1、Designation: E 582 07Standard Test Method forMinimum Ignition Energy and Quenching Distance inGaseous Mixtures1This standard is issued under the fixed designation E 582; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of minimumenergy for ignition (initiation of deflagration) and associatedfla
3、t-plate ignition quenching distances.2The complete descrip-tion is specific to alkane or alkene fuels admixed with air atnormal ambient temperature and pressure. This method isapplicable to mixtures of the specified fuels with air, varyingfrom the most easily ignitable mixture to mixtures near to th
4、elimit-of-flammability compositions.1.2 Extensions to other fuel-oxidizer combinations, and toother temperatures and pressures can be accomplished with allthe accuracy inherent in this method if certain additionalconditions are met: ( a) mixture stability and compatibility withbomb, seal, and other
5、materials is established through timetests described in Section 9;(b) the expected peak pressurefrom the test is within the pressure rating of the bomb(established as required by the particular research laboratory);(c) spark breakdown within the bomb is consistent withPaschens law for the distance b
6、eing tested; (d) the tempera-ture, including that of the discharge electrodes, is uniform; and(e) if the temperature is other than ambient, the energy storagecapacitance required is less than about 9 pF.1.3 This method is one of several being developed byCommittee E-27 for determining the hazards of
7、 chemicals,including their vapors in air or other oxidant atmospheres. Themeasurements are useful in assessing fuel ignitability hazardsdue to static or other electrical sparks. However, the quenchingdistance data must be used with great prudence since they areprimarily applicable to the ignition st
8、age and therefore, repre-sent values for initial pressure and not the smaller valuesexisting at higher pressures.1.4 This standard should be used to measure and describethe properties of materials, products, or assemblies in responseto heat and flame under controlled laboratory conditions andshould
9、not be used to describe or appraise the fire hazard orfire risk of materials, products, or assemblies under actual fireconditions. However, results of this test may be used aselements of a fire risk assessment which takes into account allof the factors which are pertinent to an assessment of the fir
10、ehazard of a particular end use.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitati
11、ons prior to use. Specific safetyprecautions are listed in Section 5.2. Terminology2.1 Definitions:2.1.1 Ignition, nthe initiation of combustion.2.1.2 Minimum Ignition Energy (MIE), nelectrical energydischarged from a capacitor, which is just sufficient to effectignition of the most easily ignitable
12、 concentration of fuel in airunder the specific test conditions.2.2 Definition of Terms Specific to This Standard:2.2.1 Ignition Quenching Distance, nMaximum spacingbetween eletrode flanges that will not permit spark ignition andflame propagation beyond the flanges, when tested under thespecified te
13、st conditions.3. Significance and Use3.1 The minimum energies provide a basis for comparingthe ease of ignition of gases. The flatplate ignition quenchingdistances provide an important verification of existing mini-mum ignition energy data and give approximate values of thepropagation quenching dist
14、ances of the various mixtures. It isemphasized that maximum safe experimental gaps, as from“flame-proof” or “explosion-proof” studies, are less than theflat-plate ignition quenching distances.4. Apparatus4.1 Reaction VesselThe recommended reaction vessel ismanufactured according to the specification
15、s of Fig. 1 and Fig.2. This is a spherical vessel, manufactured of Type 304stainless steel, and passivated after machining. The sphericalgeometry maximizes the useable spark-gap length for a givenvessel volume. The reaction vessel provides for opposed1This test method is under the jurisdiction of AS
16、TM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.04 onFlammability and Ignitability of Chemicals.Current edition approved Jan. 1, 2007. Published February 2007. Originallyapproved in 1976. Last previous edition approved in 2004 as E 582 04.2Litchf
17、ield, E. L., Hay, M. H., Kubala, T. S., and Monroe, J. S.,“ MinimumIgnition Energy and Quenching Distance in Gaseous Mixtures, BuMines, R. L.7009, August 1967, 11 pp.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.mounting of the spa
18、rk electrodes which permits rapid andconvenient variation of the gap length without the necessity foropening the vessel. The input orifice (Fig. 2, Section A-A)islocated so that the gases are introduced approximately tangen-tially to the vessel walls, thus providing a turbulent swirlingmotion that f
