EX Marking

In accordance with GOST 51330 and SAE hazardous areas depending on the frequency and duration of the presence of an explosive gas mixture is divided into three classes:

Class Zone 0. The zone in which an explosive gas mixture is present permanently or for prolonged periods.
Area Class 1 Zone in which it is probable the presence of explosive gas mixtures in normal operating conditions.
Class Zone 2. The zone in which it is unlikely the presence of explosive gas mixtures in normal operation and if it occurs, it is rare and there is a very short time.

 

The concept of "hazardous area" in the "Rules for electrical equipment" is defined as follows: Explosive area - a room or limited space in the indoor or outdoor installation, in which there are or may form explosive mixtures. According to GOST R 51330.9-99, explosive zone - a zone in which there are or may form an explosive gas mixture in volume, requiring special protection measures in the design, manufacture and operation of electrical equipment. In these zones to ensure safety should be used in explosion-proof electrical equipment performance. Explosion-proof electrical equipment - electrical equipment, which provides for positive measures to eliminate or impede the possibility of ignition of the surrounding explosive atmosphere due to its operation of electrical equipment (PUE).

 Explosion-proof equipment.
The following levels of explosion protection:

electrical equipment increased reliability against explosion - explosion-proof electrical equipment where explosion protection is only guaranteed at a recognized normal operation. Emblem of the level in the marking of electrical equipment is the number 2.
explosion-proof electrical equipment - explosion-proof electrical equipment where explosion protection is provided both during normal operation and when recognized the likelihood of damage, defined operating conditions, except for damage to means of protection. Emblem of the level in the marking of electrical equipment is the number 1.
osobovzryvobezopasnoe electrical equipment - explosion-proof electrical equipment, which in relation to the explosion-proof electrical equipment taken additional means of protection, provided the standards on the types of protection. Emblem of the level in the marking of electrical equipment is the number 0.

Categories and groups of explosive mixtures:

Table 1. Categories of explosive mixtures of gases and vapors with air
Category mixture Name mix BEMZ. mm
I Rudničnyj methane more 1,0
II Industrial gases and vapors -
IIA Industrial gases and vapors more 0,9
IIB Industrial gases and vapors more 0,5 before 0,9
IIC Industrial gases and vapors before 0,5
BEMZ- maximum experimental safe gap - the maximum gap between the flanges, which does not pass through the transfer of the shell of the explosion to the environment at any concentration of the mixture in the air.

 

Table 2. Groups of explosive mixtures of gases and vapors from the air divided by the auto-ignition temperature
Group Auto-ignition temperature of the mixture C
Т1 higher 450
Т2  300 to 450
Т3  200 to 300
Т4 higher 135 to 200
Т5  100 to 135
Т6  85 to 100

Type and marking of explosion protection.

In accordance with GOST 51330 Marking of explosion-proof electrical equipment shall include the symbol "Ex", indicating that the electrical equipment meets this standard and the standards on the types of protection; Signs types of protection are also regulated:

1ExdIIBT4
1   -level of protection
Ex - a sign of explosion-proof electrical equipment manufactured in accordance with the standard
d   - type of protection
IIB - category explosive mixture
T4 - temperature class

 

Table 3. Level of protection
level of protection definition
2 Explosion-proof electrical equipment where explosion protection is only guaranteed at a recognized normal operation
1 Explosion-proof electrical equipment where explosion protection is provided both during normal operation and when recognized the likelihood of damage, defined operating conditions, except for damage to means of protection
0 0 Explosion-proof electrical equipment, which in relation to the explosion-proof electrical additional means of protection adopted, the standards stipulated in the types of protection

 

