1、December 2016 English price group 20No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 13.230!%S“2599148www.din.deDIN
2、EN ISO/IEC 80079-20-2Explosive atmospheres Part 202: Material characteristics Combustible dusts test methods (ISO/IEC 80079202:2016);English version EN ISO/IEC 80079202:2016,English translation of DIN EN ISO/IEC 80079-20-2:2016-12Explosionsfhige Atmosphren Teil 202: Werkstoffeigenschaften Prfverfahr
3、en fr brennbare Stube (ISO/IEC 80079202:2016);Englische Fassung EN ISO/IEC 80079202:2016,Englische bersetzung von DIN EN ISO/IEC 80079-20-2:2016-12Atmosphres explosives Partie 202: Caractristiques des produits Mthodes dessai des poussires combustibles (ISO/IEC 80079202:2016);Version anglaise EN ISO/
4、IEC 80079202:2016,Traduction anglaise de DIN EN ISO/IEC 80079-20-2:2016-12SupersedesDIN EN 6124122(VDE 0170/01711522):199604www.beuth.deDocument comprises 52 pagesDTranslation by DIN-Sprachendienst.In case of doubt, the German-language original shall be considered authoritative.02.17 DIN EN ISO/IEC
5、80079-20-2:2016-12 2 A comma is used as the decimal marker. Start of application The start of application of this standard is 2016-12-01. National foreword This document (EN ISO/IEC 80079-20-2:2016) has been prepared by Technical Committee IEC/TC 31 “Equipment for explosive atmospheres” in collabora
6、tion with Technical Committee CEN/TC 305 “Potentially explosive atmospheres Explosion prevention and protection” (Secretariat: DIN, Germany). This standard includes safety requirements. The responsible German body involved in its preparation was DIN-Normenausschuss Sicherheitstechnische Grundstze (D
7、IN Standards Committee Safety Design Principles), Working Committee NA 095-02-09 AA Kenngren fr Stube, Gase und Dmpfe. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. DIN and/or DKE shall not be held responsible for identifying an
8、y or all such patent rights. Amendments This standard differs from DIN EN 61241-2-2 (VDE 0170/0171-15-2-2):1996-04 as follows: a) the test specified in DIN EN 61241-2-2 (VDE 0170/0171-15-2-2):1996-04 has been included in the test scheme of DIN EN ISO/IEC 80079-20-2:2016; b) the calculation R0300C) l
9、ower temperature using lower and higher values of test material volume. If necessary the temperature is reduced further in 10 K (or 20 K if 300 C) steps until no ignition is obtained after 3 attempts for each volume. If a flame is seen in the furnace this shall be considered as an ignition. Single s
10、parks are not considered as an ignition. 8.1.3.4 Recording of test results the minimum ignition temperature is recorded as the lowest temperature of the furnace at which ignition was obtained using the above procedure minus 20 K for furnace temperatures above 300 C and minus 10 K for furnace tempera
11、tures at or below 300 C. If no ignition is obtained even when the furnace temperature is at 600 C this fact shall be stated in the report noting that this is the maximum temperature obtainable in the BAM furnace. If no ignition is obtained and the maximum test temperature was below 600 C the maximum
12、 temperature at which no ignition is obtained shall be stated in the report too. 8.2 Test for MIT of dust layer 8.2.1 General The apparatus consists of a heated plate and a dust ring. 8.2.2 Heated surface The heated surface shall consist of a circular metal plate and shall provide a working area of
13、at least 200 mm in diameter and be not less than 20 mm in thickness. The plate shall be heated electrically and its temperature shall be controlled. The heated surface and its control device shall satisfy the following performance requirements: a) the heated surface shall be capable of attaining a m
14、aximum temperature of 400 C without a dust layer in position; b) the temperature of the heated surface shall be constant to within 5 K throughout the period of a test; c) when the heated surface has reached a steady state, the temperature across the surface shall be uniform to within 5 K when measur
15、ed across two diameters at right angles, as depicted in Annex A. This requirement shall be satisfied at nominal surface temperatures of 200 C and 350 C. The variance across the surface is to be checked periodically, but not for every test; d) the temperature control shall be such that the recorded s
16、urface temperature does not change by more than 5 K during the placing of the dust layer, and it shall be restored to within 2 K of the previous value within 5 min of placing the dust layer; e) temperature control and measurement devices shall be calibrated and shall have limits of accuracy of 3 K;
17、NOTE The maximum deviation from the nominal surface temperature shall not exceed 8 K due to points c) and e). DIN EN ISO/IEC 80079-20-2:2016-12 EN ISO/IEC 80079-20-2:2016 (E) 20 f) a thermocouple shall be connected to a temperature recorder to record the temperature of the surface during a test. 8.2
18、.3 Dust layers The dust layer shall be formed without compression of the layer. The layer shall then be levelled by drawing a straight edge across the top of the ring. Any excess should be swept away. Dust layers shall be prepared by filling the cavity formed by placing a metal ring of appropriate h
19、eight on the heated surface and levelling the layer to the top of the ring. The ring shall have an internal diameter of nominally 100 mm. The ring shall be left in place during a test. A given dust shall be tested in a layer of 5,0 mm 0,1 mm depth. NOTE The same apparatus can be used for measuring t
