ASTM E2931 - 13

    Standard Test Method for Limiting Oxygen (Oxidant) Concentration of Combustible Dust Clouds

    Active Standard ASTM E2931 | Developed by Subcommittee: E27.05

    Book of Standards Volume: 14.02


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    Significance and Use

    5.1 This test method provides a procedure for performing laboratory tests to evaluate relative deflagration parameters of dusts.

    5.2 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, shut down or operate a process while avoiding the creation of flammable dust-gas atmospheres therein, or to pneumatically transport materials safely. NFPA 69 provides guidance for the practical use of LOC data, including the appropriate safety margin to use.

    5.3 Since the LOC as measured by this method may vary with the energy of the ignitor and the propagation criteria, the LOC should be considered a relative rather than absolute measurement.

    5.4 If too weak an ignition source is used, the measured LOC would be higher than the “true” value and would not be sufficiently conservative. This is an ignitability limit rather than a flammability limit, and the test could be described as “underdriven.” Ideally, the ignition energy is increased until the measured LOC is independent of ignition energy (that is, the “true” value). However, at some point the ignition energy may become too strong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relative to the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame with no real propagation beyond the ignitor (1-3).5 This LOC value would be overly conservative.

    5.5 The recommended ignition source for measuring the LOC of dusts in 20-L chambers is a 2500-J pyrotechnic ignitor.6 This ignitor contains 0.6 g of a powder mixture of 40 % zirconium, 30 % barium nitrate, and 30 % barium peroxide. Measuring the LOC at several ignition energies will provide information on the possible overdriving of the system to evaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber such as a 1-m3 chamber (1-3).

    5.6 The values obtained by this testing technique are specific to the sample tested (particularly the particle size distribution) and the method used and are not to be considered intrinsic material constants.

    Note 1Much of the previously published LOC data (4). were obtained using a spark ignition source in a 1.2-L Hartmann chamber and may not be sufficiently conservative. The European method of LOC determination EN 14034–4 uses two 1000-J pyrotechnic igniters in the 20-L chamber.

    1. Scope

    1.1 This test method is designed to determine the limiting oxygen concentration of a combustible dust dispersed in a mixture of air with an inert/nonflammable gas in a near-spherical closed vessel of 20 L or greater volume.

    1.2 Data obtained from this method provide a relative measure of the deflagration characteristics of dust clouds.

    1.3 This test method should be used to measure and describe the properties of materials 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 that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.

    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 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. Specific precautionary statements are given in Section 8.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    NFPA Publications

    NFPA69 Standard on Explosion Prevention Systems

    CEN/CENELEC Publications

    EN14034–4 Determination of the explosion characteristics of dust clouds--Part 4: Determination of the limiting oxygen concentration LOC of dust clouds

    ASTM Standards

    D3173 Test Method for Moisture in the Analysis Sample of Coal and Coke

    D3175 Test Method for Volatile Matter in the Analysis Sample of Coal and Coke

    E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

    E1226 Test Method for Explosibility of Dust Clouds

    E1515 Test Method for Minimum Explosible Concentration of Combustible Dusts

    E2079 Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors


    ICS Code

    ICS Number Code 13.230 (Explosion protection)

    UNSPSC Code

    UNSPSC Code


    DOI: 10.1520/E2931

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