Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is drafted in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 6165-2008 Test method of the performance of high efficiency particulate air filter—Efficiency and resistance, and the following main technical changes have been made with respect to GB/T 6165-2008:
——The efficiency test method of filter with MPPS ≤ 0.1 μm is added (see 4.4 hereof);
——The basic performance requirements, maintenance and calibration cycle requirements of the unified high efficiency particulate air filter are added (see 5.1 hereof);
——The efficiency calculation equation by counting method is adjusted (see 5.2.5.1 and 5.2.5.2 hereof; 5.3.6 of Edition 2008);
——The description of aerosol particle size distribution characteristics measured by sodium flame method is defined (see 5.3.1 hereof; 6.2.1 of Edition 2008);
——The requirements for sampling system of filter test device by sodium flame are revised, and the requirements for dilution system are deleted (see 5.3.2.1 hereof; 6.2.2 of Edition 2008);
——Annex G is deleted (see Annex G of Edition 2008).
This standard was proposed by the Ministry of Housing and Urban-Rural Development of the People's Republic of China.
This standard is under the jurisdiction of the National Technical Committee on HVAC and Purification Equipment of Standardization Administration of China (SAC/TC 143).
The previous editions of this standard are as follows:
——GB/T 6165-1996, GB/T 6165-2008;
——GB/T 6166-1985.
Test method of the performance of high efficiency particulate air filter—
Efficiency and resistance
1 Scope
This standard specifies the terms and definitions, symbols and abbreviations of HEPA and ULPA filter mediums and filter efficiency and resistance test, the selection of test methods, the performance test methods of HEPA and ULPA, and the performance test methods of HEPA and ULPA filter mediums.
This standard is applicable to the test of HEPA and ULPA filter mediums used to filter aerosols and the efficiency and resistance of filters, and may serve as a reference for the efficiency and resistance test of HEPA and ULPA filter mediums and filters.
2 Normative references
The following documents are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1236 Industrial fans—Performance testing using standardized airways
GB/T 2624.2 Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full—Part 2: Orifice plates
GB/T 2624.3 Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full—Part 3: Nozzles and Venturi nozzles
GB 11120 Lubricating oils for turbines
GB/T 12564 Generic specification for photomultiplier tubes
GB/T 13554 High efficiency particulate air filter
GB/T 14295 Air filter
GB 50243 Code of acceptance for construction quality of ventilation and air conditioning works
JJF 1190 Calibration specification for airborne particle counter
JJG 172 Tilting tube micromanometers
JJG 875 Digital pressure gauges
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3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 13554 and the following apply.
3.1.1
penetration
ratio of the aerosol concentration after filtration of the filter element to the aerosol concentration before filtration when the filter element is tested
3.1.2
efficiency
ratio of the amount of aerosol filtered by the filter element to the amount of aerosol before filtration when the filter element is tested
3.1.3
rated air flowrate
technical parameter identifying the working capacity of a filter, indicating the maximum air volume flow per unit time to ensure the efficiency of the filter
Note: It is provided by filter manufacturer.
3.1.4
resistance
static pressure difference before and after the filter element under certain test wind speed or air flowrate. For the filter, it is the static pressure difference before and after the filter under rated air flowrate
3.1.5
filter medium
unfolded flat filter material for filtering aerosols
3.1.6
high efficiency particulate air filter; HEPA
air filter used for air filtration and tested by the counting method specified in this standard, and the filtration efficiency without static elimination treatment and after static elimination treatment under rated air flowrate is not less than 99.95%
3.1.7
ultra low penetration air filter; ULPA
air filter used for air filtration and tested by the counting method specified in this standard, and the filtration efficiency without static elimination treatment and after static elimination treatment under rated air flowrate is not less than 99.999%
3.1.8
HEPA filter medium
filter medium for making high efficiency particulate air filter
3.1.9
ULPA filter medium
filter medium for making ultra low penetration air filter
3.1.10
aerosol generator
device for generating standard aerosol for test
3.1.11
particle number concentration
number of particles in the measured particle size range per unit volume of gas (air)
3.1.12
particle size
nominal diameter of a particle measured by some measurement method (optical or aerodynamic equivalent test)
3.1.13
particle size efficiency
filtration efficiency of a filter element for particles of a certain particle size
3.1.14
most penetrating particle size; MPPS
particle size corresponding to the lowest point of the sizing efficiency curve of the tested filter element when the test is carried out according to the counting method specified in this standard
3.1.15
minimum filter efficiency
filtration efficiency of the tested filter element for the most penetrating particle size under given operating conditions, generally known as MPPS efficiency
3.1.16
median particle diameter
corresponding particle size value when the cumulative distribution of aerosol particle size accounts for 50% of the total amount, which is generally expressed by count median particle diameter and mass median particle diameter
3.1.17
sampling flow rate
volume flow rate of air sampled by the measuring element of the test instrument when measuring the particle concentration upstream or downstream of the filter element
3.1.18
sampling duration
effective time of air sampling upstream or downstream of the tested high efficiency particulate air filter element at the sampling volume flow rate
3.1.19
coincide error
error caused by the presence of multiple particles in the scattering cavity of a particle counter at a given time
Note: The coincide error will lead to low count concentration and high average particle size in the measurement results.
