1、Designation: G 125 00Standard Test Method forMeasuring Liquid and Solid Material Fire Limits in GaseousOxidants1This standard is issued under the fixed designation G 125; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last 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 a procedure for measuring thethreshold-limit conditions to allow equilibrium of combustionof
3、materials in various oxidant gases under specific testconditions of pressure, temperature, flow condition, fire-propagation directions, and various other geometrical featuresof common systems.1.2 This test method is patterned after Test Method D 2863-95 and incorporates its procedure for measuring t
4、he limit as afunction of oxidant concentration for the most commonly usedtest conditions. Sections 8, 9, 10, 11, 13, and 14 for the basicoxidant limit (oxygen index) procedure are quoted directlyfrom Test Method D 2863-95. Oxygen index data reported inaccordance with Test Method D 2863-95 are accept
5、able sub-stitutes for data collected with this standard under similarconditions.1.3 This test method has been found applicable to testingand ranking various forms of materials. It has also foundlimited usefulness for surmising the prospect that materials willprove “oxygen compatible” in actual syste
6、ms. However, itsresults do not necessarily apply to any condition that does notfaithfully reproduce the conditions during test. The fire limit isa measurement of a behavioral property and not a physicalproperty. Uses of these data are addressed in Guides G 63 andG 94.NOTE 1Although this test method
7、has been found applicable fortesting a range of materials in a range of oxidants with a range of diluents,the accuracy has not been determined for many of these combinations andconditions of specimen geometry, outside those of the basic procedure asapplied to plastics.NOTE 2Test Method D 2863-95 has
8、 been revised and the revised TestMethod has been issued as D 2863-97. The major changes involve sampledimensions, burning criteria and the method for determining the oxygenindex. The aim of the revisions was to alignTest Method D 2863 with ISO4589-2. Six laboratories conducted comparison round robi
9、n testing onself-supporting plastics and cellular materials using D 2863-95 andD 2863-97. The results indicate that there is no difference between themeans provided y the two methods at the 95 % confidence level. Nocomparison tests were conducted on thin films. The majority of ASTMCommittee G4 favor
10、s maintaining the D 2863-95 as the backbone ofG 125 until comprehensive comparison data become available.1.4 One very specific set of test conditions for measuringthe fire limits of metals in oxygen has been codified in TestMethod G 124. Test Method G 124 measures the minimumpressure limit in oxygen
11、 for its own set of test conditions. Itsdetails are not reproduced in this standard. A substantialdatabase is available for this procedure, although it is muchsmaller than the database for Test Method D 2863-95.NOTE 3Warning: During the course of combustion, gases, vapors,aerosols, fumes or any comb
12、ination of these are evolved which may behazardous.NOTE 4Precaution: Adequate precautions should be taken to protectthe operator.1.5 The values stated in SI units are to be regarded as thestandard.1.6 This basic standard should be used to measure anddescribe the properties of materials, products, or
13、 assemblies inresponse to heat and flame under controlled laboratory con-ditions and should not be used to directly describe or appraisethe fire hazard or fire risk of materials, products or assembliesunder actual fire conditions. However, results of this test maybe used as elements of a fire risk a
14、ssessment which takes intoaccount all of the factors which are pertinent to an assessmentof the fire hazard of a particular end use. The standard hasmore applicability in this regard at predicting the fire behaviorof materials and components that are close in size to the testcondition, than for syst
15、ems that are much different (for ex-ample: comparing a test rod to a valve seat rather thancomparing a test rod to a house or a particle)1.7 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 e
16、stablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 618 Practice for Conditioning Plastics and ElectricalInsulating Materials for Testing21This test method is under the jurisdiction of A
17、STM Committee G04 onCompatibility and Sensitivity of Materials in Oxygen-Enriched Atmospheres and isthe direct responsibility of Subcommittee G4.01 on Test Methods. Portions havebeen adopted from Test Method D 2863 95 that is under the jurisdiction of ASTMCommittee D20 on Plastics.Current edition ap
18、proved Nov. 10, 2000. Published January 2001. Originallypublished as G 125 95. Last previous edition G 125 95.2Annual Book of ASTM Standards, Vol 08.01.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.D 1071 Test Method for Volumetric Measurement of Gas-eous Fu
