1、Institute of Environmental Sciences and Technology IEST-RP-CC034.4 Contamination Control Division Recommended Practice 034.4 HEPA and ULPA Filter Leak Tests 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
2、: informationiest.org Web: www.iest.org 2 IEST 2016 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-CC034.4 IEST-RP-CC034.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 3 This Recommended Practice was prepared by and is under the jur
3、isdiction of Working Group 34 of the IEST Con-tamination Control Division (WG-CC034). The following WG voting members contributed to the development of this edition of this Recommended Practice: R. Vijayakumar, WG-CC034 Chair, AERFIL Taguhi Arakelian, Jet Propulsion Laboratory Eugene Bryan, Milholla
4、nd however, it is the responsibility of the customer and supplier to specify which leak-test method is used and the acceptance criteria for each application. A brief guideline on in-situ leak testing based on the procedures recommended in this RP is provided in section 8. CAUTION: Testing in accorda
5、nce with this RP may involve hazardous materials, operations, and equipment. This RP does not purport to address all of the safety problems associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to determine the applicability of regulat
6、ory limitations prior to use of this RP. 2 REFERENCES The following documents are incorporated into this RP to the extent specified herein. If no specific edition is cited, the most recent edition should be used. Where specific editions are cited, subsequent revisions of these publications do not au
7、tomatically supersede the cited editions and users should investigate the applicability of revised editions. 2.1 Reference documents IEST-RP-CC001: HEPA and ULPA Filters IEST-RP-CC002: Unidirectional-Flow, Clean-Air Devices IEST-RP-CC006: Testing Cleanrooms 8 IEST 2016 All rights reserved Institute
8、of Environmental Sciences and Technology IEST-RP-CC034.4 IEST-RP-CC007: Testing ULPA Filters IEST-RP-CC013: Calibration Procedures and Guidelines for Select Equipment Used in Testing Cleanrooms and Other Controlled Environments IEST-RP-CC014: Calibration and Characterization of Optical Airborne Part
9、icle Counters IEST-RP-CC021: Testing HEPA and ULPA Filter Media IEST-RP-CC028: Minienvironments IEST-RP-CC036: Testing Fan Filter Units ISO 14644-1 Cleanrooms and associated controlled environmentsPart 1: Classification of air cleanliness by particle concentration ISO 14644-3 Cleanrooms and associat
10、ed controlled environmentsPart 3: Test methods MIL-STD-282: Filter Units, Protective Clothing, Gas-Mask Components, and Related Products: Performance Test Methods 2.2 Sources and addresses Referenced documents may be obtained from the following sources: IEST Institute of Environmental Sciences and T
11、echnology Arlington Place One 2340 S. Arlington Heights Road, Suite 620 Arlington Heights, IL 60005-4510, USA Phone: 847-981-0100 Fax: 847-981-4130 Website: www.iest.org ISO (National Standards) IEST Arlington Place One 2340 S. Arlington Heights Road, Suite 620 Arlington Heights, IL 60005-4510, USA
12、Phone: 847-981-0100 Fax: 847-981-4130 Website: www.iest.org MIL-STD Standardization Document Order Desk 700 Robbins Avenue Building 4, Section D Philadelphia, PA 19111-5098, USA Phone: 215-695-3321 Website: dodssp.daps.dla.mil NSF NSF International 789 N. Dixboro Road P.O. Box 130140 Ann Arbor, MI 4
13、8105, USA Phone: 734-769-8010 Website: www.nsf.org IEST-RP-CC034.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 9 3 TERMS AND DEFINITIONS The following terms have special meaning in the context of this RP. aerosol A gaseous suspension of fine solid or liquid parti
14、cles. aerosol generator A device that can supply an aerosol from an oil or microsphere source, in a concentration range and with a mean size suitable for the measurements described in this RP. aerosol photometer (or photometer) An instrument that measures mass concentrations of aerosol using the for
15、ward light scattering principle for multiple particle scattering. For the applications described in this RP, the instrument should be capable of measuring aerosol concentrations of up to 100 g/L and have a threshold sensitivity capable of measuring 0.0001 g/L. The device should have a detection limi
16、t of at least 0.1 the designated leak. The device should have a volumetric flow rate of 28.3 L/min (1.0 ft3/m). calibrated equipment Test equipment that has been calibrated in accordance with the manufacturers recommendations or accepted indus-try practices. challenge aerosol An aerosol derived from