3.1.20
monodisperse aerosol
aerosol with a geometric standard deviation of particle size is less than 1.15 (σg < 1.15) when described by distribution equation
3.1.21
quasi-monodisperse aerosol
aerosol with a geometric standard deviation of particle size is not less than 1.15 and not greater than 1.50 (1.15 ≤ σg ≤ 1.50) when described by distribution equation
3.1.22
polydisperse aerosol
aerosol with a geometric standard deviation of particle size is greater than 1.50 (σg>1.50) when described by distribution equation
3.1.23
sodium flame method
method for calculating the mass efficiency of filter elements by testing the mass concentration upstream and downstream of filter elements with sodium flame photometer in case of polydispersed NaCl aerosol. For filter medium and filter tests, the counting peak diameter of test aerosol particles is (0.09 ± 0.02) μm, and the geometric standard deviation of counting shall not be greater than 1.90
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3.1.24
oil mist method
method for calculating the mass efficiency of the filter element by testing the mass concentration upstream and downstream of the filter element with an oil mist meter in case of polydispersed liquid aerosols with an average mass diameter of 0.28 μm to 0.34 μm
3.1.25
particle counting method with quasi-monodisperse aerosol
method for calculating the counting efficiency of the filter medium by testing the counting concentration upstream and downstream of the filter medium with condensation particle counter (CPC) or optical particle counter (OPC) in case of quasi-monodisperse aerosols (such as solid particle NaCl or liquid particle DEHS, etc.) with counting median diameter of particles of 0.10 μm to 0.30 μm and the geometric standard deviation of not greater than 1.50
3.1.26
particle counting method with monodisperse aerosol
method for calculating the counting efficiency of filter elements by testing the counting concentration upstream and downstream of filter elements with condensation particle counter (CPC) in case of monodisperse aerosol. Monodisperse aerosol can be generated by several methods, such as differential mobility analyser (DMA), diffusion battery, evaporation and condensation method, polystyrene latex spheres (PSL), etc.
3.1.27
particle counting method with polydisperse aerosol
method for calculating the counting efficiency of filter elements by testing the counting concentration upstream and downstream of filter elements with optical particle counter (OPC) in case of polydisperse aerosol
3.1.28
correlation ratio
ratio of particle concentrations in upstream and downstream sampling systems when the test system is not equipped with a tested filter and keeps a stable aerosol concentration
Note: When an optical particle counter (OPC) is used in the test system to test the aerosol concentration in the upstream and downstream of the tested filter in sequence, the correlation ratio indicates the difference between the upstream and downstream sampling systems due to the particle loss in the upstream and downstream sampling pipelines, the dilution ratio of the diluent (if the upstream sampling adopts the diluent) and the difference between the upstream and downstream sampling duration; when two optical particle counters (OPC) are used respectively in the test system to test the upstream and downstream aerosol concentration of the tested filter, the correlation ratio indicates the difference caused by the different sampling flow rate and counting efficiency of the upstream and downstream sampling counters.
3.2 Abbreviations
For the purposes of this document, the following abbreviations apply.
CPC: Condensation particle counter
DEHS: [sebacic acid-bis (2-ethyl-) ester (commonly known as di-ethyl-hexyl-sebacate)]
DMA: Differential mobility analyser
MPPS: Most penetrating particle size
OPC: Optical particle counter
PAO: Poly alpha olefin
PSL: Polystyrene latex spheres
HEPA: High efficiency particulate air filter
ULPA: Ultra low penetration air filter
4 Selection of test methods
4.1 This standard gives three test methods: counting method, sodium flame method and oil mist method, where counting method is the reference method.
