Many industrial sectors, such as petroleum, chemical, and coal defense, may often leak or spill out various flammable and explosive gases, liquids, and various dusts and fibers during various processes of production, processing, transportation, and storage. . After mixing these substances with air, it may become a dangerous mixture with baoxza. When the concentration of the mixture reaches the baoxha concentration range, once the fire source appears, it will cause serious accidents such as baozha and fire. Electrical equipment used in such hazardous environments must have been certified by a professional agency to have an explosion-proof performance. Therefore, explosion-proof technology is available.
According to the division of the hazardous environment formulated by the International Electrotechnical Commission (IEC), it is clearly defined that, under atmospheric conditions, dust or fibrous combustible substances and air-shaped yang mixture are ignited and ignited and transferred to the unburned mixture. Baozha Dust environment, known as the Class I environment. Under atmospheric conditions, a mixture of gases, vapors, or combustible substances in the form of mists and air that burns after ignition and reaches all unburned mixtures is a baozha-like atmosphere, known as a Class II environment.
Hazardous locations are areas where hazardous environments appear or are expected to occur in quantities sufficient to require special measures for the construction, installation, and use of electrical equipment. The hazardous locations are divided into different areas based on the frequency and duration of the security environment.
(1)Baozha Dust Environmental Danger Zone Division:
According to the frequency and duration of the occurrence of combustible dust/air mixture and the thickness of the dust layer, it can be divided into 20 zones, 21 zones and 22 zones.
- Zone 20: Zone 20, where flammable dust continuously or frequently appears during normal operation, in an amount sufficient to form a flammable dust-air mixture and/or to create an uncontrollable and extremely thick layer of dust and inside the container. The EN50281-1-1 standard specifies the structure and design of the electrical equipment housing used in Zone 20. IEC 60241-11 supplements the electrical equipment used in Zone 20, including intrinsically safe explosion protection. Zone 20 Application Category 1 (Dust) Electrical Equipment.
- Zone 21: Zone 21, during normal operation, there may be sites where the amount of dust is sufficient to form a mixture of flammable dust and air but not in zone 20. This area includes sites that are directly adjacent to the point where dust is discharged, where dust is present, and where flammable dust and air mixtures are likely to produce flammable concentrations under normal operating conditions. Mills, coal, grain warehouses, and packaging lines are surrounded by typical 21-zone locations. In Zone 21, the formation of baozha dust may occur due to dust leakage.
- Zone 22: Zone 22, a site where flammable dust clouds occur occasionally under unusual conditions and are present only for a short period of time, or where flammable dust occasionally accumulates or there may be a dust layer and a flammable dust air mixture is produced. If it cannot be ensured that the flammable dust accumulation or dust layer can be excluded, the non-21 area should be divided. Zone 22 must use category 3 (dust) explosion-proof electrical equipment. If the dust in the baozha environment is electrically conductive dust, type 2 (dust) explosion-proof electrical equipment shall be used in accordance with EN50281-1-2.
(2) The hazardous area division of Baozha gas environment:
According to the frequency and duration of the occurrence of flammable gases, hazardous areas are divided into Zone 0, Zone 1 and Zone 2.
- Zone 0: Zone 0, Baozha Gas atmospheres are continuously or prolonged. The hazardous environment exists for more than 1000 hours/year.
- Zone 1: zone1. In normal operation, there may be places where baozha gas atmospheres occur. The hazardous environment exists between 10-1000 hours/year.
Zone 2: zone2. In the normal operation, baozha atmosphere cannot occur. If it occurs occasionally and only for a short period of time, the hazardous environment exists for less than 10 hours/year. Herein, "normal operation" refers to normal driving, running, parking, loading and unloading of flammable substances, opening and closing of closed container lids, safety valves, discharge valves, and all plant equipment operating within their design parameters. <br> <br> gas group and temperature group
For class II baozha gas atmospheres, the baozha gas is divided into three groups of A, B, and C according to the maximum test safety gap or the minimum ignition current ratio of the baozha gas mixture. Gas grouping and ignition temperature are related to the mixed concentration of flammable gas and air under certain ambient temperature and pressure.