20、he ignition temperatures of layers with depths greater than 5 mm. The layer ignition temperatures for thicker layers (e.g. 12,7 mm) can be estimated by interpolation between experimentally determined points or extrapolation for a number of test thicknesses. 8.2.4 Dust layer temperature The temperatu
21、re shall be measured within the layer at a height of between 2 mm and 3 mm from the surface of the plate, at the centre of the dust layer at a location centered on the dust ring 10 mm. This temperature shall be measured at 1 min intervals over the test period. NOTE An infrared camera is often used a
22、s an additional detection system for the temperature rise or glowing. 8.2.5 Ambient temperature measurements The ambient temperature shall be measured not more than 1 m from the heated surface, but shielded from heat convection and radiation from the surface. The ambient temperature shall be within
23、the range 15 C to 35 C. 8.2.6 Dust layer temperature test method The apparatus shall be set up under a hood capable of extracting smoke and fumes. The temperature of the heated surface shall be adjusted to the desired value and shall be allowed to become steady within the prescribed limits of 8.2.2.
24、 The metal ring shall be filled with the dust to be tested and levelled off. The recording of the dust layer temperature shall then be started. The test shall be continued until it is ascertained either that the layer has ignited, or has heated above the plate temperature without igniting (self-heat
25、ing) and is subsequently cooling down. Ignition shall be considered to have occurred if: a) visible glowing or flaming is observed; or b) a temperature of 450 C is measured in the dust layer; or c) a temperature rise of 250 K above the temperature of the heated plate is measured in the dust layer. I
26、f, after a period of 30 min, no further temperature increase is apparent the test should be terminated and repeated at a higher temperature. If ignition occurs the test shall be repeated at a lower temperature, if necessary, prolonging the test beyond 30 min. Testing is continued until a temperature
27、 is found which is high enough to cause ignition in the layer, but which is no more than 10 K higher than a temperature which fails to cause ignition. Tests shall be repeated with fresh layers of dust until a minimum ignition temperature of the dust layer has been determined. This shall be the lowes
28、t temperature of the plate, rounded DIN EN ISO/IEC 80079-20-2:2016-12 EN ISO/IEC 80079-20-2:2016 (E) 21 down to the nearest integral multiple of 10 C, at which ignition occurs in a layer of given thickness. If the lowest temperature at which ignition occurs is already an integral multiple of 10 K, i
29、t is not rounded down by 10 K. The highest value of temperature at which ignition does not occur, or is deemed not to occur, shall also be recorded. This temperature shall not be more than 10 K lower than the minimum temperature at which ignition does occur, or is deemed to occur, and it shall be co
30、nfirmed by at least three tests. For the purpose of this standard, the tests shall be discontinued if ignition of a dust layer does not occur below a heated surface temperature of 400 C. This fact shall be reported as the result of the test. Times to obtain ignition, or times to reach the maximum te
31、mperature in the case of no ignition, shall be measured to the nearest 5 min from the time of placing the dust layer on to the heated surface, and shall be reported. Where a dust layer fails to ignite at a temperature of less than 400 C, the maximum duration shall be reported. 8.2.7 Recording of res
32、ults The report shall state that the determination of minimum ignition temperature of the dust layer has been carried out in accordance with this standard. The ignition tests shall be reported in the manner shown in Table 1 (showing results in descending order of surface temperature rather than in t
33、he order in which tests were performed): Table 1 Example of ignition test report Depth of layer Surface temperature Result of test Time to ignition or to reach the highest value of temperature without ignition Max. temperature in dust layer mm C min 5 180 Ignition 16 196 170 Ignition 36 193 160 No i
34、gnition 40 154 160 No ignition 38 156 160 No ignition 42 152 150 No ignition 62 141 The ignition temperature shall be recorded in accordance with 8.2.6 for each depth of layer. In the example given in Table 1 the minimum ignition temperature for the 5 mm layer would be recorded as 170 C. Tests in wh
35、ich the heated surface temperature differed by more than 20 K from the recorded minimum ignition temperature need not be reported. The test report shall then include a brief description of the nature of the combustion following ignition, noting especially behaviour such as unusually rapid combustion
36、 or violent decomposition. Factors likely to affect the significance of the results shall also be reported; these include difficulties in the preparation of layers, distortion of layers during heating, decrepitation, melting and evidence of flammable gas generated during heating of the dust. DIN EN
37、ISO/IEC 80079-20-2:2016-12 EN ISO/IEC 80079-20-2:2016 (E) 22 8.3 Method for determining minimum ignition energy of dust/air mixtures 8.3.1 General A test apparatus is described in this standard to measure the minimum ignition energy of a dust/ air mixture by an electrically generated high-voltage d.
