Supplying Vacuum to Cleanrooms
A central principle in the design of cleanrooms and biocontainment suites is the need to minimize capital, operating, and energy costs while creating an efficient, high performance space. Clearly, this is a core objective in the design of any lab space, but when the space must be effectively isolated from the remainder of the facility, and costs several hundred dollars per square foot, the design challenge is only magnified. One way to achieve space efficiency in such critical areas is to locate most utilities outside the controlled environment, but this can pose problems in the case of the scientific vacuum utility used in biological, chemical, and materials labs.
Positive and negative pressure environments
The negative pressure environment of a biosafety lab (BSL) is designed to contain biological materials; a central vacuum system that sucks potentially hazardous materials out of the lab and transfers them elsewhere violates the foremost design objective for such spaces. Biosafety laboratories needing only one or two aspiration workstations can always use an integrated vacuum aspiration stations (Fig. 1) within or adjacent to the biosafety cabinet (BSC) and exhausted through the cabinet’s HEPA filters. Multiple vacuum workstations within the biocontainment space, however, can consume very expensive square footage, complicate exhaust management and add heat load on the HVAC system.
In planning a cleanroom, on the other hand, locating vacuum pumps outside the room is desirable—both for the space-conserving benefits in the cleanroom and to minimize the risk that pump exhaust may add to the room’s particulate load. Vacuum control then becomes the challenge; the pump is outside the room and vacuum control is needed inside. You could handle that problem by installing the pumps inside the cleanroom, and exhausting pumps to the outside. That achieves the control objective, but once again at the cost of the pumps occupying precious space and generating heat load.
Both of these design challenges—supplying vacuum for the positive pressure environment of the cleanroom and negative pressure environment of the biosafety lab—can be addressed by relying on local vacuum networks.
Modular vacuum networks
Local vacuum networks are powered by a quiet, compact, oil-free vacuum pump that can be installed inside or outside the lab. Vacuum is delivered to multiple users in the lab space with easy-to-install tubing and specialized vacuum ports (turrets) designed to reduce the “cross-talk” that is typical between users of traditional vacuum systems. These flexible, modular networks can be used to supply vacuum to an entire facility of adjacent work areas, or installed only in individual rooms, including mobile labs or leased space. Further, vacuum available on the local networks can be two orders of magnitude deeper than that available through conventional central systems, extending the range of applications that can be supported without dedicated pumps.
In the biocontainment suite, the dry pump would be installed within the controlled space in support of the containment objective, supplying vacuum to as few as two or as many as 16 workstations. Each workstation is equipped with 0.2 micron sterile filters to keep bio-aerosols out of the vacuum lines. Since all flow within the vacuum network moves toward the single vacuum pump, control of exhaust is much simpler than with multiple pumps; the single exhaust line leaves the room through the HEPA filters that manage all ambient airflow. Locating the pump within the contained space, and HEPA-filtering the exhaust, provide extra protection against aerosol release beyond that offered by the workstation filters. The pump generates only about as much heat as a couple of light bulbs, minimizing heat gain that needs to be managed for energy efficiency and comfort. Exceptionally long maintenance cycles—years in normal use—virtually eliminate need for service access.
In the cleanroom, the objective is to minimize the release of contaminating particulates. In this instance, the network pump would be installed (and exhausted) outside of the controlled space, so no particulates that may be drawn into the vacuum system are recirculated into the room. The network is plumbed from the pump to the interior, where individual workstations may be optionally equipped with electronic controls that can provide unique, programmable vacuum conditions to each workstation (Fig. 2). And once again, the single, external pump saves precious space within the expensive facility, without sacrificing the control that might otherwise call for a dedicated pump inside the cleanroom.
Modular local vacuum networks offer a modern means to deliver isolated, controlled vacuum economically to critical environments—including to modular and mobile lab—while saving space, energy, and heat load. The many advantages of local vacuum networks make them an ideal choice when designing vacuum utilities for biocontainment suites and cleanrooms.
Peter Coffey is Vice President – Marketing for VACUUBRAND Inc. He can be contacted at firstname.lastname@example.org. www.vacuubrand.com
This article appeared in the November/December 2013 issue of Controlled Environments.