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[GB/T 12476.8-2010] Electrical apparatus for use in the presence of combustible dust -- Part 8: Test methods -- Methods for determining the minimum ignition temperatures of dust
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Basic data | Standard ID | GB 12476.8-2010 (GB12476.8-2010) | | Description (Translated English) | [GB/T 12476.8-2010] Electrical apparatus for use in the presence of combustible dust -- Part 8: Test methods -- Methods for determining the minimum ignition temperatures of dust | | Sector / Industry | National Standard | | Classification of Chinese Standard | K35 | | Classification of International Standard | 29.260.20 | | Word Count Estimation | 28,285 | | Date of Issue | 2010-08-09 | | Date of Implementation | 2011-08-01 | | Quoted Standard | GB/T 6005-2008; GB/T 6919 | | Adopted Standard | IEC 61241-2-1-1994, IDT | | Regulation (derived from) | Announcement of Newly Approved National Standards No. 3, 2010 (No. 158 overall) | | Issuing agency(ies) | General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China | | Summary | This Chinese standard provides two methods to determine the minimum ignition temperature of dust test methods. This method does not apply with explosives characteristics of the material. Method A (Chapter 4) applies to determine the cause deposition on the surface of the heat required to provide a minimum of dust layer thickness decomposition temperature and/or the minimum ignition temperature. The method is particularly suitable for exposure to the environment of the industrial equipment on the hot surface with a thin layer of dust in the form of dust. Method B (Chapter 5) applies to determine the required sample will lead dust clouds or other solid particulate sample minimum ignition temperature. This test is part of the adoption of this method A determines the minimum ignition temperature of a dust layer after the additional test, Method B Note on. Note 1: Due to constant temperature furnace operation method determines the dust particles in the furnace residence time is short, this test method is applicable to dust to dust cloud short existence industrial equipment, this test method are small, the results are not necessarily representative of all industrial conditions. Note 2: This method does not apply to this test method over time can be specified in tB Jiong from pyrolysis or combustion gases formed during the formation of dust accumulation. | GB 12476.8-2010: [GB/T 12476.8-2010] Electrical apparatus for use in the presence of combustible dust -- Part 8: Test methods -- Methods for determining the minimum ignition temperatures of dust
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Electrical apparatus for use in the presence of combustible dust.Part 8. Test methods.Methods for determining the minimum ignition temperatures of dust
ICS 29.260.20
K35
National Standards of People's Republic of China
Combustible dust Electrical Equipment
Part 8. Test methods
Determining the minimum ignition temperature of a dust
Part 8. Testmethods-
(IEC 61241-2-1.1994, IDT)
Issued on. 2010-08-09
2011-08-01 implementation
Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
Standardization Administration of China released
Table of Contents
Preface Ⅰ
Introduction Ⅱ
1 Scope 1
2 Normative references 1
3 Terms and definitions
4 Method A. Dust layer on a heated surface temperature constant 2
5 Method B. dust cloud when the furnace thermostat 5
Appendix A (normative) Method A. the structure and surface heating surface temperature distribution measuring 7
Appendix B (normative) thermostatic oven structure 12
Figure A.1 heating plate diagram (Method A) (not to scale) 8
Figure A.2 for forming a dust layer metal ring (Method A) 9
Figure A.3 typical ignition temperature of a dust layer on the heated surface/time curve (Method A) 10
Surface temperature measurement (Appendix A Method A) 11 Figure A.4
Figure A.5 typical surface temperature distribution (Method A) 11
Figure B.1 thermostatic oven assembly (Method B) 13
Figure B.2 quartz tube (Method B) 14
Figure B.3 glass pipe and dust holder (Method B) 15
Figure B.4 furnace shell 20SWG seamless stainless steel tube (Method B) 16
Figure B.5 top and bottom covers (Method B) 17
Figure B.6 18
Figure B.7 19
Figure B.8 20
Figure B.9 oven rack base 21
Figure B.10 dust spray system (Method B) 22
Table B.1 assembly device (Method B) 12
Foreword
All technical content in this section is mandatory.
GB 12476 "combustible dust electrical equipment" is divided into several parts.
--- Part 1. General requirements
--- Part 2. Selection and installation
--- Part 3. combustible dusts exist or may exist Classification of hazardous areas
--- Part 4. Intrinsic safety "iD"
--- Part 5. Housing protection type "tD"
--- Part 6. protective encapsulation "mD"
--- Part 7. protective positive pressure "pD"
--- Part 8. Test methods for determining the minimum ignition temperature of a dust
--- Part 9. Test method for determination of the dust layer resistivity
--- Part 10. Test methods for dust and air mixture Determination of minimum ignition energy
Part of this section is GB 812 476, equivalent using IEC 61241-2-1.1994 "combustible dust Electrical apparatus
Part 2. Test methods - Section 1. determining the minimum ignition temperature of a dust "(in English).
