GB/T 38301-2019Determination of limiting oxygen concentration (LOC) of flammable gases and vapours (English PDF)

1 Scope

This Standard specifies the method for determining the limiting oxygen concentration of flammable gas (vapor).

This Standard is applicable to the determination of the limiting oxygen concentration of flammable gas (vapor) under normal pressure.

2 Normative References

The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this document.

GB/T 803 Determination of Explosion Indices of Combustible Gases in Air

GB/T 5907.1 Fire Protection Vocabulary - Part 1: General Terms

GB/T 5907.2 Fire Protection Vocabulary - Part 2: Fire Prevention

GB/T 12474 Method of Test for Explosion Limits of Combustible Gases in Air

GB/T 16425 Determination for Minimum Explosive Concentration of Dust Cloud

GB/T 21844 Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)

3 Terms and Definitions

For the purpose of this document, the terms and definitions given in GB/T 5907.1, GB/T

4 Reagents and Materials

The air used in the test shall be purified; if it is synthetic air, it shall be indicated in the report.

The purity of the inert gas used in the test shall be no less than 99.8% (volume fraction).

If it is a mixed inert gas, it shall be stated in the report.

The flammable gas (vapor) determined in the test may be a single substance, a mixture or process-sampling (known or unknown composition); thereof, the purity of the single substance and the single substance in the mixture shall be no less than 99.8% (volume fraction). If a large amount of gas volatilizes in the liquid mixture, and the gas and liquid phase components change with time, liquid phase substances shall be used for testing and sampling.

5 Test Device

The test device of limiting oxygen concentration adopts tubular device (T) or ball device (B, including cylindrical). The tubular device shall meet the requirements of test devices specified in GB/T12474. The ball device may be a 20L spherical stainless-steel explosion tank, a 1m³ cylindrical container, a 5L or 12L short-ring-necked bottle, which shall meet the requirements of test devices specified in GB/T 16425, GB/T 803, and GB/T 21844, respectively.

6 Test Methods

7 Calibration of Test Device

The test device is calibrated according to the requirements of GB/T 12474, GB/T 16425, and GB/T 803. The installed device is calibrated by ethylene with a purity of no less than 99.9% (the volume fraction of the lower explosion limit of ethylene is 2.7%, and the volume fraction of the upper explosion limit is 36%) before the formal measurement.

If the measured result meets the following requirements, that is to say, the device is operating normally:

a) The error of the repeatability test results measured by the same laboratory shall not exceed 5%;

b) The error of the repeatability test results measured by the different laboratories shall not exceed 10%.

8 Test Report

The test report shall include the following contents:

a) The type and purity of the flammable gas (vapor) to be tested;

b) The type and purity of the inert gas; and the composition, purity and source, etc. of the air;

c) Environmental conditions during the test;

d) Test device, tubular device or ball device, test device container shape, volume and ignition method, etc.;

e) The explosion limit is determined according to relevant standards or by using explosion area diagrams;

f) The Limiting oxygen concentration, LAC [Translator Note: here it should be LOC];

g) If the test operation deviates from this Standard, it shall be explained; h) Test date. […]