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Aerosol Photometers: The Gold Standard in HEPA Filtration Testing

Aerosol Photometers: The Gold Standard in HEPA Filtration Testing. Presented by: Dave Crosby Tim McDiarmid Don Largent Air Techniques International www.ATItest.com info@ATItest.com. Introductions. Agenda. History of Photometry Science of Photometry Applications of Photometry.

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Aerosol Photometers: The Gold Standard in HEPA Filtration Testing

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  1. Aerosol Photometers:The Gold Standard in HEPA Filtration Testing Presented by: Dave Crosby Tim McDiarmid Don LargentAir Techniques International www.ATItest.com info@ATItest.com

  2. Introductions

  3. Agenda • History of Photometry • Science of Photometry • Applications of Photometry

  4. History of Photometers & HEPA Filters

  5. History of Photometers & HEPA Filters “You can’t have one without the other”

  6. The photometer was first since there was a need David Sinclair, Ph.D. (Nephelometer) (Not portable and had logarithmic display)

  7. Air Pollution Research 1933

  8. WW II generated a high priority need It all started in 1942

  9. Some Key Players Wendell Anderson, Humphrey Gilbert, Dr. Melvin First

  10. Captured WW II German Gas Masks • The US had performed no gas mask development since WW 1 • German masks used cellulose asbestos media patented by Dräger Werke in 1933 • Wendell Anderson working with H&V developed media comparable to the German sample

  11. M10A1 Canister

  12. Tank & APC M-25 Mask

  13. Smoke Penetrometer to test the gas mask paper & filters

  14. First Linear Photometer

  15. Space Filter • US military needed filtration of room areas for people and used gas mask media for a pleated filter for larger air flow (1943-1948) • Know as “Collective Protection” • Used cardboard spacers between pleats, which had high air flow resistance

  16. Cardboard Pleat

  17. Manhattan Project • Humphrey Gilbert safety engineer at Los Alamos was sent to Oak Ridge • Filters used in Manhattan Project were very thick with extremely high pressure drop • Foresaw need for high efficiency air filters in HVAC systems

  18. Absolute Air Filter • Gilbert (now with AEC) unhappy with Army Space filter and its limitations • AEC in 1948 gives Author D. Little a contract to redesign filter and find a supplier • Walter Smith Ph.D. comes up with corrugated cardboard separator idea

  19. Improved Pleated Filter Design

  20. HEPA Filter Development • First Air Cleaning Seminar for AEC personnel held June 1951 at Harvard Air Cleaning Laboratory • First Handbook on Air Cleaning distributed at meeting • Fires at several weapons plants made need for high temperature and water resistance necessary

  21. Second Air Cleaning Conference held in Ames, IA 1952Melvin W. First Ph.D.Presented four research papers

  22. Military develops procedures and Apparatus to test High Efficiency filters and related products Penetrometers Q-127 Low Flow Q-76 Med. Flow Q-107 High Flow Rough Handling Water Repellency etc.

  23. HEPA Development for Fire & Water Resistance (1953)

  24. First HEPA Guide (1961)

  25. Willis Whitfield (1961) Discovery of Laminar Flow at Sandia National Labs

  26. SNL Demonstrates Clean Room Concept in Chicago for IES(T) (1962)

  27. First “In Place Filter Test”

  28. First Portable Linear Photometer TDA-2 (1962)

  29. JM-1000 Photometer (1964)

  30. Next Portable Photometer TDA-2A (1964) Cabinet covered in white Formica (White Rooms) First Scanning Probe

  31. Next Portable Photometer TDA-2B (1965-66) Ergonomic front panel design

  32. First Commercial Standards (1967)

  33. First Commercial Standards (1967)

  34. Discussion

  35. What is a Filter

  36. Before Photometry… • What is a Filter? • Filtration Mechanics • MPPS • How to Test a Filter • Efficiency • Leak (Integrity)

  37. What is a Filter? Separation of one phase from another • Solids or liquids in Air (Home Furnace) • Solids in liquid (Auto Oil/Gas) • Liquid in Air (Air oil separators) • Liquid in liquid (RO) • Gas in Gas (Activated Carbon)

  38. What is a Filter? A Controlled Leak! Filtration controls the amount of impurity that is allowed to pass. There is no such thing as a ‘perfect’ filter (no resistance and 100% efficiency)

  39. Filtration Types • Materials • Fibers • Fibrous Structures • Micropores • Performance • High Efficiency • Low Efficiency

  40. What are we dealing with? Solids or liquids in Air & Fibrous Filters Other structures are more common in ultra filtration and special applications

  41. Fibrous Filters • Typically Depth Filters • Filtration throughout media depth • Very low to very high particle removal • Fibrous Filter Construction • Filter Disks/Pads • Pleated Cartridges • Bags/Pockets

  42. Filtration Mechanics • Pressure Drop • Single Filter Efficiency • Collection Mechanisms

  43. Darcy’s Law ΔP

  44. Darcy’s Law

  45. HVAC CLEANROOM Filter Pressure Drop Pressure Drop Linear Pressure Drop Inertial Velocity (Darcy Law) Regime Regime

  46. Filtration Assumptions • Fibers are in cross flow • Particles are ‘collected’ upon contact with fiber • Uniform fiber diameter • Uniform particle size

  47. Single Fiber Efficiency Single Fiber Efficiency ηs = Air Volume swept out by fiber Particles collected by fiber . Particles in volume of air geometrically swept out by fiber

  48. Fiber Structure - HEPA

  49. Particle Collection Mechanics • Sieving • Inertial Impaction • Diffusion • Interception

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