This part of IEC 61241-2-1.1994 includes the following editorial changes.
--- Remove the IEC 61241-2-1.1994 Foreword;
--- Increase the national standard foreword.
This section of the Appendices A and B are normative appendix.
This part is proposed by the China Electrical Equipment Industrial Association.
This part of the National explosion-proof electrical equipment Standardization Technical Committee (SAC/TC9) centralized.
This part mainly drafted by. Explosion Protection Electric Institute.
This part of the main participants. National explosion-proof electrical products for Quality Supervision and Inspection Center blast Electric Co., Ltd., Fushun Coal Research Institute
Shun Branch.
The main drafters of this section. Shu Dynasty, Chen school, Chen Rui, Liu Ying Qi, Li Changhe record, Huang Jianfeng.
Introduction
GB 12476 of the provisions of this section for determining the minimum ignition temperature of a dust.
--- Method A. constant dust layer on the heated surface (Chapter 4);
--- Method B. when the dust cloud thermostatic oven (Chapter 5).
A method of determining the minimum on the heated surface dust layer ignition temperature.
Method B is determined by a predetermined constant temperature heating furnace dust cloud minimum ignition temperature.
Test method is versatile, it can be used for comparison, however, in some industrial applications may require further testing.
Determining the minimum ignition temperature of the method is not applicable Explosives recognized, for example, black powder, dynamite or a possible under certain circumstances
A mixture of similar characteristics.
If you suspect an explosion characteristics of danger may be a small amount of dust into the device above the surface temperature to 400 ℃ or higher
To get the index, the test should be away from the operator.
Combustible dust Electrical Equipment
Part 8. Test methods
Determining the minimum ignition temperature of a dust
1 Scope
This part of GB 12476 specifies two test methods for determining the minimum ignition temperature of the dust of.
This method does not apply to a substance having Explosives properties.
Method A (Chapter 4) adapted to determine the cause will be deposited on the surface of the heat regulations requiring minimum decomposition temperature of the dust layer thickness and/or points
Minimum ignition temperature. The process is particularly suitable for surfaces exposed to the hot environment of industrial equipment with a thin layer of dust present in the form of dust.
Method B (Chapter 5) adapted to determine the lowest temperature of the dust cloud will lead to a predetermined sample or other solid particles in the sample ignited. The test
Test as an additional test in the present section A method of determining the minimum after the dust layer ignition temperature.
B Note on methodology.
Note 1. Since the method of operation of the thermostatic oven dust particles determines the short residence time in the furnace, the test method is applicable to short-term dust to dust cloud exists
Industrial Equipment. This test method is small, its results are not necessarily representative of all industrial conditions.
Note 2. This method is not used in this test method over time may be specified in the decomposition from high temperature or dust accumulated gas formed during the formation of smoldering.
2 Normative references
The following documents contain provisions which, through reference in this Part of GB 12476, constitute provisions of this part. For dated reference documents
Member, all subsequent amendments (not including errata content) or revisions do not apply to this section, however, encouraged to reach under this section
Parties to research agreement to use the latest versions of these documents. For undated reference documents, the latest versions apply to this
section.
GB/T 6005-2008 Test sieves - Metal wire cloth, perforated plate and electroformed sheet - basic mesh size (ISO 565.
1990, MOD)
GB/T 6919 Air quality vocabulary (GB/T 6919-1986, eqvISO 4225. 1980)
3 Terms and Definitions
GB 12476 This section uses the following terms and definitions.
3.1
Dust dust
In the air can settle down on its own weight, but also sustainable solid fine particles suspended in air for a period of time (including
GB/T 6919 defined dust and particles).
3.2
Ignite the dust layer ignitionofadustlayer
If the material began flameless combustion or flaming, or during the test measured temperature of 450 ℃ or more, or a temperature higher than a predetermined heat
Surface temperature of 250K or higher, shall be deemed ignition occurs.
3.3
The minimum ignition temperature of a dust layer minimumignitiontemperatureofadustlayer
Minimum ignition temperature of the hot surface of the predetermined thickness of the dust layer occurs on hot surfaces.
Note 1. Since the process in the range of wider industrial processes, the dust layer may depend on local conditions for ignition. This test method is not necessarily representative of all
Industrial conditions, there may need to consider some of the dust layer thickness, and environmental factors such as temperature distribution exists.
