Background
Explosion-proof electrical products, also known as Ex products, refer to electrical equipment specially used in industrial sectors such as petroleum, chemical, coal, textile, food processing and military industry where flammable liquids, gases, vapors or combustible dust, fibers and other explosive hazards may occur. Ex products must be certified as explosion-proof before being used in explosive hazardous locations. The present global explosion-proof certification systems mainly include IECEx, ATEX, UL-cUL, CCC and etc. The following content mainly focuses on the CCC certification of explosion-proof electrical products in China, and the in-depth explanation for other explosion-proof certification systems will be released in lateral periodicals.
The present compulsory certification scope of domestic explosion-proof electrical products includes 18 types, such as explosion-proof motors, explosion-proof switches, control and protection products, explosion-proof transformer products, explosion-proof starter products, explosion-proof sensors, explosion-proof accessories, and Ex components. The domestic compulsory certification of explosion-proof electrical products adopts the certification method of product testing, initial factory inspection and follow-up surveillance.
Explosion-proof Certification
The explosion-proof certification is classified based on the explosion-proof electrical equipment classification, explosion-proofing type, product type, explosion-proof construction and safety parameters. The following content mainly introduces the equipment classification, explosion-proofing type and explosion-proof construction.
Equipment Classification
Equipment used in explosive atmosphere is divided into Group I, II, and III. Group IIB equipment may also be used in the working condition of IIA, while Group IIC equipment may also be used in the working condition of IIA and IIB. IIB equipment may be used in the working condition of IIIA. And IIIC equipment is applicable for the working condition of IIIA and IIIB.
|
Electrical Equipment Groups |
Applicable Environment |
Subgroups |
Explosive Gas/Dust Environment |
EPL |
|
Group I |
Coal mine gas environment |
—— |
—— |
EPL Ma、EPL Mb |
|
Group II |
Explosive gas environment other than coal mine gas environment |
Group IIA |
Propane |
EPL Ga、EPL Gb、EPL Gc |
|
Group IIB |
Ethylene |
|||
|
Group IIC |
Hydrogen and acetylene |
|||
|
Group III |
Explosive dust environments other than coal mines |
Group IIIA |
Inflammable catkins |
EPL Da、EPL Db、EPL Dc |
|
Group IIIB |
Non-conductive dust |
|||
|
Group IIIC |
Conductive dust |
Explosion-proofing Type
Explosion-proof electrical products should be certified according to their explosion-proofing type. Products can be categorized as one or more explosion-proofing types of the following table.
|
Explosion-Proof Type |
Explosion-Proof Structure |
Protection Level |
General Standard |
Specific Standard |
|
Flameproof Type “d” |
Enclosure Material: Light metal, non-light metal, non-metal(Motor) Enclosure Material: Light metal (cast aluminum), non-light metal (steel plate, cast iron, cast steel) | da（EPL Ma或Ga） |
GB/T 3836.1 Explosive Atmospheres – Part 1: Equipment – General Requirements |
GB/T 3836.2 |
| db（EPL Mb或Gb） | ||||
| dc（EPL Gc） | ||||
|
Increased Safety Type “e” |
