Engsysco

Wei Sun, P.E.ASHRAE Fellow

Distinguished Lecturer“Clean Spaces” Technical Committee (TC9.11) Chair (07-10)“Healthcare Facilities” Technical Committee (TC9.6) Member“Laboratory Systems” Technical Committee (TC9.10) Member

Society CTTC Committee Chair (12-13)IEST (Institute of Environmental Sciences and Technology)

Society President (2016-2017)

ISO 14644 Cleanroom StandardsUSA Delegate

Engsysco, Inc.President

Ann Arbor, Michigan, USA

Web: www.engsysco.com Email: wsun@engsysco.com

Cleanrooms and HVAC SystemsDesign Fundamentals

ENERGY in BUILDINGS – Northern HellasThessaloniki, Greece May 5, 2018

New Book: ASHRAE Design Guide for Cleanrooms

Basics about airborne particles, cleanliness classifications and cleanroomsDetermination of cleanroom airflow quantity –a) Traditional “table” methodb) New modeling method (to avoid air over-supply)Renovation options to lower fan energy consumptionSelection of proper air loop configurations to save energy and enhance performanceNew demand flow control methods – manual and automatic approachesSamples of renovation photos and ideasSummary

Outline

Cleanroom - A special enclosed area, its environment typically has the following controlled parameters:

TemperatureHumiditySound and VibrationLightingetc.

Common Requirements

Airflow PatternRoom PressureParticle Contamination (Airborne, Surface & Liquid-borne)Microbial Contamination(Airborne, Surface & Liquid-borne) Electrostatic Discharge (ESD)Gaseous ContaminationProcess Specifics

Special Requirements

Cleanroom Design Considerations(Applications and Controlled Parameters)

SemiconductorMicroelectronicPharmaceuticalBiotechnology

AerospaceAutomotiveMedical DevicesOptical Devices

HospitalUniversity Labs Food ProcessingMiscellaneous

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-14644-1 Classification of Air Cleanliness

ISO-14644-2 Cleanroom Testing for Compliance

ISO-14644-3 Methods for Evaluating & Measuring Cleanrooms & Associated Controlled Environments

ISO-14644-4 Cleanroom Design & Construction

ISO-14644-5 Cleanroom Operations

ISO-14644-6 Terms, Definitions & Units

ISO-14644-7 Enhanced Clean Devices

ISO-14644-8 Molecular Contamination

ISO-14698-1 Biocontamination: Control General Principles

ISO-14698-2 Biocontamination: Evaluation & Interpretation of Data

ISO-14698-3 Biocontamination: Methodology for Measuring Efficiency of Cleaning Inert Surfaces

Cleanroom Standards in US (Previous US Federal Standard and Current ISO Standards)

Air Cleanliness Classifications (Current ISO-14644 Standard & Previous US FS-209 Standard)

FS 209 ISO 14644 FS 209 ISO 14644 FS 209 ISO 14644 FS 209 ISO 14644 FS 209 ISO 14644 FS 209 ISO 14644

Particles/ft3 Particles/m3 Particles/ft3 Particles/m3 Particles/ft3 Particles/m3 Particles/ft3 Particles/m3 Particles/ft3 Particles/m3 Particles/ft3 Particles/m3

1 10 22 100 24 10 4

1 3 35 1,000 7.5 237 3 102 1 35 810 4 350 10,000 75 2,370 30 1,020 10 352 83100 5 100,000 750 23,700 300 10,200 100 3,520 832 291000 6 1,000,000 237,000 102,000 1,000 35,200 8,320 7 29310,000 7 10,000 352,000 83,200 70 2,930100,000 8 100,000 3,520,000 832,000 700 29,300

9 35,200,000 8,320,000 293,000

0.1 µm 0.5 µm 5.0 µm0.3 µm 1 µmFS 209 Class

ISO 14644 Class

0.2 µm

FS 209EAir Cleanliness Class Definition - FS 209

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

0.01 0.1 1 10

PARTICLE SIZE, μm

PAR

TIC

LES

PER

CU

BIC

MET

ERS

FS-1

FS-100,000

FS-10,000

FS-1,000

FS-100

FS-10

These Two Standards Similar? (Air Cleanliness Class Definitions )

Air Cleanliness Class Definition - ISO 14644

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

0.01 0.1 1 10

PARTICLE SIZE, μm

PAR

TIC

LES

PER

CU

BIC

MET

ERS

ISO-1

ISO-2

ISO-3

ISO-6

ISO-9

ISO-8

ISO-7

ISO-5

ISO-4

ISO 14644

Air Cleanliness Class Definition Comparison Between FS 209 and ISO 14644

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

0.01 0.1 1 10

PARTICLE SIZE, μm

PART

ICLE

S PE

R CU

BIC

MET

ERS

ISO-1

ISO-2

ISO-5

ISO-4

ISO-3

ISO-6

ISO-9

ISO-8

ISO-7

FS-1

FS-100,000

FS-10,000

FS-1,000

FS-100

FS-10

These Two Standards Similar? (Comparison of FS-209E and ISO-14644 in Overlapping Chart)

They are NOT identical, but roughly equivalent under certain classes and particle sizes.