4.2 For high efficiency particulate air filter and its medium, any one of the three methods can be adopted for efficiency test according to requirements, however the test method and test results shall be indicated at the same time. In the production test of HEPA filter medium, rapid test methods such as sodium flame method and particle counting method with quasi-monodisperse aerosol should be adopted under the condition of clear comparison relationship with the reference method.
4.3 For ultra low penetration air filter and its medium, counting method shall be adopted for efficiency test. In the production test of ULPA filter medium, rapid test methods such as particle counting method with quasi-monodisperse aerosol should be adopted under the condition of clear comparison relationship with the reference method.
4.4 For air filters and its medium with MPPS not greater than 0.1 μm, the particle counting method with monodisperse aerosol is adopted as the reference method. In the end-of-manufacturing inspection of this kind of air filter, the counting method can be used to measure the particles in the range of 0.1 μm to 0.2 μm under the condition of clear comparison relationship with the reference method, and the test results shall be corrected according to the comparison relationship with the reference method.
5 Performance device and test method of HEPA and ULPA
5.1 Requirements for test device
5.1.1 Fan
5.1.1.1 Air flowrate
The air flowrate shall be calculated as 1.3 times of the maximum air flowrate of the tested air filter.
5.1.1.2 Air pressure
Air pressure shall include at least the sum of the following items:
a) Duct resistance (1.2 times of calculated resistance);
b) Air inlet filter resistance (2 times of its initial resistance);
c) Maximum resistance of the tested filter;
d) Resistance of air flowrate measuring device;
e) For the sodium flame test device, the positive pressure value (not less than 600 Pa) required for sampling after the filter shall be considered.
5.1.1.3 Air flowrate stability
During the test, the air flowrate of the test device shall be stable within 2% of the set value.
5.1.2 Air duct
5.1.2.1 Materials
PVC plastic or other corrosion-resistant materials should be used in the sodium flame test device from spray box to buffer box; stainless steel air duct should be used for the rest of the sodium flame test device and other test devices. The wall thickness of air duct should not be less than 1 mm. When necessary, the air duct shall be grounded and anticorrosive.
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5.1.2.2 Dimensions of front and rear pipe sections of air flowrate measuring device
When the standard orifice plate is used, the dimensions of the front and rear pipe sections shall be designed according to the relevant requirements of GB/T 2624.2; when standard nozzles are used, the dimensions of the front and rear pipe sections shall be designed according to the relevant requirements of GB/T 2624.3.
5.1.2.3 Angle of connection pipe of tested filter
The included angle of diffusion section and convergence section of the tested filter connection pipe shall not be more than 14° and 30° respectively, and shall meet the relevant requirements of GB/T 1236.
5.1.2.4 Air duct tightness
The manufacture, installation and inspection of air ducts in the test device shall meet the relevant requirements of GB 50243 for medium pressure system, and the joints of air ducts shall be welded. For air duct tightness, the duct shall be pressurized under the pressure of 2 kPa for leakage test, and the air leakage shall not be greater than 1.64 m3/(h·m2).
5.1.3 Inlet air filtration
5.1.3.1 Pre-filter
The pre-filter shall meet the relevant requirements of GB/T 14295 for medium-effect filter.
5.1.3.2 High efficiency particulate air filter
The high efficiency particulate air filter shall meet the relevant requirements of GB/T 13554. When a heater is set upstream of the filter, the temperature resistance of the filter shall not be lower than 60°C.
5.1.4 Air speed uniformity of upstream sampling section
Adjust the operating air flowrate of the test device to the maximum test air flowrate, and evenly distribute 9 measuring points on the section of the sampling point upstream of the test air duct according to the cross-sectional area of the air duct as shown in Figure 1 to test the air speed respectively. The deviation between the measured air speed of each measuring point and the average value of each measuring point shall not be more than 10%.
a) Square air duct b) Circular air duct
Keys:
a——Side length of square air duct;
D——Diameter of circular air duct.