38、c. spark. 8.3.2 Test equipment 8.3.2.1 Spark generation circuit Annex C describes some suitable forms of circuit, all of which shall have the following characteristics: the inductance of the discharge circuit shall be 1 mH to 2 mH except when the data is to be used for the assessment of electrostati
39、c discharges with low inductance when the inductance of the discharge circuit shall not exceed 25 H; the ohmic resistance of the discharge circuit shall be as low as possible and not more than 5 ; the electrode material shall be stainless steel, brass, copper or tungsten; electrode diameter and shap
40、e: (2,0 0,5) mm. Electrodes with rounded tips can be used to reduce corona effects that can occur with pointed electrodes, and which may give incorrect values of spark energy. If pointed electrodes are used, corona effects should be carefully considered; the electrode gap shall be 6 mm minimum; capa
41、citors shall be of the low-inductance type, resistant to surge current; the capacitance of the electrode arrangement shall be as low as possible; and insulation resistance between the electrodes shall be sufficiently high to prevent leakage currents. NOTE Typically, a minimum resistance between the
42、electrodes of 1012 is used for a minimum ignition energy of 1 mJ, and 1010 for a minimum ignition energy of 100 mJ. 8.3.2.2 Test vessel for determination of minimum ignition energies by electrically generated high-voltage d.c. sparks The recommended vessel is the modified Hartmann tube (see Figure 4
43、). Other vessels can be used, provided that the calibration requirements in 8.3.3 are met. A modified Hartmann tube made of transparent material with a volume of 1,2 l is used as the explosion vessel. The dust dispersion system at the base of the tube is of the “mushroom-shaped“ type around which th
44、e sample is loosely scattered. A blast of compressed air at 700 kPa overpressure is used to disperse the dust in the glass cylinder where it is ignited by a spark between two electrodes. DIN EN ISO/IEC 80079-20-2:2016-12 EN ISO/IEC 80079-20-2:2016 (E) 23 Figure 4 Modified Hartmann tube 8.3.3 Test pr
45、ocedure The combustible dust to be tested is uniformly dispersed in air at atmospheric pressure and temperature and the dust/air mixture is subjected to a spark discharge from a charged capacitor. The energy value of the discharge is calculated from the formula: W = 0,5 C U2where W is the stored ene
46、rgy in joules (J); C is the total discharge capacitance, in farads (F); U is the voltage of the charged capacitor in volts (V). NOTE 1 At spark energies above 100 mJ, the spark resistance can become so small that the circuit resistance is no longer negligible compared with the spark resistance, part
47、icularly when the circuit contains an inductance coil of the order of 1 mH. In such cases the net spark energy can be obtained from the equation: W = I(t) U(t)dt where I(t) is the spark current, and U(t) is the spark voltage; both of which are obtained by measurement. NOTE 2 Further information rela
48、tive to the calculation of spark energies is contained in Annex C. It is necessary to take account of the following possible influences on the test: Ignition delay time (i.e. turbulence); dust concentration; voltage to which the capacitor is charged; IEC DIN EN ISO/IEC 80079-20-2:2016-12 EN ISO/IEC 80079-20-2:2016 (E) 24