0.1µm 0.2

µm 0.3µm 0.5

µm 1µm 5.0

µm

Clas

s 1 Clas

s 2 Clas

s 3 Clas

s 4 Clas

s 5 Clas

s 6 Clas

s 7 Clas

s 8Cl

ass 9

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

Particle Count / m3

Particle Size (Channel)Cleanliness Class

Cleanroom Particle Counts Per ISO Classification

Class 1Class 2Class 3Class 4Class 5Class 6Class 7Class 8Class 9

ISO 14644 Classification(Airborne Particle Sizes, Counts and Classifications)

1. Particles larger than 100 microns can be seen with naked eyes. 2. Next step particles ranging from 0.01 to 100 microns are main

interest of contamination for years.3. Atoms and molecules used to be considered too small as

industrial contamination, but not any more after introduction of the concern of Airborne Molecular Contamination (Non-solid, in gas or vapor phase).

0.1 0.2 0.3 0.5 1 5 10 1000.01

Particles Within ISO-14644 DefinedCleanliness Classifications

Macro ParticlesUltrafine Particles

Particle Size in µm

Airborne Particulates(Airborne Particle Sizes, Counts and Classifications)

Sources of Contamination

Description Control Methods

Infiltration through doors, and cracks at windows, and walls

Tighter exterior wall construction, exterior zone pressurization, vestibules at main entrances, and seal space penetrations.

Outdoor air

Makeup air entering through the air conditioning systems

Multiple level filtrations External

Indoor transfer air between rooms

Infiltration through doors, windows, and wall penetrations for pipes, ducts, etc.

Seal wall penetrations, multiple level pressurizations & depressurizations to obtain proper airflow directions

People

Largest source of internal particles: skin scales, hair, textile fibers

Garments, proper gowning procedures, air shower before entry

Work surface shedding

Rubbing one item against another

Use cleanroom suitable or rated furniture

Process equipment

Spray, painting, welding, grinding

Local filtration and exhaust

Raw and semi-finished material During transport

Equipment washing, cleaning and sterilization before entry, use airlock & pass-through

Liquids, pressurized gases used in process

During preparation, processing and packaging

Local exhaust

Chemicals used for cleaning Out-gassing to room Use cleanroom suitable

or rated cleaners

Internal

Room construction materials

Dust generated from wall, floor, ceiling, door, fibrous insulation

Constructed with special building materials

Particle Sources & Control

Non-Unidirectional(Conventional) Flow

UnidirectionalFlow

Mixed Flow

Mini-EnvironmentFlow

Room Airflow Patterns

Ballroom Office and Support Areas

One Big Cleanroom

Service Area

Service Area

Mini-Environment

Service Chase

Office and Support Areas

Cleanrooms

Service Area

Service Area

C C C C

C C C C

Office and Support Areas

Cleanrooms

Service Area

Service Area

R R R R R

Smallrooms

Multiple Clean

R R R R R

Shared Return Air Chase (TYP)

Mini-Cleanrooms

Less-clean Cleanroom

Cleanroom Floor Arrangements

Class

US 209 ISO

Ceiling Filter Coverage

HEPA or

ULPA

9 5% - 15% 100,000 8 5% - 15% 10,000 7 15% - 20% 1,000 6 25% - 40% 100 5 35% - 70%

HEPA

10 4 60% - 90% 1 3 60% - 100%

2 80% - 100% 1 80% - 100%

ULPA

Typical Ceiling Filter Coverage

Raised Floor

Cleanroom

Submains

Chemical Supply Systems Process Supply Systems

Gas Cabinets

Basement

Perforated Slab Process Exhaust

Waff le Slab

Ceili ng + Filter

Pump

Scrubbed Exhaust Air

Fan Tow er

Return Air

Stair Case

Visitors Corr idor

Maint. Corr idor

Pressurized Plenum

Silencer

Cooling CoilMake-Up Air

Process Corr idor

ITRI

Pressurized Plenum (Fan Tower) Arrangement

Stair Case

Scrubbed Exhaust Air

Ret urn Air

SubmainsMake-Up Air Process Supply Submains

Basement

Scrubber

Cleanroom

Process Supply Syst emsGas Cabinets

4.8m

0.0m

3.6m

9.6m

4.8m

2.2m

3.5m

ITRI

Fan Filter Units (FFU) Arrangement

Cleanroom Airflow Quantity(Much Higher Flow Rate for Cleanrooms)

During “unoccupied mode” in evenings and weekends, particle generation inside cleanrooms typically is much lower, therefore energy saving from airflow rate reduction could be significant.

