on them. And there’s no vibration.”

The 44-in.-diameter stainless-steel duct runs from the roof down through the elevator shaft to the basement ceiling, then turns and runs adjacent to the building’s main entryway stairs (which run from the ground level to the basement). Because of various activities in the surrounding area, including a nearby science building and one site used for graduate ceremonies, excessive noise from the fans would have been unacceptable. But the only sound generated by the system is the faint noise of high-speed airflow, even when both fans were running close to maximum capacity.

Greater Efficiency, Less Energy
Knighton credited the mixed-flow impeller technology. “It has to be directly attributable to these mixed-flow fans. We even avoided the use of sound attenuators at the fans or in the duct.” By operating without sound attenuators, the exhaust system operates with greater efficiency while using less energy. Tepfer added that, “ The ventilation systems have been fully tested and run through all their paces, and they are performing beautifully.”

According to Knighton, “The exhaust system extends into 15 laboratories and equipment galleys; the system serves a combination of fume hoods, general laboratory exhaust, and local exhaust, in numerous laboratories, including semiconductor laboratories, nanofabrication laboratories, a photolithography laboratory, a bio prep lab, and an inorganic prep lab.”

Along with quiet operation, the fans are also barely visible. Since the fans were located on the roof of the building adjacent to the underground ISC building, in the space between the building’s stair and elevator towers, they were partly concealed. To make sure they weren’t noticed, said Tepfer, “we built a metal screen around them.” The screen was actually more for sound containment than for obscuring the fans, said Tepfer. “I don’t think anyone objected to seeing the fans, but we just wanted to make sure that the sound was contained and sent upward and not down to adjacent campus areas.”

The mixed-flow impeller fans featured a large plenum at the fan inlet and a high exhaust plume height, factors that appealed to the ISC project design team, especially given the density of buildings surrounding the ISC. So far, the re-entrainment of contaminated air has not been an issue in the new facility. But Tepfer is cautious. “Because there are quite a number of science buildings in the area and they are fairly closely packed, it is not far from the roof of one building to the air intake of another. It is a problem that we deal with on a case-by-case basis.”

The underground ISC building is in the final stages of completion, with many of the research instruments yet to be relocated there. The new facility, with its nanotechnology and microtechnology capabilities, should be of particular interest to companies in the electronics industry interested in joint projects. In addition to the equipment and facility, partners will find a wealth of talented graduate students to work on their projects. It is a work in progress, according to Tepfer. “The equipment is still somewhat scattered, in about four or five places, but now they are going to be in one place.” That equipment, in the hands of the University’s teaching and student talent, should help the ISC become a formidable research facility for years to come.

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