Shenhai Explosion-Proof
Define
The explosion protection rating, temperature class, explosion protection type, and applicable area marking are essential factors for evaluating explosion-proof electrical equipment. This information is used to describe the level of protection against explosions, the temperature range in which the equipment can operate safely, the type of explosion protection provided, and the designated areas where the equipment is suitable.
Taking Ex demo IIC T6 GB as an example
EX
This symbol indicates that the electrical equipment meets one or more explosion-proof types in the explosion-proof standards;
In accordance with the specifications outlined in Article 29 of the GB3836.1-2010 standard, it is a requirement for explosion-proof electrical equipment to bear the distinct “Ex” marking in a prominent position on its external body. Additionally, the equipment’s nameplate must display the necessary explosion-proof marking along with the certification number that verifies its
compliance.
Demb
The displayed explosion protection type of the explosion-proof electrical equipment determines the specific explosive hazard zone it is designed for.
Explosion Proof Type
| Explosion proof type | Explosion proof type marking | Notes |
|---|---|---|
| Flameproof type | d | |
| Increased safety type | e | |
| Pressurized | p | |
| Intrinsically safe type | ia | |
| Intrinsically safe type | ib | |
| Oil invasion type | o | |
| Sand filling type | q | |
| Adhesive sealing type | m | |
| N-Type | n | The protection levels are classified as MA and MB. |
| SpeciaL type | s | The classification encompasses nA, nR, and n-concave types |
Note: The table exhibits the prevalent explosion protection types for electrical equipment, presenting a combination of various explosion protection methods to form hybrid explosion protection types.
For instance, the designation “Ex demb” signifies a hybrid explosion protection type for the electrical equipment, incorporating flameproof, increased safety, and encapsulation methods.
The classification of zones in areas prone to gas explosion hazards:
In areas where explosive gases and flammable vapors combine with air to form explosive gas mixtures, three zone classifications based on the level of danger are established:
Zone 0 (referred to as Zone 0): A location where explosive gas mixtures continuously, frequently, or persistently exist under normal circumstances.
Zone 1 (referred to as Zone 1): A location where explosive gas mixtures may occur under normal circumstances.
Zone 2 (referred to as Zone 2): A location where explosive gas mixtures are not expected to occur under normal circumstances, but may only appear briefly during abnormal occurrences.
Note: Normal circumstances refer to the regular startup, shutdown, operation, and maintenance of equipment, while abnormal circumstances pertain to potential equipment malfunctions or
inadvertent actions.
The correlation between areas at risk of gas explosions and their corresponding explosion protection types.
| Gas group | Maximum test safety gap MESG (mm) | Minimum ignition current ratio MICR |
|---|---|---|
| IIA | MESG≥0.9 | MICR＞0.8 |
| IIB | 0.9＞MESG＞0.5 | 0.8≥MICR≥0.45 |
| IIC | 0.5≥MESG | 0.45＞MICR |
Note: Considering the specific circumstances in our country, the utilization of e-type (increased safety) electrical equipment is restricted to Zone 1, allowing for:
Wiring boxes and junction boxes that do not generate sparks, arcs, or hazardous temperatures during regular operation are classified as either d or m types for the body and e type for the wiring section.
For instance, the explosion protection designation of the BPC8765 LED explosion-proof platform light is Ex demb IIC T6 GB. The light source compartment is flameproof (d), the driver circuit section is encapsulated (mb), and the wiring compartment features increased safety (e) for explosion-proof construction. As per the aforementioned specifications, this light can be used in Zone 1.
II
The equipment category of an explosion-proof electrical device determines its suitability for specific explosive gas environments.
Explosion-proof equipment is defined as electrical devices that, under specified conditions, do not ignite the surrounding explosive environment.
Hence, products labeled with the aforementioned explosion-proof designation (EX demb IIC) are exclusively suitable for all explosive gas environments, excluding coal mines and underground areas.
C
The gas group of an explosion-proof electrical device determines its compatibility with specific explosive gas mixtures.
Definition of Gas Group:
In all explosive gas environments, except for coal mines and underground areas (i.e., environments suitable for Class II electrical equipment), explosive gases are categorized into three groups, namely A, B, and C, based on the maximum experimental safety gap or minimum ignition current ratio of the gas mixtures. The gas grouping and ignition temperature are dependent on the concentration of combustible gas and air under specific environmental temperature and pressure conditions.
The relationship among explosive gas mixtures, gas groups, and the maximum experimental safety gaps or minimum ignition current ratios:
| Gas group | Maximum test safety gap MESG (mm) | Minimum ignition current ratio MICR |
|---|---|---|
| IIA | MESG≥0.9 | MICR＞0.8 |
| IIB | 0.9＞MESG＞0.5 | 0.8≥MICR≥0.45 |
| IIC | 0.5≥MESG | 0.45＞MICR |
Note: The left table reveals that smaller values of explosive gas safety gaps or minimum current ratios correspond to higher levels of risk associated with explosive gases. Hence, there is an increased demand for stricter gas grouping requirements in explosion-proof electrical devices.