19、el Samples3D 2444 Test Method for Impact Resistance of Thermoplas-tic Pipe and Fittings by Means of a Tup (Falling Weight)4D 2863-95 Test Method for Measuring the Minimum Oxy-gen Concentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)5D 2863-97 Test Method for Measuring the Minimum
20、 Oxy-gen Concentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)6G 63 Guide for Evaluating Nonmetallic Materials for Oxy-gen Service7G 94 Guide for Evaluating Metals for Oxygen Service7G 124 Test Method for Determining the Combustion Be-havior of Metallic Materials in Oxygen-Enrich
21、ed Atmo-spheres7G 128 Guide for the Control of Hazards and Risks inOxygen Systems72.2 Other Standards:ISO 4589-2 PlasticsDetermination of burning behaviorby oxygen indexPart 2: Ambient temperature test83. Terminology3.1 Definitions:3.1.1 oxygen compatibility, nthe ability of a substance tocoexist wi
22、th both oxygen and a potential source(s) of ignitionwithin the acceptable risk parameter of the user (at an expectedpressure and temperature). (See Guide G 128.)3.1.2 oxygen index, nthe minimum concentration of oxy-gen, expressed as a volume percent, in a mixture of oxygen andnitrogen that will just
23、 support flaming combustion of a materialinitially at room temperature under the conditions of TestMethod D 2863. (See Test Method D 2863.)3.2 Definitions of Terms Specific to This Standard:3.2.1 fire limit, nthe threshold limit conditions that willjust support sustained combustion of a material und
24、er acombination of specified conditions and at least one variableparameter (typically oxidant concentration, diluent nature,pressure, temperature, geometry, flow or flame parameters,etc.).3.2.2 oxidant compatibility, nthe ability of a substance tocoexist with both an oxidant and a potential source(s
25、) ofignition within the acceptable risk parameter of the user (at anexpected pressure and temperature).3.2.3 oxidant index, nthe minimum concentration of anoxidant such as oxygen, nitrous oxide, fluorine, etc., expressedas a volume percent, in a mixture of the oxidant with a diluentsuch as nitrogen,
26、 helium, carbon dioxide, etc., that will justsupport sustained combustion of a material initially at givenconditions of temperature, pressure, flow conditions, propaga-tion direction, etc. (See also, oxygen index.)3.2.3.1 DiscussionThe oxidant index may be more spe-cifically identified by naming the
27、 oxidant: oxygen limit (orindex), nitrous oxide limit (or index), fluorine limit (or index),etc. Unless specified otherwise, the typical oxidant is taken tobe oxygen, the typical diluent is taken to be nitrogen, and thetypical temperature is taken as room temperature.3.2.4 pressure limitthe minimum
28、pressure of an oxidant(or mixture) that will just support sustained combustion of amaterial initially at given conditions of oxidant concentration,temperature, flow condition, propagation direction, etc.3.2.4.1 DiscussionThe pressure limit may be more spe-cifically identified by naming the oxidant:
29、oxygen pressurelimit, nitrous oxide pressure limit, fluorine pressure limit, etc.3.2.5 temperature limitthe minimum temperature of anoxidant (or mixture) that will just support sustained combus-tion of a material initially at given conditions of oxidantconcentration, temperature, flow condition, pro
30、pagation direc-tion, etc.3.2.5.1 DiscussionThe temperature limit may be morespecifically identified by naming the oxidant: oxygen tempera-ture limit, nitrous oxide temperature limit, fluorine temperaturelimit, etc.4. Summary of Test Method4.1 The threshold limit condition (minimum oxidant con-centra
31、tion, minimum pressure, minimum temperature, etc.) thatwill just support sustained combustion under equilibriumconditions is measured in a test apparatus. The equilibrium isestablished by the relation between the heat generated from thecombustion of the specimen (that may be augmented by theheat of
32、decomposition of some oxidants) and the heat lost tothe surroundings as measured by one or the other of twoarbitrary criteria, namely, a time of burning or a length ofspecimen burned. This point is approached from both sides ofthe critical threshold condition in order to establish the firelimit.5. S
33、ignificance and Use5.1 This test method provides for measuring of the mini-mum conditions of a range of parameters (concentration ofoxidant in a flowing mixture of oxidant and diluent, pressure,temperature) that will just support sustained propagation ofcombustion. For materials that exhibit flaming
34、 combustion,this is a flammability limit similar to the lower flammability9limit, upper flammability limit, and minimum oxidant forcombustion of gases (1). However, unlike flammability limitsfor gases, in two-phase systems, the concept of upper andlower flame limits is not meaningful. However, limit
