The selection of explosion-proof electrical equipment requires comprehensive consideration of multiple factors. The following is a detailed explanation for you:
1、 Understand the characteristics of explosive hazardous environments
1. Classification of Hazardous Substances:
(1) Gases or vapors: classified into different groups based on their explosive characteristics, such as IIA, IIB, and IIC. For example, hydrogen, acetylene, etc. belong to Group IIC with high explosive hazards; Common combustible gases such as ethylene generally belong to Group IIB; Some relatively less flammable gases, such as propane, belong to Group IIA. Understanding these groups is crucial for selecting explosion-proof electrical equipment that can adapt to the corresponding level of explosion hazard.
(2) Combustible dust: It also needs to be classified based on its flammability and explosive characteristics. Different types of dust have different characteristics such as ignition temperature and minimum ignition energy, such as metal dust (such as aluminum powder), coal dust, grain dust, etc. They form explosive hazardous environments in different production environments, and explosion-proof equipment suitable for handling such dust needs to be selected.
2. Classification of hazardous areas:
(1) Gas environment:
Zone 0: refers to an environment where explosive gas mixtures occur continuously or for a long time. For example, in certain chemical production areas such as reaction vessels and sealed containers storing flammable and explosive gases, explosion-proof electrical equipment with the highest protection level applicable to Zone 0 must be selected in this area, such as Ga grade equipment.
Zone 1: An environment where explosive gas mixtures may occur during normal operation. For example, in areas such as pipeline connections and near valves in petrochemical enterprises, equipment that meets Zone 1 explosion-proof requirements, such as Ga or Gb grade equipment, needs to be selected.
Zone 2: An environment where explosive gas mixtures are unlikely to occur during normal operation, and even if they do, they are only present for a short period of time. For example, in some well ventilated workshop edge areas or places where flammable and explosive gases are intermittently used, for Zone 2, Gc or Ga or Gb equipment with relatively lower protection levels can be selected, but explosion-proof requirements still need to be met.
(2) Dust environment:
Zone 20: An area where combustible dust clouds in the air continuously, long-term, or frequently appear in explosive environments. For example, in some dust processing workshops, the equipment inside the dust collector and key parts of the dust conveying pipeline must be able to withstand the risk of high concentration dust explosion, and the highest protection level equipment, such as Da level equipment, needs to be selected.
Zone 21: During normal operation, combustible dust clouds in the air are likely to occasionally appear in explosive environments. For example, around some open dust processing equipment, explosive environments may be formed due to the dust generated during operation, and explosion-proof equipment suitable for Zone 21, such as Da or Db level equipment, needs to be selected.
Zone 22: During normal operation, combustible dust clouds in the air are generally not likely to appear in explosive environments, and even if they do, their duration is brief. For example, in some areas that are far away from dust sources and have good ventilation, but there is still a possibility of a small amount of dust suspended, for Zone 22, explosion-proof equipment with relatively low protection levels can be selected, but it is also necessary to ensure that it can withstand the impact of dust explosions when necessary, such as Da Db or Dc level devices.
2、 Determine the explosion-proof type of the equipment
1. Explosion proof type "d":
Working principle: The shell of explosion-proof equipment can withstand the pressure generated by the internal explosive mixture explosion and prevent the spread of explosive flames to the explosive mixture around the shell. Its shell has sufficient explosion-proof and anti reliability strength, and even if there is an explosion inside, it will not have a direct impact on the surrounding environment.
Applicable scenarios: Suitable for hazardous areas such as Zone 1 and Zone 2 where flammable gases and vapors are present. For example, some motors, switches, and other equipment in the petrochemical industry often use explosion-proof types because these devices may generate ignition sources such as arcs and sparks during operation. Explosion proof enclosures can effectively isolate these potential hazards from the surrounding environment.
2. Increased safety type "e":
Working principle: Under normal operating conditions, by adding safety measures to the equipment, such as using high-quality insulation materials, strengthening the reliability of electrical connections, and limiting the surface temperature of the equipment, the possibility of sparks and high temperatures is reduced, thereby improving the safety of the equipment.
Applicable scenarios: Usually used in areas with relatively low levels of danger such as Zone 2, as well as auxiliary components of Zone 1 equipment that require high safety, such as the casing of certain lighting fixtures, motor junction boxes, etc. In these scenarios, increased safety devices can reduce costs and complexity while ensuring a certain level of security.
3. Intrinsic safety type "i":
Working principle: Essentially safe devices limit the energy in the circuit, so that the sparks and heat generated during normal operation and fault conditions are not sufficient to ignite the explosive mixture around them. This is usually achieved through the use of special circuit designs, low-energy components, and reliable isolation measures.