The temperature group is the electrical equipment used in Baozha environment divided according to its maximum surface temperature. When the highest surface temperature electrical equipment work under the most unfavorable operating conditions in the specified range, it may cause the surrounding baowa environment to ignite electrical The maximum temperature reached by any surface of the device that is not visible or on any electrical device. The temperature group of the baozha gas atmosphere is divided into six groups. When the basic ambient temperature is assumed to be 40°C, the temperature of each group is -T1 - 450°C.
-T2--300°C,
-T3--200°C,
-T4--135°C,
-T5--100°C,
-T6--85°C.
Here are some typical gas groups and temperature groups for baozha gas.
For Baozha type dust environment, according to the lighting temperature of dust is divided into three groups of T11, T12, T13, corresponding to the ignition temperature of -T11 - more than 270 °C;
-T12---200°C;
-T13---150°C.
For electrical equipment whose voltage does not exceed 1.2V, whose current does not exceed 0.1A, and whose energy does not exceed 20 microjoules or whose power does not exceed 25mw, after being approved by the explosion-proof inspection department, it can be directly used in the factory baoshi gas environment and under the coal mine. .
The basic principle of 3baozha protection
There are many types of combustibles used in industrial production. The quantity is large and the production process is complex. Therefore, various protective measures must be taken according to different conditions. From the formation of baozha destructive power, baozha generally needs to have 5 conditions:
(1) Flammable substances (sources of release) that provide energy;
(2) Auxiliary combustion oxidizer (oxidant);
(3) Uniform mixing of flammable substances and oxidizers;
(4) The mixture is placed in a relatively closed space (surrounding body);
(5) Ignition sources with sufficient energy.
The ignition source, combustible material and combustion improver in the above conditions are the three elements of burning baozha. Explosion protection technology is based on these baozha conditions, and adopts corresponding technical measures and management measures to achieve the purpose of preventing accidents.
(1) Inhibition of combustible concentration Baozha intensity is closely related to the concentration of baozha mixture. Baozha intensity is similar to the sinusoidal curve of the periodicity in terms of concentration change. The point is called baozha floor concentration or baozha ceiling concentration. Below the lower limit of baozha, the mixture cannot be ignited because the calorific value of the flammable substance is so low that it cannot maintain the minimum temperature required for the flame to propagate in the mixture; if the concentration increases gradually beyond the baozha upper limit concentration, although the combustible material Increase, but the oxygen concentration of the combustion support is lower than the chemical equivalent value, it can not meet the need for complete combustion of the mixture, nor will it occur.
Therefore, the occurrence of baozha accidents can be prevented through the control of the concentration of combustibles, or the destructive power that can be caused by baozha accidents can be minimized.
(2) Control of oxygen concentration When inert gas is added to the baozha atmosphere, on the one hand, the oxygen component of the baozha atmosphere can be diluted, reducing the chance of the action of molecules and oxygen molecules of the combustible material, and also making combustible components homogenous. The molecular segregation creates a barrier that does not burn between the layers; when the activated molecules collide with the inerting medium particles, the activated molecules lose the activation energy and cannot react. On the other hand, if the combustion reaction has already taken place, the resulting free radicals will interact with the inerting medium particles, causing them to lose their activity, leading to a disruption of the combustion chain reaction; at the same time, the inerting medium will absorb a large amount of heat released from the combustion reaction, making The heat cannot accumulate, and the combustion reaction does not spread to other combustible components, which suppresses the combustion reaction.
Therefore, the addition of an inerting medium in the combustible/air baozha atmosphere reduces the range of the combustible component baozha. When the inertizing medium is increased to a sufficient concentration, the upper limit and the lower limit of the baoxya can be coincided with each other, and the concentration of the inerting medium is increased. Combustion air mixture will no longer burn.
