GB/T 4797.6-2013 Classification of environmental conditions Natural environmental conditions Dust, sand, salt spray GB/T4797.6-2013 |tt||Standard compression package decompression password: www.bzxz.net
This part of GB/T4797 explains the characteristics of dust, sand and salt spray that occur in nature, and the effects of these environmental factors on products exposed to them during storage, transportation and use. Although the effects of these environmental factors are often closely related to wind, this part does not involve wind environmental factors. For related content, please refer to GB/T4797.5.
class="f14" style="padding-top:10px; padding-left:12px; padding-bottom:10px;"> GB/T4797 standard is currently divided into the following eight parts:
———GB/T4797.1 Natural environmental conditions for electrical and electronic products Temperature and humidity;
———GB/T4797.2 Natural environmental conditions for electrical and electronic products Altitude and air pressure, water depth and water pressure;
———GB/T4797.3 Natural environmental conditions for electrical and electronic products Biology;
———GB/T4797.4 Natural environmental conditions for electrical and electronic products Solar radiation and temperature;
———GB/T4797.5 Classification of environmental conditions for electrical and electronic products Natural environmental conditions Precipitation and wind;
———GB/T4797.6 Classification of environmental conditions Natural environmental conditions Dust, sand, salt spray;
———GB/T4797.7 Classification of environmental conditions for electric and electronic products Natural environmental conditions Earthquake vibration and shock;
———GB/T4797.8 Classification of environmental conditions for electric and electronic products Natural environmental conditions Fire exposure.
This part is Part 6 of GB/T4797.
This part was drafted in accordance with the rules given in GB/T1.1-2009.
This part replaces GB/T4797.6-1995 "Natural environmental conditions for electric and electronic products Dust, sand, salt spray". Compared with GB/T4797.6-1995, the main changes are as follows:
———4.3 Added Table 4 of the data of the world's major deserts;
———Added Figure 7, and the data of the original Table 9 was incorporated as a description of the figure.
This part adopts the revised IEC60721-2-5:1991 "Classification of environmental conditions Part 2: Natural environmental conditions Section 5: Dust, sand, salt spray" by redrafting.
The technical differences between this part and IEC60721-2-5:1991 and their reasons are as follows:
———Based on the measured data in China, Table 5, Table 8, Figure 3, Figure 5, Figure 8 are added, and the subsequent serial numbers are adjusted accordingly;
———6.1 Supplements China's salt spray data, and adds 6.1.3 "Particle size";
———Added Chapter 7 "Salt dust fog in saline-alkali areas";
———Added two informative appendices: Appendix B "Movement of sand and dust in airflow" and Appendix C "Transport and distribution of salt spray particles from the sea to the land".
Compared with IEC60721-2-5:1991, this part has been mainly revised for the following editorial purposes:
———The foreword and introduction of IEC60068-2-61:1991 have been deleted, and the foreword of the national standard has been added;
———The references in Appendix B of the original IEC have been deleted.
This part was proposed and managed by the National Technical Committee for Standardization of Environmental Conditions and Environmental Testing for Electrical and Electronic Products (SAC/TC8). The
drafting organizations of this part are: China Electric Power Research Institute Co., Ltd., Defense Technology Research and Test Center of China Aerospace Science and Industry Corporation, Ningbo Ouzhi Electric Technology Co., Ltd., Ningbo Jiesheng Ocean Development Co., Ltd., Wuxi Sunan Test Equipment Co., Ltd., Ningbo Runzhou Auto Parts Co., Ltd., Ningbo Sichuang Electromechanical Co., Ltd. The
main drafters of this part are: Chen Xinxin, Li Hongmin, Ke Cilong, Ni Yiming, and He Bo.
The previous versions of the standards replaced by this part are:
———GB/T4797.6—1995.
The following documents are indispensable for the application of this document. For any dated referenced document, only the dated version applies to this document. For any undated referenced document, its latest version (including all amendments) applies to this document.
