GB/T 38301-2019 English PDF (GB/T38301-2019)

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GB/T 38301-2019: Determination of limiting oxygen concentration (LOC) of flammable gases and vapours
GB/T 38301-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 13.220.01
C 80
Determination of Limiting Oxygen Concentration
(LOC) of Flammable Gases and Vapors
ISSUED ON: DECEMBER 10, 2019
IMPLEMENTED ON: APRIL 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
Introduction ... 4
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 Reagents and Materials ... 8
5 Test Device ... 8
6 Test Methods ... 8
7 Calibration of Test Device ... 12
8 Test Report ... 12
Appendix A (Informative) Example of LAC Determination ... 13
Bibliography ... 15
Determination of Limiting Oxygen
Concentration (LOC) of Flammable Gases and Vapors
Warning - After igniting the flammable gas, inert gas and air mixture in
accordance with the method specified in this Standard, even if flame
propagation is not formed, it cannot be completely assumed that the mixture
shall not explode.
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
6.1 Test principle
Use tubular device or ball device to test and determine the explosion area of flammable
gas (vapor), air and inert gas. By increasing the volume fraction of inert gas, test and
determine the limiting air concentration, LAC, of flammable gas (vapor); and then
further calculate and determine the limiting oxygen concentration, LOC, of the
flammable gas to be tested.
6.2 Test procedures
6.2.1 General requirements
According to the following test procedures, repeat the test four times to determine the
limiting air concentration, LAC, of the flammable gas to be tested. After the gas is
equipped, it shall be stirred evenly:
--- Step 1: Determine the lower explosion limit, LEL, and upper explosion limit, UEL,
concentration LOC ± 0.2% [calculated value by Formula (1)]. The concentration of
oxygen analysis equipment shall be calibrated within the range of 0%~21% volume
fraction. When measuring by the tubular device specified in GB/T 12474, the oxygen
concentration shall be measured at the outlet of the container before starting ignition.
When measuring by the ball device specified in GB/T 16425 and GB/T 803, the mixture
shall be measured in the ball to be evenly mixed and sampled for oxygen concentration
measurement before ignition.
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.