(3) The control temperature of the ignition source has a particularly significant effect on the chemical reaction rate. For the general reaction, if the initial concentration is equal, the reaction rate is accelerated by approximately 2 to 4 times for each 10°C increase in temperature. Therefore, temperature (which is usually referred to as the ignition source) speeds up the reaction, causing the initial factor of Baozha accident, and controlling the ignition source makes one of the important measures to prevent the Baozha accident.
(4) One of the important features of weakening baozha pressure and shock wave baozha phenomenon is that when baozha material baozha, high-temperature and high-pressure gas products swell at a very high speed, so that the pressure inside the enclosure body is suddenly increased, and the enclosure body bursts to form a shock wave. Destructive power. In order to prevent or reduce the sudden increase in the pressure in the surrounding body caused by the explosion, the enclosure should be relatively closed as much as possible.
4 Types of explosion-proof electrical equipment
(1) Flameproof structure: EExd
Electric sparks and arcs can ignite baozha mixtures. The gap-proof flameproof structure established by Germany is a more reliable method for preventing arcs and other ignited baozha mixtures. The explosion-proof structure of electrical equipment is extremely widely used in hazardous areas. It can not only prevent the fire flame from baozha, but also the housing can withstand certain overpressure. It has a sufficiently strong enclosure that can withstand 1.5 times the maximum baozha pressure and must not be smaller than 3.5 x 10pa. It is ensured that no deformation or damage occurs, no permanent deformation occurs, and there is a certain structural gap so that the ejected combustion products are cooled down to a temperature lower than the autoignition temperature of the external baozha mixture by a certain length of the flange. The structural gap can be composed of a plane joint surface or a cylinder joint surface, and can also be composed of a curved path, a thread or a barrier type structure. In addition to this. Such as micro-holes, nets, laminations, sand and other structures also belong to the explosion-proof form of this principle. Flameproof electrical equipment used underground in coal mines must be stronger.
Equipment used for Class I mining face shall be made of steel plate or cast steel. Class I equipment for non-excavating face shall have a shell with a grade not lower than that of HT25-47 grey cast iron. Class I portable equipment And type II equipment, the shell can be made of light alloy with tensile strength of not less than 117.6N/mm (12kg/mm) and magnesium content of not more than 0.5% (weight ratio).
(2) Increased safety structure: EExe
The increased safety structure is also widely used in explosion-proof electrical equipment such as motors, transformers, lamps, and electrical equipment with inductive coils. It adopts a series of safety measures on the equipment, such as the use of high-quality insulating materials, lowering the temperature rise, increasing the electrical clearance, and improving the quality of the wire connection so that it will not generate sparks, arcs or dangerous temperatures to the maximum extent possible. Or, the use of effective protective elements to produce sparks, arcs or temperatures that do not ignite the baoxsa mixture to achieve explosion-proof purposes.
Another type of explosion-proof measure similar to the increased safety type is the so-called non-spark type, which is an electrical device that does not generate sparks and dangerous high temperatures during normal operation, and it cannot generate detonation faults. Compared with the safety-enhancing type, there is no provision for additional additional measures to improve the safety and reliability of the equipment. Therefore, the safety of the sparkless type is lower than that of the increased safety type and can only be used in hazardous environments in Zone 2.
(3) positive pressure type structure: p
The explosion-proof principle of this structure of electrical equipment is to ensure that the pressure of the internal protective gas is higher than the surrounding to prevent the mixture from entering the enclosure, or that a sufficient amount of protective gas passes through the enclosure to reduce the concentration of the internal baozha mixture below the lower limit of baozha.
