IEST RP-CC001 6-2016 HEPA and ULPA Filters.pdf

1、 Institute of Environmental Sciences and Technology IEST-RP-CC001.6 Contamination Control Division Recommended Practice 001.6 HEPA and ULPA Filters Arlington Place One 2340 S. Arlington Heights Road, Suite 620 Arlington Heights, IL 60005-4510 Phone: (847) 981-0100 Fax: (847) 981-4130 E-mail: informa

2、tioniest.org Web: www.iest.org 2 Copyrighted material Institute of Environmental Sciences and Technology IEST-RP-CC001.6 This Recommended Practice was prepared by and is under the jurisdiction of Working Group 001 of the IEST Contamination Control Division (WG-CC001). The following WG voting members

3、 contributed to the development of this edition of this Recommended Practice. R. Vijayakumar, WG-CC001 Chair, AERFIL Anthony Caughron, TEC Services, Inc. Daniel Dennison, NNE Pharmaplan, Inc. Keith Flyzik, Micro-Clean, Inc. Donna Kasper, Hollingsworth i.e., 50% of the particles are smaller than the

4、count medi-an diameter and 50% are larger than the count median diameter. discrete-particle counter (DPC) An instrument, such as an optical particle counter or condensation nucleus counter, capable of resolving and counting responses from individual particles. The device should be capable of measuri

5、ng and sizing the challenge aerosols over the particle size range of interest. The threshold size of the DPC should be equal to or smaller than the particle size(s) being measured. DOP or DEHP Dioctyl phthalate (DOP) or di(2-ethylhexyl) phthalate (DEHP); CAS# 117-81-7. DOS or DEHS Dioctyl sebacate (

6、DOS) or di(2-ethylhexyl) sebacate (DEHS); CAS# 122-62-3. HEPA (high-efficiency particulate air) filter An extended-medium, dry-type filter in a rigid frame when tested at rated airflow having a minimum particle collection efficiency of 99.97% for 0.3-m mass median diameter particles of DOP when test

7、ed in accordance with MIL-STD-282. Laskin nozzle A nozzle used as part of a system to generate a heterogeneous aerosol from a liquid, such as PAO, DOP, or other oil, that uses a source of compressed gas as shown in IEST-RP-CC013. Laskin-nozzle-generated aerosol An aerosol generated by a Laskin nozzl

8、e from PAO, DOP, or other oil. mass mean diameter of aerosol The particle diameter size that is the average particle size of the mass distribution of the aerosol. Typically, because the mass of a particle varies as the cube of its diameter, most of the mass of an aerosol tends to be in the larger si

9、zes, result-ing in the mass mean being larger than its count or number mean. mass median diameter of aerosol (MMD) The 50th percentile of the mass distribution of the aerosol; i.e., 50% of the mass of the aerosol is made up of particles smaller than the mass median diameter and 50% of the mass of th

10、e aerosol is made up of particles larger than the mass median diameter. 12 Copyrighted material Institute of Environmental Sciences and Technology IEST-RP-CC001.6 microspheres (or PSL) Monodisperse or polydisperse sized particles usually made of polystyrene latex (PSL). Monodisperse particle size is

11、 traceable to the National Institute of Standards and Technology (NIST) or other national standards bodies with respect to the diameter. NOTE: PSL refers to a common type of highly uniform spheres, or a suspension thereof, used to generate a solid aerosol. PSL is useful for leak testing filters wher

12、e other aerosols may contaminate the filters in an unacceptable manner. The term latex refers to an emulsion in water of finely divided particles of synthetic rubber, plastic, or other elastomer, and is not to be confused with natural rubber latex. most-penetrating particle size (MPPS) The particle

13、size at which a given filter has its highest penetration (or lowest efficiency); i.e., the worst-case particle size with respect to filtration efficiency. From filtration theory, the efficiency is higher for particle sizes smaller or larg-er than the MPPS. In practice, the MPPS of a filter is consid

14、ered to be within a measured size range typical in commer-cial instruments rather than at one unique particle size. PAO (4 cSt poly-alpha-olefin) A grade of PAO with a viscosity of 4 centistokes at 100 C. With reference to filter testing, PAO also refers to a poly disperse aerosol of the described m

15、aterial. penetrometer A self-contained instrument for the determination of penetration characteristics of very high-efficiency filter medium and filter units with thermally generated DOP, in accordance with MIL-STD-282. photometer (see aerosol photometer) PSL (see microspheres) scanning A method for

16、 disclosing leaks in HEPA and ULPA filters where the inlet of the sampling probe of an aerosol photome-ter or discrete-particle counter is moved in a series of parallel, slightly overlapping strokes across the test area at a dis-tance of approximately 2.5 cm (1 in.) from the filter face and at a rat

