Testing Fan Filter Units

Monroe A. BrittManager, Research & Technology

Clarcor Air Filtration ProductsLouisville, KY

502 969 2304 x1260 -- mbritt@clcair.com

Testing Fan Filter Units

Objectives• To develop procedure for testing Fan Filter

Units that will be recognized and used by manufacturers, consultants, contractors, and end-users

• IEST has formed tentative Working Group to prepare Recommended Practice for publication

• First Meeting – Held November 4, 2003, Approx 15 Attendees

• Next Meeting – April at ESTECH – Las Vegas

Approach to Test Procedure• Develop procedures that can be readily

conducted in manufacturers facility or after installation of units in cleanrooms

• Instrumentation should be apparatus commonly used is the cleanroom industry

• Standardized Reporting Form• Conduct blind “Round Robin” test program

between various manufacturers and test labs to verify uniformity of test results

Testing Fan Filter Units

• Physical Size -- Up to 4 Ft. x 4 Ft. Units • Test Parameters Air Flow – CFM Power (watts, amps, PF, volts) Available External Static Pressure Sound (pressure and power levels) Filter Air Velocity Uniformity - FPM Vibration

Air Flow - CFM• Efficiency of Media -- HEPA Media, ULPA Media, ePTFE• Media Pack -- Depth of Pack & Pleat Spacing• Pre-Filters Various Efficiency Levels of Particulate Filters Gas Phase Filters• Room/Enclosure Pressurization and Exit Losses• Inlet Duct Connections & Duct Work• Height of Plenum above FFU Air Inlet• Current -- 50 or 60 Hertz• Acoustical Packages• Other Variables

Air Flow - CFM

• Required Air Flow Expressed as Velocity -- FPM

Expressed as Volume -- CFM

• CFM = Area x FPM Area is Active Flow Area of Filter

(Typical 2 x 4 filter Without Center Bar Contains 7.15 Ft2 of Active Filter Flow Area)

• CFM at 90 FPM 90 FPM X 7.15 Ft2 = 640 CFM

Fan Filter Unit (FFU)

• FFU’s Without Constant Flow Control

AC Units

ECM Units

• FFU’s With Constant Flow Control

AC Units

ECM Units

Air Flow - CFM vs Static Pressure

FanHousing

Filter

Flow Hood

TestPlenum

Resistance(Pre-Filter)

StaticPressureTap

Measure CFM Static Pressure Watts, Amps, PF, Volts

Watt Meter

Transition Needed For 4 x 4 FFU

Air Flow - CFM vs External Static Pressure

Air Flow - CFM

Pre

ssu

re -

Inc

he

s W

.G.

HEPA Filter

ULPA Filter

ULPA Filterw/Pre-Filter

FFU’s w/o Constant Flow Control

No Scale

Air Flow vs Watts

Air Flow - CFM

Po

we

r C

on

su

mp

tio

n –

Wat

ts

HEPA Filter

ULPA FilterULPA Filterw/Pre-Filter

FFU’s w/o Constant Flow Control

No Scale

Air Flow - CFM vs External Static Pressure

Air Flow - CFM

Pre

ssu

re -

Inc

he

s W

.G.

ULPA Filter

ULPA Filterw/Pre-Filter

FFU’s with Constant Flow Control

HEPA Filter

Rated Air FlowNo Scale

Air Flow vs Watts

Air Flow - CFM

Po

we

r C

on

su

mp

tio

n –

Wat

ts

HEPA Filter

ULPA FilterULPA Filterw/Pre-Filter

FFU’s with Constant Flow Control

No Scale

Air Flow---Power---Static Pressure

Minimum Reporting Data• Complete Description of Fan Unit, Final

Filter, and Pre-Filter -- Part Numbers, Construction Codes, etc

• Nominal Rated Air Flow Air Flow - CFM Watts, Amps, Power Factor, Volts, Hertz Available External Static Pressure Dimensions and Active Filter Flow Area

Sound Pressure and Power Levels

• Background Levels -- Recorded as First Step

• Sound Pressure Levels -- To be Measured as Overall dBA, Overall dBL, and as dBL for Octave Bands -- Used to Report Sound Levels and Establish NC Curves for One Fan Filter Unit Installed in Typical Operating Environment

• Sound Power Level -- To be Determined as Overall dB and as dB

for Octave Bands -- Used by Acoustical Engineers to Predict Sound Pressure Levels in Actual Operating Environments. These Calculations Will Consider Number of FFU’s, Location of FFU’s and Sound Characteristics of Materials, Equipment, and Other Activity in the Individual Cleanroom

Sound Pressure LevelTest Environment --- 8 x 8 x 8 Soft Wall Room

8 Ft.

8 Ft.

3 ft.

7 Ft.MicLocation

Concrete Floor - No Covering

Acoustical Tiles

Sound Pressure Levels Minimum Reporting Data

• Complete Description of Fan Unit, Final Filter, and Pre-Filter -- Part Numbers, Construction Codes, etc

• Nominal Rated Air Flow Background Sound Pressure - dBL & dBA

Background Octave Band Sound Pressure - dB

Overall Sound Pressures -- dBL & dBA

Octave Band Sound Pressures – dB

Sound Power LevelTest Environment --- 8 x 8 x 8 Soft Wall Room

8 Ft.

8 Ft.

3 In.

7 Ft.

Plane of MicLocations

Concrete Floor - No Covering

Acoustical Tiles

Sound Power Levels• Sub-divide active filter area into equal square

areas, maximum of 12” x 12”, minimum of 4 areas/filter

• Measure overall sound levels for center points• Average all sound levels measured -- LP

• Compute Sound Power Level for FFU -- LW

LW = LP + 10 Log (S1/S0) LW = Sound Power Level, dB re 10 -12 Watts LP = Sound Pressure Level, dB re 10-5 N/m2 S1 = Total Area of Measurement Surfaces - m2 S0 = 1.0 m2

Sound Power Level

Minimum Reporting Data

• Complete Description of Fan Unit, Final Filter, and Pre-Filter -- Part Numbers, Construction Codes, etc

• Nominal Rated Air Flow

Grid with Measured Values – dB

Average of Measured Values -- dB

Calculated Overall Sound Power -- dB

Air Velocity Uniformity

• Sub-divide active filter area into equal square areas, maximum of 12” x 12”, minimum of 4 areas/filter

• Measure center point velocity for each area at 6 inches downstream of filter or protective grid

• Take measurements for minimum of 5 seconds, using apparent average during that period as value for reporting

Air Flow Uniformity Minimum Reporting Data• Complete Description of Fan Unit, Final

Filter, and Pre-Filter -- Part Numbers, Construction Codes, etc

• Nominal Rated Air Flow Grid with Measured Values – FPM Standard Deviation of Measured Values

Vibration

“Site Under Construction”

Current Plans

• Mount FFU in stiff aluminum frame that

will simulate proper sized ceiling grid

• Suspend frame by flexible cables

• Measure vibrations at corner of frame

• Comments/Input Solicited

Future Activity

• Complete “Working Draft” of Proposed RP• Develop Comprehensive Data Reporting Form• Distribute Draft to First Meeting Members and All

Interested Parties• Solicit Comments and Recommendations• IEST Working Group Next Official Meeting April 25 – 28 , 2004 Riveria -- Las Vegas, NV WG 036 Meets On April 26 at 8:00 AM