Cleanrooms and HVAC Systems Design Fundamentals

Transcription

1 Cleanrooms and HVAC Systems Design Fundamentals Belgrade, Serbia April 28, 2017 Wei Sun, P.E. ASHRAE Distinguished Lecturer Society Technology Transfer Committee Chair (12-13) Clean Spaces Technical Committee (TC9.11) Chair (07-10) Healthcare Facilities Technical Committee (TC9.6) Member Laboratory Systems Technical Committee (TC9.10) Member IEST (Institute of Environmental Sciences and Technology) Society President Engsysco ISO Cleanroom Standards USA Delegate Engsysco, Inc. President Ann Arbor, Michigan, USA Web:

2 Cleanroom Design Considerations (Applications) Semiconductor Medical Devices Microelectronic Optical Devices Pharmaceutical Hospital Biotechnology University Labs Aerospace Food Processing Automotive Miscellaneous

3 Cleanroom Design Considerations (Controlled Parameters) Cleanroom - A special enclosed area, its environment typically has the following controlled parameters: Temperature Humidity Sound and Vibration Lighting etc. Common Requirements Airflow Pattern Room Pressure Particle Contamination (Airborne, Surface & Liquid-borne) Microbial Contamination (Airborne, Surface & Liquid-borne) Electrostatic Discharge Gaseous Contamination Process Specifics Special Requirements

4 Cleanroom Standards in US (Previous US Federal Standard and Current ISO Standards) U.S. Federal Standard 209E Airborne particulate cleanliness classes in cleanrooms and clean zones (former US standard, canceled in November 2001) ISO Document ISO-14644: Cleanrooms and Associated Controlled Environments ISO Classification of Air Cleanliness ISO Cleanroom Testing for Compliance ISO Methods for Evaluating & Measuring Cleanrooms & Associated Controlled Environments ISO Cleanroom Design & Construction ISO Cleanroom Operations ISO Terms, Definitions & Units ISO Enhanced Clean Devices ISO Molecular Contamination ISO Biocontamination: Control General Principles ISO Biocontamination: Evaluation & Interpretation of Data ISO Biocontamination: Methodology for Measuring Efficiency of Cleaning Inert Surfaces

5 These Two Standards Similar? (Comparison of FS-209E and ISO in Combined Table) FS 209 Class ISO Class 0.1 µm 0.2 µm 0.3 µm 0.5 µm 1 µm 5.0 µm FS 209 ISO FS 209 ISO FS 209 ISO FS 209 ISO FS 209 ISO FS 209 ISO Particles/ft 3 Particles/m 3 Particles/ft 3 Particles/m 3 Particles/ft 3 Particles/m 3 Particles/ft 3 Particles/m 3 Particles/ft 3 Particles/m 3 Particles/ft 3 Particles/m , , , , , , , , ,000, , ,000 1,000 35,200 8, , , ,000 83, , , ,000 3,520, , , ,200,000 8,320, ,000

6 PARTICLES PER CUBIC METERS 100,000,000 These Two Standards Similar? Air Cleanliness Class Definition Comparison Between FS 209 and ISO (Comparison of FS-209E and ISO in Overlapping Chart) 10,000,000 ISO-9 FS-100,000 1,000,000 FS-1,000 ISO-8 FS-10, ,000 FS-100 ISO-7 ISO-5 10,000 FS-10 ISO-4 ISO-6 1,000 FS-1 ISO ISO-2 10 ISO PARTICLE SIZE, μm They are NOT identical, but roughly equivalent under certain classes and particle sizes.

7 ISO Classification (Airborne Particle Sizes, Counts and Classifications in 3D Illustration) Class 1 Class 2 Class 3 Class 4 Class 5 Class 6 Class 7 Class 8 Class 9 Cleanroom Particle Counts Per ISO Classification 100,000,000 10,000,000 1,000, ,000 10,000 1, Particle Count / m µm 0.2 µm 0.3 µm 0.5 µm 1 µm 5.0 µm Particle Size (Channel) Cleanliness Class

8 Particle Sources & Control Sources of Contamination Description Control Methods External Internal Outdoor air Indoor transfer air between rooms People Work surface shedding Process equipment Raw and semifinished material Liquids, pressurized gases used in process Chemicals used for cleaning Room construction materials Infiltration through doors, and cracks at windows, and walls Makeup air entering through the air conditioning systems Infiltration through doors, windows, and wall penetrations for pipes, ducts, etc. Largest source of internal particles: skin scales, hair, textile fibers Rubbing one item against another Spray, painting, welding, grinding During transport During preparation, processing and packaging Out-gassing to room Dust generated from wall, floor, ceiling, door, fibrous insulation Tighter exterior wall construction, exterior zone pressurization, vestibules at main entrances, and seal space penetrations. Multiple level filtrations Seal wall penetrations, multiple level pressurizations & depressurizations to obtain proper airflow directions Garments, proper gowning procedures, air shower before entry Use cleanroom suitable or rated furniture Local filtration and exhaust Equipment washing, cleaning and sterilization before entry, use airlock & pass-through Local exhaust Use cleanroom suitable or rated cleaners Constructed with special building materials