17、e based on the leak penetration to be detected and the upstream concentration of the challenge aerosol. single particle counter (see discrete-particle counter) standard local penetration The penetration that would be measured by a photometer or particle counter with a 28.3-L/min (1-ft3/min) sample f

18、low rate when the sample probe is stationary over the leak. thermal generator A device that produces a liquid aerosol by means of an evaporation-condensation process in the absence of controlled nucleation. The particle size distribution and mass median diameter (MMD) of an aerosol produced by a the

19、rmal gen-erator are measurably different from those of an aerosol from a Laskin nozzle. thermally generated aerosol An aerosol generated by quenching (condensing) vapor that has been evaporated from oils such as DOP or PAO by heat. MIL-STD-282 Thermal Aerosol A thermally generated DOP aerosol that m

20、eets the MIL-STD-282 requirement which specifies that the light polar-ized by the aerosol is 29 1 as measured by an optical owl. This aerosol has a mass mean of 0.3 m. (Penetrome-ters built to meet this standard have reported count mean sizes closer to 0.2 m with a narrow distribution.) ULPA (ultra-

21、low-penetration air) filter A throwaway, extended-medium, dry-type filter in a rigid frame, having a minimum particle-collection efficiency of 99.999% (that is, a maximum particle penetration of 0.0010%) when tested in accordance with the methods of IEST-RP-CC007. IEST-RP-CC001.6 Institute of Enviro

22、nmental Sciences and Technology Copyrighted material 13 4 PERFORMANCE 4.1 General 4.1.1 Penetration Penetration should be measured in accordance with section 9 of this RP and should correspond with the classifications listed in section 4.2 for the type of filter specified. Nanoparticle penetration:

23、Nanoparticles are generally considered to be those particles that have diameters smaller than 100 nm. The mechanisms for particle capture by HEPA and ULPA filters described in this RP lead to the com-monly known penetration curve with its distinct most-penetrating particle size (MPPS). Current resea

24、rch by Pui et al. shows that this type of penetration curve is valid for particles as small as 20 nm. That is, testing and classifying filters at or near the MPPS per this RP will yield the worst-case classification even when nanoparticles are involved. 4.1.2 Resistance to airflow The resistance of

25、the filter should be measured at the rated volumetric airflow, for all sizes of most filters. Filters con-structed to meet ASME AG-1 requirements are tested to 33 mm (1.3 in.) w.g. The resistance should be determined from pressure measurements upstream and downstream of the filter, using appropriate

26、 measurement practices and equipment as agreed upon between the customer and the supplier. It is recommended that measurements be made in a direction normal (perpendicular) to the flow direction to minimize the effects of velocity pressure. When it is not possi-ble to test filters at the standard te

27、mperature of 70 F (21.1 C), it is recommended that the resistance be corrected for the temperature effect on the viscosity, as shown in IEST-RP-CC007. Other resistance parameters may be specified by agreement between the customer and the supplier. 4.1.3 Airflow uniformity Some or all types of filter

28、s referred to in this document may be used in applications requiring uniform airflow velocities at the rated airflows. When measured across the face of the filter, the velocity of the airflow should be uniform within limits agreed to between the customer and the supplier. Typically, the airflow unif

29、ormity is the average velocity 20%. Appropriate methods of measurement may be found in IEST-RP-CC002, NSF/ANSI 49, or as agreed upon between the customer and the supplier. 4.1.4 Outgassing Filters referred to in this document may be used in applications requiring low outgassing of molecular contamin

30、ants. The amount and type of outgassing allowable is to be determined by agreement between the customer and the sup-plier. Recommended practices for measuring outgassing may be found in IEST-RP-CC031 or as agreed upon be-tween customer and supplier. 4.2 Performance levels Specification of performanc

31、e based on leak criteria should be more stringent for testing the filter as manufactured than for testing by field bench test or after installation. Filter Types AD are tested using a 0.3 m mass median diameter (MMD) aerosol generated in the method specified in MIL-STD-282. If alternate methods are

32、used to generate the test aerosol, the aerosol size should be verified to be equivalent to that generated by the method specified in MIL-STD-282 using either the Tyndall Owl specified in MIL-STD-282 or by other methods, such as electrostatic classification. Users should be aware that the mass median

33、 diameter of this aerosol is approximately 0.3 m, whereas its count (number) mean diameter is smaller. In other words, the effi-ciency of this filter may be much higher at 0.3 m compared to its efficiency when tested per MIL-STD-282. Type C filters are often used for isolators, workstations, and bio

34、safety cabinets that require periodic in situ (field) filter leak testing with Laskin nozzle generated aerosols. However, if in situ testing will be conducted using thermally gener-ated aerosol with a smaller aerosol size, for safety it is recommended that these filter types be specified at 99.995%.