Enclosure Material: Light metal, non-light metal, non-metal(Motor) Enclosure Material: Light metal (cast aluminum), non-light metal (steel plate, cast iron, cast steel) | eb（EPL Mb或Gb） |
GB/T 3836.3 |
|
| ec（EPL Gc） | ||||
|
Intrinsically Safe Type “i” |
Enclosure Material: Light metal, non-light metal, non-metalCircuit
Power Supply Method |
ia（EPL Ma、Ga或Da） |
GB/T 3836.4 |
|
| ib（EPL Mb、Gb或Db） | ||||
| ic（EPL Gc或Dc） | ||||
|
Pressurized Enclosure Type “p” |
Pressurized Enclosure (Structure)Continuous Airflow, Leakage Compensation, Static Pressure
Built-in System |
pxb（EPL Mb、Gb或Db） |
GB/T 3836.5 |
|
| pyb（EPL Gb或Db） | ||||
| pzc（EPL Gc或Dc） | ||||
|
Liquid Immersion Type “O” |
Protective LiquidEquipment Type: Sealed, Non-sealed | ob（EPL Mb或Gb） |
GB/T 3836.6 |
|
| oc（EPL Gc） | ||||
|
Powder Filling Type “q” |
Enclosure Material: Light metal, non-light metal, non-metalFilling Material | EPL Mb或Gb |
GB/T 3836.7 |
|
|
“n”型 Type “n” |
Enclosure Material: Light metal, non-light metal, non-metal(Motor) Enclosure Material: Light metal (cast aluminum), non-light metal (steel plate, cast iron, cast steel)
Protection Type: nC, nR |
EPL Gc |
GB/T 3836.8 |
|
|
Encapsulation Type “m” |
Enclosure Material: Light metal, non-light metal, non-metal | ma（EPL Ma、Ga或Da） |
GB/T 3836.9 |
|
| mb（EPL Mb、Gb或Db） | ||||
| mc（EPL Gc或Dc） | ||||
|
Dust Ignition-Proof Enclosure “t” |
Enclosure Material: Light metal, non-light metal, non-metal (Motor) Enclosure Material: Light metal (cast aluminum), non-light metal (steel plate, cast iron, cast steel) |
ta（EPL Da） |
GB/T 3836.31 |
|
| tb（EPL Db） | ||||
| tc（EPL Dc） |
Note: Protection level is a subdivision of explosion-proof types associated with equipment protection levels, used to distinguish the likelihood of equipment becoming an ignition source.
Requirements on Cells and Batteries
In explosion-proof electrical products, cells and batteries are controlled as critical components. Only primary and secondary cells and batteries as specified in GB/T 3836.1 can be installed within explosion-proof electrical products. The specific cells and batteries used and the standards they must comply with should be determined based on the selected explosion-proof type.
Primary Cell or Battery
|
GB/T 8897.1 Type |
Cathode |
Electrolyte |
Anode |
Nominal Voltage (V) |
Maximum OCV (V) |
|
—— |
Manganese Dioxide |
Ammonium chloride, zinc chloride |
Zinc |
1.5 |
1.725 |
|
A |
Oxygen |
Ammonium chloride, zinc chloride |
Zinc |
1.4 |
1.55 |
|
B |
Graphite Fluoride |
Organic electrolyte |
Lithium |
3 |
3.7 |
|
C |
Manganese Dioxide |
Organic electrolyte |
Lithium |
3 |
3.7 |
|
E |
Thionyl Chloride |
Non-aqueous inorganic substance |
Lithium |
3.6 |
3.9 |
|
F |
Iron Disulfide |
Organic electrolyte |
Lithium |
1.5 |
1.83 |
|
G |
Copper Oxide |
Organic electrolyte |
Lithium |
1.5 |
2.3 |
|
L |
Manganese Dioxide |
Alkali metal hydroxide |
Zinc |
1.5 |
1.65 |
|
P |
Oxygen |
Alkali metal hydroxide |
Zinc |
1.4 |
1.68 |
|
S |
Silver Oxide |
Alkali metal hydroxide |
Zinc |
1.55 |
1.63 |
|
W |
Sulfur Dioxide |
Non-aqueous organic salt |
Lithium |
3 |
3 |
|
Y |
Sulfuryl Chloride |
Non-aqueous inorganic substance |
Lithium |
3.9 |
4.1 |
|
Z |
Nickel Oxyhydroxide |
Alkali metal hydroxide |
Zinc |
1.5 |
1.78 |
Note: Flameproof type equipment can only use primary cells or batteries of the following types: Manganese Dioxide, Type A, Type B, Type C, Type E, Type L, Type S, and Type W.