Note 2. during the test, to take the necessary health precautions to protect workers, such as prevention of fire, explosion, inhalation of smoke and toxic combustion properties
Health hazards.
3.4
Dust cloud ignited ignitionofadustcloud
The initial energy of the explosion into the air dust cloud metastasis.
3.5
Dust cloud ignition temperature ignitiontemperatureofadustcloud
The lowest temperature in the furnace air contained in the inner wall of the furnace occurred when the dust cloud ignited.
Note. during the trial, to take the necessary health precautions to protect workers, such as prevention of fire, explosion, inhalation of smoke and toxic combustion properties
Health hazards.
4 Method A. Dust layer on a heated surface at a constant temperature
4.1 Preparation of dust samples
After preparation of the samples should be aimed at the uniform representative dust used in the test.
Typically, dust samples were tested to be able to woven wire mesh screen through a nominal size of 200μm aperture or hole center square hole test sieve (attached
Plus size, see GB/T 6005). If necessary, through a nominal pore size are tested for the coarse dust test sieve of 500μm
The report should explain the actual situation.
Sieve dust or temperature or moisture content of any significant changes in dust related properties during sample preparation, such as the use of the test shall be reported
Report explained.
4.2 test device
It is shown in Figure A.1 test device, its main characteristics and performance requirements given in detail in the following sub-clauses. To meet this
The method of making these requirements are specified in Appendix A.
4.2.1 heated surface
Heated surface by a circular metal plate, and should provide a minimum diameter of 200mm and a thickness of at least 20mm of work
Area. Metal plate should be electrically heated, the temperature of the metal plate should be controlled by means of a thermocouple a sensitive element fixed to the metal thermocouple
Board near the site of the center, which contacts the inner surface of the metal plate 1mm ± 0.5mm range and good thermal contact with the metal plate.
Similar thermocouples shall be fixed in a similar manner in the vicinity of the thermocouple temperature control, and should be connected to the logger, recording during the test metal
The temperature of the plate surface. Heated surfaces and controls shall meet the following performance requirements.
a) In the case of non-heated surface dust layer should be able to reach a maximum temperature of 400 ℃;
b) throughout the test period, the heated surface temperature fluctuations should be stable within ± 5K range;
c) When the heated surface reaches a steady state, with the program set forth in Appendix B through two diameters measured at right angles on the surface by
Temperature fluctuations should always be within ± 5K range. It should meet the requirements of a nominal surface temperature of 200 ℃ and 350 ℃ time;
d) the temperature should be controlled so that the surface temperature fluctuations recorded in a period not exceeding ± 5K dust layer is formed, and in the formation of 5mm
When the surface temperature of the dust layer fluctuations should be able to recover in the value range of ± 2K;
e) temperature control and measuring equipment shall be calibrated within ± 3K deviation limit range.
4.2.2 dust layer thermocouple
Sensitive thermocouple Cr alloy or other suitable material (having a diameter of 0.20mm ~ 0.25mm) should be pulled through a heated surface
Tight, and with heated surfaces parallel to the height of 2mm ~ 3mm distance between the heating surface, the contact at the top center of the plate. The thermocouple should
Logger is connected during the test to determine the characteristics of the dust layer.
4.2.3 Temperature Measurement
Thermocouple temperature measurement should be carried out or use the automatic compensation of cold termination point at a fixed reference junction in either case, the calibration
Should meet 4.2.1e) requirements.
4.2.4 ambient temperature measurement
Ambient temperature should be placed away from the heated surface is not more than 1m, convection and thermal radiation from the surface of the thermometer to measure the impact.
Ambient temperature should be in the range of 15 ℃ ~ 35 ℃.
4.2.5 dust layer
Preparation of the dust layer should be installed with the appropriate metal ring cavity height of the heating surface by filling the top layer of dust ring
Highly consistent. NW metal ring should be 100mm, located at both ends of the metal ring with a diameter through the test thermocouple groove (see
Figure A.2). During the test should be the ring in place.
Provisions dust shall be tested in a layer thickness of 5.0mm ± 0.1mm. In order to predict (see 4.6), you can use a second thickness
(Eg 12.5mm ± 0.1mm or 15.0mm ± 1mm), such a request to the appropriate height of the metal ring.
Forming a layer of dust 4.2.6
Forming a layer of dust should not make excessive compression, which uses a spatula dust added to the metal ring, the blade main lateral movement, dusting dust straight
Slightly overflowing into the ring so far, then top with a ruler across the metal ring drag, excess dust should be swept away.
Each type dust dust layer is formed in the manner described above should be aware of the quality of the paper and then the weight is measured, the dust should be based on quality
Filling volume and ring volume calculations derived density and recorded.