Table 4. Types of explosion protection
d - flameproof enclosure
Explosion-proof electrical equipment Exd may contain fine-sparking components and incendiary devices, and may also contain explosive mixtures. Interior design is such that the equipment can withstand an internal explosion of gas-air mixture and spread with sufficient energy for an external explosion. The connections, covers and openings are constructed with fire-resistant properties of the passages (the slits and grooves), which should be checked periodically and continuously maintain the desired state, to maintain the integrity of this form of protection. Switching devices, motor starters, circuit breakers, heaters, lamps, sensors, alarms, cable glands.
е - protection of species е
The components used in the equipment do not cause dangerous sparking and temperatures during normal operation. The equipment is usually designed for the maximum permissible voltage 11 KV. High efficient and most reliable electrical connections and insulation. The level of protection against dust and moisture almost completely reduces the risk of contamination. The two main requirements Exe is to protect the equipment from external influences on the level of at least IP54 for the gas / vapor (IP6X dust) and the index of toughness at least 7 nm.
Since this form of protection is used in Zones 1 and 2, it is preferred instead Exd instrument, because it is designed for an easier way to testing and maintenance. Another "over" is that the equipment is usually carried out Exe lighter materials, which often reduces its cost.
Terminal and connection boxes, posts and control cabinets, switchgear, lighting, alarms, cable glands.
I - The intrinsically safe circuit
Explosion-proof equipment (subgroup Ex ia and Ex ib) data types include the chain, which because of the low spark energy potential can not produce the ignition of an explosive mixture. Exib equipment safely only when one is damaged and can be used in zone 1. Equipment Exia safely at two lesions and can be used in zone 0. Ex parts or circuits can be placed in an enclosure having another form of protection, such as .exe or Exd, although in this case the housing is not always require frequent inspection.  
P - Filling or blowing pressurized shell
Protection equipment type 'p' is a combination of a positive static pressure inside the electrical enclosure and a constant stream of air or inert gas to expel the explosive mixture from the body in the event of its occurrence. Overall reliability and safety of the system depends substantially on the blowing and monitoring schedule. Motors, switchgear and control devices, high-current devices, analyzers.
O - The oil filling the shell
Permitted only in areas where the risk of explosive atmospheres is low (zone 2). Equipment such as 'about' is used in the presence of sparking immersion oil components in the constant control mode of ventilation, for example in switchgear. Transformers, starting resistance.
q - Quartz filling shell
Enclosure Type q, powder or sand filler, where the arcing and sparking devices. This ventilation is necessary. Often used for energy conservation, liberated at malfunction of electrical and electronic components, such as the failure of the fuse. This form of protection is often associated with the parts inside the .exe equipment, for example, the starting device of fluorescent lamps. Transformers, capacitors, fuses.
m - Encapsulation
Method - potting (encapsulating) components or equipment, forming arcs and sparks, to ensure there is no access available explosive mixtures and temperature control under normal conditions and faults that prevent a fire. Indicators switching low power devices, sensors.
n - protection of species n
Equipment protected form 'n' is considered not having an incendiary ability because during normal operation does not produce an arc or spark dangerous temperature. The concept is close Exe philosophy, but applies only in areas with a weak probability of explosive atmospheres (zone 2). Ehn equipment is divided into four subgroups:
sparking Ex nA - used components that do not produce arcs or sparks;
Ex nC isolated components of petrol ability, for example, the lamp socket - isolated to avoid getting them explosive gases or vapors;
energy limitation Ex nL - low-energy schemes eliminate the possibility of ignition;
Ex nR restricted air movement - based on compaction and sealing equipment in order to eliminate the ingress of an explosive mixture on hot surfaces and flammable components.
All devices for Zone 2, other than switching devices.

 

Table 5. The first number - from solids and dust protection
0   no protection
1 Protection against solid objects greater than 50 mm in diameter (protection against accidental contact with the body of a large area with live or moving parts inside the machine shell)
2 Protection against solid objects with a diameter of 12.5 mm (protection from possible contact of fingers with live or moving parts inside the machine shell)
3 Protection against solid objects greater than 2.5 mm in diameter (protection against possible contact tools, wire, etc. With live or moving parts inside the machine shell)
4 Protection against solid objects larger than 1 mm (protection from possible contact of fingers with live or moving parts inside the machine shell)
5 Dust protection. Personal protection against contact with live or moving parts inside the enclosure unit
6 Full protection against dust. Complete protection of persons against contact with live or moving parts inside the enclosure unit

 

Table 6. The second digit - protection against water
0   no protection
1 Protection against vertically falling water drops
2 Protection against dripping water on the shell, is inclined at an angle of 15 ° to the vertical
3 Protection against rain falling on the shell, is inclined at an angle up to 60 ° to the vertical
4 Protection against splashing water in any direction
5 Protection against water jets in any direction
6 Protection from water waves
7 Protection against short-term immersion in water
8 Protection during prolonged immersion in water
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