35、s cantypically be determined for variations in other parameters suchas the minimum oxidant for combustion (the oxidant index),the pressure limit, the temperature limit, and others. Measure-ment and use of these data are analogous to the measurementand use of the corresponding data for gaseous system
36、s. That is,the limits apply to systems likely to experience completepropagations (equilibrium combustion). Successful ignition3Annual Book of ASTM Standards, Vol 05.05.4Annual Book of ASTM Standards, Vol 08.04.51995 Annual Book of ASTM Standards, Vol 08.02.6Annual Book of ASTM Standards, Vol 08.02.7
37、Annual Book of ASTM Standards, Vol 14.04.8ISO 4589-2 First edition 1996-07-15, International Organization for Standard-ization, Geneve, Switzerland, 1996.9The boldface numbers in parenthesis refer to the references listed at the end ofthis guide.G 1252and combustion below the measured limits at othe
38、r conditionsor of a transient nature are not precluded below the threshold.Flammability limits measured at one set of conditions are notnecessarily the lowest thresholds at which combustion canoccur. Therefore direct correlation of these data with theburning characteristics under actual use conditio
39、ns is notimplied.6. Abstract6.1 A well-established procedure for measuring an oxidantlimit, the oxygen index, of plastics (See Test Method D 2863)is reviewed, then variations commonly used to collect data foroxidant compatibility purposes are described. In the test, aseries of specimens is placed in
40、 a preadjusted oxidant mixtureand deliberately ignited. Specimens that do not “burn” areretested in higher concentrations. Specimens that do burn areretested in lower concentrations. When the operator is confi-dent that the threshold has been determined by a suitablenumber and spread of negative tes
41、ts below the threshold, thelowest positive is reported as the oxidant index.6.2 Similar test methods apply when the oxidant concentra-tion is held constant and the temperature, pressure or other keyfactor is varied. In some cases, apparatus modification orreplacement is necessary, such as a pressuri
42、zed vessel isrequired to complete some tests (see Test Method G 124).Relatively little work (1-18) has been done using oxidantsother than oxygen, diluents other than nitrogen, pressure,temperature, or other properties as the variable parameter.7. Variations7.1 A number of variations of the procedure
43、 have been used.The principle variables have been oxidant, diluent, pressure,temperature, flow condition and flow direction. Relatively littlework has been done for most of these variables (1-18). Thereis some qualitative and even quantitative understanding of themanner in which these variables affe
44、ct the fire limits ofmaterials, but the understanding is largely incomplete. Finally,the database for most combinations of variables is small (onlyTest Method D 286395 and Test Method G 124 have signifi-cant databases) and so the ability to draw strong conclusions islimited. Nonetheless, where data
45、is obtained for two or morematerials, these data are useful to the evaluation of thosematerials. Care is necessary in comparing materials that havenot been tested in similar procedures.7.2 OxidantsChanging the oxidant may cause the greatestchanges in results for other constant conditions (1, 2, 3).O
46、xidants behave dramatically different, because their basicchemistry with differing materials is different. For example,even though nitrous oxide is a combination of nitrogen andoxygen, it behaves much differently than a similar oxygen/nitrogen mixture. During combustion, nitrous oxide decom-poses to
47、 release heat that renders it more able to supportcombustion than a simple mixture. Fluorine is very reactiveand produces more gaseous product species which changes itsbehavior in higher purity oxidant. There are data available invarying amounts for the oxidants: oxygen, nitrous oxide,fluorine, nitr
48、ogen trifluoride, and nitrogen (nitrogen is anoxidant in some cases, a diluent in others).7.3 DiluentsVarying diluents can have a significant effectalthough much less impressive than oxidant, pressure or evenflow direction (1-8). Diluents thermal conductivity and heatcapacity appear to be the most s
49、ignificant properties. Reactivityis a second issue. For example, nitrogen does not participate inmost polymer combustions but can react with some metals andexhibit widely different diluent natures. Among the diluentsused to date are nitrogen, helium, argon, carbon dioxide, neon,and xenon.7.4 PressuresPressure has a dramatic effect on the firelimit (1, 4, 5, 8, 9, 10, 11). The role of pressure is complex, yetit is one of the most important variables because oxygensystems employ a range of pressures to 82 MPa (12000 psig).7.5 TemperaturesThe fole of temperature ap