4.3 Program
4.3.1 General
Exposure to high temperatures in the particulate or porous solid particles normally ignite in advance, ahead of time is greater than or less than the self-heating (due to the air
Gas oxidation) duration. Not produced in the combustion of solid particles spread, according to the level of exposure temperature, self-heating only
It can produce a temporary rise (although sometimes obvious). Also, when approaching the minimum required ignition temperature, ignition "incubation period" is usually more than
In the cloud of dust and gas many times more or vapor ignition time (in minutes or hours rather than seconds). In view of the above two reasons, recognized powder
Dust layer is significantly larger than the minimum ignition temperature of a dust cloud or the minimum ignition temperature of gases and vapors is low. Therefore, does not appear on a predetermined temperature
Lit only because of the early termination of the test.
The key on the hot surface of the layer of dust appears on a predetermined temperature ignition of dust layer depends on the heat rate ( "self-heating") and around the ring
Equilibrium rate of heat loss between the territory. Therefore, the temperature prescribed material appears light depends on the thickness of the dust layer, two or more provisions dust
Thickness measured values can be used to predict (see 4.6).
Under the proposed procedure, if the following conditions shall be deemed to occur ignition.
a) visible light or combustion (Figure A.3 in 3a)); or
b) measuring the temperature of 450 ℃; or
c) measuring the temperature of the heating plate to a temperature above 250K (Figure A.3, 3c)).
For the above item b) and item c), if it can prove that the reaction did not develop into the light-emitting or combustion, shall not be deemed to arise ignited. Should make
Thermocouple temperature measurement (see 4.2.2). Typically this would indicate that, as long as the temperature of the heated surface is sufficiently high, the temperature of the dust layer
It will gradually warmed to the maximum surface temperature may exceed the heat, and then slowly drops below the stable value of the heated surface temperature (Fig A.3
In 3b)). This feature is dust layer itself exothermic phenomenon may often be accompanied by dust color, but no quick and visible dust layer
combustion. If the temperature of the heated surface of the slightly higher temperature of the dust layer is measured will continue to rise rather than reach a maximum value. certain
Self-heating stage more than one of these materials, it may sometimes be necessary to extend the experiment to fully investigate this possibility. Organic dust
Combustion usually was charred state, followed by a dust layer will be expanded and leave dust residue with glowing smoldering. By certain
Split metal dust layer is formed, characterized by relatively light suddenly appeared abnormal dust layer rapidly expanding hot smoldering combustion.
When a predetermined thickness of the dust layer is the minimum ignition temperature measurement, the test is repeated each time using a fresh layer of dust. On the test
By adjusting the heating temperature of the surface until you find the temperature is high enough to cause ignition of dust layers up to and just above the ignition temperature can lead to
10K. The maximum temperature should not occur ignited by continuing to verify the test of time long enough to identify any self-heating of the slip
It is reduced, i.e. the temperature measuring point dust layer is reduced to less than the surface temperature of the heat stable value.
4.3.2 Method
Equipment should be installed in the absence of airflow place, preferably in the smoke and dust can be sucked under the hood.
Heated surface temperature should be adjusted to a desired value, and it should be in a stable 4.2.1b) prescribed limits. Require a high degree of metal ring
Should be aligned with the center of the heated surface is placed, the ring is full of dust again, and flattened in 2min time and then turn on the dust layer thermocouple
Recording instrument.
The test shall be continued until there is visible burning or thermocouple recorded data to determine the dust layer has been ignited, or determine the presence of their own
But exothermic ignition did not happen, and then the temperature decreased.
If there is no self-heating time after 30min, the test should be stopped, and the temperature increase is repeated. If ignition occurs
Or self-heating, the test should be repeated to lower the temperature. If necessary, to extend the test for longer than 30min, continue testing until the
Now the temperature high enough to cause ignition or dust layer until the self-heating, but can cause ignition or just above the self-heating temperature of 10K.
4.3.3 Results
Experiment with fresh dust layer is repeated until the determination of the minimum ignition temperature. The temperature should be rounded to the predetermined thickness of the dust
10 ℃ minimum temperature closest integer multiple ignition occurs when the layer. If according to the test thermocouple readings that the ignition occurred (see
4.3.1), the minimum ignition temperature should be higher than the lowest temperature rounded to the nearest whole multiple of at least 10 ℃ lower 10K.
Ignition did not occur or that the maximum temperature does not occur when the ignition should also be recorded. The temperature should be higher than the occurrence of ignition or considered fat
Students ignited lowest temperature, low temperature does not exceed 10K, but the temperature should be at least three times after experimental verification.