Figure 1 Layout of measuring points for air speed and aerosol concentration uniformity at upstream sampling section
5.1.5 Aerosol concentration uniformity at upstream sampling section
Adjust the operating air flowrate of the test device to the maximum test air flowrate, start the aerosol generator and maintain stable operation, and evenly distribute 9 measuring points on the section of the sampling point upstream of the test air duct according to the cross-sectional area of the air duct as shown in Figure 1 to test the aerosol concentration respectively. The deviation between the measured aerosol concentration at each measuring point and the average value at each measuring point shall not be more than 10%.
5.1.6 Upstream aerosol concentration stability
Adjust the operating air flowrate of the test device to the maximum test air flowrate, start the aerosol generator and maintain stable operation, and sample at the sampling point upstream of the test air duct. The fluctuation of the measured aerosol mass concentration or the count concentration within the given particle size range within 30 min shall not be greater than 10%.
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5.1.7 Requirements for general test apparatus
Air flowrate test devices may be designed, installed, used and calibrated in accordance with the relevant requirements of GB/T 2624.2 and GB/T 2624.3 using standard orifice plates or nozzles and shall meet the following requirements:
a) Pressure test devices for differential pressure measurements of filter resistance and flow rate shall have an accuracy of not less than 2 Pa and shall be periodically verified and calibrated according to the relevant requirements of JJG 172 or JJG 875 depending on the pressure test device selected.
b) Counters shall be periodically verified and calibrated in accordance with the relevant requirements of JJF 1190. The photoelectric measuring instrument in sodium flame photometer shall be tested and calibrated periodically according to the relevant requirements of GB/T 12564. The oil mist meter shall be calibrated according to the requirements of 5.4.3.1.1.4.
5.1.8 Sampling correlation ratio at upstream and downstream
When the aerosol generator works stably, the filter is not installed in the test section and the dilution is not installed in the upstream sampling section, the correlation ratio of each particle size block shall be 1.00 ± 0.03. After installing the diluent at the upstream sampling section, the correlation ratio of each particle size block shall be tested and confirmed regularly.
5.1.9 Resistance standard parts
5.1.9.1 Orifice plates (or other resistance standard parts) with known resistance shall be tested regularly according to 5.2.4.2.4.
5.1.9.2 The resistance standard parts shall be properly stored and kept when not in use to prevent damage.
5.1.9.3 The test for resistance standard parts shall meet the following requirements:
a) At least 4 air flowrate state points shall be selected for testing within the air flowrate range of the test device.
b) During each test, the deviation between the resistance test result and the calibration value at each air flowrate state point shall not be more than 3%. Otherwise, the necessary inspection, maintenance and calibration shall be carried out for the pipeline sealing and the pressure gauge of the flow test device.
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c) Contrast validation tests can be performed using resistance standard parts and reference test devices.
5.1.10 Reference filter
5.1.10.1 For the test device, a reference filter with known efficiency shall be prepared, and the efficiency test shall be carried out regularly according to the methods specified in 5.2, 5.3 or 5.4.
5.1.10.2 A minimum of two reference filters shall be prepared, of which one is for the primary reference filter and the other one is for standby. The filter mediums selected for reference filters shall not be materials that are difficult to maintain stable filtration efficiency for a long time. The reference filter shall be properly stored and kept when not in use to prevent damage.
5.1.10.3 Reference filters shall be used according to the following requirements:
a) The deviation between each efficiency test value of the reference filter and the mantissa of the calibration value (the first non-9 value of the efficiency value) shall not exceed ± 5.
b) The primary reference filter shall be selected first during each test. If the deviation between the efficiency test value and the calibration value of the primary reference filter exceeds the requirement of item a), the standby reference filter shall be tested. If the efficiency test value of the standby reference filter meets the requirements of this standard, the primary reference filter shall be replaced.
c) If the deviation between the efficiency test value and the calibration value of the primary reference filter and the standby reference filter exceeds the requirements of item a), the sampling system of the test device and the aerosol test device shall be inspected, calibrated and maintained as necessary.
5.1.11 Calibration of test device
See Table 1 for the calibration period and requirements of test device.