9 Airborne Particle Physical Controls Filtration Dilution Isolation Utilizing HEPA & ULPA filters to remove particles from supply air HEPA: >99.97% 0.3μm MMD) ULPA: >99.999% 0.12μm MMD) Diluting internally contaminated air with filtered clean air Higher air change rate, better dilution Isolating particle generations with barriers, or removing directly from major sources Process exhaust Mini-environment

10 Microbiological Contamination & Control Unlike non-viable particles which can t reproduce, microorganisms could reproduce at a rapid rate if nutrition and environment are favorable. Microorganism can be classified as bacteria, algae, fungi, protozoa and viruses. Some of these are essential, and harmless, while others are harmful and dangerous. Control Methods Physical: Heat Radiation Filtration Chemical: Sterilization Disinfection

11 ISO Standard Classifications Occupancy States As Built: Installation is complete with all services connected and functioning, but with no production equipment materials and no personnel present. At Rest: Installation is complete with equipment installed and operating in a manner agreed between the customer and supplier, but with no personnel present. Operational: Installation is functioning in the specified manner, with specified number of personnel present and working in the manner agreed upon.

12 Pharmaceutical Grade vs. Classification Maximum P ermitted N umber of P articles P er m 3 ( equal to or above ) EU Pharmaceutical Cleanliness Grade Cleanliness Classification Grade At Rest In Operation FS 209 ISO µ m 5.0 µ m 0.5 µ m 5.0 µ m 0.5 µ m 5.0 µ m A 3, , , B 3, ,000 2,000 1, , C 350,000 2,000 3,500,000 20,000 10, , 000 2, 930 D 3,500,000 20,000 Not defined Not defined 100, , 520,000 29, 300

13 Microbial Contamination Limits In Operation Recommended limits for microbial contamination in the operation state (average values)

14 Control of Particles and Microbial Sterilized and Non-sterilized Product Operation Non-sterilized product or container Design Requirements USA FDA Particle cleanliness ISO 8 (Controlled Area) Maximum viable Organisms (cfu) Room Airflow EU Grade C 2.5/ft 3 100/m 3 20 ACH or higher minute cleanup time Room Pressure 12.5 Pa Positive Sterilized product or container Particle cleanliness Maximum viable Organisms (cfu) ISO 5 in ISO 7 Background (Critical Area) ISO 5: 0.1/ft 3 A: 1/m 3 ISO 7: 2.5/ft 3 B: 5/m 3 Grade A in Grade B Background Room Airflow 90±20 fpm m/s Room Pressure 12.5 Pa Positive

15 Typical Ceiling Filter Coverage US 209 Class ISO Ceiling Filter Coverage 9 5% - 15% 100, % - 15% 10, % - 20% 1, % - 40% % - 70% % - 90% % - 100% 2 80% - 100% 1 80% - 100% HEPA or ULPA HEPA ULPA

16 Room Airflow Volume/Quantity (Traditional Approaches: Table Methods) IEST RP-12.1 (Before 2007) ISO Class Classification FS Class Air Change Per Hour (ACH) Range 8 100, , ,

17 Room Airflow Patterns Non-Unidirectional (Conventional) Flow Mixed Flow Unidirectional Flow Mini-Environment Flow

18 Cleanroom Floor Arrangements Service Area Ballroom Office and Support Areas One Big Cleanroom Service Area Service Chase Office and Support Areas Service Area R R R R R Multiple Cleanrooms Small Clean rooms Shared Return Air Chase (TYP) R R R R R Service Area Service Area Mini-Environment Office and Support Areas C C C C Cleanrooms C C C C Mini-Cleanrooms Less-clean Cleanroom Service Area

19 Pressurized Plenum (Fan Tower) Arrangement Scrubbed Exhaust Air Visitors Corridor Silencer Waff le Slab Process Corridor Fan Tow er Maint. Corridor Raised Floor Ceili ng + Filter Stair Case Pressurized Plenum Cleanroom Return Air Basement Make-Up Air Cooling Coil Perforated Slab Process Exhaust Submai ns Gas Cabinets Pump Chemical Supply Systems Process Supply Systems ITRI

