1. History of HEPA Update to today
Per Lindblom
Hollingsworth & Vose
April 22, 2010

2. Presentation Historical review HEPA Filter Media choices
Next Generation Micro fiberglass HEPA media

3. National Defense Research Council
Diffusion
The National Defense Research Council (NDRC), solicited the assistance of a number of university and industrial scientists in the search for better smoke filters.
This effort resulted in important U.S. advances in the theory and technology of aerosol filtration.
1942 Dr. Irving Langmuir developed a general theory for mechanical filtration
1943 LaMer and Sinclair developed instruments to measure the filtration efficiency of DOP smoke (0.30 µm) particles
Interception

4. H&V develops Gas Mask Media
The British sent filter paper extracted from captured German gas mask canisters to the U.S. Army Chemical Warfare Service Laboratories (CWS) in the early days of the WW II.
NRL analyzed media from a captured German gas mask in early WW II
had unusually high particle retention characteristics, acceptable resistance to airflow, good dust storage, and resistance to plugging from oil-type screening smokes.
H&V developed US version of this media for gas mask. Media would be known as CWS type 6.

5. The Collective Protector
Gas masks where practical in the field but less so for Army HQ.
To address this type of problem, the U.S. Army Chemical Corps developed a mechanical blower and air purifier known as a “collective protector” filter unit.
the gas mask canister smoke filter was refabricated into a filter constructed of deep pleats separated by a spacer panel and sealed into a rigid rectangular frame using rubber cement.
Picture: PATTON CONFERS WITH EISENHOWER on plan for reduction of Fort Driant. On left is General Patton, on right General Eisenhower.

6. Manhattan Project In 1942 the top secret Manhattan Project was formed.
The Project created potential air pollution problems that could be solved only by using air filters with filter media characteristics similar to those of the CWS filter.
The U.S. Army Chemical Corps became the sole supplier of high-performance filters to the Manhattan Project
The filters developed in the process was called “superinterception” or “super-efficiency” filters; later referred to as “absolute” filters

7. Post World War II
CWS Filter media relied on raw materials coming from overseas.
AEC comissioned Arthur D. Little to find domestic sources.
Johns Manville and Owen Corning developed sub-micron diameter glass fibers.
an all-glass-fiber paper made partly from super-fine glass fibers with diameters substantially less than 1.0 μm.
The use of Glass allowed much greater control of manufacturing procedures and production of better, more uniform papers.

8. The Conception of HEPA
1953 Walter Smith working with Arthur D. Little developed the ‘absolute’ filter for the AEC
Arthur D. Little also started the first commercial filter manufacturing company, the Cambridge Filter Company.
By 1957, three firms were fabricating absolute filters.
In 1960 the first laminar flow bench was invented at Sandia National Laboratory

9. The Birth of HEPA
HEPA filters, an acronym invented by Humphrey Gilbert, from his 1961 AEC report called High-Efficiency Particulate AirFilter Units, Inspection, Handling, Installation.
A HEPA filter was defined as a throwaway, dry-type filter with:
a minimum particle removal efficiency of percent ( which was later raised to percent) for a 0.3-μm monodisperse particle cloud;
a maximum resistance of 1 inches water gauge (in.wg) when operated at rated airflow capacity
a rigid frame

10. HEPA Filtration enables Technology.
1960’s NASA develops contamination control technology around HEPA filtration after loosing several unmanned satellites.
NASA establishes clean room standards for US Manned Space Program in the late 60’s
AEC –drives standards and quality control of Filter media
Cleanroom Technology enables
Lunar Landing
Silicon Chips

11. Evolvement of HEPA Filters
Customer demand of higher handling Higher Air volume at a given efficiency.
Using less filters in a system
Reducing cost.

12. HEPA Filter Media HEPA media Microfiber Glass PTFE membrane
Synthetic Charged Media
Nanofibers

13. Comparison Microfiber Glass vs. Membrane
Depth Filters
Randomly oriented intertangled fibers laid into a mat.
Typically using a Fourdrinier process
Submicron glass fibers
Glass fiber paper has a very low “solidity” That is, the volume of the sheet contains a low percentage of solid material and a very high percentage of void area.
Easy to process
PTFE Membrane
Surface Filter
Biaxially stretched about 800% into a microporous structure.
Higher Gamma/Alpha
Inert –no outgassing
High Cost

14. Next Generation Microfiber Glass HEPA Filter Media
Per Lindblom
Paul Smith

15. PerForm ® Perfect Formation High Performance
The importance of Formation will follow
High Performance
Filter Media 4 -Cost Effective Solutions 15