19、acilitates mixing. A sight glass permits directobservation of flame initiation and propagation throughout thereaction volume.4.2 Electrode Assembly:4.2.1 The electrodes (Fig. 1) have metal tips flanged withglass plates. The tips screw into18-in. stainless steel rodswhich extend through inserts in th
20、e bomb walls to permitexternal electrical connections. Gas seals are provided betweenthe reaction vessel and the inserts and between the inserts andthe18-in. rods by O-ring seals (see Fig. 2, Assembly). Theglass flange material should be either borosilicate or high silicaand the flanges should be fa
21、stened to the stainless steel tipswith a thin layer of epoxy cement. The facing surfaces shouldNOTE 1Tolerance is 6 0.010 in., unless noted.NOTE 2Break all sharp edges.NOTE 3Material is Type 304 stainless steel.NOTE 4Thread depth is 75 to 80 %.NOTE 51 in. = 25.4 mm.FIG. 1 Electrode Assembly (I)E5820
22、72be planar and coplanar to 0.001 in. (0.025 mm) or 1 % of theintended test gap, whichever is larger.4.2.2 Two inserts are required to carry the18-in. rodsthrough the walls of the reaction vessel. At least one of theseinserts must be made of high-electrical resistivity insulatingmaterial. Hard rubbe
23、r, phenolic plastic, poly(methyl methacry-alate) (PMMA), and many other materials are suitable for usewith the alkane and alkene fuels. In the excepted cases (othersimilarly energetic fuels), the insulating material must not reactwith or absorb the fuel being tested.4.2.3 Where the test arrangement
24、is optimized through theuse of a “double-ended power supply, (see Fig. 3(b) twoinsulating inserts are required. Otherwise, one of the insertsmay be machined from Type 304 stainless steel.4.2.4 Insulation between the two electrodes should exceed1012V as discussed in 4.3.3.4.2.5 Measurement of the gap
25、 width is made by availabletechniques and implements most suitable for the gap distancebeing measured. Calibrated leaf gages, inside micrometers, orvernier calipers are suitable, depending upon the gap distance.NOTE 1Tolerance is 6 0.010 in., unless noted.NOTE 2Break all sharp edges.NOTE 3Material i
26、s Type 304 stainless steel.NOTE 4Thread depth is 75 to 80 %.NOTE 51 in. = 25.4 mm.FIG. 2 Electrode Assembly (II).E582073The measurements should be made with a repeatability of60.001 in. (0.025 mm) or 1 %, whichever is most conserva-tive. To facilitate such measurements, it is helpful to have leafgag
27、es of known thicknesses for frequently used gap distances.High-quality machinists micrometers will generally provideadequate accuracy.4.3 Power Supply and Electrical Circuit:4.3.1 The power supply should be of the oscillator type, sothat its filter condensers will be electrically small. The maxi-mum
28、 output current should be about 1 mA.NOTE 1Caution: With such a power supply, the probability of lethalshock to the operator from the high-voltage circuits becomes negligible.However, all usual and normal hazards to personnel will exist on the60-Hz supply, main-side of the power supply.4.3.2 The pow
29、er supply can be single-side with one high-voltage output terminal and one low-voltage, neutral, or groundterminal (see Fig. 3(a).Alternatively, the power supply may bedouble-ended with two high-voltage output terminals, onenegative and one positive, together with a center-tappedgrounding or neutral
30、 connection (see Fig. 3(b). For maximumtesting flexibility, the power supply should deliver variable oradjustable output voltage differences between 1 and 30 kV.NOTE 2The double-ended power supply should be used only inconjunction with two insulating inserts. The metal bomb structure mustthen be con
31、nected to the power supply center point and connected tosystem ground. The double-ended power supply gives somewhat highergap breakdown voltages at larger spark gaps and, thus, somewhat lowerignition energies. This consideration should be of importance only if thevery highest quality data are requir
32、ed.4.3.3 The output filter capacitors of the power supply mustbe isolated from the discharge energy storage capacitance byan isolating resistor. The resistive-capacitive time constant ofthe charging circuit containing the energy storage capacitanceshould be several seconds; 1012V is a desirable valu
33、e for themost easily ignitable mixture (energy storage capacitance of 8to 12 pF) with the value reduced inversely as the energystorage capacitance is increased for less easily ignitable mix-tures. Two resistors should be used in series, four with thedouble-ended supply. One resistor shall be immedia
34、tely at thepower supply terminal, the other at the bomb energy storagecapacitance. Supply-line electrical insulation needs to begreater than 1014V to be consistent with 1012V seriesresistance. Such resistance is most easily achieved through airinsulation with appropriately rounded corners to reduce
