1、Designation: G 125 00 (Reapproved 2008)Standard 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 revi
2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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
3、 of combustionof 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 MethodD 2863-95 and incorporates its procedure
4、 for measuring thelimit as a function of oxidant concentration for the mostcommonly used test conditions. Sections 8, 9, 10, 11, 13, and14 for the basic oxidant limit (oxygen index) procedure arequoted directly from Test Method D 2863-95. Oxygen indexdata reported in accordance with Test Method D 28
5、63-95 areacceptable substitutes for data collected with this standardunder similar conditions.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” i
6、n actual systems. 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 andG94.NOTE 1Although this
7、 test method 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
8、D 2863-95 has 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 align Test Method D 2863 withISO 4589-2. Six laboratories conducted compari
9、son round robin 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 ASTMComm
10、ittee G4 favors 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 l
11、imit in oxygen 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.(WarningDuring the course of combustion, gases, vapors,aerosols, fumes or a
12、ny combination of these are evolved whichmay be hazardous.) (WarningAdequate precautions shouldbe taken to protect the operator.)1.5 The values stated in SI units are to be regarded as thestandard. No other units of measurement are included in thisstandard.1.6 This basic standard should be used to m
13、easure anddescribe the properties of materials, products, or 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,
14、results of this test maybe used as elements of a fire risk assessment 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 component
15、s that are close in size to the testcondition, than for systems 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)1This test method is under the jurisdiction of ASTM Committee G04 onCompatibility and Sensitivity of Ma
16、terials in Oxygen Enriched Atmospheres and isthe direct responsibility of Subcommittee G04.01 on Test Methods. Portions havebeen adopted from Test Method D 2863-95 that is under the jurisdiction of ASTMCommittee D20 on Plastics.Current edition approved April 1, 2008. Published July 2008. Originallya
17、pproved in 1995. Last previous edition approved in 2000 as G 125 00.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is there
18、sponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 1071 Test Methods for Volumetric Me
19、asurement of Gas-eous Fuel SamplesD 2444 Test Method for Determination of the Impact Re-sistance of Thermoplastic Pipe and Fittings by Means of aTup (Falling Weight)D 2863 Test Method for Measuring the Minimum OxygenConcentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)D 2863-95 T
20、est Method for Measuring the Minimum Oxy-gen Concentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)3D 2863-97 Test Method for Measuring the Minimum Oxy-gen Concentration to Support Candle-Like Combustion ofPlastics (Oxygen Index)3G63 Guide for Evaluating Nonmetallic Materials for
21、Oxy-gen ServiceG94 Guide for Evaluating Metals for Oxygen ServiceG 124 Test Method for Determining the Combustion Be-havior of Metallic Materials in Oxygen-Enriched Atmo-spheresG 128 Guide for Control of Hazards and Risks in OxygenEnriched Systems2.2 Other Standards:ISO 4589-2 PlasticsDetermination
22、of burning behaviorby oxygen indexPart 2: Ambient temperature test43. Terminology3.1 Definitions:3.1.1 oxygen compatibility, nthe ability of a substance tocoexist with both oxygen and a potential source(s) of ignitionwithin the acceptable risk parameter of the user (at an expectedpressure and temper
23、ature). (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 support flaming combustion of a materialinitially at room temperature under the conditions of TestMethod D 2863. (See Test Method D 28
24、63.)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 under acombination of specified conditions and at least one variableparameter (typically oxidant concentration, diluent nature,pressure, t
25、emperature, 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) ofignition within the acceptable risk parameter of the user (at anexpected pressure and temperature).3.2.3 oxidant index, nthe minimu
26、m 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, helium, carbon dioxide, etc., that will justsupport sustained combustion of a material initially at givenconditions of temperature, pr
27、essure, 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 oxidant: oxygen limit (orindex), nitrous oxide limit (or index), fluorine limit (or index),etc. Unless specified otherwise, the typica
28、l 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 pressure of an oxidant(or mixture) that will just support sustained combustion of amaterial initially at given conditions of oxidant co
29、ncentration,temperature, flow condition, propagation direction, etc.3.2.4.1 DiscussionThe pressure limit may be more spe-cifically identified by naming the oxidant: oxygen pressurelimit, nitrous oxide pressure limit, fluorine pressure limit, etc.3.2.5 temperature limitthe minimum temperature of anox
30、idant (or mixture) that will just support sustained combus-tion of a material initially at given conditions of oxidantconcentration, temperature, flow condition, propagation direc-tion, etc.3.2.5.1 DiscussionThe temperature limit may be morespecifically identified by naming the oxidant: oxygen tempe
31、ra-ture limit, nitrous oxide temperature limit, fluorine temperaturelimit, etc.4. Summary of Test Method4.1 The threshold limit condition (minimum oxidant con-centration, minimum pressure, minimum temperature, etc.) thatwill just support sustained combustion under equilibriumconditions is measured i
32、n 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 decomposition of some oxidants) and the heat lost tothe surroundings as measured by one or the other of twoarbitrary criteria, namely,
33、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. Significance and Use5.1 This test method provides for measuring of the mini-mum conditions of a range of parameters (concentration ofoxi
34、dant in a flowing mixture of oxidant and diluent, pressure,temperature) that will just support sustained propagation ofcombustion. For materials that exhibit flaming combustion,2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. F
35、or Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4ISO 4589-2 First edition 1996-07-15, International Organization for Standard-ization, Geneve, Switzerland, 1996.G 125 00 (2008)2this is a flammability limit similar to the
36、lower flammability5limit, 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, limits cantypically be determined for variations in other par
37、ameters 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 systems. That is,the limits apply to systems likely to experie
38、nce completepropagations (equilibrium combustion). Successful ignitionand combustion below the measured limits at other 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 com
39、bustion canoccur. Therefore direct correlation of these data with theburning characteristics under actual use conditions 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 commonl
40、y used to collect data foroxidant compatibility purposes are described. In the test, aseries of specimens is placed in a preadjusted oxidant mixtureand deliberately ignited. Specimens that do not “burn” areretested in higher concentrations. Specimens that do burn areretested in lower concentrations.
41、 When the operator is confi-dent that the threshold has been determined by a suitablenumber and spread of negative tests 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, press
42、ure or other keyfactor is varied. In some cases, apparatus modification orreplacement is necessary, such as a pressurized 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, pressu
43、re,temperature, or other properties as the variable parameter.7. Variations7.1 Anumber of variations of the procedure 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 vari
44、ables (1-18). Thereis some qualitative and even quantitative understanding of themanner in which these variables affect the fire limits ofmaterials, but the understanding is largely incomplete. Finally,the database for most combinations of variables is small (onlyTest Method D 2863-95 and Test Metho
45、d G 124 have signifi-cant databases) and so the ability to draw strong conclusions islimited. Nonetheless, where data 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 procedur
46、es.7.2 OxidantsChanging the oxidant may cause the greatestchanges in results for other constant conditions (1, 2, 3).Oxidants behave dramatically different, because their basicchemistry with differing materials is different. For example,even though nitrous oxide is a combination of nitrogen andoxyge
47、n, it behaves much differently than a similar oxygen/nitrogen mixture. During combustion, nitrous oxide decom-poses to 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 hi
48、gher purity oxidant. There are data available invarying amounts for the oxidants: oxygen, nitrous oxide,fluorine, nitrogen 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
49、 oxidant, pressure or evenflow direction (1-8). Diluents thermal conductivity and heatcapacity appear to be the most significant 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 variable