Table 1 Calibration period and requirements of test device
Item Calibration period Standard subclauses and requirements referred
Air flowrate stability During each test 5.1.1.3
Air duct tightness When the test device is completed and there are major structural adjustments 5.1.2.4
Air speed uniformity at upstream sampling section Every 2 years 5.1.4
Aerosol concentration uniformity at upstream sampling section Every 2 years 5.1.5
Upstream aerosol concentration stability Per year 5.1.6
Test device for flow rate; Per year 5.1.7
Test device for pressure Per year 5.1.7
Counter, sodium flame photometer and oil mist meter Per year 5.1.7
Correlation ratio at upstream and downstream sampling Every test day 5.1.8
Resistance standard parts Every 3 months 5.1.9
Reference filter Every 3 months 5.1.10
5.2 Counting method
5.2.1 Test principle
Aerosol generator is used to generate aerosol which meets the test requirements, and OPC is used to test the particles in the range of 0.1 μm to 0.3 μm upstream and downstream of the tested filter, and the diameter counting efficiency is calculated. If the upstream aerosol concentration exceeds the upper limit concentration of OPC, the sampling air shall be diluted to reduce the coincide error of OPC counting. The dilution of sampling air can be achieved by diluent or by the difference of sampling flow rate between OPCs at upstream and downstream.
5.2.2 Test methods
Particle counting method with monodisperse aerosol or particle counting method with polydisperse aerosol can be selected for efficiency test. The air duct system of the two methods is the same, but the aerosol generator and the corresponding test device are different. When particle counting method with monodisperse aerosol is used in the test, if the filter medium used in the filter has passed the test by particle counting method with monodisperse aerosol and its MPPS has been obtained, the median particle diameter of monodisperse aerosol count selected in the filter test shall be within 10% of its MPPS. Otherwise, the filter manufacturer shall determine, in consultation with the user, the range of the median diameter of the test aerosol count.
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5.2.3 Test devices
5.2.3.1 The filter performance test device by counting method is mainly composed of aerosol generator, air duct system and aerosol sampling and detection device. See Figure 2 for the schematic diagram of the test device. Different test devices are allowed, but the requirements of 5.1 shall be met, and the test results of the same filter shall be consistent with the standard test device.
Keys:
1——Fan; 12——Orifice flowmeter;
2——High efficiency particulate air filter; 13——Sampling pipe after filtration;
3——Straight pipe section; 14——Valve;
4——Aerosol inlet; 15——Diluent;
5——Stable section; 16——Particle sampling system;
6——Static pressure ring before filtration; 17——Micromanometer;
7——Sampling pipe before filtration; 18——Thermometer;
8——Tested filter; 19——Hygrometer;
9——Static pressure ring after filtration; D——Diameter of the upstream pipeline of the tested filter;
10——Reducer; d——Diameter of the downstream pipeline of the tested filter;
11——Straight pipe section; X——Dilution ratio.
Figure 2 Schematic diagram of filter performance test device by counting method
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5.2.3.2 The measuring device shall be OPC, and the test range of OPC particle size shall include at least 0.1 μm, 0.2 μm and 0.3 μm.
5.2.4 Filter detection
5.2.4.1 Operating parameters
5.2.4.1.1 Test air
An electric heater shall be set in the air duct system to ensure that the temperature in the system is within (23 ± 5)°C and the relative humidity is not greater than 75%.
5.2.4.1.2 Aerosol testing
Oily liquid aerosols such as DEHS and PAO generated by spraying should be used for testing aerosols. When solid aerosols are used for testing, necessary electrostatic neutralization treatment shall be carried out, and the consistency between the test results and oily liquid aerosols shall be verified by reference filters.
5.2.4.1.3 Spray air pressure
The pressure of clean compressed air into the sprayer shall meet the requirements of aerosol generator.
5.2.4.1.4 Spray air volume
Under the prescribed pressure, the amount of compressed air entering each sprayer shall be constant.
5.2.4.1.5 Upstream aerosol dilution
When OPC measures aerosol concentration, the original aerosol shall be diluted in most cases, and the dilution ratio shall be in the range of 10x to 1,000x. The specific value depends on the initial aerosol concentration and the measuring equipment used, and it shall be ensured that the tested aerosol concentration does not exceed the maximum saturation concentration of OPC.
5.2.4.1.6 Aerosol sampling volume
The aerosol sampling volume is determined by the sampling volume and sampling duration of OPC, which shall ensure that the downstream aerosol count concentration has statistical significance.
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5.2.4.2 Detection steps
5.2.4.2.1 Operation preparation
5.2.4.2.1.1 When the aerosol generator is turned on and there is no tested filter in the test device, the aerosol count concentration of the upstream and downstream shall be measured respectively, and the correlation ratio of the upstream and downstream samples shall be calculated.