20 Fan Filter Units (FFU) Arrangement Scrubbed Exhaust Air 3.5m 2.2m 3.6m 9.6m Cleanroom Stair Case 4.8m Ret urn Air 4.8m 0.0m Basement Make- Up Air Gas Cabinets Process Suppl y Syst ems Submains Process Supply Submains Scrubber ITRI

21 + Particle Migration Control (Room Pressure Control) Total Room Supply Airflow (SA) Total Room Exhaust and/or Return Airflow (EA+RA) Scennario 1: Room Prerssurized SA - (EA+RA) = ΔV = ΣQ > 0 Total Room Supply Airflow (SA) Room Positively Pressurized Total Room Exhaust and/or Return Airflow (EA+RA) Total Leakage Airflows ΣQ Offset Flow ΔV

22 Particle Migration Control (Room Pressure Control) Total Room Supply Airflow (SA) Total Room Exhaust and/or Return Airflow (EA+RA) Scennario 2: Room Non-Prerssurized SA - (EA+RA) = ΔV = ΣQ = 0 Total Room Supply Airflow (SA) Total Room Exhaust and/or Return Airflow (EA+RA) Room Non-Pressurized Total Leakage Airflows ΣQ = 0 Offset Flow ΔV = 0

23 Particle Migration Control (Room Pressure Control) Total Room Supply Airflow (SA) Total Room Exhaust and/or Return Airflow (EA+RA) Scennario 3: Room De-prerssurized SA - (EA+RA) = ΔV = ΣQ < 0 Total Room Supply Airflow (SA) - Total Room Exhaust and/or Return Airflow (EA+RA) Room Negatively De-pressurized Total Leakage Airflows ΣQ Offset Flow ΔV

24 Why Do Particles Migrate (Exchange) Between Cleanroom and Adjacent Area(s)? (1) Particles can migrate through cracks, such as minor leaks on walls, ceiling, joints, duct/pipe penetrations, etc. and air gap between door and frame, when a pressure differential exists across the cleanroom enclosure. ΔP=0 Neutral ΔP>0 Pressurized ΔP<0 De-Pressurized Corridor Cleanroom Corridor Cleanroom Corridor Cleanroom Pressure differential can force particles to migrate (in or out) through cracks on cleanroom enclosure.

25 Why Do Particles Migrate (Exchange) Between Cleanroom and Adjacent Area(s)? (2) Particles can also migrate through these cracks when a particle concentration difference exists across the cleanroom enclosure due to mass diffusion until an equilibrium is reached. ΔP=0 Neutral ΔP=0 Neutral ΔP=0 Neutral Corridor Cleanroom Corridor Cleanroom Corridor Cleanroom ΔC= One-Class Difference ΔC= Two-Class Difference ΔC= Three-Class Difference Particle concentration difference can force particles to migrate (in or out) through cracks on cleanroom enclosure.

26 Particle Net Gain/Loss through Migration By two forces: Under pressure difference (air movement by force) Under particle concentration difference (mass diffusion) Based on the combination of conditions, these two forces could work in the same or opposite directions. What is the combined effect? The prevailing force determines the particle net gain or loss through migration into cleanroom.

27 Particle Migration Control (Airlock) Air Lock An intermediate room between adjacent areas with different cleanliness to minimize particles, microbial and/or fume migrations. AIRFLOW AIRLOCK ++ AIRFLOW CORRIDOR + CLEANROOM +++ CASCADING AIRLOCK AIRFLOW AIRLOCK ++ AIRFLOW CORRIDOR + BUBBLE AIRLOCK CLEANROOM - Type Cascading Bubble Sink Dual Compartment AIRFLOW AIRLOCK - - AIRFLOW CORRIDOR + CLEANROOM - AIRFLOW AIRLOCK ++ CLEANROOM - CORRIDOR - AIRLOCK - - AIRFLOW SINK AIRLOCK DUAL COMPARTMENT AIRLOCK

