by Grant Canfield and Reid Lerner
Architects and engineers transform “Building 391” into an optical lens finishing facility
Well-known as one of the nation's top defense engineering centers, Lawrence Livermore National Laboratory (LLNL; Livermore, CA) has also conducted numerous programs intended for scientific and commercial applications.
These research and development programs, often thought of as less sensational and newsworthy than the weapons programs, have yielded advances in medical, environmental, energy and communications technologies, with a wide breadth of applications.
Coolers are located on the Mezzanine.
Many of these R&D programs have emerged in recent years, some due to LLNL's role in the development of high-power laser systems. As laser technology advanced, managers and directors of the laboratory's laser programs became increasingly aware of the need for a specific support facility. Federal funding was granted for the design and construction of the Optics Assembly Facility, where final stages of production of large optical lenses used in various laser-based research and scientific programs would be conducted.
The development program for the Optics Assembly Facility included a straightforward catalog of functions. The lenses, generally two to three feet in diameter, are manufactured at other locations, then crated and shipped to LLNL for finishing. Upon arrival, the lenses are uncrated, inspected and cleaned prior to the application of special surface coatings to control the refractive index or other optical properties. Certain lenses are polished to enhance their accuracy of focus. After bench testing for quality assurance, the finished lenses are carefully repackaged for shipment to various other research facilities at LLNL for installation into high-power laser assemblies. All these optical operations, which until then were conducted in assorted makeshift accommodations, would be consolidated in the new Optics Assembly Facility.
Mapping the project
Planners realized that optical work of this nature would demand extremely clean conditions. Working closely with scientists from the laser programs to accommodate their functional requirements, they developed a space program. The main processing effortthe Optics Cleaning and Coating Laboratoryrequired a 6,250 square foot ballroom-type ISO Class 5 (Class 100) cleanroom environment with vertical laminar flow, which, using cleanroom curtains or soft walls, must be further divisible into various minienvironments. A 2,100-square-foot ISO Class 7 (Class 10,000) cleanroomthe Pre-Cleaning and Optics Transfer Laboratorywas required for the preparation of lenses and equipment prior to moving them into the central ISO Class 5 space. Other new spaces to be provided in this project included gowning rooms for entry to the clean environments, appropriately pressurized airlocks for the transfer of materials and personnel, and a loading dock and related spaces for the receiving and reshipping of crated lenses and supplies.
Facility planners identified a portion of an existing building that seemed suited for the conversion. Building 391 had a number of features that led to its selection for this project.
The building shell was in good condition and had a central high-bay area of 40 feet. Some of the project spaces had previously been in use as cleanrooms, although not at the stringent cleanliness levels required for assembling laser optics. Existing cleanroom mechanical equipment was in generally good condition, and adaptable for reuse.
But there were also some problems with Building 391 that would have to be addressed by the designers, and it was apparent that significant alterations and improvements were necessary. For example, there were other existing research programs housed in an adjacent wing of the same building, and existing laser and photo labs in spaces next to the project work area. These operations need to be operating during the remodel process. The access floor system would have to be upgraded to comply with current structural codes. A deionized (DI) water system would have to be provided to accommodate the cooling demands of the lasers to be housed in the new facility. Most significantly, there was just not enough floor space within the building to accommodate the additional air handling equipment and ductwork that would be required.
With a program that called for modifying and reusing as much of the original equipment and infrastructure as possible, this project required sophisticated expertise not only in cleanroom design, but also in difficult retrofit or remodel projects. In 1998, GEZ Architects Engineers, a multi-discipline consulting firm in San Francisco, was selected to provide the architectural and engineering design services for transforming Building 391 into the new Optics Assembly Facility.
The plan of Building 391 is organized around a central high-bay space flanked by low-bay structures, sitting above a utility basement, and built partially into a hill on the south side. The cleanroom space in the central high-bay area was flanked on the south by existing laboratories, and on the north by a fan room housing the air handlers for the cleanroom area. There were no empty adjacent spaces that could accommodate additional air handlers, fans or other mechanical equipment.
Ducts, located in the Mezzanine, supply filtered air to the ISO Class 5 cleanroom.