35、 When specifying these filters tested with aerosol photometers, a special note clarifying this requirement is recommend-ed. Alternatively, a Type K filter may be specified as agreed to between user and supplier. 14 Copyrighted material Institute of Environmental Sciences and Technology IEST-RP-CC001

36、.6 4.2.1 Type A filter A filter that has been tested at rated flow in accordance with section 9.1.1. The minimum filter efficiency of the encap-sulated filter for this type of filter is 99.97% when tested with MIL-STD-282 Thermal Aerosol. 4.2.2 Type B filter A filter that has been tested for overall

37、 penetration at rated flow and at 20% of rated flow, in accordance with sec-tion 9.1.1. The minimum filter efficiency of the encapsulated filter in this type is 99.97% when tested with MIL-STD-282 Thermal Aerosol. It is possible for a HEPA filter to have a leak and still pass the overall penetration

38、 at its rated flow. A filter with a leak will have a higher penetration at 20% of rated flow than at 100% rated flow. A filter without a leak will have an equal or lower penetration at the lower flow rate. 4.2.3 Type C filter A filter that has been tested for overall penetration in accordance with s

39、ection 9.1.1 and, in addition, has been leak test-ed in accordance with IEST-RP-CC034. The minimum filter efficiency of the encapsulated filter in this type is 99.99% when tested with MIL-STD-282 Thermal Aerosol. The designated leak for this filter is 0.010%. 4.2.4 Type D filter A filter that has be

40、en tested for overall penetration in accordance with section 9.1.1 and, in addition, has been leak test-ed in accordance with IEST-RP-CC034. The minimum filter efficiency in this type is 99.999% when tested with MIL-STD-282 Thermal Aerosol. The designated leak for this filter is 0.0050%. 4.2.5 Type

41、E filter A filter that has been designed and constructed in strict accordance with ASME AG-1 Section FC and tested according to MIL-STD-282. The minimum efficiency is 99.97%. 4.2.6 Type F filter A filter that has been efficiency tested at rated flow in accordance with the methods of IEST-RP-CC007 an

42、d, in addi-tion, has been leak tested in accordance with IEST-RP-CC034. The minimum efficiency for this filter type is 99.9995% and is determined as the lower efficiency when tested for particle size ranges of 0.10.2 m and 0.20.3 m. The des-ignated leak for this filter is 0.00250%. 4.2.7 Super ULPAT

43、ype G filter A filter that has been tested in accordance with IEST-RP-CC007 for overall penetration and has been tested for leaks in accordance with IEST-RP-CC034. The minimum efficiency for the Type G filter is 99.9999% at its MPPS, where the MPPS is determined according to IEST-RP-CC021. The desig

44、nated leak for this filter is 0.00010%. NOTE: Due to the very low penetration and hence very low counts downstream of these filters, in practice, only the medium for this filter is tested for efficiency and the filter is tested only for leaks. 4.2.8 Type H filter A filter that has been efficiency te

45、sted at rated flow in accordance with the methods of IEST-RP-CC007. The minimum efficiency for this filter type is 99.97% and is determined as the lower efficiency when tested for particle size ranges of 0.10.2 m and 0.20.3 m. 4.2.9 Type I filter A filter that has been efficiency tested at rated flo

46、w and 20% of rated flow in accordance with the methods of IEST-RP-CC007. The minimum efficiency for this filter type is 99.97% and is determined as the lower efficiency when tested for particle size ranges of 0.10.2 m and 0.20.3 m. IEST-RP-CC001.6 Institute of Environmental Sciences and Technology C

47、opyrighted material 15 4.2.10 Type J filter A filter that has been efficiency tested at rated flow in accordance with the methods of IEST-RP-CC007 and, in addi-tion, has been leak tested in accordance with IEST-RP-CC034. The minimum efficiency for this filter type is 99.99% and is determined as the

48、lower efficiency when tested for particle size ranges of 0.10.2 m and 0.20.3 m. The des-ignated leak for this filter is 0.010%. 4.2.11 Type K filter A filter that has been efficiency tested at rated flow in accordance with the methods of IEST-RP-CC007 and, in addi-tion, has been leak tested in accor

49、dance with IEST-RP-CC034. The minimum efficiency for this filter type is 99.995% and is determined as the lower efficiency when tested for particle size ranges of 0.10.2 m and 0.20.3 m. The des-ignated leak for this filter is 0.0080%. 5 CONSTRUCTION GRADES Several construction grades are defined here to distinguish among the types of service the filter units may experience. Certain specifications and applications correspond to each of the construction grades listed below. Types of tests and their purposes are detailed in each section. These tes