28 Particle Migration Control (Airlock Selection) How To Select An Airlock? Answer questions below: Is the room in positive or negative pressure? Has fume or bio contamination? If containment is needed? If personal protection is needed? Type of Cleanroom Positive pressure No fume or bio agent No containment needed Negative pressure Has fume or bio agent contamination Containment needed Negative pressure Has fume or bio agent contamination Containment needed Negative pressure Has toxic fume or hazardous bio agent contamination, or has potent compound substances Containment needed Personal protection needed Selection of Airlock Functionality of Airlock Cascading Prevent cleanroom being contaminated from dirty corridor air Bubble Sink Dual Compartment Prevent cleanroom being contaminated from surrounding spaces through cracks Prevent cleanroom being contaminated from dirty corridor air Prevent cleanroom fume or bio agent releasing to corridor Prevent cleanroom being contaminated from dirty corridor air Allow cleanroom fume or bio agent releasing to airlock. No personal protective equipment is needed Prevent cleanroom being contaminated from dirty corridor air Prevent cleanroom fume or bio agent releasing to corridor Personal protective equipment (such as pressurized suit and respirator) is required Relative Pressure Relationship Cleanroom: +++ Airlock: ++ Corridor: + Cleanroom: - Airlock: ++ Corridor: + Cleanroom: - Airlock: - - Corridor: + Cleanroom: - Neg. Airlock: - - Pos. Airlock: ++ Corridor: -

29 Particle Migration Control (Pressure Stabilizer) Pressure Stabilizer A dynamic control approach: Use an pressure-adjustable automatic relief damper as a leakage regulator to maintain a minimum room pressure when a door is opened.

30 Traditional Rules-of-Thumb Design Methods Flow Percentage Method (Example: VA Hospital Std.) Neutral: SA (RA+EA) = 0 Positive (+): SA - (RA+EA) = 15% of SA Positive (++): SA - (RA+EA) = 30% of SA Negative (-): (RA+EA) SA = 15% of SA Negative (- -): (RA+EA) SA = 30% of SA Flow Differential Method (Example: CDC Guideline) Neutral: SA (RA+EA) = 0 Positive : SA - (RA+EA) = Min. 60 L/s (125 CFM) Negative : (RA+EA) SA = Min. 60 L/s (125 CFM) Problem with these rule-of-thumb approaches: Each room may have different air-tightness on enclosure, a fixed offset value ΔV without field adjustment capability could cause problem in control.

31 Load Characteristic and Air Loop Selections (For Energy Conservation and Performance) Cleanroom often requires higher airflow rate to dilute room contaminated air in order to lower particle concentration, so its airflow rate over cooling load ratio is typically higher, or much higher than a normal ratio range for commercial spaces (CFM/Ton= , or L/s/Ton= ). Mismatch design (higher airflow rate to a relative smaller cooling load) could cause a cooling coil to have a sensible cooling only without latent heat removal which may result poor humidity control inside cleanrooms. For ISO Class 6 or cleaner cleanrooms, the flow rate/cooling ratio may be beyond the reach of a single AHU unit can handle to avoid mismatch, multiple air-handing systems (loops) are often utilized to ensure performance and save energy.

32 HVAC Schematic and Diagram (Primary Loop Alone Air-Handling System) HEPA FILTER For ISO Class 7, 8, 9 (FS-209 Class 10,000, 100,000) Typical Application: CFM/Ton ratio: (L/s/Ton ratio: ) AHU Unit SA C C H C Efficiency Ea OA+RA OA Makeup Air Co Efficiency Eb SA Supply Air Space Impurity Concentration Space Particle Generation Cs RA Return Air Cs Q G EA Leakage Air Cs Deposition D Exhaust Air Ce

33 HVAC Schematic and Diagram (Primary-Secondary Loops Air-Handling Systems) HEPA FILTER FILTER For ISO Class 4, 5, 6, 7 (FS-209 Class 10, 100, 1,000, 10,000) Typical Application: CFM/Ton ratio: 800-5,000 (L/s/Ton ratio: 400-2,500) Primary flow/secondary flow ratio: 2-10 Primary Fan Unit Secondary Makeup Unit SA Efficiency Eb OA+RA OA Treated Makeup Air C1 C C H C Efficiency Ea OA Makeup Air Co Efficiency Ec SA Supply Air Space Impurity Concentration Space Particle Generation Cs RA Return Air Cs Q G EA Leakage Air Cs Deposition D Exhaust Air Ce

34 HVAC Schematic and Diagram (Primary-Secondary-Tertiary Loops Air-Handling Systems) HEPA FILTER FILTER For ISO Class 1, 2, 3, 4 (FS-209 Class 1, 10) Typical Application: CFM/Ton ratio: 2,500-25,000 (L/s/Ton ratio: 1,250-12,500) Primary flow/secondary flow ratio: 2-10 Secondary flow/tertiary flow ratio: 2-5 Primary Fan Unit Secondary AHU Unit Tertiary Makeup Unit SA Efficiency Eb OA+RA OA+RA2 Treated Makeup Air C1 C C H C Efficiency Ea OA Treated Makeup Air C1 C C H C Efficiency Ea OA Makeup Air Co Efficiency Ec RA1 RA2 SA Supply Air Q Leakage Air Cs Space Impurity Cs Concentration Space Particle Generation G Deposition D RA Return Air EA Exhaust Air Ce Cs

