Selecting hazardous area equipment, what we need to know

Hazardous Area Classification

An industrial area is considered a hazardous area when it contains three fundamental components: A flammable substance (which can be a gas, liquid, or solid), an oxidizer, and a source of ignition. The flammable substance can be anything from gasses and liquids such as hydrogen, gasoline and kerosene, to solid particulate such as dust or small fibers. The oxidizer is usually just the oxygen present in the open air. The source of ignition can be something obvious like a spark or open flame, or something seemingly more innocuous like excessive heat which can cause spontaneous combustion of certain materials.

Hazardous area standards require the use of specially certified equipment for use in areas with all three of the above-mentioned explosive compositions. There are basically two opinions on the classification of explosive hazardous places by major industrial countries in the world.

One is represented by IEC (International Electrotechnical Commission), including Germany, the United Kingdom, Italy, Japan, Australia, and other countries. Its definition is basically the same as that of IEC (see the definition of each region in my country, and the IEC standard is equivalently adopted in my country-China). In Europe, the famous ATEX certification is also based on IEC rules.

The other is the division of North American countries such as the United States and Canada, represented by the definition of NEC (National Electrical Code).

1. What is the explosion-proof grade?

The explosion-proof grade is used to indicate the explosion-proof performance of explosion-proof equipment. Generally speaking, the explosion-proof grade of explosion-proof electrical equipment is divided according to the type of equipment used, the temperature group of the explosive gas mixture, and the explosion-proof type of explosion-proof electrical equipment.

Those equipment"s explosion-proof performance can be read on their labels.

Explosion-proof hazardous label ( IECEX)

For example: Ex e IIC T6 Gb / Ex tb IIIC T85℃ Db IP66

Explosion-proof hazardous area division

Zoning definitions for hazardous areas. Described by frequency of flammable gases and/or dust in hazardous areas

Example: Filling station with Ex zones (Hazardous locations)

GAS AND VAPORS AND DUST CLASSIFICATION

Group is a detailed classification of the types of combustibles

The protection requirements increasing as : IIC > IIB > IIA ,IIIC > IIIB > IIIC. So it means the equipment label marks IIC it can also support to use in IIB IIA envioronment.

Temperature group

The temperature class is the maximum ambient surface temperature that the equipment can achieve (under the maximum applicable dust layer). Giving this rating helps prevent burning based on the ignition point of the material present in the area. This is used to determine the ambient operating temperature of the device. Approved products will also have a maximum ambient operating temperature. Most facilities will want to operate at or below 80% of the maximum ambient operating temperature. Examples of common temperature ratings on devices are T1 (450°C), T3 (200°C), T4 (135°C), and T6 (85°C).

The protection requirements increase as: T6＞T5＞T4＞T3＞T2＞T1

Type of protection

As mentioned previously, there are several methods by which devices can prevent explosions in hazardous areas. First, an explosion-proof, flame-proof, or powder-filled device is one in which the explosion is contained and extinguished. Second, limiting the energy of the device to a point where combustion becomes impossible even in the presence of a flammable material, effectively removing the ignition source, is known as intrinsically safe or nonincendive. A non-incendive device prevents ignition under normal conditions. An intrinsically safe device prevents ignition in doublefault conditions. Lastly, a device can simply keep the flammable materials out of the electrical or heat producing components through pressurization, encapsulation, oil emersion, fiber and flying protection, or protection by enclosure.

Below is a simple list for checking:

Equipment Protection Level ( EPL )

Equipment Protection Level (EPL) is defined by the international standard IEC/EN 60079. The assigned EPL of equipment indicates the risk level or ‘likelihood’ that the equipment can become a source of ignition.

The EPL depends on the explosive atmosphere type: gas (G), dust (D), or mines (M). Below is a simple list introducing its EPL level and its suitable installation Zone.

2. What is the protection level?

Usually the protection level can be expressed as IPXX, so we often say the IP protection level. The IP protection level is composed of two numbers. The first number represents the level of the electrical appliance being dust-proof and preventing the intrusion of foreign objects (the foreign objects referred to here contain Tools, human fingers, etc. should not touch the live parts of the electrical appliance to avoid an electric shock). The second number indicates the degree of airtightness of the electrical appliance against moisture and water intrusion. The larger the number, the higher the protection level. The following table:

Lamps with a high degree of protection are usually used in humid and dusty environments. Due to the excellent protective performance of the lamps, it will prevent liquid, dust and other substances from entering the lamps and lanterns, so as to protect the lamps.

For example, The SZSW8135 Ex mark is EX d IIC T6 Gb / Ex tD A21 IP 66 T80℃， The meaning of the explosion-proof grade is shown in the figure above. It can be used in dangerous places where flammable gas and dust exist which can prevent arcs, sparks, and high temperatures that may be generated inside the lamp from igniting flammable gases and dust in the surrounding environment, so as to achieve the purpose of explosion-proof.

IP66, the 1st number "6" means that the lamp can completely prevent dust and foreign objects from entering, 2nd number "6" means it can prevent large waves and water immersing in the electrical appliances installed on the deck when using.

After clearly understanding the meaning of the explosion-proof level and protection level of lamps, I believe that everyone can easily distinguish the difference between explosion-proof lamps and protection levels of lamps. All in all, the explosion-proof level and protection level of a lamp refer to the performance of the lamp in different aspects, and the two can coexist, but cannot be mixed. When you choose a lamp, please refer to its use environment to select its both performance.

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