Type

of F

acili

ties

Air Change Per Hour (ACH)6 25 600

15 ̶ Mainly to Dilute and Remove Particles

Cleanroom Spaces

General Purpose Spaces ̶ To Meet Heating & Cooling Loads

IEST RP-12.1 (Before 2013)

Classification

ISO Class FS -209 Class

Air ChangePer Hour (ACH)

Range8 100,000 5 – 487 10,000 6 0 – 906 1,000 150 – 2405 100 240 – 4804 10 300 – 5403 1 360 – 5402 360 – 6001

Airflow Quantity(Dilution-Based Traditional Approaches: Table Method)

Intuitively, ACH value should be based on the required cleanliness class and the activities performed in the space. Activities that generate higher level of particles would need higher ACH than those that generate at lower level.

Cleanroom airflow rate should be ideally provided “as needed” instead of “picking an arbitrary rate from the table”, a better approach should be similar as those of building heating/cooling load calculations utilized today.

Airflow Quantity(Problems of Traditional Approaches)

IEST RP-12.3 (2015)

Airflow Quantity(New Method – Use Equations/Modeling to Estimate)

CO = Outdoor make-up air concentration (count/m3)ACH = Air change per hour in cleanroom (1/hr)G = Particle generation rate in room (count/m3/hr)EUC= Combined filters' efficiency (in series) inside make-up AHU and recirculation

fan/AHU units (%)EH = HEPA or ULPA filter efficiency in cleanroom (%)θ = Percentage of generated particles deposited on exposed surfaces (%)m = Ratio of outside air (OA) in supply air (SA)

Equation to calculate average room particle concentration:

Airborne particle concentration CS(cleanliness class) is a function of multiple variables:

Make-up AHU fan & filters

Recirculation fan

Cleanroomparticle concentration CS

EACe

OA

SA

RA RA

CO

CS

Surface deposition D

Particle generation G

HEPAfilter EH

Leakage airQ

EU

CS

)1()(

)1()1()1(

mEEEEmACH

GCmEE

CHUCHUC

OHUC

S -××-++

×-+××-×-

=

q

Effect of Room Particle Generation Rate G

Variables’ Significances on Air Cleanliness(Example: Case-Specific Analysis)

Effect of Final HEPA Filter Efficiency EH

Effect of AHU Combined Filters’ Efficiency EUC Effect of Outdoor Air Intake Concentration Co

Select equipment, machinery, furniture and room construction materials with lower particle generation levelIsolate and remove high-concentration particles generated in cleanroomEnhanced surface cleaning protocol to minimize surface particles to become airborne particlesDesign return and exhaust air systems effectively for particle exitMaintain proper pressurization, depressurization could cause particle gain through leakage

Since many variables can affect the room air cleanliness, so more options are available than using a high ACH rate (or velocity) alone to ensure a specified cleanliness, sometimes, options below may be more cost effective:

Options to Lower Fan Energy Consumption (Based on Modeling Technique)

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=300-500, or L/s/Ton=150-250).

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.

Load Characteristic and Air Loop Selections (For Energy Conservation and Performance)

HVAC Schematic and Diagram(Primary Loop Alone Air-Handling System)

For ISO Class 7, 8, 9 (FS-209 Class 10,000, 100,000)Typical Application:

CFM/Ton ratio: 300-500 (L/s/Ton ratio: 150-250)

RA

EA

SA

Q

OAOA+RASA

Space Impurity Concentration

ExhaustAir

LeakageAir

Particle Generation

Deposition

Cs

Space

D

G

Efficiency Ea

SupplyAir

ReturnAir

MakeupAirCo

CeCs

Cs

HC

FILT

ERCC

AHU Unit

HEP

A

Efficiency Eb

HVAC Schematic and Diagram(Primary-Secondary Loops Air-Handling Systems)

