ASTM E2079-07(2013)
(Test Method)Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors
Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors
SIGNIFICANCE AND USE
5.1 Knowledge of the limiting oxygen (oxidant) concentration is needed for safe operation of some chemical processes. This information may be needed in order to start up or operate a reactor while avoiding the creation of flammable gas compositions therein, or to store or ship materials safely. NFPA 69 provides guidance for the practical use of LOC data, including the appropriate safety margin to use.
5.2 Examples of LOC data applications can be found in references (2-4).Note 2—The LOC values reported in references (5-7), and relied upon by a number of modern safety standards (such as NFPA 69 and NFPA 86) were obtained mostly in a 5-cm diameter flammability tube. This diameter may be too small to mitigate the flame quenching influence impeding accurate determination of the LOC of most fuels. The 4-L minimum volume specified in Section 7 would correspond to a diameter of at least 20 cm. As a result, some LOC values determined using this standard are approximately 1.5 vol % lower than the previous values measured in the flammability tube, and are more appropriate for use in fire and explosion hazard assessment studies.
5.3 Much of the previous literature LOC data (5-7) were measured in the flammability tube.
SCOPE
1.1 These test methods cover the determination of the limiting oxygen (oxidant) concentration of mixtures of oxygen (oxidant) and inert gases with flammable gases and vapors at a specified initial pressure and initial temperature.
1.2 These test methods may also be used to determine the limiting concentration of oxidizers other than oxygen.
1.3 Differentiation among the different combustion regimes (such as the hot flames, cool flames and exothermic reactions) is beyond the scope of these test methods.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 These test methods should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2079 − 07 (Reapproved 2013)
Standard Test Methods for
Limiting Oxygen (Oxidant) Concentration in Gases and
Vapors
This standard is issued under the fixed designation E2079; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 NFPA Publication:
NFPA 69 Standard on Explosion Prevention Systems
1.1 These test methods cover the determination of the
2.3 NTIS Publications:
limiting oxygen (oxidant) concentration of mixtures of oxygen
Bulletin 503 Coward, H.F., and Jones, G.W., Bureau of
(oxidant) and inert gases with flammable gases and vapors at a
Mines, “Limits of Flammability of Gases and Vapors,”
specified initial pressure and initial temperature.
NTIS AD701575, 1952
1.2 These test methods may also be used to determine the
Bulletin 627 Zabetakis, M.G., Bureau of Mines, “Flamma-
limiting concentration of oxidizers other than oxygen.
bility Characteristics of Combustible Gases and Vapors,”
1.3 Differentiation among the different combustion regimes
NTIS AD701576, 1965
(such as the hot flames, cool flames and exothermic reactions) Bulletin 680 Kuchta, J.M., Bureau of Mines, “Investigation
is beyond the scope of these test methods. of Fire and ExplosionAccidents in the Chemical, Mining,
and Fuel-Related Industries — A Manual,” NTIS
1.4 The values stated in SI units are to be regarded as
PB87113940, 1985
standard. No other units of measurement are included in this
standard.
3. Terminology
1.5 These test methods should be used to measure and
3.1 Definitions—See also Terminology E1445.
describe the properties of materials, products, or assemblies in
3.1.1 flammable—capable of propagating a flame.
response to heat and flame under controlled laboratory con-
3.1.2 ignition—the initiation of combustion.
ditions and should not be used to describe or appraise the fire
3.1.3 limit of flammability—the boundary in composition
hazard or fire risk of materials, products, or assemblies under
space dividing flammable and nonflammable regions.
actual fire conditions. However, results of this test may be used
as elements of a fire risk assessment which takes into account
3.1.4 limiting oxygen (oxidant) concentration (LOC) of a
all of the factors which are pertinent to an assessment of the
fuel-oxidant-inert system—the oxygen (oxidant) concentration
fire hazard of a particular end use.
atthelimitofflammabilityfortheworstcase(mostflammable)
1.6 This standard does not purport to address all of the fuel concentration.
3.1.4.1 Discussion—Limiting oxygen (oxidant) concentra-
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- tion is also known as minimum oxygen (oxidant) concentration
or as critical oxygen (oxidant) concentration.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Summary of Test Method
2. Referenced Documents
4.1 A mixture containing one or more flammable compo-
2.1 ASTM Standards:
nents (fuel), oxygen (oxidant) and inert gas(es) (such as
E1445 Terminology Relating to Hazard Potential of Chemi-
nitrogen, carbon dioxide, argon, etc.) is prepared in a suitable
cals
test vessel at a controlled initial temperature and made to the
specified initial pressure. Proportions of the components are
These test methods are under the jurisdiction of ASTM Committee E27 on
determined by a suitable means. Ignition of the mixture is
Hazard Potential of Chemicals and are the direct responsibility of Subcommittee
attempted and flammability is determined from the pressure
E27.04 on Flammability and Ignitability of Chemicals.
rise produced. The criterion for flammability is a pressure rise
Current edition approved Oct. 1, 2013. Published October 2013. Originally
approved in 2000. Last previous edition approved in 2007 as E2079 – 07. DOI:
10.1520/E2079-07R13.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from National Fire Protection Association (NFPA), 1 Batterymarch
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Park, Quincy, MA 02169-7471, http://www.nfpa.org.
