1、Designation: E918 83 (Reapproved 2011)Standard Practice forDetermining Limits of Flammability of Chemicals at ElevatedTemperature and Pressure1This standard is issued under the fixed designation E918; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, 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 practice covers the determination of the lower andupper concentration limits of fla
3、mmability of combustiblevapor-oxidant mixtures at temperatures up to 200C and initialpressures up to as much as 1.38 MPa (200 psia). This practiceis limited to mixtures which would have explosion pressuresless than 13.79 MPa (2000 psia).1.2 This practice should be used to measure and describethe pro
4、perties of materials, products, or assemblies in responseto heat and flame under controlled laboratory conditions andshould 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 ase
5、lements of a fire risk assessment which takes into account allof the factors which are pertinent to an assessment of the firehazard of a particular end use.1.3 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety proble
6、ms associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E681 Test Method for Concentration Limits of Flammabil
7、-ity of Chemicals (Vapors and Gases)2.2 Other Documents:Bulletin 503 Bureau of Mines, “Limits of Flammability ofGases and Vapors,” NTIS AD701575Bulletin 627 Bureau of Mines, “Flammability Characteris-tics of Combustible Gases and Vapors,” NTIS AD7015763. Terminology3.1 Definitions:3.1.1 lower limit
8、of flammability or lower flammable limit(LFL)the minimum concentration of a combustible sub-stance that is capable of propagating a flame through ahomogeneous mixture of the combustible and a gaseousoxidizer under the specified conditions of test.3.1.2 upper limit of flammability or upper flammable
9、limit(UFL)the maximum concentration of a combustible sub-stance that is capable of propagating a flame through ahomogeneous mixture of the combustible and a gaseousoxidizer under the specified conditions of test.3.2 Definitions of Terms Specific to This Standard:3.2.1 propagation of flamesas used in
10、 this practice,acombustion reaction that produces at least a 7 % rise of theinitial absolute pressure,P2P11.07.NOTE 1This 7 % rise in pressure corresponds to 1 psia (0.007 MPa)per atmosphere of initial pressure.4. Summary of Practice4.1 A mixture of gaseous or vaporized fuel with a gaseousoxidizer i
11、s prepared in a steel or other appropriate metal vesselat a controlled temperature and pressure. Proportions of thecomponents are determined by measurement of partial pres-sures during filling of the vessel. Ignition of the mixture isattempted with a fuse wire, and flammability is deduced fromthe pr
12、essure rise produced. Fuel concentration is varied be-tween trials until the limits of flammability have been deter-mined. Composition of the mixtures which fix the flammablelimits are confirmed by appropriate analysis.5. Significance and Use5.1 Knowledge of flammable limits at elevated temperatures
13、and pressures is needed for safe and economical operation ofsome chemical processes. This information may be needed in1This practice is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.04 onFlammability and Ignitability
14、 of Chemicals.Current edition approved Aug. 1, 2011. Published August 2011. Originallyapproved in 1983. Last previous edition approved in 2005 as E918 83 (2005).DOI: 10.1520/E0918-83R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
15、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.order to start up a reactor without passing through a flamma
16、blerange, to operate the reactor safely and economically, or tostore or ship the product safely.5.2 Limits of flammability data obtained in relatively cleanvessels must be carefully interpreted and may not always beapplicable to industrial conditions. Surface effects due tocarbon deposits and other
17、materials can significantly affectlimits of flammability, especially in the fuel-rich region. Referto Bulletin 503 and Bulletin 627.6. Limitations6.1 This practice is not applicable to mixtures which un-dergo spontaneous reaction before ignition is attempted.6.2 Measured limits of flammability are i
18、nfluenced byflame-quenching effects of the test vessel walls. The vesseldescribed in this practice is suitable for use with most mixturesat elevated temperatures and pressures. For certain amines,halogenated materials etc., which have large ignition-quenching distances, tests may need to be conducte
19、d in largerdiameter vessels.7. Apparatus7.1 Fig. 1 is a schematic diagram of the apparatus; detailsand dimensions are presented in Annex A1. The apparatusconsists of a metal pressure vessel with a minimum volume of1 L and a minimum inside diameter of 76 mm (3 in.), aninsulated chamber equipped with
20、a source of controlled-temperature inert gas, an ignition device with appropriatepower supply, remotely controlled valves, pressure measuringequipment, and a venting system for handling overpressuring.8. Safety Precautions8.1 Adequate shielding must be provided to prevent injuryin the event of equip
21、ment rupture. The apparatus is set up sothat the operator is isolated by a blast-proof wall from the testvessel while the vessel contains a charge of reactants, includingthe time while the vessel is being filled. The test apparatusshould be equipped with interlocks so that the ignition sourcecannot