For this section, if the temperature does not appear on the heated surface temperature below 400 ℃ dust layer ignition, the test should be interrupted. In this case
As a result of the test shall be recorded.
In order to obtain the ignition time or the maximum temperature reached ignition time does not appear, it should be prepared on the heated surface layer of dust about 5min
After measured and recorded.
If the temperature is below 400 ℃ ignite the dust layer does not appear, it should record the longest duration.
4.4 Criteria for passing the test
An operator with results at different times, and the test results obtained in different laboratories are obtained, if the selection
Ignition temperature difference of more than 10K, shall be considered ineligible.
Since the physical properties of the dust and causes the dust layer status during the trial period, the validity of the test results may sometimes imprecise. If there
This case, the record of the case (see 4.5), and all results should be regarded as equally effective.
Test records shall include a brief description of the characteristics of combustion after ignition, in particular, indicate the status of combustion, for example, abnormally fast or burn drama
Lie decomposed. Factors that may affect the validity of the results should also be recorded, and these factors include the preparation of a dust layer of difficulty in heating, burst,
Evidence of deformation during the melting layers of dust and the dust is heated during the formation of combustible gases.
4.5 Results Report
The test report shall include the name of test material, sources and types (if the name is not included), the test date and identification, as well as the ambient temperature
Density of the material to be tested (see 4.2.6).
The report should have been carried out indicate the minimum ignition temperature of dust layer was measured in accordance with the provisions of this section.
Ignition test shall be shown in table format (the way to the surface temperature results in descending order, rather than sequential tests are shown) into
Rows.
The thickness of the dust layer
mm
surface temperature
test results
Lit or unlit reach the maximum temperature time
min
ignite
ignite
Unlit
Unlit
Unlit
Unlit
It shall be recorded for each ignition temperature of dust layer thickness in accordance with the provisions of 4.3.3.
In the example given in the above table, 5mm thick dust layer minimum ignition temperature recorded was 170 ℃.
The minimum ignition temperature of the heated surface of the recording of the temperature difference between the test need not exceed ± 20K record.
4.6 Application of the results
The ignition temperature value is applied to the test used in the thickness of the dust layer A method in accordance with this section to determine the minimum. For some timber
Material, the number of test results can be used although the linear interpolation or linear extrapolation draw thickness and the minimum ignition temperature (Unit. Kelvin
Temperature K) is the reciprocal of the curve, to evaluate the minimum thickness of the heated surface centered or thick layers of dust ignition temperature, but it is best to use
The thickness required to do testing.
Note 1. The above is the easiest prediction program, in theory, have a certain rationality. Better analysis to thermal explosion theory will be other shape
Ignite the dust-like layer (eg, dust layer on the curved surface) were evaluated. However, if it is to disparities in exposure conditions, especially
Uniformly exposed to a high temperature environment, rather than non-uniform environment (e.g., on a hot plate) accurate prediction of the ignition, it is preferable to use different ring
The results of the test procedure throughout closer (eg, lit in an oven) obtained.
Note 2. If you plan to conduct a thorough prediction, best determined by the thickness of two or more layers of dust ignition temperature and focus on a greater thickness.
5 Method B. When the thermostat furnace dust cloud
5.1 Preparation of dust samples
After preparation of the samples should be aimed at the uniform and representative dust used in the test.
Typically, dust samples were tested should pass a nominal size of 71μm aperture of woven wire mesh cloth or perforated plate square hole sieve test
(Additional dimensions, see GB/T 6005-2008). If necessary, through the nominal dimensions of coarse dust particles 500μm test sieve
Test, the test report shall indicate the actual situation.
Any significant change in the relevant characteristics of dust during sample preparation, sieve or temperature or moisture such as dust used shall be the test
Mortem report stated.
5.2 Test apparatus
Structural testing device detail shown in Figure B.1 ~ Figure B.10 and Table B.1. Thermostatic oven heated quartz tube mounted vertically, open to the atmosphere
Opening at the lower end of the thermostatic oven. The upper end of the furnace is connected by a glass pipe and dust container. Open the release from the reservoir of compressed air solenoid valve
Dust blown into a thermostatic oven. Thermostatic oven is fixed on the test bench, so can easily lower end of the observation tube.
Mirror below the furnace tube installed to be able to observe the interior of the furnace tube.
Thermocouples used regularly calibrated, so as to maintain the temperature exceeds 500 ℃, the measurement result deviation ± 1%, is lower than 300 ℃
± 3%.
After the test device is assembled, and the accuracy of the device to be used in other places to compare the results obtained powder (eg lycopodium).
5.3 Progra...
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