5.2.4.2.1.2 Visually inspect the filter medium in the tested filter for defects, cracks and holes; check the joint part of the filter frame corner and whether the frame and filter medium are sealed, whether there is gap and whether there is abnormality in structure. The filter that passes the visual inspection can be used for testing.
5.2.4.2.1.3 Install the tested filter securely on the test section in the direction of the air flow indicated by the arrow.
5.2.4.2.2 System startup
5.2.4.2.2.1 Start the fan, adjust the fan frequency converter and the air duct end valve to make the air flowrate of the air duct system reach the test air flowrate.
5.2.4.2.2.2 Regulate the temperature in the system within the range of (23 ± 5)°C and the relative humidity of not greater than 75%.
5.2.4.2.3 Preliminary test
With the aerosol generator turned off and the test filter in place, the downstream aerosol count concentration shall be tested to check the background concentration.
5.2.4.2.4 Resistance detection
Use a micromanometer to test the resistance of the filter section under the test air flowrate, and minus the air resistance of the test section to obtain the filter resistance.
5.2.4.2.5 Aerosol generator startup
Start the aerosol generator, adjust the parameters of the aerosol generator according to the product instructions and maintain it stable.
5.2.4.2.6 Detection of filter efficiency
The filter efficiency shall be detected according to the following requirements:
a) Test aerosol shall be uniformly mixed with test air. In order to measure the efficiency of particle size, at least three tests shall be carried out on the particle size ranges of 0.1 μm to 0.2 μm and 0.2 μm to 0.3 μm respectively, and the average value and the lower limit of filtration efficiency with confidence of 95% shall be calculated respectively, and the lower value shall be selected as the counting test efficiency of the tested filter.
b) During the efficiency test, two OPCSs can be used to measure at the same time, or one OPC can be used to measure the upstream and downstream of the tested filter successively. When the second measurement method is adopted, the OPC shall be purged before each downstream aerosol concentration test, so that the counting concentration of OPC has dropped to a level that can reliably measure the downstream aerosol concentration before starting to measure the downstream concentration.
c) In order to ensure good repeatability and statistical significance of the detection results, the total number of downstream particles detected in each efficiency test cycle shall not be less than 100.
5.2.4.2.7 Detection of other parameters
During the detection, the temperature, humidity and static pressure in the air duct where the tested filter is located and the temperature, humidity and atmospheric pressure of the environment shall be measured at the same time.
5.2.5 Calculation of filter efficiency
5.2.5.1 The filtration efficiency E of the tested filter shall be calculated using Equation (1) according to the measurement results of the number of particles before and after the filter by OPC. The first digit after the last 9 is taken as the significant digit for E value, and the second digit shall be rounded off according to the principle of rounding. For example, the measured value E = 99.976%, after rounded off, E = 99.98%.
(1)
where,
E——the filtration efficiency of the tested filter;
A2——the concentration of downstream aerosol particles, particles/m3;
A0——the background concentration of downstream aerosol particles, particles/m3;
A1——the concentration of upstream aerosol particles, particles/m3;
R——the correlation ratio.
5.2.5.2 The lower limit efficiency E95%,min of the confidence interval with 95% confidence shall be calculated using Equation (2).
(2)
where,
E95%,min——the lower limit efficiency of confidence interval with 95% confidence;
A1,95%min——the lower limit of upstream aerosol concentration with confidence of 95%, in particles/m3; according to Poisson distribution, the lower confidence limit of particle count with confidence of 95% calculated by measured particle concentration is shown in Table 2;
A2,95%max——the upper limit of downstream aerosol concentration with confidence of 95%, in particles/m3; according to Poisson distribution, the upper confidence limit of particle count with confidence of 95% calculated by measured particle concentration is shown in Table 2.