Applicable scenarios: Widely used in hazardous areas such as Zone 0, Zone 1, and Zone 2, especially in places with extremely high safety requirements, such as sensors, transmitters, controllers, and other equipment in chemical automation control systems. Due to its inherently safe nature, it can ensure that explosions will not occur even in complex work environments.
4. Positive pressure type 'p':
Working principle: By filling the device casing with protective gas (usually clean air or inert gas), the internal pressure is higher than the external environmental pressure, thereby preventing external explosive mixtures from entering the interior of the casing. At the same time, maintaining positive pressure inside the casing can ensure that even if there is a malfunction inside the device, it will not cause an explosion.
Applicable scenarios: Commonly used for equipment that needs to work in special environments, such as explosion-proof electrical equipment in environments containing corrosive gases or high humidity. For example, in some offshore oil platforms, the use of positive pressure design in electrical control cabinets can effectively prevent corrosion of electrical components inside the equipment by seawater and corrosive gases, while ensuring safe operation in hazardous environments.
5. Oil immersed type "o":
Working principle: Immerse electrical equipment or components in insulating oil, so that ignition sources such as arcs and sparks generated inside the equipment cannot ignite external explosive mixtures under the cooling and isolation effect of the insulating oil. Insulating oil can also play a good role in insulation and heat dissipation, improving the reliability and safety of equipment.
Applicable scenarios: Suitable for some high-power electrical equipment in hazardous areas such as Zone 1 and Zone 2, such as transformers, oil immersed motors, etc. In these devices, insulating oil not only provides explosion-proof protection, but also meets the high requirements for insulation and heat dissipation of the equipment.
6. Filling sand mold "q":
Working principle: Fill the equipment casing with solid materials such as granular quartz sand, completely burying electrical components or circuits in the sand. This can effectively prevent the propagation of sparks and arcs, while also providing insulation and heat dissipation.
Applicable scenarios: Commonly used in some special explosion-proof situations, such as in environments containing explosive dust, or in places that require mechanical shock and vibration. For example, in some electrical equipment underground in coal mines, sand filling design can ensure stable operation of the equipment in harsh working environments and prevent explosion accidents from occurring.
7. Type n:
Working principle: The n-type equipment adopts a special structural design and material selection, so that it will not generate sparks, arcs or high-temperature surfaces that are sufficient to ignite the surrounding explosive mixture under normal operation and fault conditions. It mainly achieves explosion-proof safety by limiting energy release, using special insulation materials, and protective measures.
Applicable scenarios: n-type equipment is suitable for explosive gas environments with relatively low levels of danger, such as Zone 2, as well as some specific combustible dust environments. For example, some small electronic devices, instruments, etc. can adopt n-type explosion-proof design to meet the requirements for use in general hazardous environments.
8. Anti dust ignition shell "t":
Working principle: The anti dust ignition shell "t" mainly achieves explosion-proof performance by restricting the entry of combustible dust and limiting the surface temperature of the shell through shell protection.
Applicable scenarios: Suitable for lighting equipment, production equipment, etc. in places with combustible dust such as pharmaceuticals, food, textiles, etc.
3、 Consider other selection factors
1. Environmental conditions:
(1) Temperature: In addition to considering the temperature group requirements in explosive hazardous environments, it is also necessary to consider the temperature variation range of the actual operating environment of the equipment. For example, explosion-proof electrical equipment installed outdoors in some high-temperature workshops or cold regions needs to choose products that can adapt to the corresponding temperature conditions. High temperature environment may affect the heat dissipation performance of equipment and the normal operation of electrical components, while low temperature environment may cause problems such as brittle equipment materials and decreased battery performance.
(2) Humidity: High humidity environments may have an impact on the insulation performance of equipment and the corrosion of metal components. In humid environments such as marine environments or wet production areas of some chemical enterprises, it is necessary to choose explosion-proof electrical equipment with good moisture-proof performance, such as using sealed structures, moisture-proof coatings, or special insulation materials. For some critical equipment, dehumidification devices or heaters may also be required to maintain a dry environment inside the equipment.
(3) Corrosive substances: In environments with corrosive gases, chemical liquids, or dust, the casing materials and internal electrical components of equipment need to have corrosion resistance. For example, in acid and alkali production workshops or offshore platforms of chemical enterprises, it is necessary to choose corrosion-resistant stainless steel shells, special anti-corrosion coatings, or use corrosion-resistant electrical components. In addition, it is necessary to regularly maintain and inspect the equipment, promptly clean up the accumulation of corrosive substances, and extend the service life of the equipment.
