This standard specifies the product classification, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of flameproof low-voltage cable junction boxes for coal mines. This standard applies to flameproof low-voltage cable junction boxes for coal mines (hereinafter referred to as "junction boxes"). MT 429-1995 Flameproof low-voltage cable junction boxes for coal mines MT429-1995 Standard download decompression password: www.bzxz.net

Coal Industry Standard of the People's Republic of China
Flameproof low-voltage cable junction box for coal mines
1 Subject content and scope of application
MT429-1995
This standard specifies the product classification, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of flameproof low-voltage cable junction boxes for coal mines.
This standard applies to flameproof low-voltage cable junction boxes for coal mines (hereinafter referred to as "junction boxes"). 2 Reference standards
GB 156
Rated voltage
Packaging, storage and transportation pictorial symbols
Metal tensile test method
Rated current of electrical equipment
Basic test methods for low-voltage electrical appliances
GB1410
GB 1497
Test methods for volume resistivity and surface resistivity of solid insulating materialsBasic standards for low-voltage electrical appliances
GB/T2423.4Basic environmental test procedures for electric and electronic productsTest Db: Alternating damp heat test methodGB 2900.35
Electrical terminologyExplosion-proof electrical apparatus for explosive atmospheresGB 3836.1
GB 3836. 2
General requirements for explosion-proof electrical equipment for explosive atmospheres Explosion-proof electrical equipment for explosive atmospheres Flameproof electrical equipment "d" GB/T4942.2 Protection grade of low-voltage electrical enclosures GB10111 Method for random sampling using random numbers GB11020 Test method for determining the combustion performance of solid electrical insulating materials after exposure to ignition sources JB834 Tropical low-voltage electrical appliances
JB4262 Rubber-sheathed cable entry device for explosion-proof electrical appliances 3 Product classification
3.1 Type
3.1.1 The explosion-proof type is the mining flameproof type.
3.1.2 The cable entry device type is divided into the compression nut type and the pressure plate type. 3.7.3 According to the purpose, it is divided into the connecting cable type and the branch cable type. 3.2 Model and meaning
Approved by the Ministry of Coal Industry of the People's Republic of China on October 5, 1995 326
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Implementation on December 1, 1995
3.3 Basic parameters
MT 429-1995
Characteristic code of shell material (plastic S, steel G, cast iron T) Number of entry devices
Rated voltage (V)
Rated current (A)
Design number (represented by 1, 2, ··, 50 in sequence) Low voltage
Junction box
3.3.1 Rated voltage: AC 36, 127, 380, 660, 1140V, DC 12, 24, 36, 48V.
3.3.2 Rated current: 10, 20, 40, 63, 100, 160, 200, 315, 400, 500A. 3.3.3 Rated frequency of AC power supply: 50Hz. 3.3.4 The junction box is for long-term working.
4 Technical requirements
The product shall comply with the requirements of this standard and be manufactured in accordance with the drawings and technical documents approved by the prescribed procedures. 4.1
The junction box shall be able to work normally under the following conditions: 4.2
Ambient air pressure 86~110kPa,
Ambient temperature -20～+40℃;
Relative air humidity is not more than 98% (at +25℃); underground coal mine with methane explosive gas mixture, without significant shaking and severe impact vibration; Pollution level: Level 3;
g. Installation category: I.
4.3 The electrical clearance and creepage distance between conductive parts of different potentials in the junction box and between conductive parts and grounding bodies such as the shell should not be less than the provisions of Table 1 after considering the correct connection of the cable. 327
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Rated voltagebzxZ.net
Minimum electrical clearance
MT429--1995
Electrical clearance and creepage distance
Minimum creepage distance, mm
Note: I, Ia are groups divided according to the comparative tracking index (CTI) of the insulating material. 4.4 When the insulation of the junction box is subjected to the power frequency withstand voltage test, there should be no breakdown and flashover phenomenon. 2
The temperature rise of the terminal in the junction box should not exceed the value specified in Table 2, and the maximum temperature of its outer shell surface is 150℃. 4.5
Table 2 Limit temperature rise of terminal blocks
Material of terminal wax
Bare copper
Bare yellow pot
Tin-plated copper (or brass)
Silver-plated or nickel-plated copper (or brass)
Other metals
Temperature rise of terminal blocks, K
4.6 After the alternating damp heat test, the insulation resistance values ​​of the junction box under different rated insulation voltages shall comply with the provisions of Table 3, and be able to withstand the power frequency withstand voltage test specified in Article 4.4 of this standard, and there shall be no rust on the flameproof surface. Table 3 Insulation resistance values
Rated insulation voltage (U.), V
Minimum insulation resistance, MQ
60U660
800
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