Under normal circumstances, there must be no dead angle inside the electrical equipment that affects safety. In normal operation, the air pressure or inflation pressure of the air outlet must not be lower than a certain value, otherwise it will immediately send an alarm or cut off the power supply. Sparks and arcs inside the equipment must not be blown out from any gap or outlet. The positive pressure type structure is not related to the grade of the material used in Baozha, and it is mostly used in equipment or large-scale electrical equipment in which the internal components are easily damaged, or it is difficult to make other explosion-proof structures in the form of auto-ignition points T4 and T5. On the device.
(4) sand-filled structure: q
The sand-filled structure is filled with sand or other specified powder material in the shell so that the arc or high temperature generated in the shell cannot ignite the surrounding baozha gas environment under the specified use conditions.
When the medium used for the granular solid (usually quartz sand) as the isolation medium, known as the sand-filled electrical equipment; and the medium used when the curing material filler (usually epoxy resin), the ignition source sealed in the Inside the filler, and outside the baozha mixture is also called encapsulated electrical equipment.
(5) Intrinsically Safe Structure: EExi
The essential safety structure is only applicable to weak current loops, such as test instruments, control devices and other small electrical equipment. Whether under normal circumstances or under abnormal conditions, EDM or dangerous temperature will not detonate the Baozha material, so the higher safety of the explosion-proof structure, in which the surface temperature of all components on the circuit or equipment must be less than the provisions To prevent ignition caused by thermal effects.
The electrical circuit of the intrinsically safe explosion-proof structure must be isolated from other circuits in order to prevent electromagnetic or electrostatic induction of the mixed wire, and in particular, the external wiring of the structure must take careful measures to ensure the explosion-proof performance of electrical equipment and wiring.
(6) Explosion-proof oil-filled structure: o The explosion-proof oil-filled structure has nothing to do with the boost level and is suitable for small-scale operation switches. The filled fluid should have high chemical stability. In order to observe the height of the oil level, the equipment should be equipped with an oil level indicator or oil level signal device.
Oil-immersed explosion-proof switches, controllers, and other equipment, due to deterioration or leakage of oil, are difficult to repair and require special attention. In addition, the equipment can no longer be used when the explosion-proof performance is impaired due to tilting or shaking of the oil surface.
(7) explosion-proof structure of baoxa dust environment dust explosion-proof electrical equipment is to limit the maximum surface temperature of the enclosure and the use of "dust-tight" or "dust-proof" enclosures to limit dust entry to prevent ignition of flammable dust. This type of equipment will be installed live parts in a protective enclosure, which limits the entry of dust, so that the source of ignition and dust isolation to prevent Baozha. According to the difference in the dust-proof structure of the device, the device is divided into A-type device or B-type device. According to the dustproof level of the equipment shell, the equipment is divided into 20, 21 and 22 grades, which are applicable to dust dangerous places in the 20, 21 or 22 areas.
5 choice of explosion-proof type
For the baozha-type gas environment in different regions (Type II environment), different types of explosion-proof types need to be selected according to actual needs.
It may be easy to see in normal practical use that many explosion-proof electrical products use a variety of explosion protection methods in one product. For example, lighting devices may employ increased safety protection (housing and terminal box), flameproof protection (switch), and encapsulation type protection (ballast). This enables manufacturers to use the most suitable composite explosion protection method. One thing to note is that the order of the explosion protection methods listed on the product nameplate will often tell the user the structure of the product. If a product is identified as Exde, it is most likely to be a flameproof type with increased safety components. Another product, labeled Exed, is most likely not a flameproof enclosure (such as stainless steel or reinforced polyester glass) with a flameproof switch or component mounted therein. Both products may be suitable for Zone 1, but they use different explosion protection measures to achieve the same purpose. According to their actual needs and the information they understand, they can choose to provide an explosion-proof product that provides the best balance between cost, performance and safety.
