GB/T 36370-2018Cleanroom and associated controlled environments—Guidelines of application of air filters (English PDF)

3.1 Air filter

A filter used to remove suspended particulate matter and certain gaseous pollutants from a gas stream.

3.2 Efficiency

Under test conditions, the ratio of the count rate of the filter or filter material trapping particles to the upstream particle count rate, or the mass concentration and the upper The ratio of the mass concentration of the swim is expressed in %.

3.3 Penetration rate

Under the test conditions, the ratio of the particle concentration downstream of the filter to the upstream concentration is expressed in %.

3.4 Most easily penetrated particle size

Particle size for the highest filter penetration (lowest filtration efficiency) for a given filter.

Note: It is the most difficult to filter the particle size of the particles. In theory, the filtration efficiency of particles larger or smaller than MPPS is higher than that at MPPS; in practical applications, The MPPS of the filter is a range of particle sizes measured by the instrument, not a unique particle size.

3.5 MPPS efficiency

Under the test conditions, the lowest point of the filter efficiency curve, that is, the efficiency value corresponding to the MPPS.

3.6 Sub-high efficiency filter

Y-HEPA filter

EPA filter

A filter with an MPPS efficiency of less than 99.95% but not less than 85% under test air volume.

3.7 High efficiency filter

HEPA filter

ISO 35H to ISO 45H, the filter with MPPS efficiency below 99.999% but not less than 99.95% under test air volume.

3.8 Ultra-efficient filter

ULPA filter

ISO 50U and higher grade filters, filters with MPPS efficiency of 99.999% under test air volume.

3.9 Sodium flame method

A method of detecting filtration efficiency. Sodium chloride aerosol with a specific mass median diameter and specific particle size distribution upstream of the filter The characteristic intensity of the sodium-containing aerosol flame upstream and downstream of the filter was measured by a flame photometer to determine the filtration efficiency.

Note: Also known as the "flame photometer method".

3.10 Turbidity meter method

A liquid or solid aerosol with a specific mass median diameter and a specific particle size distribution upstream of the filter, using a light scattering principle photometric test A method of measuring the upstream and downstream aerosol mass concentrations to determine the filtration efficiency.

Note: Also known as the "photometer method". Commonly used turbidity meter methods are. traditional DOP method, oil mist method and the like.

3.11 Purification unit; FFU

A filter unit that integrates a HEPA or ULPA filter, a static pressure tank, a fan, and an air speed adjustment device.

Note: Also known as "fan filter unit".

3.12 Prefilter

A filter set to protect the next stage filter and extend its life.

Note: Also known as "pre-filter".

3.13 Organic outgas

The filter manufactures gaseous compounds that may be released from the material.

3.14 End filter

The last stage air filter of the air supply system.

3.15 Adsorption capacity

The amount (mass or moles) of a specified adsorbate that can be contained by the filter media in a gas phase air purification plant.

Note: Desorption capacity is referred to during desorption.

3.16 Removal efficiency

The air chemical filter removes the percentage (%) of the gas phase contaminant or its concentration fraction during the specified test time.

3.17 Pressure drop

The pressure difference between the front and rear ends of the air chemical filter.

3.18 Resilience

The parameter that measures the desorption capacity of the adsorbent or chemical filter is expressed as the remaining capacity (residual fraction).

3.19 PTFE tensile film filter

A filter material formed by compounding a polytetrafluoroethylene film and other auxiliary materials. Among them, the filtering material is Teflon drawing A fibrous porous film formed.

Note: The PTFE film for making high-efficiency filters is about 10µm~20µm thick, and the fiber diameter is only tens of nanometers. Therefore, it is sometimes called "membrane filtration" material or "Nanofiltration" material.

3.20 Electret filter media

A polymeric filter material that can store charge for a long period of time.

5.1 Overview

5.1.1 Ordinary filters are classified into coarse, medium, high, medium, efficient, efficient and ultra efficient. Coarse, medium and high in the purification air conditioning system Medium-effect as a pre-filter protects the functionality of the various components and protects high-efficiency filters and ultra-efficient filters.

5.1.2 The function and function of the efficient and ultra-efficient filter is to ensure the cleanliness level required by the production process for the environment. The end of the system.

5.2 End High Efficiency Filter

5.2.1 Filtration efficiency

Generally, for ISO 6 and lower non-unidirectional flow clean rooms, the end filter has a filtration efficiency no lower than ISO 35H (for the most The filtration efficiency of the easily penetrating particles is not less than 99.95%). If the user agrees with the supplier, the sodium flame method and aerosol turbidity can also be used. The minimum efficiency of the method or other methods is not less than 99.97% or other agreed values.