16. Evolution of Filter Manufacturer Needs
Increasing sophistication of equipment
Greater emphasis on productivity
Higher pleating speeds
Minimize downtime
Reduction of waste
Minimize filter repairs / touch-ups
Reduction in manufacturing variance
Improved filter performance
Lower pressure drop for a given efficiency/class
Hence lower energy demand in usage 16

17. H&V Product Development
Objectives
Increase uniformity of fiber distribution
Improve processability
Elimination of contaminants
Reduce variation in media
Physical properties
Improved Filtration characteristics creating Higher performance Low pressure drop
Actions
Quantitative measurement of media formation
Major capital investments in machine modifications
In-line web analysis
Defect detecting and tracking
Optimisation of the media design 17

18. Increase uniformity of fiber distribution
To improve consistency of pleat shape
To improve laminarity of flow through the filter
To Increase the filter “gamma”
Reduce pressure drop
Reduce energy demand
Measured and predicted by “Formation Index” 18

19. Improved Formation: A lower Formation Index is better H&V PerForm HEPA
H&V Ashrae
Formation Index = 4.0
Typical HEPA
Formation Index = 5.2
Typical Ashrae
Formation Index = 6.5 19

20. Formation - Conclusions
Formation of the media has significantly improved due to machine and media design changes
Lower F.I. means the media has:
Fewer Fibre clumps and pills
Better overall fiber distribution
Minimal air entrapment (air bubbles)
Lower F.I. means the media pleats better and results in:
Neat sharp pleat tips
Even air flow distribution
Lower filter pressure drops
Higher filter gamma
HIGHER PLEATER PRODUCTIVITY 20

21. Improved Processing Characteristics
Typical HEPA Media
PerForm ® H&V HEPA Media 21

22. Improved Performance of the media
Gamma =
log
Pressure Drop
100
% Pen
Gamma is higher when
Pressure drop is lower
Penetration is lower
Two medias, with the same flat sheet gamma:
The media with the lower formation index gives
Better defined pleat tips and:
Higher filter gamma 22

23. Influence of Formation on filter gamma
Two medias with the same flat sheet gamma, one with better formation 23

24. Improved Flat Sheet Gamma
Typical H13/H14 HEPA:
Gamma = 12
Pressure Drop (ΔP) = 30.5 mm H2O (max. DOP penetration 0.03%)
PerForm ® H13/H14 HEPA:
Gamma = 14
% lower ΔP for the same efficiency.
Pressure Drop (ΔP) = 27 mm H2O (max. DOP penetration 0.03%) 24

25. Improved Filtration Properties: Gamma
Previous Industry standard media
H&V media 2007
PerForm media 2009 25

26. Filter Media 4 cost effective solutions
Driven by higher gamma:
Both
Higher flat sheet gamma
Higher filter gamma
Filter
Design
Criteria
Longer Life
Lower Energy Costs
Less Media 26

27. Filter Media 4 cost effective solutions
Design
Criteria
Longer Life
Lower Energy Costs
Less Media
PerForm ®
Lower pressure drop for a given efficiency
Cost engineer by removing media area
Increase the media face velocity and still meet spec.
Still achieve a lower pressure drop for the same efficiency
eg. Save 11% of the cost of the media 27

28. Reducing media area 28

29. Filter Media 4 cost effective solutions
Design
Criteria
Longer Life
Lower Energy Costs
Less Media
Driven again by higher gamma
Lower pressure drop means larger delta to the final pressure drop
Longer loading time and longer life 29

30. Every 1 Pa lower pressure drop
Filter Media 4 cost effective solutions
Filter
Design
Criteria
Longer Life
Lower Energy Costs
Less Media
Energy demand
E= (q x Δp)/ η x T x c/1000
e.g 1 Pa, 50% eff, 600x1200mm 0.45m/s, 0.15 USD/kwh
-> $0.85
q air flow (m3/sec)
Δp average pressure drop (Pa)
T running time (hrs)
η fan efficiency
c cost of energy in USD per kWh
Rule of Thumb:
Every 1 Pa lower pressure drop
Saves $ 1 /yr 30

31. Filter Media 4 cost effective solutions
USD
Per Filter ! 31

32. Filter Media 4 cost effective solutions
To summarise
Media consistency
Minimise defects
Measurable F.I.
Lower F.I.
Redesigned media
Higher gamma and Lower pressure drops
Productivity improvements
Less downtime
Less scrap or re-work
Faster pleating speeds
Filter improvements
Sharper pleats
Higher flat sheet gamma
Higher filter gamma
Filter cost savings
Cost engineer, Less media
Lower energy demand
Longer filter life 32

33. Thank you … Any questions?