GB/T4797.5 Classification of environmental conditions for electric and electronic products Natural environmental conditions Precipitation and wind (GB/T4797.5—2008, IEC60721-2-2:1988, MOD)
GB/T10593.2—2012 Measurement methods of environmental parameters for electric and electronic products Salt spray
ISO9225:2012 Corrosion of metals and alloys—Corrosivity of atmospheres—Measurement of environmental parameters affecting corrosivity of atmospheres)
Foreword III
1 Scope1
2 Normative references1
3 Effects of dust, sand and salt spray on products1
4 Natural dust and sand environment1
4.1 Classification of dust and sand1
4.2 Types and characteristics of dust 2
4.3 Factors affecting the dust environment 5
5 Dust in shutter boxes and enclosed areas 8
5.1 Characteristics of dust 8
5.2 Factors affecting the dust environment 9
6 Salt spray 9
6.1 Characteristics of salt spray 9
6.2 Factors affecting the salt spray environment 12
7 Salt spray in saline-alkali areas 13
7.1 Distribution of saline soil 13
7.2 Salt composition of saline soil 14
7.3 Formation and impact of salt spray 14
Appendix A (Informative Appendix) Examples of how dust concentration varies with altitude 15
Appendix B (Informative Appendix) Movement of dust in air currents16
Appendix C (Informative Appendix) Transport and distribution of salt spray particles from the sea to the land 19

ICS 19.020
National Standard of the People's Republic of China
GB/T 4797.6—2013
Replaces GB/T4737.61995
Classification of environmental conditions
Natural environmental conditions
Dust, sand, salt mist
Classification of environmental conditions-Environmental conditions appearing in natureDust, sand, salt mist(IEC 60721-2-5:1991, Classification of environmental conditions-- Part 2:Environmcntal conditions appearing in nature --Section 5: Dust, sand, salt mist,MOD)2013-11-12 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
2014-03-07 Implementation
2 Normative Reference Documents
3 Effects of Dust, Sand and Salt Spray on Products
4 Natural Dust and Sand Environment
4.1 Classification of Dust and Sand
1.2 Types of Dust and Sand and Questions to be Traceable
Factors Affecting Dust Environment
5 Dust in Shutter Boxes and Enclosed Fields
Characteristics of Dust
Factors Affecting Dust Environment
6 6.1 Characteristics of salt fog
6.2 Factors affecting salt fog environment
7 Salt fog in saline-alkali areas
7.1 Distribution of saline soil
7.2 Salt composition of salt-affected soil
7.3 Formation and impact of salt dust fog
Appendix A (informative appendix) Examples of changes in dust concentration with height Appendix B (informative appendix) Movement of dust in airflow
Appendix C (informative appendix) Transport and distribution of salt fog particles from the sea to the land GB/T4797.6—2013
The GB/T4797 standard is currently divided into the following eight parts: - G13/T 4797,1
Electrical and electronic products natural environmental conditions temperature and degree; GB/T4707.2 Electrical.1 Electronic products natural environmental conditions altitude and air pressure, water depth and water pressure, electrical and electronic products natural environmental conditions biology; GB/T 4797.3
-GB/T4797.4 Electrical T. Electronic products natural environmental conditions solar radiation and temperature: G3/T 4797.5
GB/T 4797.6
GB/1 4797.7
Electrical power plant product environmental conditions classification natural environmental conditions precipitation and wind: environmental conditions classification and natural environmental conditions dust, sand, salt spray; GB/T 4797.6--2913
Electrical. Electronic products environmental conditions classification natural environmental conditions ground vibration and shock; Electrical II electronic products environmental conditions classification natural environmental conditions fire exposure. GB/T 4797.8
This part is the sixth part of GB/T4797.
This part was drafted according to the rules given in HB3/T1.1-2009. This part replaces GB/T4797.6--19 "Natural environmental conditions for electrical and electronic products, dust, sand, salt spray", and compared with GB5/T4797.%1995, the main changes are as follows:
-4.3 Added data table 1 of the world's major deserts,-Added Figure 7 and moved the numbers in the original table 9 as the illustration of the figure. This part uses the re-starting method to modify and adopt IEC60721-2-5:1991 Classification of environmental conditions Part 2: Natural environmental conditions Section 5: Dust, sand, fog\.