Commonly used explosion-proof measures 1, explosion-proof / EEx "d";
2, increase safety / EEx "e";
3, intrinsically safe EEx "i";
4, positive pressure / "p";
5, filled with oil / "o";
6, sand filling / "q";
7, no spark EEx"n";
8, potting "m" and so on
According to the division of the hazardous environment formulated by the International Electrotechnical Commission (IEC), it is clearly defined that, under atmospheric conditions, dust or fibrous combustible substances and air-shaped yang mixture are ignited and ignited and transferred to the unburned mixture. Baozha Dust environment, known as the Class I environment. Under atmospheric conditions, a mixture of gases, vapors, or combustible substances in the form of mists and air that burns after ignition and reaches all unburned mixtures is a baozha-like atmosphere, known as a Class II environment.
Hazardous locations are areas where hazardous environments appear or are expected to occur in quantities sufficient to require special measures for the construction, installation, and use of electrical equipment. The hazardous locations are divided into different areas based on the frequency and duration of the security environment.
(1)Baozha Dust Environmental Danger Zone Division:
According to the frequency and duration of the occurrence of combustible dust/air mixture and the thickness of the dust layer, it can be divided into 20 zones, 21 zones and 22 zones.
- Zone 20: Zone 20, where flammable dust continuously or frequently appears during normal operation, in an amount sufficient to form a flammable dust-air mixture and/or to create an uncontrollable and extremely thick layer of dust and inside the container. The EN50281-1-1 standard specifies the structure and design of the electrical equipment housing used in Zone 20. IEC 60241-11 supplements the electrical equipment used in Zone 20, including intrinsically safe explosion protection. Zone 20 Application Category 1 (Dust) Electrical Equipment.
- Zone 21: Zone 21, during normal operation, there may be sites where the amount of dust is sufficient to form a mixture of flammable dust and air but not in zone 20. This area includes sites that are directly adjacent to the point where dust is discharged, where dust is present, and where flammable dust and air mixtures are likely to produce flammable concentrations under normal operating conditions. Mills, coal, grain warehouses, and packaging lines are surrounded by typical 21-zone locations. In Zone 21, the formation of baozha dust may occur due to dust leakage.
- Zone 22: Zone 22, a site where flammable dust clouds occur occasionally under unusual conditions and are present only for a short period of time, or where flammable dust occasionally accumulates or there may be a dust layer and a flammable dust air mixture is produced. If it cannot be ensured that the flammable dust accumulation or dust layer can be excluded, the non-21 area should be divided. Zone 22 must use category 3 (dust) explosion-proof electrical equipment. If the dust in the baozha environment is electrically conductive dust, type 2 (dust) explosion-proof electrical equipment shall be used in accordance with EN50281-1-2.
(2) The hazardous area division of Baozha gas environment:
According to the frequency and duration of the occurrence of flammable gases, hazardous areas are divided into Zone 0, Zone 1 and Zone 2.
- Zone 0: Zone 0, Baozha Gas atmospheres are continuously or prolonged. The hazardous environment exists for more than 1000 hours/year.
- Zone 1: zone1. In normal operation, there may be places where baozha gas atmospheres occur. The hazardous environment exists between 10-1000 hours/year.
Zone 2: zone2. In the normal operation, baozha atmosphere cannot occur. If it occurs occasionally and only for a short period of time, the hazardous environment exists for less than 10 hours/year. Herein, "normal operation" refers to normal driving, running, parking, loading and unloading of flammable substances, opening and closing of closed container lids, safety valves, discharge valves, and all plant equipment operating within their design parameters. <br> <br> gas group and temperature group
For class II baozha gas atmospheres, the baozha gas is divided into three groups of A, B, and C according to the maximum test safety gap or the minimum ignition current ratio of the baozha gas mixture. Gas grouping and ignition temperature are related to the mixed concentration of flammable gas and air under certain ambient temperature and pressure.
