This standard specifies the method for determining the maximum test safety gap of flammable gases or vapors under normal temperature and pressure conditions. This standard applies to the classification of flammable gases or vapors and the selection of flameproof electrical equipment. GB 3836.11-1991 Method for determination of maximum test safety clearance of explosion-proof electrical equipment for explosive environments GB3836.11-1991 Standard download and decompression password: www.bzxz.net

National Standard of the People's Republic of China
Explosion-proof electrical equipment for explosive atmospheres
Method of determination of maximum experimental safe gap
Electrical apparatus for explosive atmospheresMethod of test for ascertainment of maximum experimental safe gap
GB3836.11—91
IEC79-1A—1975
This standard is equivalent to the international standard IEC79-1A (1975) "Method for determination of maximum test safety gap". 1Subject content and scope of application
This standard specifies the method for determining the maximum test safety gap of flammable gases or vapors under normal temperature and pressure conditions. This standard applies to the classification of flammable gases or vapors and the selection of flameproof electrical equipment. Note: For liquids whose vapor pressure is very low under temperate conditions and cannot form the required vapor concentration, the ambient temperature should be 5°C higher than the temperature that produces the required vapor pressure.
2 Terms
2.1 Explosive gas mixtures
Under atmospheric conditions, gases, vapors, mist-like flammable substances are mixed with air. After ignition, combustion will occur throughout the range Spread the mixture.
2.2 Maximum test safety gap
Under the test conditions specified in the standard, after the test gas or mixture of steam and air of all concentrations in the shell is ignited, it cannot ignite the outside of the shell through the 25mm long joint surface The maximum gap between two parts of the enclosure cavity for an explosive gas mixture. 2.3 Flameproof joint surface
In order to prevent the internal explosion from propagating to the explosive gas mixture around the shell, the joint surface where the opposing surfaces of the various components of the flameproof shell fit together.
2.4 Planar explosion-proof joint surface
The opposite surface is a flat surface, and the length of the joint surface is a linear explosion-proof dry joint surface. 2.5 Flameproof joint surface length
The shortest path length from the inside of the explosion-proof enclosure through the explosion-proof joint surface to the outside of the explosion-proof enclosure. 2.6 (Explosionproof joint surface) gap
The distance between the opposite surfaces of the explosion-proof joint surface. For circular explosion-proof joint surfaces, it is the radial gap (diameter difference). 2.7 Concentration of the most explosive mixture
Under specified conditions, the mixture flame is most likely to propagate through the joint surface and ignite the surrounding explosive mixture. 2.8 The concentration of the mixture most easily ignited (for electric sparks). Under the specified conditions, the concentration of the mixture required for minimum electric energy to ignite was approved by the State Administration of Technical Supervision on 1991-05-27 and implemented on 1992-02-01
3 Test Method Overview
GB3836.11-91
The test is conducted under normal temperature and pressure (20℃, 105Pa). A standard shell with a specified volume, flameproof joint surface length L and an adjustable gap 9 is placed in the test chamber, and the standard shell and the test chamber are simultaneously filled with a known explosive gas mixture of the same concentration (hereinafter referred to as mixture), then ignite the mixture inside the standard enclosure, and observe through the observation window on the box whether the mixture outside the standard enclosure is ignited and explodes. By adjusting the gap of the standard shell and changing the concentration of the mixture, find the maximum gap that does not cause detonation at any concentration. This gap is the maximum test safety space (MESG) that needs to be measured. 4 Test device
4.1 Mechanical strength
The test device is shown in the figure. The entire test device should be able to withstand a pressure of 15×10'Pa. When the standard shell withstands this explosion pressure, it should not produce obvious elastic deformation and cause the gap 9 to increase instantaneously. 4.2 Standard shell
The standard shell is a spherical container with a net internal volume of 20cm and a flameproof joint surface length of 25mm. 4.3 Test box
The test box is a cylindrical box with an inner diameter of 200mm and a height of 75mm. 4.4 Gap adjustment
The gap of the standard housing can be adjusted with a dial indicator. The upper shell "1" of the standard shell is pressed upward by a strong spring on a dial indicator that can be fine-tuned. Use the dial indicator to accurately adjust and measure the gap g value of the flameproof joint surface. The thread diameter of the dial indicator is 16mm and the pitch is 0.5mm.