Table 2 Particle count confidence interval with 95% confidence based on Poisson distribution
Particle count Lower confidence limit Upper confidence limit Particle count Lower confidence limit Upper confidence limit
0 0.0 3.7 35 24.4 48.7
1 0.1 5.6 40 28.6 54.5
2 0.2 7.2 45 32.8 60.2
3 0.6 8.8 50 37.1 65.9
4 1.0 10.2 55 41.4 71.6
5 1.6 11.7 60 45.8 77.2
6 2.2 13.1 65 50.2 82.9
8 3.4 15.8 70 54.6 88.4
10 4.7 18.4 75 59.0 94.0
12 6.2 21.0 80 63.4 99.6
14 7.7 23.5 85 67.9 105.1
16 9.4 26.0 90 72.4 110.6
18 10.7 28.4 95 76.9 116.1
20 12.2 30.8 100 81.4 121.6
25 16.2 36.8 n (n > 100) n ? 1.96
n + 1.96
30 20.2 42.8
5.3 Sodium flame method
5.3.1 Test principle
The atomization drying method is used to test the artificial NaCl aerosol close to the MPPS range of the filter medium. The dried NaCl crystal can be screened by pre-filtration of the medium efficiency filter. The count peak particle size of the test aerosol particles shall be (0.09 ± 0.02)μm, and the geometric standard deviation shall not be greater than 1.90. The NaCl aerosol upstream and downstream of the filter is collected to the burner and burned under the hydrogen flame. The sodium flame light generated by the combustion is transformed into a current signal and detected by the photoelectric measuring instrument. The filtering efficiency of the filter is calculated from the measured current value.
5.3.2 Test device
5.3.2.1 The filter performance test device by sodium flame method is mainly composed of NaCl aerosol generator, air duct system and aerosol sampling and detection device. The schematic diagram of the test device is shown in Figure 3.
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Keys:
1——Prefilter; 20——Filter detection box;
2——Fan frequency conversion cabinet; 21——Orifice flowmeter;
3——Draught fan; 22——Iris valve;
4——Soft joint; 23——Micromanometer;
5——Air duct; 24——Temperature controller;
6——Electrical heater; 25——Background filter box;
7——High efficiency particulate air filter (HEPA); 26a——Three-way switching valve (background/after filtration);
8——Reducer; 26b——Three-way switching valve (original/after background filtration);
9——Spray box; 27——Vent valve;
10——Sprayer; 28——H2 generator;
11——On/off valve; 29——H2 constant flow valve;
12——Separate cylinder; 30——Burner;
13——Pressure gauge; 31——Photoelectric converter;
14——Spray solenoid valve; 32——Photoelectric measuring instrument;
15——Relief valve; 33——Temperature and humidity meter;
16——Drying pipe section; 34——Spray flowmeter;
17——Buffer tank; 35——Background filtered flowmeter;
18——Fixed blade ring; 36——Original flowmeter;
19a——Front sampling pipe; 37——H2 flowmeter;
19b——Rear sampling pipe; D——Pipe diameter.
Figure 3 Schematic diagram of filter performance test device by sodium flame method
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5.3.2.2 The NaCl aqueous solution with mass concentration of 2% in the spray box is atomized by a sprayer with clean compressed air to form aerosol mist droplets containing salt and mixed with clean hot air from heating and filtering of fans. In the mixing drying section, the water in the mist droplet evaporates, and when the air flow reaches the buffer tank, the test aerosol has formed a uniform polydispersed solid aerosol. If necessary, a medium efficiency filter can be set at the outlet of the buffer tank to screen the test aerosol closer to the MPPS range of the filter. When setting the medium efficiency filter, the concentration of NaCl aqueous solution can be increased to 10% in order to obtain the test aerosol mass concentration meeting the efficiency test requirements. The length of the downstream pipe section of the buffer tank shall meet the mixing demand of aerosol at the section of the front sampling pipe nozzle (if necessary, a diverter can be set at the outlet of the buffer tank). The air flowrate and static pressure of the air duct system are controlled by the fan frequency converter and the iris valve respectively, and the air flow after the test is discharged from the end of the air duct.
5.3.2.3 Aerosol sampling is pressed into the detection system by the static pressure in the air duct through the front and rear sampling pipes of the tested filter. By changing the position of the valve, the aerosol before and after the filter is sampled alternately, and the original, filtered and background aerosols are sent to the burner respectively. The original aerosol can flow into the burner only after mixing (i.e. dilution) with the clean air filtered by the background filter in the mixer. In the burner, the Na atom in the aerosol is excited by the high temperature of H2 flame and emits a characteristic light with a wavelength of 589 nm, whose intensity is directly proportional to the mass concentration of the aerosol. Sodium light intensity value is changed into photocurrent value through photoelectric converter and detected by photoelectric measuring instrument. The resistance of the filter section is detected by connecting the static-pressure rings on both sides of the tested filter to the micromanometer. The result minus the resistance of the filter detection box is the filter resistance.