22、be activated unless the operator has taken necessarysteps to protect personnel and equipment. Activation of theignition source should be possible only from a positionshielded from the test vessel.8.2 The test vessel shall be fitted with a rupture disk ventedoutside any enclosed area. Fuel may inadve
23、rtently be ventedinside the heated chamber or inside the enclosed area, so theheated chamber should be fitted with an inert gas purge and theFIG. 1 Schematic Diagram of Test ApparatusE918 83 (2011)2area should be adequately ventilated to prevent buildup of anexplosive mixture in the large space.8.3
24、Undesirably energetic explosions may be produced iftests are made at high initial pressures with mixtures wellwithin the flammable range. Very strong oxidizers greatlyincrease explosion severity and also greatly increase thefuel-rich limit. To help in avoiding testing highly energeticmixtures, limit
25、s of flammability should first be determined atatmospheric pressure. These limits are covered in MethodE681. With this knowledge, the operator should proceed incautious steps of initial pressure increase to work at higherpressures and temperatures.9. Preparation of Apparatus9.1 Clean and dry the tes
26、t vessel and other gas-handlingequipment. Make sure that no oil, grease, or other combustibleis left inside the parts.9.2 Assemble the equipment as shown in Fig. 1. Purge thevessel with inert gas and then evacuate the system.9.3 Set the zero and gain on the pressure transducers so thattheir output r
27、epresents true pressure after the test vessel is atthe working temperature.METHOD ASAMPLE COMPONENTS WHICHHAVE ADEQUATE VAPOR PRESSURE AT ROOMTEMPERATURE10. Procedure10.1 Attach pressure regulators to the supply cylinders ofgases to be used in the tests. Connect the regulators to themanifold of remo
28、tely-controlled metering valves.10.2 Flush each line from the supply cylinder to the meter-ing valve. Evacuate the test vessel and manifold. By use of theremotely controlled valves, add to the test vessel the compo-nent most appropriately added first; usually, this is the smallestcomponent. Close th
29、e ball valve next to the test vessel andevacuate or purge the manifold.10.3 Add the second component up to the desired pressure,as measured by the transducer. Repeat the clearing of themanifold and add components until the desired partial pressureof each component has been added to the test vessel.
30、Obtainmixing of gas in the test vessel by adding the largest compo-nent last and at high velocity.NOTE 2Both fast addition of the last component and restricting the tipof the dip tube are necessary to achieve homogeneity. One way to add gasat high velocity with low risk of overshooting is to make us
31、e of aquick-opening dump valve on the pneumatic actuator system for themetering valve. The last component should be added in less than 15 s.NOTE 3Where the vessel configuration will permit, an internal mixingdevice may be used.NOTE 4If the pressure and temperature do not hold steady after acomponent
32、 is added this may indicate reaction prior to ignition. Reactionof a halogen will probably cause a pressure drop. Reaction of oxygen willprobably cause a pressure rise.10.4 Close the remotely controlled valve between the testvessel and the low-range pressure transducer in order to protectthis transd
33、ucer from explosion pressure.10.5 Allow the test gas mixture to equilibrate to testconditions.10.6 Early in the test series, use an appropriate method suchas gas chromatography to confirm composition of gas mixturesmade ready for explosion test. Make any changes in techniquenecessary to ensure homog
34、eneous mixture. These mixturesmay not have the composition expected, due to nonideal gasbehavior. Errors will vary with the order of mixing, tempera-ture, pressure, and the particular materials.Also, the greater thedead volume in tubing etc., not involved in mixing with thecharge in the cylinder, th
35、e greater will be the difference fromexpected composition. If the composition is wrong makeadjustments in partial pressure to get desired composition.10.7 Record the temperature and pressure of the test gas.10.8 Activate the pressure recording equipment.10.9 Attempt ignition of the gas mixture by ap
36、plying 115 Vacross the fuse wire.10.10 Record the maximum pressure.10.11 Vent the test vessel through the exhaust valve. Purgethe vessel with inert gas from the manifold.10.12 Install another spark plug fitted with a fuse wire.NOTE 5By having the spark plug positioned in front of a socketwrench-size
37、d hole in the wall of the heated chamber, the plug can bechanged without appreciably cooling off the chamber. Use a deep socketwrench which fits the bushing, not the spark plug.10.13 Vary fuel concentration (percent of the total vaporpressure) as required to find the minimum concentration, L1,that g
38、ives flame propagation and the maximum concentration,L2, below L1, that does not give flame propagation. Flamepropagation by this method is defined as a pressure ratioP2P1of 1.07 or more. Record values for L1and L2measured bypressure during filling of the test vessel and by analysis of themixtures.
