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1、 Explosion proof electrical equipment "d"
Explosion proof enclosure: capable of withstanding the explosive pressure of internal explosive gas mixtures and preventing internal explosions from spreading to the surrounding explosive mixture of your equipment enclosure. Create a sturdy enclosure for electrical equipment, with gaps between all seams less than the maximum test safety gap for the corresponding combustible gas. If combustible gas enters the enclosure and is ignited by sparks, causing an explosion, the explosion flame is confined within the enclosure and cannot ignite explosive mixtures in the environment outside the enclosure, thereby ensuring environmental safety.
The explosion-proof shell must meet two basic conditions:
1. The shell has sufficient mechanical strength to withstand internal explosive pressure without damage, and does not produce permanent deformation that affects explosion-proof performance
2. All seams and gaps on the outer shell wall that are connected to the outside are less than the corresponding maximum test safety clearance
Main explosion-proof measures:
1. Material requirements for explosion-proof shell
2. Requirements for gap length, width, and surface smoothness of explosion-proof joint surfaces
3. Requirements for fasteners and threaded holes
4. Requirements for Transparent Components
5. Requirements for adhesives and sealants
6. Grounding
7. Cable and conduit entry device
8. Chain or warning signs, etc
Reference standards for explosion-proof design of explosion-proof electrical products:
GB/T 3836.2-2021 "Explosive Atmosphere Part 2- Equipment Protected by Flameproof Enclosures" d "
2、 Positive pressure electrical equipment "p"
Positive pressure casing: Fresh air or inert gas at a certain pressure is introduced into the casing of the equipment to prevent flammable gases from entering the interior of the casing, thereby preventing the ignition source from coming into contact with explosive gases and achieving the purpose of explosion prevention.
Key explosion-proof measures for positive pressure electrical equipment:
1. The pressure of the protective gas (fresh air or inert gas) inside the equipment casing should be at least 50Pa higher than the ambient pressure
2. Before powering on electrical equipment, the equipment casing should be flushed with protective gas (usually using protective gas that is 5 times the net volume of the casing for flushing)
Therefore, the equipment needs to be equipped with blowers, pipelines, and wind pressure relays, which are generally used for large electric motors and control switch devices
Reference standards for explosion-proof design of positive pressure electrical products:
GB/T 3836.5-2021 "Explosive Atmosphere Part 5: Equipment Protected by Positive Pressure Shell" p ""
3、 Oil filled electrical equipment "o"
Oil filled casing: Immerse all or part of the equipment in the oil inside the casing, so that the equipment cannot ignite explosive gases above the oil level or outside the casing.
Main explosion-proof measures:
1. Immerse live parts at least 25mm below the oil level
2. Transformer oil that meets the standard GB2536
3. The oil temperature is not allowed to exceed 100 ° C
4. Set oil level indicator
5. Insulation and sealing materials should be oil resistant
6. The maximum on-off capacity of the equipment is 75% of the safe value for ignition test
This explosion-proof type is mainly used for transformers and high-voltage switches
Reference standards for explosion-proof design of oil filled electrical equipment:
GB/T 3836.6-2017 Explosive Atmosphere Part 6: Equipment Protected by Liquid Immersion Type "O"
4、 Sand filled electrical equipment "q"
Sand filled shell: The shell is filled with sand material, so that under specified usage conditions, the arc, flame, shell wall, and sand surface generated inside the shell cannot ignite the surrounding explosive mixture.
Main explosion-proof measures:
1. The shell is filled with sand material and has a certain safe height
2. The particle size of quartz sand is 0.25-1.6mm, and the moisture content does not exceed 0.1%
3. Electrical clearance
4. Shell protection level
This explosion-proof type is mainly suitable for products such as fuses and capacitors
Reference standards for explosion-proof design of sand filled electrical equipment:
GB/T 3836.7-2017 《Explosive atmospheres - Part 7: Equipment protected by sand filled molds "q"》
5、 Sealed electrical equipment "m"
Pouring the parts of the equipment that may generate sparks or high temperatures into the sealing agent (resin) prevents them from igniting the surrounding explosive mixture
Main explosion-proof measures：
1. Seal the electrical components with resin, and the free surface of the sealing agent should not be less than 3mm thick compared to the sealed components or conductors
2. There are regulations on the dielectric strength, water absorption, light resistance, heat and cold resistance, and surface resistance of the sealing agent
3. Surface temperature limit
Reference standards for explosion-proof design of sealed electrical equipment:
GB/T3836.9-2021《Explosive Environment Part 9Equipment protected by pouring type "m"
6、 Intrinsic safety electrical equipment i
Under the specified experimental conditions, the electrical sparks or thermal effects generated by the normal operation of the equipment's circuit or the specified fault conditions cannot ignite the specified explosive mixture. The main explosion-proof measure of intrinsic safety type is to limit the energy in the circuit, so that the generated spark energy is less than the corresponding minimum ignition energy.
Main explosion-proof measures:
1. Voltage and current limitations of circuits
2. Limitations of capacitors and inductors in circuits
3. Isolation of intrinsic safety circuits and non intrinsic safety circuits
4. Requirements for reliable components and assemblies
5. Regulations on safety barriers
6. Fault analysis and testing regulations, etc
Applicable products: weak current equipment for measurement, control, communication, etc
Reference standards for explosion-proof design of intrinsically safe electrical equipment:
GB/T 3836.4-2021《Explosive Environment Part 9：Devices protected by intrinsic safety type "i"
7、 Increased safety electrical equipment "e"
On equipment structures that do not generate sparks, arcs, or potentially ignite explosive mixtures under normal operating conditions, measures should be taken to improve safety to avoid these phenomena under normal and recognized overload conditions (including motor stalling conditions) for electrical equipment.
Increased safety electrical equipment does not have explosion-proof enclosures and protective media, and it adopts comprehensive safety measures:
1. Restricting the types of devices
2. The electrical clearance and creepage distance are relatively large
3. Good insulation material
4. Specify the conductor connection method
5. Reduce temperature rise
6. Improve the protection level of the shell
7. Equipped with appropriate protective devices, etc
Applicable products: asynchronous motors, transformers, junction boxes, etc
Reference standards for explosion-proof design of increased safety electrical equipment:
GB/T 3836.3-2021《Explosive Environment Part 3：Devices protected by increased safety type "e"
8、 Non sparking electrical equipment "n"
A type of explosion-proof electrical equipment that, during normal operation and under certain conditions specified in this standard (only referring to light source failure conditions of lamps), cannot ignite the surrounding explosive environment
The non sparking type originally only referred to electrical equipment that does not generate sparks or arcs during normal operation, such as AC asynchronous motors. Based on this, some safety measures are taken, such as using non sparking materials for fan blades, an IP44 or IP54 enclosure protection level, and appropriately increasing electrical clearances and creepage distances. Later, this explosion-proof concept was expanded to electrical products that generate sparks during normal operation, and measures such as gas sealing, simple ventilation, or energy limitation were taken according to their situation to achieve a certain level of safety,. Due to the expansion of this explosion-proof type, the term "spark free" is no longer very precise and is now often referred to as the "n" type.
nType devices can be divided into two categories:
1. The equipment does not generate sparks or arcs during normal operation, such as asynchronous motors, transformers, lighting fixtures, and junction boxes. Plug in device, etc
2. Sparks or arcs are generated during normal operation of equipment, such as switches, relays, etc
nReference standards for explosion-proof design of electrical equipment:
GB/T 3836.8-2021《Explosive Environment Part 8：Equipment protected by "n" type》
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