Standards volume information, refer to the standard’s Document Summary page on Available from National Technical Information Service (NTIS), 5285 Port
the ASTM website. Royal Rd., Springfield, VA 22161, http://www.ntis.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2079 − 07 (2013)
of≥7 % above the initial absolute test pressure. Fuel, oxygen ignition-quenching distances, tests may need to be conducted
(oxidant), and inert gas proportions are varied between trials in vessels larger than that specified below.
until:
7. Apparatus
4.1.1 L—The lowest oxygen (oxidant) concentration for
7.1 The test vessel must have a volume of at least 4 L.
which flame propagation is possible for at least one combina-
tion of fuel and inert gas (the “worst case” or most flammable
NOTE 3—A survey of practitioners of this method indicates that test
fuel concentration range), and
vessels in the size range of 4 to 35 L are used.
4.1.2 H—The highest oxygen (oxidant) concentration for
7.2 Test vessels must be nearly spherical. The maximum
which flame propagation is not possible for the same worst
aspect ratio of the test vessel (the ratio of largest to smallest
case fuel concentration range, are identified.
internal dimension) must be smaller than or equal to two.
NOTE 1—The 7 % pressure criterion may not be appropriate for certain
fuelandoxidantmixtures.Thisisalsothecaseifthetestenclosurevolume 7.3 Test vessel may be equipped with a means of mechani-
is small, or when the ignition energy is substantially larger than 10 J. It is
cal agitation to ensure uniform mixing of components before
therefore a prudent practice to perform exploratory tests in the vicinity of
an ignition attempt.
limit mixtures to evaluate the validity of the selected pressure rise
criterion. See, for example (1).
7.4 If tests are to be conducted at an elevated temperature,
the test vessel may be heated using a heating jacket, heating
5. Significance and Use
mantle or placed inside a heated chamber. The heating system
must be capable of controlling the gas temperature inside the
5.1 Knowledge of the limiting oxygen (oxidant) concentra-
test vessel to within 63°C both temporally and spatially. An
tion is needed for safe operation of some chemical processes.
appropriate device such as a thermocouple should be used to
This information may be needed in order to start up or operate
monitor the gas temperature within the test vessel.
a reactor while avoiding the creation of flammable gas com-
positions therein, or to store or ship materials safely. NFPA 69
7.5 Ignition point must be positioned near the center of the
provides guidance for the practical use of LOC data, including
vessel and away from any surfaces or obstacles inside the test
the appropriate safety margin to use.
vessel.
5.2 Examples of LOC data applications can be found in
7.6 One design of an acceptable test vessel is described in
references (2-4).
Appendix X1.
NOTE 2—The LOC values reported in references (5-7), and relied upon
7.7 The maximum allowable working pressure (MAWP) of
by a number of modern safety standards (such as NFPA 69 and NFPA86)
the test vessel at the maximum test temperature must exceed
were obtainedmostlyina5-cmdiameterflammabilitytube.Thisdiameter
may be too small to mitigate the flame quenching influence impeding
the maximum expected deflagration pressure.
accurate determination of the LOC of most fuels. The 4-L minimum
7.8 Pressure Transducers:
volume specified in Section 7 would correspond to a diameter of at least
20 cm. As a result, some LOC values determined using this standard are 7.8.1 Low-Range Transducer—A low-range pressure trans-
approximately 1.5 vol % lower than the previous values measured in the
ducer may be used for the purpose of making partial pressure
flammability tube, and are more appropriate for use in fire and explosion
additions of gases and vapors to the test vessel. The transducer
hazard assessment studies.
and its signal conditioning/amplifying electronics should have
5.3 Much of the previous literature LOC data (5-7) were
an accuracy, precision and repeatability sufficient to accurately
measured in the flammability tube.
resolve the required changes in the gas partial pressure for the
component used in lowest concentration. The transducer
6. Limitations
shouldbeprotectedfromdeflagrationpressuresbymeansofan
isolation valve. A pressure gage may be used if an error
6.1 These test methods are not applicable to mixtures which
analysis is performed to demonstrate that the internal volume
undergo spontaneous reaction before ignition is attempted.
of the pressure gage and piping will not significantly affect the
6.2 These test methods are limited to mixtures which have
test mixture.
maximum deflagration pressures less than the maximum work-
7.8.2 High-Range Transducer—This transducer has the pur-
ing pressure of the test apparatus.