(4) Mechanical shock and vibration: Explosion proof electrical equipment may be affected by mechanical shock and vibration near some mechanical equipment or during transportation. Therefore, it is necessary to choose equipment with sufficient mechanical strength and seismic performance, such as using sturdy shell structures, special installation methods, or shock absorbers. For some explosion-proof electrical equipment installed on mobile devices, their reliability and stability in dynamic environments also need to be considered.
2. Electrical parameters:
(1) Voltage and current: Select explosion-proof electrical equipment with appropriate voltage and current levels according to the actual working requirements of the equipment. Ensure that the rated voltage and current of the equipment can meet the requirements of the load, and that there will be no overload or short circuit faults during normal operation and startup. At the same time, it is necessary to consider the stability and fluctuation range of the power supply to ensure that the equipment can work properly.
(2) Power and frequency: For some high-power explosion-proof electrical equipment, such as motors, frequency converters, etc., it is necessary to choose the appropriate model and specifications according to their power requirements. In addition, attention should be paid to whether the operating frequency of the equipment matches the power frequency, especially in some imported equipment or special application scenarios, frequency conversion or compatibility issues may need to be considered.
(3) Grounding and insulation requirements: Explosion proof electrical equipment must have good grounding and insulation performance to ensure safe operation. When selecting, attention should be paid to the grounding method and grounding resistance requirements of the equipment, as well as the performance and grade of the insulation material. For some equipment in special environments, double insulation or reinforced insulation measures may also be required to improve the safety of the equipment.
3. Equipment functionality and reliability:
(1) Functional requirements: Select explosion-proof electrical equipment with corresponding functions according to the needs of actual application scenarios. For example, in the field of lighting, it is necessary to choose suitable explosion-proof lamps, including parameters such as lighting intensity, light distribution, color temperature, etc; In automation control systems, it is necessary to select explosion-proof sensors, controllers, and other equipment that meet communication protocols and control requirements. In addition, it is necessary to consider whether the operation mode and display function of the device meet the convenience requirements for actual use.
(2) Reliability and maintainability: Choosing explosion-proof electrical equipment with high reliability and easy maintenance can reduce the risk of equipment failure and maintenance costs. When selecting, you can refer to information such as equipment quality certification, brand reputation, and user evaluations to understand the reliability and durability of the equipment. At the same time, it is also necessary to consider the maintenance requirements of the equipment, such as whether it is easy to replace parts and whether regular calibration is required. Some advanced explosion-proof electrical equipment may have self diagnosis and remote monitoring functions, which can detect faults in a timely manner and issue warnings, improving the reliability and maintenance efficiency of the equipment.
4. Costs and benefits:
(1) Equipment price: On the premise of meeting explosion-proof requirements and functional requirements, the price factor of the equipment needs to be considered. There are significant price differences among explosion-proof electrical equipment of different brands, models, and specifications, which require reasonable comparison and selection. At the same time, it is necessary to consider the service life and operating costs of the equipment, and comprehensively evaluate the cost-effectiveness of the equipment.
(2) Installation and maintenance costs: In addition to the price of the equipment itself, installation and maintenance costs also need to be considered. Some complex explosion-proof electrical equipment may require professional installation, commissioning, and maintenance personnel, which will increase additional costs. Therefore, when selecting equipment, it is necessary to choose equipment that is easy to install and maintain, in order to reduce later operating costs. In addition, the energy-saving performance of the equipment also needs to be considered. Choosing high-efficiency and energy-saving products can reduce long-term energy consumption costs.
5. Regulatory and standard requirements:
(1) International and domestic standards: The selection of explosion-proof electrical equipment must comply with relevant international and domestic regulations and standards. For example, in China, it is necessary to comply with the GB/T3836 series standards, etc; Internationally, it is necessary to comply with standards such as the IECEx certification system, and electrical equipment installed and used in EU countries and regions must meet the requirements of the EN60079 series standards. These standards specify the classification, level, performance requirements, testing methods, etc. of explosion-proof electrical equipment to ensure the safe operation of the equipment in hazardous environments.
(2) Industry specific requirements: Different industries may have their own specific explosion-proof requirements and standards. For example, the petrochemical industry, coal mining industry, pharmaceutical industry, etc. all have their own industry standards and regulations. When selecting, it is necessary to fully understand the special requirements of the industry and choose explosion-proof electrical equipment that meets the corresponding standards. In addition, it is necessary to pay attention to local regulations and policies to ensure that the selection and use of equipment comply with legal requirements.
Welcome everyone to delve deeper together!
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