The technical differences between this part and IEC60721-2-5:1991 and their reasons are as follows: 1. Based on the measured data in my country, Table 5, Table 8, Figure 3, Figure 8, and the subsequent serial numbers are adjusted accordingly: 1. 6.1 Supplement my country's salt spray data, add 6.1.3 "Particle size"; add the content of Chapter 7 "Salt dust fog in the point-to-alkali ratio area"; 1. Add Appendix 13 "Movement of sand and dust in small airflow" and Appendix ("Transport and distribution of salt spray particles from the sea to the land" two porcelain appendices.
Compared with IFC60721-2-5.1991, this part mainly makes the following abridged modifications: Delete IEC60068-2-61:199 1's foreword and introduction, added the national standard foreword; - deleted the original IEC Appendix B references.
This part was proposed and adopted by the National Technical Committee for Standardization of Environmental Conditions and Environmental Tests for Electrical and Electronic Products (SAC/1C8). Drafting units of this part: China Electric Power Research Institute Co., Ltd., Aerospace Science and Industry Defense Technology Research and Test Center, Ningbo Ouzhi Electric Technology Co., Ltd., Ningbo Jiesheng Haifu Development Co., Ltd., Wuxi Sunan Test Equipment Co., Ltd., Ningbo Runzhou Auto Parts Co., Ltd., Ningbo Sichuang Electromechanical Co., Ltd.
The main drafters of this part are Chen Xinxin, Li Hongmin, Ke Jielong, Ni Yiming, and He Bo. The previous versions of the standards replaced by this part are: GB/T 4797.61595.
1 Fan Chen
Environmental condition classification Natural environmental conditions
Dust, sand, salt spray
GB/T 4797.6—2013
This part of GB/T4797 explains the characteristics of dust, sand and salt spray that appear in natural environment[1, and the impact of these environmental factors on products exposed to them during storage, transportation and use. Although the impact of these environmental factors is often closely related to wind, this part does not involve environmental factors of wind. For relevant content, please refer to GB/T4797.5. 2 Normative references
The following documents are indispensable for the application of this document. For all references with dates, only the versions with the dates are applicable to this document. For all undated references, the latest versions (including all amendments) apply to this document GB/T4797.5 Classification of environmental conditions for electrical and electronic products Natural environmental conditions Precipitation and wind (GB/T4797.52008, IFC 60721-2-2;1988,M0D)
GJ3/[0593,2—2012 Methods for measuring environmental parameters of electrical products Salt spray IS09225:2012 Corrosion of metals and alloys: Corrasivity of atmospheres: Measurement of envirunriental parameterg corrosivity of 3.13
2) Entering into sealed containers or sealed bodies; deteriorating electrical performance, such as contact failure, contact resistance change, and track resistance change of potentiometers; causing wear or failure of bearings, shafts, rotors and other moving parts; c)
Surface erosion (erosion corrosion);
causing optical surfaces to blur;
causing lubricants to be contaminated;
reducing thermal conductivity;
causing working vents, track linings, ducts, filters, holes, etc. to become clogged; h)
generating static electricity during high-speed movement (such as sandstorms), affecting communication systems. 3.2 The combination of air, sand and other environmental factors such as water vapor can have serious effects on products, such as corrosion and mold growth. Hot and humid atmosphere combined with chemically corrosive substances can cause corrosion. In the atmosphere, salt spray can also produce similar effects. 3.3 Consideration of ion conduction and the influence of corrosive dust (such as deicing salt, etc.) 4 Natural dust and sand environment
4.1 Classification of dust and sand
Based on different aerodynamic characteristics, dust and sand are distinguished as follows; 1
GB/T 4797.6—2013
Dust: It can be defined as material particles with no specified source or composition, with a size between 1 μm and 150 μm, which are emitted from natural air flow and have a diameter less than 7!Particles of sand can stay in the atmosphere for a long time. Sand: It is a non-compacted refractory material condensed from rock fragments. Its basic composition is round quartz particles, ranging in size from 150μm to 100cm. When this term is used in sedimentary petrology, it is for particles with a size between 10μm and 1000μm. Particles with a diameter greater than 150μm cannot stay in the air unless they are constantly subjected to strong natural or induced airflow or turbulence. 4.2 Types and characteristics of sand and dust
4.2.1 Types of sand and dust
Most of the sand and dust in the natural world is mainly composed of quartz. In sandy lands and similar dusty areas, sand and dust can cause damage to products. The main characteristic of sand is its high hardness, which can cause rapid wear or damage to products, especially moving parts. However, material abrasion usually occurs when sand and dust are combined with high-speed airflow or sand and dust for a long period of time. 4.2.2 Characteristics of sand and dust
The most important characteristics of natural dust are its non-absorption and chemical inertness, but when the atmosphere contains moisture or other gases, it may cause corrosion to the enterprise.