The filtration efficiency of the end filter of ISO Class 5 clean room is not lower than ISO 40H (the filtration efficiency of the most easily penetrated particle size is not Less than 99.99%). If the user agrees with the supplier, a filter with a particle efficiency of not less than 99.99% for 0.3 µm particles can also be used.

ISO 4 and higher cleanrooms, the end filter is generally ULPA filter, the filtration efficiency is not lower than ISO 50U Grade (the filtration efficiency at MPPS is not less than 99.999%).

5.2.2 Factory inspection

High-efficiency filters with an efficiency specification not lower than ISO 35H shall be tested one by one before leaving the factory.

The factory inspection method for efficiency or penetration rate is determined by the customer and the supplier. Appendix B gives possible test methods. If there is no special Do not agree, the particle counting method specified in ISO 29463-2:2011 should be used.

Note: The customer and the supplier should agree on the specific test method, whether to use the scanning method or the total efficiency method, and agree on the particle measuring device and test used in the test. Aerosols, test procedures and acceptance limits.

5.2.3 Detection after installation

5.2.3.1 During the test, it is necessary to verify that there is no bypass leakage in the facility, the filter is free of defects (small holes and damage of the filter material and sealing points), no leakage (over Seepage leakage of filter frame and gasket, leakage of filter mount), see Appendix C. This test generally does not determine the filtration of the system. effectiveness. Typically, a sufficient concentration of aerosol occurs upstream of the filter (see Appendix D). Scanning downstream of the filter and around the filter, or Sampling in the air duct downstream of the filter.

Note: This test is designed to confirm that the high efficiency filtration system is installed correctly.

5.2.3.2 After installation, the filter is usually tested by the following two methods in B.6.2 and B.6.3 of GB/T 25915.3-2010.

a) in-situ filtration system aerosol turbidity meter scanning leak detection;

b) In-place filtration system particle counter scan for leak detection.

The user can use one of these two methods and refer to the corresponding procedures and acceptance limits.

5.2.3.3 For leak detection of high efficiency filters in air ducts and air handling systems, refer to the square in B.6.4 of GB/T 25915.3-2010. Methods, procedures, and acceptance limits are measured using a particle counter or aerosol turbidimeter.

Note: Efficiency testing in the filter manufacturer is performed under ideal test conditions. Differences between site conditions and test conditions and manufacturer conditions may result The results of the on-site inspection and laboratory inspection are inconsistent. Before the on-site inspection after installation, it is recommended that customers, suppliers and testers have on-site inspection methods. And the acceptance limit is agreed.

5.2.4 End filter away from the clean room

In some cases, due to factors such as the site, the clean room end filter is located in the air conditioning system, not the air supply port of the clean room. This Design can save investment, but there are some drawbacks. Cleanrooms generally do not use this design unless necessary.

5.2.5 End-of-life filter life

The length of life of the end-height filter depends primarily on the design of the filter section of the ventilation system. High efficiency of pre-filter in the system Low determines the life of the end filter.

5.2.6 Other

5.2.6.1 Organic matter and moisture on the end filter are prone to microbial growth. In order to reduce the proliferation of microorganisms, the material of the end efficient filter is not Hydrophilic materials should be used, and materials that are prone to microbial growth should not be used. The separator material with the separator filter should not be hydrophilic, flammable, or Nutritious paper organic material.

5.2.6.2 The filter material in the high efficiency filter is generally a glass fiber filter. The filter media should not contain glass with high sodium and potassium content that is easy to fall back. fiber.

5.2.6.3 Where outgassing may affect the clean environment, the filter shall be constructed of a material with low outgassing.

5.2.6.4 Filters made of electret materials may be inefficient due to the disappearance of static electricity during use. Clean room end filter is not recommended Use electret filter material.

5.2.6.5 Field repair of filters (see Appendix D).

5.2.6.6 Order elements (see Appendix D)

5.2.6.7 Teflon drawn film (ePTFE) filter (see Appendix D)

5.3 Pre-filter

5.3.1 Function and selection

5.3.1.1 To protect the next stage filter or end filter, a pre-filter should be provided in the air supply system. Pre-filter efficiency is high and low The cleanliness of the clean room has limited impact, but the filtration efficiency of the pre-filter determines the service life of the protected filter. Pre-filter should have enough Large effective filtration area to ensure a long enough life.