17、 the selected aerosol source material and used as the leak-test challenge for a filter leak test. Challenge aerosols may be produced by a variety of methods, with the choice determined by the aerosol type and the particle size characteristics. clean-air device, unidirectional flow A clean work stati
18、on or other device (other than a cleanroom or clean zone) that incorporates one or more HEPA or ULPA filters and one or more motor-blowers for the purpose of supplying unidirectional-flow, clean air to a con-trolled work space. NOTE: These devices are often referred to as clean benches. clean zone A
19、 defined space in which the concentration of airborne particles is controlled to specified limits. cleanroom A room in which the air supply, air distribution, filtration of air supply, materials of construction, pressure gradients, and operating procedures are regulated to control airborne particle
20、concentrations to meet established air cleanliness levels, as defined by ISO 14644-1. coincidence loss A particle concentration level, determined by the DPC electronics and optics, that represents the point where the presence of two or more particles simultaneously in the sensing volume of the instr
21、ument causes the instrument to interpret the combined signal erroneously as resulting from one larger particle. count or number mean diameter of aerosol The average particle size of the number distribution of the aerosol. count or number median diameter of aerosol (CMD) The 50th percentile of the nu
22、mber distribution of the aerosol; i.e., 50% of the particles are smaller than the count median diameter and 50% are larger than the count median diameter. designated leak Any penetration that has exceeded the maximum allowable penetration. diluter A device that reduces the particle concentration of
23、the challenge aerosol by the dilution ratio of the device. These devices typically mix a known volume of sample air with a known volume of particle-free or filtered air to achieve the dilution. The ratio of the two volumes is the dilution ratio. discrete-particle counter (DPC) An instrument, such as
24、 an optical particle counter or condensation nucleus counter, capable of resolving and count-ing responses from individual particles. The device should be capable of measuring and sizing the challenge aerosols 10 IEST 2016 All rights reserved Institute of Environmental Sciences and Technology IEST-R
25、P-CC034.4 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 (DOS) or di(2-ethylhexyl) se
26、bacate (DEHS); CAS# 122-62-3. Equal velocity sampling Aerosol sampled at the same velocity as the average velocity exiting the filter (face velocity) within the agreed-upon tolerance, typically -10% to +20%. Not to be confused with the theoretical idea of isokinetic sampling, which is not practical
27、in filter leak testing. field bench test A leak tests performed on HEPA or ULPA filters after unpacking at the location of use and prior to installation in the clean-air device or cleanroom. A portable test system is used. HEPA (high-efficiency particulate air) filter An extended-medium, dry-type fi
28、lter in a rigid frame, having a minimum particle collection efficiency of 99.97% for 0.3-m mass median diameter particles of DOP when tested at the rated airflow in accordance with MIL-STD-282. NOTE: The foregoing is the traditional definition for the HEPA filter. Changes in the filter manufacture,
29、end-user requirements, and testing have introduced products that vary parametrically from filters that have been considered standard according to this definition. Additional information on this topic is given in IEST-RP-CC001. integral penetration The particle penetration associated with the filter
30、efficiency rating assigned by the filter manufacturer. A 99.995% factory rated HEPA filter will have an integral penetration of 0.005%. 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
31、gas as shown in IEST-RP-CC013. Laskin-nozzle-generated aerosol An aerosol generated by a Laskin nozzle from PAO, DOP, or other oil. local leak penetration The ratio of particle concentration upstream and downstream of the filter as obtained with the stationary scanning probe positioned directly over
32、 a leak. 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 sizes, resulting in the
33、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 parti-cles smaller than the mass median diameter and 50% of the mass of the aerosol is made up o