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

RA

EAQ

OAOA+RASA

Space Impurity Concentration

ExhaustAir

LeakageAir

Particle Generation

Deposition

Cs

Space

D

G

Efficiency Eb

ReturnAir

Treated MakeupAirC1

CeCs

Cs

FILT

ER

Primary Fan Unit

HC

FILT

ERCC

Secondary Makeup Unit

OA

MakeupAirCo

SA

SupplyAir

HEP

A

Efficiency Ea

Efficiency Ec

HVAC Schematic and Diagram(Primary-Secondary-Tertiary Loops Air-Handling Systems)

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: 2-10Secondary flow/Tertiary flow ratio: 2-5

RA

EAQ

OA+RA2OA+RASA

Space Impurity Concentration

ExhaustAir

LeakageAir

Particle Generation

Deposition

Cs

Space

D

G

Efficiency Eb

ReturnAir

Treated MakeupAirC1

CeCs

Cs

FILT

ER

Primary Fan Unit

HC

CC

Secondary AHU Unit

OA

SA

SupplyAir

HEP

A

Efficiency Ea

Efficiency EcRA2RA1

HC

FILT

ERCC

Tertiary Makeup Unit

OA

MakeupAirCo

Efficiency EaTreated MakeupAirC1

AC

H R

ate

Room Particle (or Microbial) Generation Rate G

VFD Flow Control

Staged Flow Control

The strategy is to adjust or modulate the supply air rates to maintain the same or acceptable cleanliness based on continuous particle (microbial) sensing during both occupied and unoccupied modes, which are about 24% and 76% respectively of total hours during a typical week.

Demand Flow Control to Conserve Fan Energy

Manual Airflow Adjustment

Automatic Airflow Modulation(Example: Continuous Particle and/or Microbial Sensors or

Multiplex sensing for Feedback Control)

Model-Referenced Adaptive Control (MRAC) Block Diagram

Real-time Particle Sensing Model Estimated vs. Actual Response

Automatic Airflow Modulation(Example: Control Diagram, Real-time Sensing and Response)

Control Diagram

Building Systems

City water & gas servicesCold/hot water distributionsGas distributionsStorm, sanitary & vent Fire pump & automatic sprinkler systemsEmergency power generatorHVAC & Indoor comfortBuilding management

Cleanroom HVAC&R

Make-up systemRecirculation systemReturn air systemTemperature & humidity controlsRoom pressure controlAirlockNoise and vibration controlHydronic heatingComfort chilled waterCooling tower waterParticle counting

Cleanroom Process

Gas detectionStatic controlRO and DI watersProcess chilled waterChemical gases and storagesSolvent drain and collectionSolvent gas exhaustProcess vacuumScrubbed exhaustHouse vacuumAcid drain and waste neutralizationClean dry air Instrumentation air & control

Process and Building Systems

FS Class 1

FS Class 10

FS Class 100

FS Class 1,000

FS Class 10,000

FS Class 100,000

Classification

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

Vinyl or Epoxy Coated Drywall

Paint Epoxy

Epoxy / Latex Latex

Ceiling Grid 2” Aluminum Gel Seal Ceiling System

1½” Steel Gasketed

Grid Support All thread with Strut & Turn buckles

12 ga wire to grid, 10 ga wire to filter @ 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

Typical Cleanroom Construction Materials

Cleanroom Renovation Photos (1)

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.

Before AfterRetrofits

Changed from general-purpose chemical lab to ISO Class-3 Nano research lab in various aspects: Airflow rate, 100% HEPA ceiling with FFUs, tear-drop lighting, and raised floor, etc.

Cleanroom Renovation Photos (2)

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%.

Before AfterRetrofits

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.

Selective Renovation and 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

Selective Renovation and 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.

Selective Renovation and 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

Roof storm drains collected for irrigation of landscaping

Solar panels on roof to supplement electricity usage

For most cleanroom facilities, occupied time is about ¼ of total hours of a typical week, significant energy can be saved during unoccupied mode. Basic option: Monitor room particle concentrations, and use time-based reset, or manually adjust supply fan speed (flow rate) to ensure room air cleanliness when codes and regulations allow. Advanced option: Use continuous particle and/or microbial sensors or multiplex sensing techniques as feedback signals to control supply fan speed automatically. Use proper control algorithms and strategy.

Summary and Conclusion

During Design Phase

Table method to determine the airflow quantity may lead to significant over or under supply.Use modeling method to establish a mathematical relationship between “air cleanliness” and “controlling variables”, and then identify the prioritized options to lower fan energy consumption.Select a proper air loop configuration (primary alone, primary-secondary, or primary-secondary-tertiary), typically based on “supply flow rate vs. cooling” ratio.Use CFD to assist and optimize designs.

During Operation

Q & A