Secondary Cell or Battery
|
Type |
Cathode |
Electrolyte |
Anode |
Nominal Voltage |
Maximum OCV |
|
Lead-Acid (Flooded) |
Lead Oxide |
Sulfuric Acid （SG 1.25~1.32) |
Lead |
2.2 |
2.67（ Wet Cell or Battery） 2.35（ Dry Cell or Battery） |
|
Lead-Acid (VRLA) |
Lead Oxide |
Sulfuric Acid （SG 1.25~1.32) |
Lead |
2.2 |
2.35（Dry Cell or Battery） |
|
Nickel-Cadmium (K & KC) |
Nickel Hydroxide |
Potassium Hydroxide （SG 1.3) |
Cadmium |
1.3 |
1.55 |
|
Nickel-Metal Hydride (H) |
Nickel Hydroxide |
Potassium Hydroxide |
Metal Hydrides |
1.3 |
1.55 |
|
Lithium-Ion |
Lithium Cobaltate |
Liquid solution containing lithium salts and one or more organic solvents, or gel electrolyte formed by mixing liquid solution with polymers. |
Carbon |
3.6 |
4.2 |
|
Lithium Cobaltate |
Lithium Titanium Oxide |
2.3 |
2.7 |
||
|
Lithium Iron Phosphate |
Carbon |
3.3 |
3.6 |
||
|
Lithium Iron Phosphate |
Lithium Titanium Oxide |
2 |
2.1 |
||
|
Nickel Cobalt Aluminum |
Carbon |
3.6 |
4.2 |
||
|
Nickel Cobalt Aluminum |
Lithium Titanium Oxide |
2.3 |
2.7 |
||
|
Nickel Manganese Cobalt |
Carbon |
3.7 |
4.35 |
||
|
Nickel Manganese Cobalt |
Lithium Titanium Oxide |
2.4 |
2.85 |
||
|
Lithium Manganese Oxide |
Carbon |
3.6 |
4.3 |
||
|
Lithium Manganese Oxide |
Lithium Titanium Oxide |
2.3 |
2.8 |
Note: Flameproof type equipment only allows the use of Nickel-Cadmium, Nickel-Metal Hydride, and Lithium-Ion cells or batteries.
Battery Structure and Connection Method
In addition to specifying the types of batteries allowed, explosion-proof electrical products also regulate the battery structure and connection methods according to different explosion-proof types.
|
Explosion-Proof Type |
Battery Structure |
Battery Connection Method |
Remark |
|
Flameproof Type “d” |
Valve-regulated sealed (for discharge purposes only);Gas-tight;
Vented or open-cell batteries; |
Series |
/ |
|
Increased Safety Type “e” |
Sealed (≤25Ah);Valve-regulated;
Vented; |
Series (the number of series connections for sealed or valve-regulated batteries should not exceed three) |
Vented batteries should be of the lead-acid, nickel-iron, nickel-metal hydride, or nickel-cadmium type. |
|
Intrinsic Safety Type “i” |
Gas-tight sealed;Valve-regulated sealed;
Sealed with pressure release device and similar sealing methods to gas-tight and valve-regulated; |
Series, parallel |
/ |
|
Positive Pressure Enclosure Type “p” |
Sealed (gas-tight or sealed valve-regulated) orBattery volume does not exceed 1% of the net volume inside the positive pressure enclosure; |
Series |
/ |
|
Sand Filling Type “q” |
—— |
Series |
/ |
|
Type “n” |
Conforming to Increased Safety Type “ec” protection level requirements for sealed type |
Series |
/ |
|
Encapsulation Type “m” |
Sealed gas-tight batteries are allowed to be used;Batteries meeting “ma” protection level requirements should also meet intrinsic safety type battery requirements;
Single-cell vented batteries should not be used; Valve-regulated sealed batteries should not be used; |
Series |
/ |
|
Dust Ignition-Proof Enclosure Type “t” |
Sealed |
Series |
/ |
MCM Tips
When we do certification for explosion-proof electrical products, it’s crucial to first determine if the product falls within the scope of mandatory certification. Then, based on factors like the explosive environment and explosion-proof type used, we shall select the appropriate certification standards. It’s particularly important to note that batteries installed in explosion-proof electrical products must comply with the requirements specified in GB/T 3836.1 and applicable explosion-proof type standards. Apart from batteries being controlled as critical components, other critical components include the enclosure, transparent components, fans, electrical connectors, and protective devices. These components are also subject to strict control measures.
Post time: Aug-15-2024