4.5 Air Distribution System
The diameter d of the air inlet of the standard shell filled with the mixture is 3mm, and the net volume of the air inlet channel is 5cm. The air inlet of the test chamber is composed of 7 through holes with a diameter d and a diameter of 2 mm. The air inlet and outlet pipes are equipped with flame arresters "e" to prevent backfire. 4.6 Ignition source
uses electrode discharge sparks as the ignition source. The discharge gap between the electrodes is 3mm, and the discharge path is perpendicular to the flameproof joint surface of the flat flange. The electrode is placed 14mm away from the inner edge of the flange and is symmetrical to the center line between the two flat flanges. 4.7 Observation windows
Install two circular observation windows "" with a diameter of 74mm at symmetrical positions on the test box. 4.8 Material of the test device
The main components of the test device, especially the standard shell and ignition electrode, should be made of stainless steel. For some mixtures, other materials may be used to prevent corrosion or other chemical effects on the test apparatus. 5 Test procedure
GB3836.11—91
Test device
a—standard housing cavity; b—test chamber cavity, c dial indicator; d—pump; e— Flame arrester, f - observation window, m, i - valve, h - ignition electrode k - lower shell of standard shell; 1 - upper shell of standard shell 5.1 Preparation of explosive gas mixture
During the test, it should be strictly controlled The concentration of the mixture is maintained constant to avoid dispersion of test results. 5.2 Temperature and pressure
The ambient temperature during the test is 20±5℃, and pump "d" is used to maintain the pressure inside the test device at 105Pa. 5.3 Gap adjustment
First, adjust the gap to a very small value, and visually check whether the two flat flanges of the standard housing are parallel to each other through the observation window. Then adjust the flange gap to zero and calibrate whether the dial indicator scale points to zero (at this time, the torque value added to the gauge head should be very small, for example: the circumferential force added to the gauge head is about 10-2N).
5.4 Ignition
Use a car ignition coil to supply power to the electrodes inside the standard housing, and a discharge spark is formed between the electrodes for ignition. 5.5 Observation of the ignition process
Observe whether the mixture inside the standard shell is ignited through the observation window and the gap between the two flat flanges. If ignition does not occur, the test is invalid. After the interior of the standard shell is ignited, if the mixture in the test chamber ignites and explodes, a propagation phenomenon occurs. 6 Maximum test safety tunnel determination
6.1 Preliminary test
GB3836.11-91
The standard shell plane flange gap uses 0.02mm as the gap adjustment level. Adjust within the range between burst gaps. Use a mixture of a certain concentration to conduct a secondary detonation test corresponding to each gap, and find the maximum non-explosion gap 9 with a detonation rate of 0% at this concentration. and the minimum propagation gap 9100 with a propagation rate of 100%, then change the concentration of the mixture, and repeat the above test to obtain a set of 9 corresponding to different concentration mixtures within a certain concentration range. and g100 value and find 9 from it. and the minimum value of g10 and the corresponding test mixture concentration. This concentration is the most explosive mixture concentration of the mixture under the test conditions. 6.2 Confirmation test
Select the concentration of the most explosive mixture measured in the preliminary test and several concentrations near it, and repeat the test in 6.1. Each concentration corresponds to a gap test 10 times, and finally the minimum values ??of the maximum non-propagation gap and the minimum propagation gap (g.) ml and (9100) m and their corresponding concentrations of the most likely propagation mixture are determined.
6.3 Reproducibility of the maximum test safety gap
The maximum allowable difference between (g.) min measured in the confirmation test of different groups is 0.04mm. If this condition is met, Then the values ??listed in Table 1 are the corresponding maximum test safety gap values ??when (9100) mn - (9.) min is the minimum. For most flammable substances, this difference is generally within the range of one gap adjustment level (0.02mm). If the difference between the (g.) mm measured by the verification tests of different groups is greater than 0.04mm, the hydrogen calibration test device should be used to verify whether it can reproduce the hydrogen values ??listed in Table 1. If the calibration result is normal and the device is If the measured results for the specified gas are still very different, the reasons should be analyzed.
6.4 Table data
The data listed in Table 1 has the maximum test safety gap (MESG) value (g.) mn, (g19.) mn - (g.) min, the difference between the concentration of the most explosive mixture and the ambient temperature during the test. The maximum test safety gap is used to determine the level of the flameproof enclosure of electrical equipment, and the (910e) air-(g.) product characterizes the accuracy of the maximum test safety gap. Table 1
flammable gas or
serial number
1
2
3
4
5||tt ||6
7
8
9
10
11
12
13
Vapor name
carbon monoxide
methane
propane
butane
pentane
hexane
heptane|| tt | tt||co
CH.
CH.