5.3.2.4 The construction and maintenance requirements of the filter performance test device by sodium flame method are shown in Annex A, the sprayer and photometer structure are shown in Annex B. Different test devices are allowed, but the requirements of 5.1 shall be met, and the test results of the same filter shall be consistent with the standard test device.
5.3.3 Filter detection
5.3.3.1 Operating parameters
5.3.3.1.1 Test air
An electric heater shall be set in the air duct system to ensure that the air inlet temperature of the system is not lower than 5°C, the relative humidity at the inlet of the buffer tank is not higher than 30%, and the relative humidity at the downstream side of the tested filter is not higher than 60%.
5.3.3.1.2 NaCl solution concentration
Prepare NaCl solution with mass concentration of (2.0 ± 0.1)% with dry chemical pure NaCl and distilled water (natural water or tap water shall not be used).
5.3.3.1.3 Liquid level
The height of NaCl solution in the spray box shall be 90 mm to 110 mm.
5.3.3.1.4 Spray air pressure
The pressure of clean compressed air entering the sprayer shall be 0.6 MPa, and the allowable deviation is ±0.02 MPa.
5.3.3.1.5 Spray air volume
Under the prescribed pressure, the amount of compressed air entering each sprayer shall meet those specified in Table A.1.
5.3.3.1.6 Original aerosol concentration
The original mass concentration range of NaCl shall be 2 mg/m3–8 mg/m3.
5.3.3.1.7 Aerosol sampling volume
The amount of sampling air entering the burner shall be 2 L/min.
5.3.3.1.8 H2 volume
The volume of H2 entering the burner shall be 200 mL/min and shall be kept constant.
5.3.3.2 Detection steps
5.3.3.2.1 Operation preparation
5.3.3.2.1.1 Turn the turntable on the photoelectric converter to the "OFF" position. Turn on the H2 generator, ignite H2, adjust the flow rate to 200 mL/min, and start the system to start detection after the burner is preheated for 30 min.
5.3.3.2.1.2 Turn on the power switch of the photoelectric measuring instrument and preheat the photoelectric measuring system.
5.3.3.2.1.3 Take out the humidity sensitive probe from the drying vessel, connect it with the signal line led out from the hygrometer and put it into the measuring hole at the inlet of the buffer tank. Turn on the power supply of the hygrometer and press the "measurement" key. The humidity at the entrance of the buffer tank can be displayed on the hygrometer.
5.3.3.2.1.4 Visually inspect the filter medium in the tested filter for defects, cracks and holes; check the joint part of the filter frame corner and whether the frame and filter medium are sealed, whether there is gap and whether there is abnormality in structure. The filter that passes the visual inspection can be used for testing.
5.3.3.2.1.5 Place the tested filter in the box of the air duct system and clamp it.
5.3.3.2.2 System startup
5.3.3.2.2.1 Start the fan, adjust the fan frequency converter and iris valve to make the air flowrate and static pressure of the air duct system meet the detection requirements. Start the air compressor. When the pressure reaches 0.5 MPa, the spray solenoid valve will be opened, the spray pressure will reach 0.6 MPa gradually, maintain the pressure stable, and the air flow meter reading of each sprayer is stable to the design value, and check the test air flowrate again.
5.3.3.2.2.2 Measure the relative humidity of the air at the inlet of the buffer tank. If it is greater than 30%, gradually put the electric heater into operation until the relative humidity reaches the specified value.
5.3.3.2.3 Resistance detection
Use a micromanometer to test the resistance of the filter section under the test air flowrate, and minus the air resistance of the test section to obtain the filter resistance.
Foreword i
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
4 Selection of test methods
5 Performance device and test method of HEPA and ULPA
6 Performance test method of HEPA and ULPA filter mediums
Annex A (Normative) Structure and maintenance of filter performance test device by sodium flame method
Annex B (Informative) Structure diagram of components of filter and filter medium test devices by sodium flame method
Annex C (Normative) Structure and maintenance of filter test device by oil mist method
Annex D (Normative) Correction, calibration and maintenance of filter medium test device by oil mist method
Annex E (Normative) Vaporization-condensation oil mist generator in filter test device by oil mist method
Annex F (Normative) Oil mist meter
Annex G (Normative) Structure and maintenance of filter medium test device by sodium flame method
Annex H (Normative) Oil mist generator in the filter medium test device