4.2.2.2 The most notable characteristics of fine dust are usually its non-abrasiveness and absorbent properties. 4.2.3 Characteristics of sand and dust
4.2.3.1 Particle size
The approximate range of dust and sand particle size is: fine dust
coarse dust
less than 7 μm,bZxz.net
75μm~150μm;
150 μm~-100 μm.
The approximate distribution of dust and sand sizes is shown in Figure 1. TH
Grain dust
Scientific dust
Particle size/un
Figure 1 Cumulative distribution of dust particle size
4.2.3.2 Particle hardness
GH/T 4797.6—2013
The hardness of a single particle can be used to determine its ability to scratch the object it contacts. Sand, which is composed of tiny fragments of crystal quartz or other minerals, is usually slightly harder than most fused silica glasses. Therefore, sand can scratch the surface of most optical glass devices. Applying pressure on the collected sand particles can cause them to break. The hardness grades (Moore's hardness) of several common substances are shown in Table 1. Substances with higher hardness grades can scratch substances with lower hardness grades. Table 1 Hardness grades of several common substances
Mohs imperfection grade
4.2.4 Concentration
Calcite
Apatite
Orthoclase
Diamond
Representative substances
Major substances
Writing stone products, algae
Kaolin right
Galena right net (nail)||tt| |Granite, marble, serpentine
Foshan
Marble
Oaldite
Window glass
Magnetite, feldspar
Agate, quartzite, (many kinds of quartz, quartz glass, olivine
Red durastone, calcium carbide
Emerydride
Blue tumbler, carbonization
4.2.4.1 Root The mass is called the calculated concentration, that is, the mass of particles in a unit volume of air. The dust concentration in the atmosphere varies greatly with geographical location, regional climate type and conditions, and the degree of human activity. Under certain conditions, a large amount of dust is temporarily separated from the surface dust and blown away by the wind. 4.2.4.2 In temperate regions, the typical concentrations of dust encountered in various areas are shown in Table 2. Table 2 Typical dust concentrations
Rural and suburban areas
Dust concentration
0.04~-0.11
0.19~-0.45
0.50~-2.c0
4.2.4.3 Higher dust concentrations occur under induced conditions, such as those caused by direct drives and tracked vehicles. Appendix A explains the conditions caused by direct 3
GB/T 4797.6—2013
Approximate detection of dust concentration induced by helicopters and vehicles. 4.2.4.4 Typical dust concentrations at different altitudes in the desert are shown in Table 3. The movement of dust in the near-surface layer of the desert in the air flow is shown in Appendix B.
Table 3 Variation of dust concentration in the desert with increasing altitude Visibility conditions
Fire, visibility 130 km
Sandstorm, visibility 3com
Wind speed 15 m/s-~15 m/s
Dust density
4.2.4.5 Dust concentration and the probability of particle occurrence increase with increasing wind speed. Figure 2 illustrates the general situation of this system, but it varies with factors such as temperature, humidity, particle composition, etc. Particles larger than 150um are generally confined to an air layer 1m near the ground. In this layer, about half of the sand particles (by mass) move within 10mm above the ground, and the other half, most of them, move within 110cm near the ground. tt||Wind temperature/(ms)
Note: This figure is a curve of near-ground conditions (smaller than 1m) that affect the maximum particle size: 25
Figure 2 Relationship between maximum dust particle size and wind speed The measured results of the relationship between dust content in the air (pieces/cn) and wind speed in Northwest my country are shown in Figure 3. 4
)/4 period
Wind speed m
