Engineered Systems - April 2008 - (Page 43)

OK, so “easy” may not be a word that comes to mind for designing such sensitive environments. However, that doesn’t mean you can’t produce a solid cleanroom design by tackling issues in a logical sequence. This article covers each key step, down to handy application-specific tips for adjusting load calculations, planning exfiltration paths, and angling for adequate mechanical room space relative to the cleanroom’s class. BY VINCENT A. SAKRAIDA, P.E., LEED® AP M any manufacturing processes need the very stringent environmental conditions provided by a cleanroom. Because cleanrooms have complex mechanical systems and high construction, operating, and energy costs, it is important to perform the cleanroom design in a methodical way. This article will present a step-by-step method for evaluating and designing cleanrooms, factoring in people/material flow, space cleanliness classification, space pressurization, space supply airflow, space air exfiltration, space air balance, variables to be evaluated, mechanical system selection, heating/cooling load calculations, and support space requirements. STEP ONE: EVALUATE LAYOUT FOR PEOPLE/MATERIAL FLOW It is important to evaluate the people and material flow within the cleanroom suite. Cleanroom workers are a cleanroom’s largest contamination source and all critical processes should be isolated from personnel access doors and pathways. The most critical spaces should have a single access to prevent the space from being a pathway to other, less critical spaces. Some pharmaceutical and biopharmaceutical processes are susceptible to cross-contamination from other pharmaceutical and biopharmaceutical processes. Process cross-contamination needs to be carefully evaluated for raw material inflow routes and containment, material process isolation, and finished product outflow routes and containment. Figure 1 is an example of a bone cement facility that has both critical process (“Solvent Packaging,” “Bone Cement Packaging”) spaces with a single access and air locks as buffers to high personnel traffic areas (“Gown/Ungown”). STEP TWO: DETERMINE SPACE CLEANLINESS CLASSIFICATION To be able to select a cleanroom classification, it is important to know the primary cleanroom classification standard and what the particulate performance requirements are for each cleanliness classification. The Institute of Environmental Science and Technology (IEST) Standard 14644-1 provides the different cleanliness classifications (1, 10, 100, 1,000, 10,000, and 100,000) and the allowable number of particles at different particle sizes. For example, a Class 100 cleanroom is allowed a maximum of 3,500 particles/cu ft at 0.1 microns and larger, 750 particles/cu ft at 0.2 microns and larger, 300 particles/cu ft at 0.3 microns and larger, 100 particles/cu ft at 0.5 microns and larger, and 24 particles/cu ft at 1.0 microns and larger. Table 1 provides the allowable airborne particle density per cleanliness classification table. Space cleanliness classification has a substantial impact on a cleanroom’s construction, maintenance, and energy cost. It is w w w. esmag a zin e. c o m 43 http://www.esmagazine.com

Table of Contents Feed for the Digital Edition of Engineered Systems - April 2008

Engineered Systems - April 2008 Contents Editor’s Note Back2Basics HVAC Challenge Case In Point Commissioning Building Automation Energy Wiz HVACR Designer Tips This Time, Water Cooled Was All Wet Cleanroom Design In 10 Easy Steps It's Not The Heat, It's The Humidity Issues & Events Computers and Software Products Glossary Classifieds Advertiser Index Tomorrow’s Engineer

Engineered Systems - April 2008

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