pose of measuring the pressure rise on ignition of the gas
6.3 These test methods may be used up to the temperature
mixture.Itshouldhavesufficientrangetowithstandthehighest
limit of the test system.
pressure it is expected to experience while also having suffi-
cientaccuracyandresolutiontomeasuresmallpressurerisesof
6.4 Measurements of flammability are influenced by flame-
the order of 7 % of the initial absolute test pressure.
quenching effects of the test vessel walls. Further surface
7.8.3 The pressure transducer and recording equipment
effects due to deposits of carbon or other materials can
must have adequate time resolution to capture the maximum
significantly affect limits of flammability, especially in the
rate of pressure rise developed by the combustion event.
fuel-rich region. Refer to Bureau of Mines Bulletin 503 and
7.8.4 Calibration of the pressure transducer and data acqui-
Bulletin 627. For certain chemicals (for example, ammonia,
sition system must be verified over the range of pressures at
halogenated materials, and certain amines) which have large
which the system is expected to operate.
7.9 Ignition Source—Several possible means of ignition
may be used which include those described below. The means
The boldface numbers in parentheses refer to the list of references at the end of
this standard. of ignition used must be described in the test report.
E2079 − 07 (2013)
smaller test vessels, even in the absence of flammable test mixtures. The
7.9.1 Fuse Wire—Afuse wire igniter can be constructed, for
pressure rise due to igniter must be quantified before the LOC testing, and
example from a piece of No. 40 (0.076-mm diameter) copper,
must be subtracted from the peak pressure rise measured at each test (see
nichrome, or platinum wire fastened to power supply terminals
10.1.11). If the pressure rise due to igniter is a non-negligible fraction of
in such manner as to leave a filament of wire between the
the absolute pressure of the test mixture, the accompanying compressive
terminals approximately 10 mm long. A 500 VA/115 V
heating of the test mixture must be considered.
NOTE 6—Some igniters may not be capable of dissipating all or any of
isolating transformer, or a properly sized discrete discharge
their rated energy at the extremes of pressure and temperature. If there is
capacitor circuit will serve as an adequate igniter energy
any doubt, the reliability of the igniter function must be demonstrated at
supply.
the test conditions.
7.9.2 Carbon Spark—Four 2-mm diameter graphite rods
8. Safety Precautions
wrapped by the leads coming from an electrical pulse genera-
tor. The two electrical leads are separated bya6to 10-mm
8.1 Adequate shielding must be provided to prevent injury
distance.Theresultingdiscretesparkisintheformofasurface
in the event of equipment rupture. The apparatus should be set
discharge over the graphite rods.
up so that the operator is isolated from the test vessel while the
7.9.3 Continuous Electric Arc—An electric arc igniter may
vessel contains a charge of reactants, including the time while
consist of a pair of electrodes (steel or graphite) spaced
thevesselisbeingfilled.Thetestapparatusshouldbeequipped
approximately 6 mm apart across which a 30 mA arc of
with interlocks so that the ignition source cannot be activated
typically less than 1 s duration can be supplied from a
unless the operator has taken necessary steps to protect
115/15 000 volt transformer (so-called luminous tube trans-
personnel and equipment. Activation of the ignition source
former).
should be possible only from a position shielded from the test
7.9.4 Discrete Electric Spark—Anelectricsparkignitermay
vessel. The test vessel may be fitted with a rupture disk vented
consist of a pair of electrodes (steel or graphite) spaced
to a safe location.
approximately 6 mm apart across which a short duration spark
8.2 In the selection of the safe location for the vessel
(lasting for typically 1 ms or less) is caused to occur upon a
discharge, whether it is through discharge piping or through a
single discharge of a capacitor. The electrical energy stored on
rupture disk, full consideration should be given to the safety of
or discharged from the capacitor, or both, should be measured
the personnel, environment and property. The impact of both
and reported. The energy dissipated in the spark gap may also
unburntandburnttestmixtureventingmustbeconsidered,and
be measured by appropriate means. Use of at least 10 Joules of
necessary protection and mitigation measures must be imple-
nominal (stored) spark energy is recommended.
mented.
NOTE 4—Electric arcs and sparks listed in 7.9.3 and 7.9.4 may fail to
8.3 If the fuel can inadvertently be vented inside the heated
discharge when testing fuels with high dielectric strength and during tests
chamber or inside the enclosed area, the heated chamber
conducted at a high initial pressure.
should be fitted with an inert gas purge or the area should be
7.9.5 Chemical Igniter—Some materials (such as chloro-
adequately ventilated to prevent buildup of an flammable
fluoro-carbons) require a higher ignition energy than that can
mixture in the large space.
be provided by the electrical means described above. In that
8.4 It is recommended that LOC evaluations be performed
case, tests with chemical igniters (for example, electric
at atmospheric pressure prior to conducting evaluations at
matches, electrically activa
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.