This standard specifies the product classification, basic parameters, technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of factory explosion-proof lighting distribution boxes (hereinafter referred to as distribution boxes). This standard applies to the design, manufacture and inspection of distribution boxes. Distribution boxes are used in factory lighting circuits containing explosive gases and corrosive media in the surrounding environment to distribute or switch on and off lighting circuits. JB/T 6749-1993 Factory explosion-proof lighting distribution boxes JB/T6749-1993 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Factory Explosion-proof Lighting Distribution Box
Subject Content and Scope of Application
JB6749-93
This standard specifies the product classification, basic parameters, technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of factory explosion-proof lighting distribution boxes (hereinafter referred to as distribution boxes). This standard applies to the design, manufacture and inspection of distribution boxes. Distribution boxes are used in factory lighting circuits in the surrounding environment containing explosive gases and corrosive media for the purpose of power distribution or switching of lighting circuits. 2 Reference standards
GB/T13384
JB4262
JB4324
JB4375
Basic test methods for low-voltage electrical appliances
Test A: Low temperature test method
Basic environmental test procedures for electrical and electronic productsBasic environmental test procedures for electrical and electronic productsLow-voltage electrical enclosure protection grade
Explosion-proof electrical equipment for explosive gas environmentsTest Db: Alternating damp heat test method
General requirements
. Flameproof electrical appliances Gas equipment "d"
Explosion-proof electrical equipment for explosive gas environment, increased safety electrical equipment "."
Explosion-proof electrical equipment for explosive gas environmentGeneral technical requirements for packaging of electromechanical products
Rubber-sheathed cable entry device for explosion-proof electrical appliances
Chemical gas corrosion test methods for electrical productsEnvironmental conditions for outdoor and indoor corrosion sites of electrical products3 Product classification and basic parameters
3.1 Product classification
By use:
Indoor use;
b.: Outdoor use.
By anti-corrosion performance:
Anti-light corrosion;
Anti-medium corrosion;
Anti-severe corrosion.
By structural type:
Integral type;
Combined type.
According to the explosion-proof type:
Flameproof type;
Composite type (combination of flameproof type and increased safety type). 3.2 Basic parameters
3.2.1 Power supply frequency: 50Hz.
Approved by the Ministry of Machinery Industry on August 21, 1993
Implemented on October 1, 1993
JB674993
3.2.2 Rated working voltage: main circuit up to 380V, branch circuit up to 220V. 3.2.3 Rated working current: main circuit is 16~63A, branch circuit is 2.5~31.5A. 3.2.4 Number of branch circuits: 4, 6, 8, 10, 12, 16. 4 Technical requirements
The distribution box shall be manufactured according to the drawings and documents approved by the national quality supervision department in accordance with the prescribed procedures, and the "explosion-proof certificate" issued by the inspection department shall be obtained before production. 4.1 The technical indicators of the components (fuses, circuit breakers, etc.) of the distribution box shall not only comply with the provisions of this standard, but also meet the requirements of the respective product standards.
4.2 Working conditions
The light corrosion resistant distribution box shall work normally under the following conditions: a.
Altitude shall not exceed 2000m;
Ambient temperature shall be -20～40℃;
Relative humidity of ambient air shall not exceed 95% (at 25℃); in an environment containing explosive gas;
The installation inclination with the vertical plane shall not exceed 5; in a place without significant shaking and impact vibration; in an environment without gas or steam that can obviously damage insulation; in a place that can prevent dripping water and other liquids from intruding; Pollution level: Level 3;
Installation category: I;
Distribution boxes used outdoors shall adapt to: relative humidity of 100%, maximum solar radiation intensity of 1120W/m, and rainfall intensity of 6mm/min.
4.2.2 In addition to meeting the requirements of a, d, e, f, and i in 4.4.1, the working conditions of the distribution box in the place of use shall also comply with the relevant provisions of JB4375.
4.3 Structural requirements
4.3.1 The handle of the distribution box must be flexible and reliable. 4.3.2 The electrical clearance and target distance of the distribution box shall comply with the provisions of Chapter 6 and Chapter 7 of GB3836.3 in the junction box; and the provisions of Table 1 in the main cavity.
Rated insulation voltagewww.bzxz.net
Minimum electrical clearance
Minimum creepage
Material grade
Note: I, I, and Ia represent the insulation material group, which is divided into the following according to its comparative tracking index (CTI); insulation material group! ：600≤CTI
Insulating material group I：400≤CT<600；Insulating material group Ia：175≤CTI<4004.3.3 The material of the distribution box shell shall comply with the provisions of Chapter 9 of GB3336.1 and Chapter 4 of GB3836.2. Ia
4.3.4 The surface of the fasteners on the distribution box shell shall be treated with zinc passivation or other electroplating with good anti-corrosion effect, and measures shall be taken to prevent loosening. For distribution boxes with medium and heavy corrosion resistance requirements, after assembly, the exposed fasteners on the shell shall be sealed with nitrile or fluorobutane sealant.
JB6749-93
4.3.5 The metal parts of the distribution box should have reliable protective coating. 4.3.6 The outer shell of the distribution box should be equipped with internal and external grounding bolts and marked with the grounding symbol "book". The bolt diameter must comply with the provisions of Chapter 16 of GB3836.1. For distribution boxes with medium corrosion resistance and severe corrosion resistance, the grounding bolts should be made of stainless metal materials or have reliable anti-corrosion treatment. 4.3.7 The paint on the surface of the distribution box shell should meet the requirements of different anti-corrosion levels. The outer shell surface of the outdoor distribution box should be coated with light-colored paint, and the inner cavity of the non-machined surface should be coated with 1320 arc-resistant paint. 4.3.8 The flameproof surface of the flameproof distribution box should be treated with anti-corrosion and meet the requirements of different anti-corrosion levels. 4.3.9: The structural parameters of the flameproof shell of the flameproof distribution box should comply with the requirements of Chapter 7 of GB3836.2. 4.3.10. The entry devices and wiring terminals of the distribution box shall comply with the provisions of JB4262 and Chapter 15 of GB3836.1 respectively. The composite type shall also comply with the provisions of Chapter 4 of GB3836.3.
A clear permanent embossed mark "Ex\ (also the explosion-proof type, category, level and temperature 4.3.11
group mark) and a warning sign with the words "open the cover after power off" shall be set at a prominent position on the outer shell of the distribution box. 4.3.12 The nameplate of the distribution box against light corrosion shall be made of brass plated with nickel (chromium); the nameplate of the distribution box against medium corrosion and severe corrosion shall be made of acid-resistant stainless steel. After the nameplate is made, its surface shall be coated with anti-corrosion air-drying varnish. 4.4 Performance requirements
4.4.1·The distribution box shall be able to withstand the rated voltage test specified in Table 2, and there shall be no breakdown and flashover for 1min during the severe test. Table 2
Rated insulation voltage
U≤60
60U,<300
300
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