Gas groups typically associated with common explosive gases/substances:
| Gas group/temperature group | T1 | T2 | T3 | T4 | T5 | T6 |
|---|---|---|---|---|---|---|
| IIA | Formaldehyde, toluene, methyl ester, acetylene, propane, acetone, acrylic acid, benzene, styrene, carbon monoxide, ethyl acetate, acetic acid, chlorobenzene, methyl acetate, chlorine | Methanol, ethanol, ethylbenzene, propanol, propylene, butanol, butyl acetate, amyl acetate, cyclopentane | Pentane, pentanol, hexane, ethanol, heptane, octane, cyclohexanol, turpentine, naphtha, petroleum (including gasoline), fuel oil, pentanol tetrachloride | Acetaldehyde, trimethylamine | Ethyl nitrite | |
| IIB | Propylene ester, dimethyl ether | Butadiene, epoxy propane, ethylene | Dimethyl ether, acrolein, hydrogen carbide | |||
| IIC | Hydrogen, water gas | Acetylene | Carbon disulfide | Ethyl nitrate |
Example: In the case where the hazardous substances present in an explosive gas environment are hydrogen or acetylene, the gas group assigned to this environment is categorized as group C. Consequently, the electrical equipment utilized within this setting should adhere to the gas group specifications of no less than IIC level.
In the case where the substance present in the explosive gas environment is formaldehyde, the gas group designated for this environment is classified as group A. Consequently, the electrical equipment employed within this setting should adhere to the gas group specifications of at least IIA level. However, electrical equipment with gas group levels of IIB or IIC can also be used in this environment.
T6
The temperature group assigned to an explosion-proof electrical device determines the gas environment with which it is compatible in terms of ignition temperatures.
The temperature group is defined as follows:
Temperature limits, referred to as ignition temperatures, exist for explosive gas mixtures, defining the temperature at which they can be ignited. Consequently, specific requirements govern the surface temperature of electrical equipment used within these environments, necessitating that the maximum surface temperature of the equipment does not surpass the ignition temperature. Accordingly, electrical equipment is categorized into six groups, T1-T6, based on their respective highest surface temperature.
| Ignition temperature of combustible substances | The maximum surface temperature T of the equipment (℃) | Temperature group |
|---|---|---|
| t＞450 | 450 | T1 |
| 450≥t＞300 | 300 | T2 |
| 300≥t＞200 | 200 | T3 |
| 200≥t＞135 | 135 | T4 |
| 135≥t＞100 | 100 | T5 |
| 100≥t＞85 | 85 | T6 |
Based on the information provided in the left table, a clear relationship can be observed between the ignition temperature of combustible substances and the corresponding temperature group requirements for explosion-proof electrical devices. Specifically, as the ignition temperature decreases, the demands on the temperature group for the electrical devices increase.
The temperature classification correlates with the commonly encountered explosive gases/substances:
| Gas group/temperature group | T1 | T2 | T3 | T4 | T5 | T6 |
|---|---|---|---|---|---|---|
| IIA | Formaldehyde, toluene, methyl ester, acetylene, propane, acetone, acrylic acid, benzene, styrene, carbon monoxide, ethyl acetate, acetic acid, chlorobenzene, methyl acetate, chlorine | Methanol, ethanol, ethylbenzene, propanol, propylene, butanol, butyl acetate, amyl acetate, cyclopentane | Pentane, pentanol, hexane, ethanol, heptane, octane, cyclohexanol, turpentine, naphtha, petroleum (including gasoline), fuel oil, pentanol tetrachloride | Acetaldehyde, trimethylamine | Ethyl nitrite | |
| IIB | Propylene ester, dimethyl ether | Butadiene, epoxy propane, ethylene | Dimethyl ether, acrolein, hydrogen carbide | |||
| IIC | Hydrogen, water gas | Acetylene | Carbon disulfide | Ethyl nitrate |
Note: The information provided in the above table is for reference purposes only. Please consult the detailed requirements outlined in GB3836 for accurate application.
Example: If carbon disulfide is the hazardous substance in the explosive gas environment, it corresponds to temperature group T5. Consequently, the temperature group of electrical equipment used in this environment should be T5 or higher. Similarly, if formaldehyde is the hazardous substance in the explosive gas environment, it corresponds to temperature group T2. Therefore, the temperature group of electrical equipment used in this environment should be T2 or higher. It is worth mentioning that electrical equipment with temperature groups of T3 or T4 can also be used in this environment.
GB
The equipment protection level signifies the level of protection for the explosion-proof electrical apparatus, denoting the safety rating of the equipment.
The definitions of equipment protection level for explosive gas environments are provided in section 3.18.3, 3.18.4, and 3.18.5 of GB3836.1-2010.
3.18.3
Ga Level EPL Ga
Equipment intended for explosive gas environments features a “high” level of protection, ensuring it does not serve as an ignition source during regular operation, anticipated faults, or exceptional malfunctions.
3.18.4
Gb Level EPL Gb
The equipment intended for explosive gas environments features a “high” level of protection, guaranteeing that it does not serve as an ignition source during regular operation or anticipated fault conditions.
3.18.5
Gc Level EPL Gc
The equipment intended for use in explosive gas environments exhibits a “general” level of protection and does not act as an ignition source during regular operation. Supplementary protective measures can also be implemented to ensure that it does not effectively ignite in situations where ignition sources are expected to occur frequently, such as in the case of lighting fixture malfunctions.