The temperature group is the electrical equipment used in Baozha environment divided according to its maximum surface temperature. When the highest surface temperature electrical equipment work under the most unfavorable operating conditions in the specified range, it may cause the surrounding baowa environment to ignite electrical The maximum temperature reached by any surface of the device that is not visible or on any electrical device. The temperature group of the baozha gas atmosphere is divided into six groups. When the basic ambient temperature is assumed to be 40°C, the temperature of each group is -T1 - 450°C.
-T2--300°C,
-T3--200°C,
-T4--135°C,
-T5--100°C,
-T6--85°C.
Here are some typical gas groups and temperature groups for baozha gas.
For Baozha type dust environment, according to the lighting temperature of dust is divided into three groups of T11, T12, T13, corresponding to the ignition temperature of -T11 - more than 270 °C;
-T12---200°C;
-T13---150°C.
For electrical equipment whose voltage does not exceed 1.2V, whose current does not exceed 0.1A, and whose energy does not exceed 20 microjoules or whose power does not exceed 25mw, after being approved by the explosion-proof inspection department, it can be directly used in the factory baoshi gas environment and under the coal mine. .
The basic principle of 3baozha protection
There are many types of combustibles used in industrial production. The quantity is large and the production process is complex. Therefore, various protective measures must be taken according to different conditions. From the formation of baozha destructive power, baozha generally needs to have 5 conditions:
(1) Flammable substances (sources of release) that provide energy;
(2) Auxiliary combustion oxidizer (oxidant);
(3) Uniform mixing of flammable substances and oxidizers;
(4) The mixture is placed in a relatively closed space (surrounding body);
(5) Ignition sources with sufficient energy.
The ignition source, combustible material and combustion improver in the above conditions are the three elements of burning baozha. Explosion protection technology is based on these baozha conditions, and adopts corresponding technical measures and management measures to achieve the purpose of preventing accidents.
(1) Inhibition of combustible concentration Baozha intensity is closely related to the concentration of baozha mixture. Baozha intensity is similar to the sinusoidal curve of the periodicity in terms of concentration change. The point is called baozha floor concentration or baozha ceiling concentration. Below the lower limit of baozha, the mixture cannot be ignited because the calorific value of the flammable substance is so low that it cannot maintain the minimum temperature required for the flame to propagate in the mixture; if the concentration increases gradually beyond the baozha upper limit concentration, although the combustible material Increase, but the oxygen concentration of the combustion support is lower than the chemical equivalent value, it can not meet the need for complete combustion of the mixture, nor will it occur.
Therefore, the occurrence of baozha accidents can be prevented through the control of the concentration of combustibles, or the destructive power that can be caused by baozha accidents can be minimized.
(2) Control of oxygen concentration When inert gas is added to the baozha atmosphere, on the one hand, the oxygen component of the baozha atmosphere can be diluted, reducing the chance of the action of molecules and oxygen molecules of the combustible material, and also making combustible components homogenous. The molecular segregation creates a barrier that does not burn between the layers; when the activated molecules collide with the inerting medium particles, the activated molecules lose the activation energy and cannot react. On the other hand, if the combustion reaction has already taken place, the resulting free radicals will interact with the inerting medium particles, causing them to lose their activity, leading to a disruption of the combustion chain reaction; at the same time, the inerting medium will absorb a large amount of heat released from the combustion reaction, making The heat cannot accumulate, and the combustion reaction does not spread to other combustible components, which suppresses the combustion reaction.
Therefore, the addition of an inerting medium in the combustible/air baozha atmosphere reduces the range of the combustible component baozha. When the inertizing medium is increased to a sufficient concentration, the upper limit and the lower limit of the baoxya can be coincided with each other, and the concentration of the inerting medium is increased. Combustion air mixture will no longer burn.
(3) The control temperature of the ignition source has a particularly significant effect on the chemical reaction rate. For the general reaction, if the initial concentration is equal, the reaction rate is accelerated by approximately 2 to 4 times for each 10°C increase in temperature. Therefore, temperature (which is usually referred to as the ignition source) speeds up the reaction, causing the initial factor of Baozha accident, and controlling the ignition source makes one of the important measures to prevent the Baozha accident.