35 Air Handling Configuration Strategies 8 (ISO Class 1, 2, 3, 4, 5, 6, 7) (FS-209 Class 1, 10, 100, 1,000, 10,000, 100,000) Configuration-7: Fan-Filter Units For Primary Recirculation Typical Application: CFM/Ton ratio: ,000 (L/s/Ton ratio: ,500) FFU flow/ahu flow ratio: 2-50 Room sensible ratio: high to very high

36 Process and Building Systems Building Systems City water & gas services Cold/hot water distributions Gas distributions Storm, sanitary & vent Fire pump & automatic sprinkler systems Emergency power generator HVAC & Indoor comfort Building management Cleanroom HVAC&R Make-up system Recirculation system Return air system Temperature & humidity controls Room pressure control Airlock Noise and vibration control Hydronic heating Comfort chilled water Cooling tower water Particle counting Cleanroom Process Gas detection Static control RO and DI waters Process chilled water Chemical gases and storages Solvent drain and collection Solvent gas exhaust Process vacuum Scrubbed exhaust House vacuum Acid drain and waste neutralization Clean dry air Instrumentation air & control

37 Typical Cleanroom Construction Materials Classification FS Class FS Class FS Class FS Class FS Class FS Class ,000 10, ,000 ISO Class 1, 2 & 3 ISO Class 4 ISO Class 5 ISO Class 6 ISO Class 7 ISO Class 8 & 9 Wall System Aluminum Component Aluminum Component or Metal Stud Wall Panel Honeycomb Aluminum Conductive Finish Aluminum Polystyrene Core or Epoxy Coated Steel Laminated over Drywall Paint Epoxy Epoxy / Latex Latex Ceiling Grid 2 Aluminum Gel Seal Ceiling System 1½ Steel Gasketed Vinyl or Epoxy Coated Drywall Grid Support All thread with Strut & Turn buckles 12 ga wire to grid, 10 ga wire to Corner of Grid Intersection Only Floor Raised Floor with Perforated / Grated Access Concrete Covered with Epoxy Solids or Sheet Vinyl Air Return Floor Low Sidewall Low Sidewall or Ceiling

38 Selective Cleanroom Design Ideas (1) ISO-5 raised-floor large ballroom design to meet processing requirements Perforated concrete floor allows return air down to sub-floor area below. Sub-floor area (below cleanroom) houses large process/utility equipment, ducts and piping. Critical process located in a mini-environment (ISO-5) which is in an ISO-7 large cleanroom

39 Selective Cleanroom Design Ideas (2) Return air floor panels arrangement to accommodate equipment footprints (ISO-7) Shared return air chase could house some process piping and small equipment. Small pass-through on door allows small items transport while minimize door operations. Sliding doors have shorter cycle than swing doors to reduce contamination from corridor.

40 Selective Cleanroom Design Ideas (3) CFD analysis of velocity vector around a moving door (second door of an airlock) CFD to visualize particle migration from gowning room to airlock and to cleanroom Solar panels on roof to supplement electricity usage Roof storm drains collected for irrigation of landscaping

41 Selective Cleanroom Design Ideas (4) Unidirectional flow inside RAB Mixed flow in Room Lower concentration inside RAB, higher concentration near person due to recirculation air Higher concentration near face By K. Khankari 2013

42 Selective Cleanroom Renovation Ideas (1) Before After Retrofits Changed from open ballroom to multiple narrower rooms to improve airstream parallelism. Used exhaust canopies to remove high-concentration particles generated from process equipment. Room ACH reduced from 385 to 280.

43 Selective Cleanroom Renovation Ideas (2) Before After Retrofits Changed from general-purpose chemical lab to ISO Class-3 Nano research lab in various aspects: Airflow rate, 100% HEPA ceiling with FFUs, teardrop lighting, and raised floor, etc.

44 Selective Cleanroom Renovation Ideas (3) Before After Retrofits ISO-4 cleanroom (358 ACH) converted to ISO-3 cleanroom (400 ACH) with lighting-integrated ceiling (yellow light area after filtered spectrum). Replaced primary-alone AHU with primary-secondary AHU systems, reduced energy consumption about 65%.

45 Selective Cleanroom Renovation Ideas (4) Before After Retrofits Retrofitted a 22-ft height shop/storage area into a high-bay ISO-3 cleanroom for aerodynamic research. The cleanroom (280 ACH) has 2-ft wide return air chases on both sides, and 3-ft raised floor.

46