Note: This figure is for the mountain Gobi Desert, with a correct degree of 1, and the data on the relationship between sand content in the air and wind speed. 3 Relationship between sand content and wind speed in outdoor atmosphere 4.3 Factors affecting infiltration environment GB/T 4797.6—2013 4.3.1 The sand environment is affected and controlled by factors such as topography, wind, temperature, humidity and precipitation. None of these factors can dominate the dusty or dust-free area independently. Usually, two or more factors are combined to work. The most severe conditions in nature, such as the central sand dunes, usually all factors have an important influence on the high concentration of sand. The structural characteristics of the terrain can cause high-speed strong winds and cause sandstorms. For example, when air passes strongly against the mountain-type landform structure, it will significantly increase the wind speed. 4.3.2 Sand is widely distributed on the earth's land surface. Table 4 lists the world's major deserts, which are the main source of wind-blown dust in the natural world. The area composed of sand accounts for about one-fifth of the world's total land area. All continents are bordered by sandy beaches of varying widths. In many inland areas, there are large areas of sand on or near the surface, which were once covered by water. Table 4 Major deserts in the world
Desert name
Wilha Desert
Australian Desert
Halachopu
Turkish Desert
North American Desert
Santa Cedin Yami Desert
Tarshapu
Kalahari Desert
Iranian Desert
Alokama-Peru Desert
Taklimakan Desert
Australia
Southeast coast of Arabia
Southwest of the former Soviet Union
United States and West Africa
Mobility and Pakistan
Chile and Peru
X:0° km2
GB/T 4797.6—2013
The data of major deserts in China are shown in Table 5. The total area of ​​deserts in my country (including Gobi and desertified land) is 130.8×10°km2, accounting for about 13.6% of the total area of ​​land in my country.
Table 5 Main deserts in my country and their geographical locations and areas Desert name
Taklimakan Desert
Gilyandaogut Desert
Kumtag Desert
Qaidam Basin Desert (including Fengxiandi)
Badain Jaran Desert
Tengger Desert
Ulan Buh Desert
Kubqi Desert
Maowu Desert
Hunpingdake (Little Tengger) Sand
Korqin Sand
Hulunbuir Dream Run
Geographic location
Xinchuan Tali Shuyi Land
Xintong Junggar Basin
Eastern Xinjiang, western Gansu, southern Lop Nur lowland, northern Altun Mountains
Qaidam Salt Land in Qinghai
Western Alax Plateau in Inner Mongolia
Inner Mongolia occupies the eastern part of Alax Plateau
Northern Alap Plateau in Inner Mongolia, southwestern Yellow River Hetao Plain
Northern Gaoqiong in Ordos, Inner Mongolia, southwestern Yellow River Hetao Plain
Central and southern Ordos Plateau and northwestern Sui in Inner Mongolia
Inner Mongolia occupies the southern Xilinguotao League and northwestern Zhuowuda League in the eastern part of the plateau
The lower reaches of Guijiang River in the western part of the Northeast Plain
Hulunhuoer Plateau in northeastern Inner Mongolia
840.-1 29c
30c~·6C0
1 300~.1 200
26CO-34CO
1 3cO~-1 8co
1 4CO~-1 6CO
1000-1200
1300~1600
1ac-~3co
Xlo3 km\
4.3.3Compared with sand, dust particles have a very low settling velocity and can remain suspended in the air for a long time and can remain on any surface. Under dry conditions, soils with dust contents (9% by mass or less) will become at least moderately powdery, and soils with dust contents greater than 11% may be completely dusty. With the exception of Antarctica, 40% of the world's land area is arid, and another 40% is seasonally dry. Therefore, dust is expected to occur over most of the land surface during part of the year. Even in rainy areas, dust can occur if the protective cover there is destroyed. Many wet areas have good drainage, so that most unprotected soils will become dust very soon after heavy rain. 4.3.4 Figure 1 describes the occurrence of wind in areas with equal intensity. Figure 5 describes the occurrence of sandstorms in northwest my country (wind speed 5 m/s>The relationship between the occurrence frequency and wind speed frequency. 4.3.5 Figure 6 describes the settling velocity of small particles of different sizes, from which the settling time can be estimated. Thermal changes and other effects of flow on the settling of small particles should be considered.