CHio
CsHi
C.Hu
CH6
CaHi
CaHa
CoH22
CoHioo
CsH.owww.bzxz.net
CH.o
Concentration of the most explosive mixture
%
(volume ratio)
40.8
8.2
4.2
3.2
2.55
2.5||tt| |2.3
2.0
1.94
120/105(mg/L)
3.0
5.9/4.5
4.8||tt ||MESG
mm
0.94
1.14
0.92
0.98
0.93
0.93
0.91
1. 04
0.94
[1.02]1)
0.95
[1. 02]
0.92||tt ||9100—g0
mm
0.03
0.11
0.03
0. 02
0. 02
0. 02
0.02
0. 04
0.02
0. 03
0.02
serial number
14| |tt||15
16
17
18
19
20
21
22||tt ||23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39| |tt||40
41
42
43
44
45
46
47||tt ||Fflammable gas or
Vapor name
methyl acetate
ethyl acetate
propyl acetate
cyclohexane
Butyl acetate
Amyl acetate
Vinyl chloride
Methanol
Ethanol
Ethylene difluoride
Trifluorotoluene||tt| |isobutanol
butanol
pentanol
ethyl nitrite
nitrogen
1,3-butadiene
Ethylene
Ether
Ethylene oxide
City gas
Acetylene
Hydrogen
Carbon disulfide
Dioxin| |tt||isopentane
n-chlorobutane
dibutyl ether
dimethyl ether
propylene
acetonitrile
di Isopropyl ether
1,2-dichloroethane
propylene oxide
GB3836.1191
Continued Table 1
The most explosive mixtures Concentration
Molecular formula
CsH.02
CH.O
CsHroO2
CoHi2
CH1202
CH02||tt ||C2H.C1
CH.OH
C2H.OH
C2H.C2
CHsCFs
CaHoo
CHeo||tt ||CsHnOH
C2H.ONO
NHs
CHs
CH.
CHo
C2H.o
H257 %
CH2
H2
cS2
CHO2
CsH12
CH.CI
C.Hiao||tt ||CH.o
CaH.
C2HaN
C.Huo
C2H.Cl2
CHo
%||tt| |(volume ratio)
208/152(mg/L)
4.7
135(mg/L)
90(mg/L)||tt| |130(mg/L)
110(mg/L)
7.3
11.0
6.5
10.5
19.3|| tt||105/125(mg/L)
115/125(mg/L)
100/100(mg/L)
270/270(mg/L)
24.5/17.0
3.9
6.5
3. 47
~8
～21/~21
8.5
27
8.5
4.75
2.45
3.9
2.6
7.0
4.8| |tt||7.2
2.6
9.5
4.55
MESG
mm
[0.99
0. 99
(1.04]
[0.94]
[1. 02]
[0.99]
0. 99
0. 92
0.89
3.91
1.40
C0.961
[O.94]
[0.99]1)||tt| |Co.96)
[3.17]
0. 79
0.65
0. 87
0.59
[0.53]| |tt||0. 37
0. 29
0.34
0.70
0.98
1.06
0.86
0.84
0.91
1.50
.0.94
1.80
0.70
9100g.
mm
0.04
0.04
0.03
0.02
0.08
0. 05
-
0. 02
0. 02
0. 01
0.02
-
0.01
0. 01
0. 02
0.02
0. 02
0. 04
0. 02
0.06
0 .02
0. 05
0. 06
0. 05
0.03
Serial number
48
49| |tt||50
51
52
53
54
55
56
57||tt ||58
flammable gas or
vapor name
ethane
methyl isobutyl ketone
acrylonitrile
acrylic acid Methyl ester
2-hydroxybutyl acetate
methyl methacrylate
hexanol
isopropyl alcohol
ethyl acrylate
Hydrogen cyanide
Vinyl acetate
GB3836.11-91
Continued Table 1
Concentration of the most explosive mixture
Molecular formula||tt| |C,H
C.Hz20
CH,=CHCN
CH.02
CcH120
CH.02
C. Hu.OH
CHOH
C.H0
HCN
CHO2
%
(volume ratio)
5.9
3.0
7.1
5.6
4.2
3.3
3.0
5.1
4.3|| tt||18. 4
4.75
MESG
mm
0.91
0.98
0.87
0.85|| tt||0.88
0.95
0.94
0.99
0.86
0.80
0.94
9100-90|| tt||mm
0.02
0.03
0.02
0. 02
0. 02
0.15
0 . 06
0.02
0.04
0. 02
0. 02
Note: 1) Data in square brackets in the table, for example: [ 0.96] is not measured using the test device specified in the standard, but the 8L spherical test device specified in the UK. The 8L spherical standard shell is filled with the most explosive mixture inside and the most ignitable mixture outside. Other data listed in the table are measured using the test loading specified in this standard. However, generally only three tests are performed for each gap adjustment. Additional notes:
This standard is proposed by the Ministry of Mechanical and Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Explosion-Proof Electrical Equipment. This standard is drafted by the Nanyang Explosion-proof Electrical Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafters of this standard are Ji Minghuan and Xiang Yunlin.
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