5.3.1.2 Pre-filter before the end filter, the filtration efficiency is generally not less than 90%.

5.3.1.3 In the design, the pre-filter of the end filter is a HEPA filter with ISO 35H efficiency specification, and its air duct and sealing structure Should be reliable. After the filter is installed, it can be scanned for leaks downstream of the HEPA pre-filter.

5.3.2 Replacement

5.3.2.1 The pre-filter section shall have a simple and practical resistance monitoring device, and the information of replacing the pre-filter may be given accurately and intuitively. According to the supplier Or the air conditioner designer's suggestion to replace the pre-filter.

5.3.2.2 In some occasions, when the user requests to replace the pre-filter, the air-conditioning system supplies air as usual. At this time, the replacement of the pre-filter is in the air-conditioning system. When operating and operating, it should be considered for easy maintenance and replacement.

5.4 Example of high efficiency filter selection

See Appendix E.

6.1 Key parameters of performance

The key parameters of air chemical filter performance are as follows.

a) pressure drop, deltaP;

b) adsorption capacity, ms;

c) removal efficiency, E;

d) Maintain ability, mr.

6.2 Main factors affecting purification efficiency and service life

The main factors affecting filter purification efficiency and service life are as follows.

a) The advantages and disadvantages of chemical filter design and processing, the effectiveness of filter media (such as activated carbon, modified activated carbon, etc.), packing density Degree and so on.

b) After determining the type and concentration of the polluted gas, a reasonable selection of the formula and ratio of the filling medium will achieve a better purification effect.

c) The randomness and uncertainty of the pollution source will seriously affect the adsorption efficiency.

d) The amount of air passing directly through the filter, the air volume is increased, the efficiency is reduced, and the life is shortened.

e) Relative humidity affects the efficiency of the filter to a certain extent, generally the relative humidity below 70% is not obvious, but when relative When the humidity exceeds 70%~80%, the adsorption efficiency decreases rapidly.

f) The gas concentration increases and the service life decreases rapidly.

g) In the case of other adsorption parameters unchanged, the efficiency of the re-polluting gas does not reach the height of a single gas, and the chemical properties vary greatly. Especially serious.

6.3 Monitoring and replacement

The outlet of the site shall be monitored. If the concentration of pollutants in the airflow exceeds the predetermined value, it shall be replaced immediately.

Note 1. The air chemical filter produced by the filter manufacturer has a service life indicator, but this indicator is the knot measured under the test conditions specified by the standard. If it has a service life of one year, it can only be used as a reference.

Note 2. Waste filters and activated activated carbon are safe and harmless, but should be avoided during storage and pay attention to fire safety.

6.4 Setting the protection filter

It should be considered that the chemical filter itself is dust-producing, and a conventional filter having an efficiency of not less than F7 should be provided above and below it.

6.5 Chemical filter test

See Appendix F for chemical filter testing.

A.1 International Standard Filter Grouping and Classification

ISO 29463-1:2011 specifies that sub-efficient, efficient and ultra-efficient filters are measured by counting method and filter according to MPPS efficiency.

For classification, see Table A.1. The first Arabic digit in the ISO symbol represents n nines, and the second digit represents 5 or 0. E.g, The ISO 45H represents the counting method MPPS efficiency is not less than 99.995%.

For coarse and medium efficiency filters, no classification is mentioned in the international standards.

A.2 China Refrigeration and Air Conditioning Industry Association (CRAA) Recommended Classification

The classification of China Refrigeration and Air Conditioning Industry Association (CRAA430-2008) is shown in Table A.2.

Efficient (H group) and ultra high efficiency (U group) filters should be tested one by one. If the customer agrees with the supplier, the H13 filter can The efficiency is not less than 99.97% by the sodium flame method. U-group filters can only be detected using the counting method. Sub-efficient (Y group) filter does not need Detected one by one.

A.3 GB/T 13554-2008 high efficiency filter classification

The classification of high efficiency filters in GB/T 13554-2008 is shown in Table A.3.

A.4 GB/T 14295-2008 general ventilation filter classification

GB/T 14295-2008 divides the ventilation filter into coarse, medium and high-efficiency. The specific classification is shown in Table A.4.

A.5 European high efficiency filter classification

EN1822-1:2009 classification of high efficiency filters is shown in Table A.5.

A.6 European general ventilation filter classification

The classification specified in EN779:2012 is shown in Table A.6. […]