(4) One of the important features of weakening baozha pressure and shock wave baozha phenomenon is that when baozha material baozha, high-temperature and high-pressure gas products swell at a very high speed, so that the pressure inside the enclosure body is suddenly increased, and the enclosure body bursts to form a shock wave. Destructive power. In order to prevent or reduce the sudden increase in the pressure in the surrounding body caused by the explosion, the enclosure should be relatively closed as much as possible.
4 Types of explosion-proof electrical equipment
(1) Flameproof structure: EExd
Electric sparks and arcs can ignite baozha mixtures. The gap-proof flameproof structure established by Germany is a more reliable method for preventing arcs and other ignited baozha mixtures. The explosion-proof structure of electrical equipment is extremely widely used in hazardous areas. It can not only prevent the fire flame from baozha, but also the housing can withstand certain overpressure. It has a sufficiently strong enclosure that can withstand 1.5 times the maximum baozha pressure and must not be smaller than 3.5 x 10pa. It is ensured that no deformation or damage occurs, no permanent deformation occurs, and there is a certain structural gap so that the ejected combustion products are cooled down to a temperature lower than the autoignition temperature of the external baozha mixture by a certain length of the flange. The structural gap can be composed of a plane joint surface or a cylinder joint surface, and can also be composed of a curved path, a thread or a barrier type structure. In addition to this. Such as micro-holes, nets, laminations, sand and other structures also belong to the explosion-proof form of this principle. Flameproof electrical equipment used underground in coal mines must be stronger.
Equipment used for Class I mining face shall be made of steel plate or cast steel. Class I equipment for non-excavating face shall have a shell with a grade not lower than that of HT25-47 grey cast iron. Class I portable equipment And type II equipment, the shell can be made of light alloy with tensile strength of not less than 117.6N/mm (12kg/mm) and magnesium content of not more than 0.5% (weight ratio).
(2) Increased safety structure: EExe
The increased safety structure is also widely used in explosion-proof electrical equipment such as motors, transformers, lamps, and electrical equipment with inductive coils. It adopts a series of safety measures on the equipment, such as the use of high-quality insulating materials, lowering the temperature rise, increasing the electrical clearance, and improving the quality of the wire connection so that it will not generate sparks, arcs or dangerous temperatures to the maximum extent possible. Or, the use of effective protective elements to produce sparks, arcs or temperatures that do not ignite the baoxsa mixture to achieve explosion-proof purposes.
Another type of explosion-proof measure similar to the increased safety type is the so-called non-spark type, which is an electrical device that does not generate sparks and dangerous high temperatures during normal operation, and it cannot generate detonation faults. Compared with the safety-enhancing type, there is no provision for additional additional measures to improve the safety and reliability of the equipment. Therefore, the safety of the sparkless type is lower than that of the increased safety type and can only be used in hazardous environments in Zone 2.
(3) positive pressure type structure: p
The explosion-proof principle of this structure of electrical equipment is to ensure that the pressure of the internal protective gas is higher than the surrounding to prevent the mixture from entering the enclosure, or that a sufficient amount of protective gas passes through the enclosure to reduce the concentration of the internal baozha mixture below the lower limit of baozha.
Under normal circumstances, there must be no dead angle inside the electrical equipment that affects safety. In normal operation, the air pressure or inflation pressure of the air outlet must not be lower than a certain value, otherwise it will immediately send an alarm or cut off the power supply. Sparks and arcs inside the equipment must not be blown out from any gap or outlet. The positive pressure type structure is not related to the grade of the material used in Baozha, and it is mostly used in equipment or large-scale electrical equipment in which the internal components are easily damaged, or it is difficult to make other explosion-proof structures in the form of auto-ignition points T4 and T5. On the device.