There was not enough floor space, but there was enough volume. The design solution took advantage of the central bay's 40-foot height, constructing a new steel-framed equipment mezzanine over the ISO Class 5 cleanroom, within the existing building shell. By suspending a new cleanroom ceiling at 20 feet below the equipment mezzanine, a supply air plenum was created above the cleanroom. The new equipment mezzanine supported new air handlers as well as branches of ductwork charging the plenum from all the air handling units. The suspended ceiling in the cleanroom required nearly 100 percent coverage with HEPA filters in order to achieve the desired level of performance, replacing an existing system that had filter coverage of about 50 percent.
The structural system designed for the new equipment mezzanine took advantage of existing building framing. New steel beams spanned between existing building columns to support the new deck. Therefore, new steel columns were not required, nor did the concrete foundations have to be reinforced.
If it's not broken, reuse it
As much of the existing mechanical equipment as possible was preserved. The existing HVAC system was salvaged and supplemented with new fans and air handlers on the new mezzanine deck above the cleanroom. The demands of a ballroom-style cleanroom required a considerable increase in air handling capacity. Twelve new air-handling units supplemented six existing units, supplying air to the ceiling plenum, discharging into the room space via laminar flow through HEPA filters. Air flows downward through the perforated floor to a plenum subfloor, where it is pulled into a double-wall plenum, up and out, by return air fans at the equipment mezzanine. Careful organization and routing of the supply and return air ductwork in the interstitial space above the cleanroom ceiling was required in order to fit all the components into the limited volume available. Softwalls and curtains can be hung from the suspended ceiling grid to create minienvironments within the ballroom-style cleanroom area.
The existing raised access floor system, perforated to accommodate laminar airflow, was modified extensively. Seismic braces and anchors were installed, enhancing structural performance. The access floor framing system was reinforced to accommodate specific designated items of equipment used by laser program personnel for processes conducted in various mini-environments. Special structural alterations included the fabrication of steel-framed inertia platforms below the level of the raised floor, accommodating Sol Gel processing tanks, spin coaters and other vibration-sensitive equipment. The existing concrete slab subfloor was coated with epoxy, resistant to potentially hazardous chemical spills. The access floor system was grounded with the addition of copper cables connected to the structural steel frame. Perforated floor panels were cleaned and reinstalled.
A new loading dock, with related vestibule and storage areas, was added to the building for receiving and shipping lenses, equipment, chemicals and supplies.
There was no space within the building to accommodate the DI water system and tank, so a new exterior pad was built for this equipment. DI water is pumped from this location to specific points of uselaser cooling systemswithin the cleanroom.
Movement and positioning of large, heavy items is an important facet of lens finishing operations. This requirement was accommodated differently in each of the cleanroom areas. The less-stringent cleanliness requirements of the ISO Class 7 cleanroom allowed the reuse of an existing 5-ton electromechanical trolley hoist that ran the length of the high-bay. An additional benefit was this hoist could assist in the construction of the mezzanine and ceiling above the cleanroom, as well as the installation of the new fans and ductwork. Within the ISO Class 5 space, the more stringent cleanliness criteria precluded use of an electromechanical hoist; instead, new custom-fabricated floor-mounted cranes were planned.
The original facility featured conventional 2-foot by 4-foot recessed fluorescent light fixtures with prismatic sheet plastic lenses in a suspended panel ceiling, inappropriate for the new cleanroom applications. They were replaced with continuous teardrop-style fluorescent lights, ceiling mounted at 24 inches on center in the work areas. The new lights provide a better quality of illumination, with improved energy conservation as well. The teardrop cross-sectional shape of the fixtures accommodates laminar airflow from the ceiling.
The Optics Assembly Facility has proven to be an important and successful project for LLNL. The challenge to the designersto achieve a secure and operational lens finishing facility, including a large ISO Class 5 cleanroom, within a severely constricted space in an existing building, while maintaining ongoing adjacent operationscould only have been achieved through the highly integrated and coordinated contributions of a multi-disciplinary team.
Grant Canfield and Reid Lerner are engineers at GEZ Architects Engineers (San Francisco).