35、coronalosses.4.4 Measurement of Energy Storage CapacitanceThe en-ergy storage capacitance may be measured with a high-qualitycapacitance meter capable of accurate measurement in therange of 5 pF, or greater, capacity. Lower frequency instru-ments are generally preferred, since problems of lead lengt
36、hand spurious readings are minimized. If the capacitance meteris nulled with the test probe at some distance from the bomb,proximity effects will be observed as the test probe is broughtcloser to the bomb and energy-storage capacitance. Theseproximity effects must be nulled out to achieve accurate e
37、nergystorage capacitance determinations.NOTE 1Distributed capacitance must be considered as part of the energy storage capacitance.NOTE 2See 4.3 for component value guidelines.FIG. 3 Connections of Single and Double-Sided Power Supply in Circuit.E5820744.5 Measurement of Energy Storage VoltageEnergy
38、 stor-age voltage cannot ordinarily be measured with an electrostaticvoltmeter for the most easily ignitable mixtures, since themeter capacitance will probably exceed the desired energystorage capacitance. In these instances, energy storage voltagemust be measured with an electrometer voltmeter used
39、 inconjunction with a voltage divider network. Total resistance ofthe divider network should be at least 1014V.4.6 Gas-Handling SystemPlumbing for the gas-handlingsystem should be of stainless steel. A vacuum gage in thesystem is necessary and access to ambient temperature andbarometric data is desi
40、rable. Gas shut-off valves should be ofgood quality and suitable to the service.5. Safety Precautions5.1 If the recommendations of 4.3 are followed, there are nohigh-voltage hazards. The normal 60-Hz supply line hazardsexist as always when equipment is operated from such lines. Inthe interest of sta
41、bility, it is desirable to have the high-voltagepower supply and electrometer voltmeter turned-on continu-ously during a normal working period. In this case, the voltageoutput control of the power supply should be turned to itsminimum value except during the actual test. The two sparkelectrodes shou
42、ld be shorted together by two clips and a shortpiece of flexible braid. If two insulating inserts are used (4.2),the center of the braid should be connected to the metal of thereaction vessel.5.2 Normal pressure vessel problems exist, therefore, thesight glass must be in good condition and adequatel
43、y seated;and the bolts holding the two parts of the bomb together andthe insert-retaining rings must be in place and tightened. Caremust be given to the preparation of the gas mixture. The twocomponents must not be permitted to mix in the supply lines,both for reasons of personnel safety and to ensu
44、re a mixture ofknown composition.6. Preparation of Apparatus6.1 Clean the test vessel to remove residues from previoustests or if required by 6.2.6.2 Verify that the insulation resistance of high-voltageelectrode(s) to the reaction vessel walls is at least 1012V .Disassemble and clean if required.6.
45、3 Set up the desired test gap in the reaction vessel.6.4 Determine the desired energy storage capacitance (seeSection 8) and set up this value with calibrated electricalcapacitors rated for the anticipated test voltage. The smallervalues of capacitance should be trimmed with lengths of wireor metal
46、rods.7. Procedure7.1 Evacuate the reaction vessel to absolute pressures below10 mmHg (13.33 Pa).7.2 Load the desired gas mixture, as determined from thecalculations, observing the necessary safety considerations ofSection 5. First, add the minor constituent (fuel) to the desiredpartial pressure of f
47、uel. Close the main valve to the reactionvessel and evacuate the supply lines. Introduce the majorcomponent (air) into the supply lines to a pressure greater thanthat of the fuel in the reaction vessel. Open the main valve andfill the reaction vessel to the desired total pressure, then closethe main
48、 valve.NOTE 3This method of mixing, in conjunction with the mixing orificein the reaction vessel of Section A-A of Fig. 2, offers maximum uniformityand accuracy in the prepared gas mixture. When used to preparevapor-oxidizer mixtures, this method minimizes the possibility of vaporcondensation.NOTE 4
49、Experimenters desiring to use other techniques of mixturepreparation and sample injection should bear the responsibility of estab-lishing the adequacy of those techniques.7.3 Remove the electrode shunting connections.7.4 Gradually increase the applied voltage until a sparkoccurs between the spark gap electrodes. Immediately reducethe applied voltage. If no ignition is observed, repeat this forabout five sparks. If ignition is not observed then proceed asfollows:7.4.1 If breakdown voltage is in accordance with expecta-tions, either increase the energy