39、Repeat the analysis and test on composition L2toconfirm its non-flammability.10.14 Commence upper limit tests in the nonflammableregion at a concentration greater than the anticipated U2. (See10.16.) Fuel concentration at the upper limit may be substan-tially greater at elevated temperature and pres
40、sure than it is atatmospheric conditions.10.15 Remove any carbon deposits that may be left in thetest vessel after a fuel-rich explosion.NOTE 6These deposits are likely to affect subsequent results. Toremove the carbon insert through the spark plug hole an L-shaped piece of6.4-mm (14-in.) metal tubi
41、ng attached by a flexible hose to an inert gassupply. Blow inert gas vigorously around inside the test vessel until nomore carbon is displaced. Finish cleaning out the carbon by igniting, as ifit were the next sample, a fuel-lean mixture such as 6 % methane in air.After trying this burn-out procedur
42、e, remove the spark plug, insert a lightbulb through the spark plug hole, and inspect the vessel for cleanliness.Repeat the lean mixture explosion if necessary to clean the vessel.Mechanical means may also be used to remove unwanted carbon.10.16 Record the values for the highest fuel concentration,U
43、1, that will propagate a flame and the lowest concentration,U2, above U1, that will not propagate a flame. Make duplicatetests on U2.E918 83 (2011)3METHOD BFUEL WHICH MUST BE HEATED TOREACH ITS LIMITS OF FLAMMABILITY11. Procedure11.1 Set up the equipment as described in Method A exceptfor the introd
44、uction of fuel.Asmall cylinder of liquid fuel maybe placed in the heated chamber with the test vessel or heatedseparately.NOTE 7The cylinder of liquid fuel must be fitted with a pressure-relief device which discharges outside the heated chamber and outside anyother structure which would confine the
45、material. Fuels which mightundergo hazardous reaction in the heated cylinder must not be tested bythis procedure. If any uncertainty exists as to whether the sample mayreact in the heated chamber, thermal stability testing should be performed.11.2 Fit the fuel cylinder with a remotely controlled nee
46、dlevalve. If the fuel will evaporate without fractionation, place thevalve in contact with the vapor phase in the cylinder. Other-wise, place the needle valve in contact with the liquid phaseeven though this makes control of the flow more difficult.Connect the needle valve to the section of fill lin
47、e holding thelow range pressure transducer. This allows the ball valveshown at the right side of this pressure transducer to be used tokeep fuel from condensing outside the heated chamber.11.3 After the vessel is evacuated, add the fuel componentfirst. With the desired amount of fuel pressure in the
48、 test vessel,proceed with the test starting with the last sentence of 10.2.12. Calculations12.1 Calculate the lower limit of flammability (LFL) andupper limit of flammability (UFL) from the values recorded in10.13 and 10.16.LFL 5 L11 L2! (1)UFL 5 U11 U2! (2)NOTE 8Limit concentrations are usually rep
49、orted in terms of volumepercent. It is sometimes appropriate to report limits in terms of weight perunit volume at the test conditions, particularly with multicomponent fuelsor materials exhibiting a high degree of nonideal vapor phase behavior.Report, for example, x mg/l at y MPa and zC.ANNEX(Mandatory Information)A1. DIMENSIONS AND SPECIFICATIONS OF APPARATUS (FIG. 1)A1.1 Test Vessel3A1.1.1 The test vessel shall be a metal vessel having avolume no less than 1 L and a minimum inside diameter of 7.6mm (3 in.). After fabrication, the vessel shall be satisfac
