I. Selection of Explosion-Proof Electrical Equipment |
1. Select the type of explosion-proof electrical equipment according to the zone category |
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EN60079-15 |
NEC500 |
GB3836.15 |
Zone 0 |
ia Intrinsically safe electrical equipment and circuits |
Zone 1 |
d, p, e, i, q, o, m |
Flameproof, intrinsically safe capable of withstanding 2 faults, pressurized |
d, p, e (limited to junction boxes, enclosures, single-pin fluorescent lamps, etc.)
i, q, o, m |
Zone 2 |
(1) Equipment for Zone 1
(2) "n" type
(3) Equipment that does not produce sparks during normal operation |
(1) Equipment for Zone 1
(2) "n" type
(3) Equipment that does not produce sparks during normal operation |
(1) Equipment for Zone 1
(2) "n" type |
Note 1: |
For special type equipment marked with "S", it should be selected according to the zone type indicated on the equipment, and special conditions for installation and use should be noted. |
Note 2: |
According to the actual situation in China, the "e" type equipment allowed for use in Zone 1 is limited to:
a) Junction boxes and enclosures that do not produce sparks, arcs, or dangerous temperatures during normal operation, including electrical products with "d" or "m" type main body and "e" type wiring part.
b) "e" type low-voltage asynchronous motors (except those with frequent starting and harsh environmental conditions) equipped with appropriate thermal protection devices (GB3836.4 Appendix D).
c) Single-pin "e" type fluorescent lamps |
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Zone 0: Places where explosive gas atmospheres occur continuously or for long periods.
Zone 1: Places where explosive gas atmospheres are likely to occur in normal operation.
Zone 2: Places where explosive gas atmospheres are not likely to occur in normal operation, but if they do occur, they will only occur infrequently and for short periods.
2. Select the type of explosion-proof electrical equipment according to the ignition temperature of the gas or vapor
Explosion-proof electrical equipment should be selected based on its maximum surface temperature not exceeding the ignition temperature of any gas or vapor that may be present.
Explosion-proof electrical equipment and ambient temperature. |
Relationship between temperature class, surface temperature, and ignition temperature |
Temperature class of electrical equipment |
Maximum surface temperature of electrical equipment |
Ignition temperature of gas or vapor |
T1 |
450℃ |
＞450℃ |
T2 |
300℃ |
＞300℃ |
T3 |
200℃ |
＞200℃ |
T4 |
135℃ |
＞135℃ |
T5 |
100℃ |
＞100℃ |
T6 |
85℃ |
＞85℃ |
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The maximum surface temperature of electrical equipment refers to the highest surface temperature of explosion-proof electrical equipment used in explosive gas atmospheres, and this temperature must be lower than the ignition temperature of the gas or vapor present in the hazardous area. |
The ignition temperature of gas or vapor refers to the temperature at which the gas or vapor present in an explosive gas atmosphere ignites, and is a characteristic of the gas or vapor itself. |
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3. Classification/grading of gas/vapor in the site and allowable equipment category/relationship |
Classification/grading of gas/vapor in the site |
Allowable equipment category/relationship |
ⅡA (e.g., propane, pentane, benzene, gasoline, ethanol, acetaldehyde, acetone, methylamine) |
ⅡA, ⅡB, or ⅡC |
ⅡB (e.g., ethylene, dimethyl ether, coke oven gas, etc.) |
ⅡB, ⅡC |
ⅡC (e.g., hydrogen, acetylene, and carbon disulfide) |
ⅡC |
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Reference standards:
GB3836.1 (equivalent to IEC60079-0): "Electrical apparatus for explosive gas atmospheres - Part 1: General requirements"
GB3836.2 (equivalent to IEC60079-1): "Electrical apparatus for explosive gas atmospheres - Part 2: Flameproof enclosure 'd'"
GB3836.3 (equivalent to IEC60079-7): "Electrical apparatus for explosive gas atmospheres - Part 3: Increased safety 'e'"
GB3836.4 (equivalent to IEC60079-11): "Electrical apparatus for explosive gas atmospheres - Part 4: Intrinsic safety 'i'"
GB3836.13 (equivalent to IEC60079-13): "Electrical apparatus for explosive gas atmospheres - Part 13: Repair and overhaul for electrical apparatus used in explosive gas atmospheres"
GB3836.14 (equivalent to IEC60079-10): "Electrical apparatus for explosive gas atmospheres - Part 14: Classification of hazardous areas"
GB3836.15 (equivalent to IEC60079-14): "Electrical apparatus for explosive gas atmospheres - Part 15: Electrical installations in hazardous areas (other than mines)" |
II. Explosion-Proof Principles |
Explosion-proof type |
Explosion-proof principle |
Diagram |
Application examples |
Flameproof "d" |
It can withstand the explosion of a combustible mixture that has entered the enclosure without damage, and through any joint or structural opening on the enclosure, it will not ignite the external explosive atmosphere formed by the same or different gases or vapors. |
 |
Explosion-proof circuit breakers, switches, lights, starters, push buttons, operating stations, distribution boxes, motors |
Increased safety "e" |
It is an electrical equipment that takes additional measures to improve its safety level for equipment that does not produce arcs or sparks under normal operating conditions, preventing dangerous temperatures, arcs, and sparks from occurring inside and outside its components. |
 |
Explosion-proof junction boxes, enclosures, conduit boxes, transition boxes, flexible conduits, lights, motors |
Pressurized "p" |
It is an electrical equipment that achieves safety by maintaining the pressure of the internal protective gas higher than the pressure of the surrounding explosive atmosphere. |
 |
Explosion-proof analysis cabins, large motors, power distribution, instrument controllers |
Intrinsically safe "i" |
It is an electrical equipment where any spark or thermal effect produced under normal or specified fault conditions cannot ignite a specified explosive gas atmosphere. |
 |
Instrumentation, communication, alarm devices |
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III. Marking of Explosion-Proof Electrical Equipment |
Explosion-proof electrical equipment must be marked with the explosion-proof mark, which includes the explosion-proof type, equipment category, gas group, temperature class, etc. For example: Ex d ⅡB T4, indicating flameproof type, suitable for ⅡB gas group, temperature class T4. |
IV. Installation and Maintenance of Explosion-Proof Electrical Equipment |
The installation and maintenance of explosion-proof electrical equipment must comply with relevant standards and specifications to ensure its explosion-proof performance. During installation, attention should be paid to the tightness of cable entries, the integrity of flameproof joints, and the reliability of grounding. During maintenance, regular inspections should be carried out, and any damage or aging should be repaired or replaced in a timely manner. |
V. Common Problems and Solutions |
Common problems include damage to flameproof surfaces, aging of sealing gaskets, and loosening of cable entries. Solutions include repairing or replacing damaged parts, regularly replacing sealing gaskets, and tightening cable entries. |
VI. Conclusion |
Understanding the basic knowledge of explosion-proof electrical equipment is crucial for the safe use of explosion-proof electric heaters. Correct selection, installation, and maintenance can effectively prevent explosion accidents and ensure production safety. |
