I. Selection of Explosion-Proof Electrical Equipment |
1. Select the type of explosion-proof electrical equipment according to the zone classification |
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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, capable of withstanding 2 faults
Intrinsically safe type, pressurized type |
d, p, e (limited to junction boxes, boxes,
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 junction boxes that do not produce sparks, arcs, or dangerous temperatures during normal operation, including electrical products with a "d" or "m" type 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 occur infrequently and only 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 the explosive gas atmosphere ignites, and is a characteristic of the gas or vapor itself. |
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3. Relationship between gas/vapor classification/grading in the area and permitted equipment category/relationship |
Gas/vapor classification/grading in the area |
Permitted 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 internal explosion of a combustible mixture that has entered the enclosure without damage, and will not ignite an external explosive atmosphere formed by the same or different gases or vapors through any joint or structural opening on the enclosure. |
 |
Explosion-proof circuit breakers, switches, lights, starters, push buttons, operating posts, 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 on external parts. |
 |
Explosion-proof junction boxes, junction boxes, wiring 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 type "i" |
It is an electrical circuit that, under normal or specified fault conditions, does not produce sparks or thermal effects that can ignite a specified explosive gas atmosphere. |
 |
Instrumentation, communication, alarm devices, sensors, transmitters, actuators |
Oil immersion "o" |
It is an electrical equipment where the electrical components are immersed in oil to prevent contact with explosive gas atmospheres. |
 |
Transformers, switches, starting resistors |
Sand filled "q" |
It is an electrical equipment where the enclosure is filled with sand or other granular material to prevent the ignition of explosive gas atmospheres. |
 |
Capacitors, transformers, resistors |
Encapsulation "m" |
It is an electrical equipment where the parts that could ignite an explosive gas atmosphere are encapsulated in a compound to prevent contact with the explosive atmosphere. |
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Solenoid valves, sensors, control units |
Special "s" |
It is an electrical equipment that does not conform to any of the above types but has been certified as safe through testing and evaluation. |
 |
Special equipment for specific applications |
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III. Marking of Explosion-Proof Electrical Equipment |
The marking of explosion-proof electrical equipment should include the following information:
(1) Explosion-proof mark: Ex
(2) Explosion-proof type: d, e, i, p, q, o, m, n, s, etc.
(3) Gas group: ⅡA, ⅡB, ⅡC
(4) Temperature class: T1~T6
(5) Equipment protection level (EPL): Ga, Gb, Gc
Example: Ex d ⅡB T4 Gb |
IV. Installation and Maintenance of Explosion-Proof Electrical Equipment |
1. Installation should follow the manufacturer's instructions and relevant standards.
2. Cables and wiring should be properly selected and installed to maintain the explosion-proof integrity.
3. Regular inspection and maintenance should be carried out to ensure the equipment remains in good condition.
4. Any repairs should be performed by qualified personnel using approved parts and methods.
5. Do not modify the equipment without authorization. |
V. Common Problems and Solutions |
1. Problem: The equipment fails to operate properly.
Solution: Check the power supply, wiring, and internal components. Ensure the equipment is correctly installed and maintained.
2. Problem: The equipment shows signs of corrosion or damage.
Solution: Replace damaged parts immediately. Use corrosion-resistant materials in harsh environments.
3. Problem: The equipment does not meet the required explosion-proof rating.
Solution: Verify the equipment marking and ensure it is suitable for the hazardous area. Replace if necessary. |
VI. Conclusion |
Proper selection, installation, and maintenance of explosion-proof electrical equipment are crucial for safety in hazardous areas. Understanding the basic knowledge of explosion-proof electrical equipment helps ensure the safe operation of explosion-proof electric heaters and other equipment. |