34、f particles larger than the mass median diameter. microspheres (or PSL) Monodisperse or polydisperse sized particles usually made of polystyrene latex (PSL). Monodisperse particle size is traceable to the National Institute of Standards and Technology (NIST) or other national standards bodies with r
35、e-spect 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 where other aerosols may contaminate the filters in an unacceptable manner. The term latex refers to an emulsion in
36、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 size at which a given filter has its highest penetration (or lowest efficiency); i.e., the worst-case particle s
37、ize with respect to filtration efficiency. From filtration theory, the efficiency is higher for particle sizes smaller or IEST-RP-CC034.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 11 larger than the MPPS. In practice, the MPPS of a filter is considered to be wi
38、thin a measured size range typical in commercial 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 material. photo
39、meter (see aerosol photometer) PSL (see microspheres) representative upstream sample A sample of the aerosol upstream of the filter that is being leak tested, used to set the 100% point of an aerosol pho-tometer or to calculate values for discrete-particle-counter scanning. In factory test systems,
40、in field bench test sys-tems, and in unidirectional-flow, clean-air devices, a method of obtaining a representative upstream sample should be built into the device by the device manufacturer. sample acquisition time The time that the DPC accumulates counts before automatically resetting to zero and
41、restarting counting. Some counters can be set to count continuously. scanning A method for disclosing leaks in HEPA and ULPA filters where the inlet of the scanning probe of an aerosol pho-tometer or discrete-particle counter is moved in a series of parallel, slightly overlapping strokes across the
42、test area at a distance of approximately 2.5 cm (1 in.) from the filter face and at a rate based on the leak penetration to be de-tected and the upstream concentration of the challenge aerosol. scanning probe A particle-sampling probe having a rectangular opening with a minimum width of 10 mm (0.4 i
43、n.) parallel to the direction of the scan. standard local penetration The penetration that would be measured by an aerosol photometer or DPC with a 28.3-L/min (1.0-ft3/min) sample flow rate when the sample probe is stationary. super ULPA (ultra-low-penetration air) filter An extended-medium, dry-typ
44、e filter in a rigid frame, made with a filter medium having a minimum particle collec-tion efficiency of 99.9999% (i.e., a maximum particle penetration of 5 count defines leak (Np) Not applicable Counter should have continuous or long duration count mode with beep output per each particle detected A
45、erosol material Polystyrene latex (PSL) No Yes PAO Yes Caution9 DOP CAS# 117-81-7 Yes Caution9 Other Customer/supplier agreement10 Customer/supplier agreement10 NOTES: 1 Test using total leakage test method for installed filters (sections 8.4 and Appendix H2). Filter may not pass a filter media scan
46、 test. 2 Leak criteria should be less stringent than 0.010% (0.005% for type D), especially if particle size near the most penetrating particle size (MPPS) is used. 3 Membrane-type ULPA filters (PTFE or ePTFE) may exhibit a rapid increase in filter resistance when using oil-based aerosols. 4 Aerosol
47、 photometer should be sensitive enough to detect below designated-leak levels. 5 If filter use application does not permit testing using oil-based aerosols, an aerosol photometer cannot be used. Use DPC with microspheres (PSL). 6 Suitability depends on US Food consult the generator manufacturer for
48、specific limitations or operating parameters related to the test liquids. Laskin-nozzle aerosol generators are available with a variety of nozzle physical positioning configura-16 IEST 2016 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-CC034.4 tions, control methods,
49、 output couplings or connections for aerosol injection into air systems, and internal or exter-nal compressed air source options. b) Thermal aerosol generator This device generates a polydisperse aerosol from a liquid such as PAO or DOP by means of an evaporation-condensation process in the absence of a controlled nucleation. The thermal aerosol generator requires a sampled upstream challenge concentration measurement. The output of the thermal aerosol generator is significantly greater than that produced by a Laskin-nozzle aerosol generator. The particle size distr