Wind headwind/im.s
, the occurrence of wind in inland areas with moderate wind intensity Figure 4
The wind speed of tidal wind occurs throughout the year at a rate of /…. Note: This figure shows the relationship between sand-raising wind and wind speed in the Taklimakan Desert in Xinjiang. Figure 5 shows the relationship between the occurrence frequency of sand-raising wind and wind speed frequency GB/T 4797.6—2013
GB/T 4797.6—2013
: Coarse dust
Particle size/um
Note: The line is the situation of particles with a concentration of 1/m at a temperature of 0 and an atmospheric pressure of 101.3ka. Figure 6 Settling velocity of particles in static air
5 Dust in louvered boxes and enclosed areas
5.1 Dust characteristics
5.1.1 Dust characteristics
In louvered boxes and enclosed areas, dust of various materials can be found, such as quartz, water seepage, powdery matter, organic fibers, etc. 5.1.2 Distribution of particle sizes
The distribution of particle sizes varies significantly depending on whether it is outdoors, in loading and unloading vehicles or in shuttered areas. Due to the filtering effect of the shelter, the maximum particle size in shuttered and enclosed areas is smaller than in places without weather protection. The maximum particle size in shuttered and enclosed areas is about 1com
5.1.3 Dust deposition density
Typical values ​​of dust deposition density in different areas are shown in Table 6. Dust deposition values ​​are small samples of sand flowing into the measuring device from the outdoor atmosphere. They cannot be used to consider local dust in enclosed areas. For example, in mines, cement plants, sawmills and similar places, quasi-monotonous deposition occurs throughout the entire generation process.
Rural and suburban areas
Three industrial areas
5.2 Factors affecting the dust environment
5.2.1 Areas and places
Table 6 Typical dust deposition density
GB/T 4797.6—2013
Unit: grams per square hour
Dust deposition
(09.4-~15
5.2.1.1 The impact of dust in louvered or enclosed places is significantly different from that in outdoor places, such as dust storms in desert areas, dust storms on roads, and the local environment around vehicles. 5.2.1.2 Dust in enclosed and louvered places is caused by a variety of sources. Dust may be quartz, de-icing salt, fertilizer, etc., which can enter these places through ventilation holes or broken paper. 5.2.1.3 It may also be composed of small natural fibers or artificial materials, for example, from clothes or blankets commonly used in living rooms or offices.
5.2.1.4 Other sources of dust (e.g. seeds) may be present in warehouses or flour mills, etc. 5.2.1.5 The distribution of the particle size of the material varies with the type of dust. The only common point is that they have approximately the same maximum particle size. 5.1.2,
5.2.2 Effect of dust
In louvers or closed places, there are also small air movements. The basis for identifying this air flow effect is: a) sedimentation; The deposition of dust on the product can be caused by four different mechanisms: 1) deposition in stagnant air;
2) deposition on the protected surface;
3) electrostatic attraction;
1) capture by narrow channels, such as in filters with forced air circulation, air movement tends to delay or hinder the deposition of dust. b) Intrusion: The process of sand and dust invading the product may occur as follows: 1) brought into the interior by strong air circulation;
2) brought into the interior by the thermal movement of air;
3) escaped into the interior by the thermal expansion and condensation of air or the change of atmospheric pressure. 6 Salt Mold
6.1 Characteristics of Salt Mist
6.1.1 Composition
6.1.1.1 The atmosphere of the ocean and coastal areas contains a large amount of salt, including salt formed by solid particles or droplets like salt solution, and also contains various other components.
6.1.1.2 The salt content of seawater is determined by the total amount of solid matter contained in kg of seawater (expressed in grams). At this time, all bromine and iodine are replaced by an equal amount of chlorine, all carbonates are converted to oxides, and all organic matter is oxidized. 93 Dust deposition density
Typical values ​​of dust deposition density in different regions are shown in Table 6. Dust deposition values ​​are small samples of sand flowing into the measuring device from the outdoor atmosphere. They cannot be used to consider local dust in closed places. For example, in mines, cement plants, sawmills and similar places, the occurrence of single deposition is throughout the entire generation process.
Rural and suburban areas
Three industrial areas
5.2 Factors affecting the dust environment
5.2.1 Regions and places
Table 6 Typical dust deposition density
GB/T 4797.6—2013
Unit: grams per square hour
Dust deposition
(09.4-~15
5,2.1.1 The impact of dust in shuttered or enclosed places is significantly different from that in outdoor places, such as dust storms in desert areas, dust storms on the road, and the local environment around vehicles. 5.2.1.2 Dust in enclosed and shuttered places is caused by various sources, such as quartz, deicing salt, fertilizer, etc., which can enter these places through ventilation holes or broken pipes. 5.2.1.3 It may also be composed of small fibers of natural or artificial materials, for example, from clothes or carpets commonly used in living rooms or offices.
