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) Type "n"
(3) Equipment that does not produce sparks during normal operation |
(1) Equipment for Zone 1
(2) Type "n"
(3) Equipment that does not produce sparks during normal operation |
(1) Equipment for Zone 1
(2) Type "n" |
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 main body type "d" or "m" and wiring part type "e".
b) "e" type low-voltage asynchronous motors equipped with suitable thermal protection devices (GB3836.4 Appendix D), except those with frequent starting or harsh environmental conditions.
c) Single-pin "e" type fluorescent lamps |
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Zone 0: Places where explosive gas atmospheres are present 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 area and relationship with permitted equipment category |
Classification/grading of gas/vapor 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 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 interior without damage, and through any joint or structural opening on the enclosure, it will not ignite an external explosive atmosphere formed by the same or different gases or vapors. |
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Explosion-proof circuit breakers, switches, lights, starters, push buttons, control 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 on external parts. |
 |
Explosion-proof junction boxes, terminal boxes, 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. |
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Explosion-proof analysis houses, large motors, power distribution, instrument controllers |
Intrinsically safe "i" |
It is an electrical circuit in which any spark or thermal effect produced under the specified test conditions (including normal operation and specified fault conditions) cannot ignite a specified explosive gas atmosphere. |
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Instrumentation, communication, alarm devices, sensors, actuators, solenoid valves, transmitters |
Oil immersion "o" |
It is an electrical equipment in which the electrical parts are immersed in a protective liquid so that an explosive atmosphere above the liquid surface or outside the enclosure cannot be ignited. |
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Transformers, switches |
Powder filling "q" |
It is an electrical equipment in which the electrical parts are filled with a powder material so that an arc occurring inside the enclosure under the specified conditions will not ignite the surrounding explosive atmosphere. |
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Capacitors, transformers, switchgear |
Encapsulation "m" |
It is an electrical equipment in which parts that could ignite an explosive atmosphere by sparking or heating are encapsulated in a compound so that the explosive atmosphere cannot be ignited. |
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Solenoid valves, coils, sensors, actuators, transmitters, junction boxes |
Type "n" |
It is an electrical equipment that, under normal operating conditions, cannot ignite the surrounding explosive atmosphere and generally does not cause a fault that could ignite the surrounding explosive atmosphere. |
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Junction boxes, terminal boxes, lights, motors, instruments, plugs and sockets |
Special "s" |
It is an electrical equipment that does not conform to other types but can achieve the required safety level through special measures. |
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Special explosion-proof equipment |
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III. Marking of Explosion-Proof Electrical Equipment |
1. Marking of explosion-proof electrical equipment according to GB3836.1 standard |
The marking of explosion-proof electrical equipment should include the following items in order: |
a) Explosion-proof mark Ex
b) Explosion-proof type symbol (e.g., d, e, i, p, q, o, m, n, s)
c) Gas group (e.g., ⅡA, ⅡB, ⅡC)
d) Temperature class (e.g., T1, T2, T3, T4, T5, T6)
e) Equipment protection level (EPL) (e.g., Ga, Gb, Gc)
f) Additional requirements (e.g., for special conditions) |
Example: Ex d ⅡB T4 Gb |
2. Marking of explosion-proof electrical equipment according to IEC60079-0 standard |
The marking of explosion-proof electrical equipment should include the following items in order: |
a) Explosion-proof mark Ex
b) Explosion-proof type symbol (e.g., d, e, i, p, q, o, m, n, s)
c) Gas group (e.g., ⅡA, ⅡB, ⅡC)
d) Temperature class (e.g., T1, T2, T3, T4, T5, T6)
e) Equipment protection level (EPL) (e.g., Ga, Gb, Gc)
f) Additional requirements (e.g., for special conditions) |
Example: Ex d ⅡB T4 Gb |
3. Marking of explosion-proof electrical equipment according to NEC500 standard |
The marking of explosion-proof electrical equipment should include the following items in order: |
a) Explosion-proof mark Ex
b) Explosion-proof type symbol (e.g., d, e, i, p, q, o, m, n, s)
c) Gas group (e.g., ⅡA, ⅡB, ⅡC)
d) Temperature class (e.g., T1, T2, T3, T4, T5, T6)
e) Equipment protection level (EPL) (e.g., Ga, Gb, Gc)
f) Additional requirements (e.g., for special conditions) |
Example: Ex d ⅡB T4 Gb |
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IV. Installation and Maintenance of Explosion-Proof Electrical Equipment |
1. Installation requirements |
a) The installation of explosion-proof electrical equipment should comply with the requirements of GB3836.15 (IEC60079-14).
b) The installation should be carried out by qualified personnel.
c) The equipment should be installed in accordance with the manufacturer's instructions.
d) The equipment should be properly grounded.
e) The cables and wiring should be selected and installed according to the requirements of the hazardous area.
f) The equipment should be protected from mechanical damage, corrosion, and other environmental factors. |
2. Maintenance requirements |
a) The maintenance of explosion-proof electrical equipment should comply with the requirements of GB3836.13 (IEC60079-13).
b) The maintenance should be carried out by qualified personnel.
c) The equipment should be inspected regularly for damage, corrosion, and other defects.
d) The equipment should be cleaned regularly to prevent the accumulation of dust and other contaminants.
e) The equipment should be repaired or replaced if any defects are found.
f) The equipment should be tested after maintenance to ensure that it still meets the explosion-proof requirements. |
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V. Common Faults and Troubleshooting of Explosion-Proof Electrical Equipment |
1. Common faults |
a) Damage to the explosion-proof enclosure
b) Corrosion of the explosion-proof enclosure
c) Damage to the explosion-proof joints
d) Damage to the explosion-proof seals
e) Damage to the explosion-proof cables
f) Damage to the explosion-proof components |
2. Troubleshooting |
a) If the explosion-proof enclosure is damaged, it should be repaired or replaced.
b) If the explosion-proof enclosure is corroded, it should be cleaned and protected.
c) If the explosion-proof joints are damaged, they should be repaired or replaced.
d) If the explosion-proof seals are damaged, they should be replaced.
e) If the explosion-proof cables are damaged, they should be replaced.
f) If the explosion-proof components are damaged, they should be replaced. |
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VI. Safety Precautions for Explosion-Proof Electrical Equipment |
a) Before using explosion-proof electrical equipment, it should be confirmed that the equipment is suitable for the hazardous area.
b) During the use of explosion-proof electrical equipment, the equipment should be inspected regularly.
c) If any abnormality is found in the explosion-proof electrical equipment, it should be stopped immediately and inspected.
d) The explosion-proof electrical equipment should not be modified without authorization.
e) The explosion-proof electrical equipment should be maintained by qualified personnel.
f) The explosion-proof electrical equipment should be stored in a dry and ventilated place. |
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