(4) sand-filled structure: q
The sand-filled structure is filled with sand or other specified powder material in the shell so that the arc or high temperature generated in the shell cannot ignite the surrounding baozha gas environment under the specified use conditions.
When the medium used for the granular solid (usually quartz sand) as the isolation medium, known as the sand-filled electrical equipment; and the medium used when the curing material filler (usually epoxy resin), the ignition source sealed in the Inside the filler, and outside the baozha mixture is also called encapsulated electrical equipment.
(5) Intrinsically Safe Structure: EExi
The essential safety structure is only applicable to weak current loops, such as test instruments, control devices and other small electrical equipment. Whether under normal circumstances or under abnormal conditions, EDM or dangerous temperature will not detonate the Baozha material, so the higher safety of the explosion-proof structure, in which the surface temperature of all components on the circuit or equipment must be less than the provisions To prevent ignition caused by thermal effects.
The electrical circuit of the intrinsically safe explosion-proof structure must be isolated from other circuits in order to prevent electromagnetic or electrostatic induction of the mixed wire, and in particular, the external wiring of the structure must take careful measures to ensure the explosion-proof performance of electrical equipment and wiring.
(6) Explosion-proof oil-filled structure: o The explosion-proof oil-filled structure has nothing to do with the boost level and is suitable for small-scale operation switches. The filled fluid should have high chemical stability. In order to observe the height of the oil level, the equipment should be equipped with an oil level indicator or oil level signal device.
Oil-immersed explosion-proof switches, controllers, and other equipment, due to deterioration or leakage of oil, are difficult to repair and require special attention. In addition, the equipment can no longer be used when the explosion-proof performance is impaired due to tilting or shaking of the oil surface.
(7) explosion-proof structure of baoxa dust environment dust explosion-proof electrical equipment is to limit the maximum surface temperature of the enclosure and the use of "dust-tight" or "dust-proof" enclosures to limit dust entry to prevent ignition of flammable dust. This type of equipment will be installed live parts in a protective enclosure, which limits the entry of dust, so that the source of ignition and dust isolation to prevent Baozha. According to the difference in the dust-proof structure of the device, the device is divided into A-type device or B-type device. According to the dustproof level of the equipment shell, the equipment is divided into 20, 21 and 22 grades, which are applicable to dust dangerous places in the 20, 21 or 22 areas.
5 choice of explosion-proof type
For the baozha-type gas environment in different regions (Type II environment), different types of explosion-proof types need to be selected according to actual needs.
It may be easy to see in normal practical use that many explosion-proof electrical products use a variety of explosion protection methods in one product. For example, lighting devices may employ increased safety protection (housing and terminal box), flameproof protection (switch), and encapsulation type protection (ballast). This enables manufacturers to use the most suitable composite explosion protection method. One thing to note is that the order of the explosion protection methods listed on the product nameplate will often tell the user the structure of the product. If a product is identified as Exde, it is most likely to be a flameproof type with increased safety components. Another product, labeled Exed, is most likely not a flameproof enclosure (such as stainless steel or reinforced polyester glass) with a flameproof switch or component mounted therein. Both products may be suitable for Zone 1, but they use different explosion protection measures to achieve the same purpose. According to their actual needs and the information they understand, they can choose to provide an explosion-proof product that provides the best balance between cost, performance and safety.
Commonly used explosion-proof measures 1, explosion-proof / EEx "d";
2, increase safety / EEx "e";
3, intrinsically safe EEx "i";
4, positive pressure / "p";
5, filled with oil / "o";
6, sand filling / "q";
7, no spark EEx"n";
8, potting "m" and so on
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4. Fast lead time: 5-7days for samples and 15-25days for bulk order.
5. 3 or 5 year warranty with standardized after-sale serivce process.
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Jiangmen Dilin Lighting High-Tech Co., Ltd. , https://www.jmdilinlighting.com