5.2.1.4 Other sources of dust (such as seeds) may appear in warehouses or flour mills, etc. 5.2.1.5 The distribution of particle sizes of materials varies with different types of dust. The only common feature is that they have a maximum particle size that is approximately the same. 5.1.2,
5.2.2 Effects of dust
In louvers or closed places, there are also small air movements. Identifying this airflow effect The basis for use is: a) sedimentation: The deposition of dust on the product can occur by four different mechanisms: 1) deposition in stagnant air; 2) deposition on the protected surface; 3) electrostatic attraction; 1) capture by narrow channels, such as in filters with forced air circulation, where air movement tends to delay or hinder dust deposition. b) intrusion: The process of dust intrusion into the product may occur: 1) brought in by forced air circulation; 2) brought in by the thermal movement of the air; 3) brought in by the air Thermal expansion and contraction or changes in atmospheric pressure can cause the air to escape into the interior. 6 Salt Mold
6.1 Characteristics of Salt Mist
6.1.1 Composition
6.1.1.1 The atmosphere of the ocean and coastal areas contains a large amount of salt, including salt formed by solid particles or droplets like salt solution, and also contains various other components.
6.1.1.2 The salt content of seawater is determined by the total amount of solid matter contained in kg of seawater (expressed in grams). At this time, all bromine and iodine are replaced by an equal amount of chlorine, all carbonates are converted to oxides, and all organic matter is oxidized. 93 Dust deposition density
Typical values ​​of dust deposition density in different regions are shown in Table 6. Dust deposition values ​​are small samples of sand flowing into the measuring device from the outdoor atmosphere. They cannot be used to consider local dust in closed places. For example, in mines, cement plants, sawmills and similar places, the occurrence of single deposition is throughout the entire generation process.
Rural and suburban areas
Three industrial areas
5.2 Factors affecting the dust environment
5.2.1 Regions and places
Table 6 Typical dust deposition density
GB/T 4797.6—2013
Unit: grams per square hour
Dust deposition
(09.4-~15
5,2.1.1 The impact of dust in shuttered or enclosed places is significantly different from that in outdoor places, such as dust storms in desert areas, dust storms on the road, and the local environment around vehicles. 5.2.1.2 Dust in enclosed and shuttered places is caused by various sources, such as quartz, deicing salt, fertilizer, etc., which can enter these places through ventilation holes or broken pipes. 5.2.1.3 It may also be composed of small fibers of natural or artificial materials, for example, from clothes or carpets commonly used in living rooms or offices.
5.2.1.4 Other sources of dust (such as seeds) may appear in warehouses or flour mills, etc. 5.2.1.5 The distribution of particle sizes of materials varies with different types of dust. The only common point is that they have a maximum particle size that is approximately the same. 5.1.2,
5.2.2 Effect of dust
In louvers or closed places, there are also small air movements. Identification of this airflow effect The basis for use is: a) sedimentation: The deposition of dust on the product can occur by four different mechanisms: 1) deposition in stagnant air; 2) deposition on the protected surface; 3) electrostatic attraction; 1) capture by narrow channels, such as in filters with forced air circulation, where air movement tends to delay or hinder dust deposition. b) intrusion: The process of dust intrusion into the product may occur: 1) brought in by forced air circulation; 2) brought in by the thermal movement of the air; 3) brought in by the air Thermal expansion and contraction or changes in atmospheric pressure can cause the air to escape into the interior. 6 Salt Mold
6.1 Characteristics of Salt Mist
6.1.1 Composition
6.1.1.1 The atmosphere of the ocean and coastal areas contains a large amount of salt, including salt formed by solid particles or droplets like salt solution, and also contains various other components.
6.1.1.2 The salt content of seawater is determined by the total amount of solid matter contained in kg of seawater (expressed in grams). At this time, all bromine and iodine are replaced by an equal amount of chlorine, all carbonates are converted to oxides, and all organic matter is oxidized. 9
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