To do a good job in safety work, it is necessary to take preventive measures and have a certain understanding of safety hazards. Below, Zhongnuo Testing will introduce some common explosion-proof safety hazards and solutions for equipment in explosive hazardous areas.
1、 Explosion proof safety hazards in equipment selection
1. Choose ordinary electrical products in explosive hazardous areas.
2. Select electrical equipment for underground coal mines in factory premises.
3. Select explosion-proof electrical equipment for gas environments in explosive dust environments.
4. From the appearance and structure of the product, it seems to be an explosion-proof product. However, these products lack product nameplates, explosion-proof marks, and product certification information (such as explosion-proof certificate numbers). Three no products that cannot provide explosion-proof certification at the same time.
5. From the appearance and structure of the product, it appears to be an explosion-proof product. However, the brand names of these products only have the "Ex" universal logo and explosion-proof logo, without product certification information (such as explosion-proof certificate number). Unable to query, confirm whether the product has been inspected and certified by a nationally authorized testing agency.
6. A counterfeit and inferior product that has been identified by professional inspectors as an ordinary product but is labeled with explosion-proof information.
7. In hazardous areas with Class IIC substances, use Class IIB explosion-proof products.
8. The equipment selection requirement is T4 temperature group, but in reality, explosion-proof products with temperature group T1 are selected.
2、 Explosion proof electrical products themselves have safety hazards
1. Explosion proof electrical product casing is damaged.
2. The nameplate of explosion-proof electrical products is missing or unclear.
3. The isolation and sealing fillers for the explosion-proof and safety increasing composite products' explosion-proof chambers and wiring chambers do not meet the requirements.
3、 Explosion proof safety hazards in electrical equipment installation
1. The cable entry does not meet the requirements.
2. Excess inlet holes are sealed with adhesive/plastic sealing components/not sealed.
3. The fastening bolts are inconsistent, missing, loose, corroded, lacking elasticity, and flat pads.
4. The cable or wire entry port of explosion-proof electrical equipment is directly connected to the steel pipe.
5. The flexible pipe is directly connected to the equipment without a cable entry device installed.
6. The cable entry device installed for explosion-proof equipment does not match the explosion-proof type.
7. The gap between the explosion-proof joint surfaces of explosion-proof equipment is too large.
8. The explosion-proof joint surface is corroded.
9. The explosion-proof joint surface between the cover and the box is coated or padded.
10. The independent explosion-proof chambers are interconnected without isolation and sealing measures.
11. The distance between the explosion-proof joint surface and the solid obstacle is relatively small.
12. The aging of the box or the aging of the sealing gasket causes the gap to become larger, resulting in the protection level not meeting the requirements and internal water ingress.
13. The increased safety equipment has replaced or added electrical components without approval.
14. The bending of the explosion-proof interference tube is too small, the interference tube is aging, and the rubber protective layer is damaged.
4、 Problems in cable laying
1. Cable changes and damage.
2. The cable is directly connected in hazardous areas.
3. The wire is twisted in the increased safety type wiring.
4. Connect wires inside the wiring box.
5. No isolation and sealing measures were taken when the cable passed through different areas.
6. Armored cables are not equipped with armored cable entry devices.
7. The armor layer of the armored cable is exposed.
8. Idle cable ends are disposed of in hazardous areas, and excess bare copper wires are placed randomly in increased safety junction boxes without being fixed or insulated.
5、 Grounding and equipotential connection issues
1. The external grounding is not connected.
2. External grounding wire series connection, cable tray and liquid transportation pipeline equipotential connection issues.
3. The external grounding wire is less than 4mm ².
4. The external grounding bolt is corroded.
6、 Check and maintain
1. Inspection and maintenance of explosion-proof electrical equipment
For explosion-proof electrical equipment in use, a system of daily inspection and maintenance, as well as regular professional testing and inspection, should be implemented.
When explosion-proof electrical equipment is found to have decreased or failed explosion-proof performance due to external damage, atmospheric corrosion, chemical corrosion, mechanical wear, natural aging, and other reasons during inspection and maintenance. Should be repaired. The maintenance of explosion-proof electrical equipment should be carried out in accordance with GB3836.13-2013. If the explosion-proof performance of the original level cannot be restored after maintenance, it can be handled according to the following principles based on the actual technical performance:
a、 Reduce the explosion-proof rating for use;
b、 Reduced to non explosion proof electrical equipment use.
2. Failure of explosion-proof performance of explosion-proof electrical equipment
If the structure and parameters of explosion-proof electrical equipment are found to have changed during maintenance and do not match the original explosion-proof type and design, and cannot be repaired, it will be judged as invalid and quickly stopped for replacement. For example:
a、 The shell of explosion-proof electrical equipment is severely deformed and cannot be repaired;
b、 The explosion-proof surface is severely damaged and cannot be repaired;
c、 The explosion-proof gap exceeds the national standard and cannot be restored;
d、 The cracking of the explosion-proof electrical equipment casing does not meet the requirements of the original explosion-proof type.
Conclusion
1. The appeal issue is just a typical example of the common explosion-proof safety hazards of equipment in explosive hazardous areas.
2. For a long time in the past, people mainly focused on hazardous chemicals or explosive gas environments regarding explosion hazards; There is less attention paid to the explosion hazards of combustible dust and fibrous materials. In fact, once combustible dust and fibrous materials explode, their harm is no less than that of gas explosions. For example, accidents such as the flax fiber explosion in Harbin flax factory in the 1980s, the metal dust explosion in Kunshan last year, and the starch dust explosion in New Taipei, Taiwan this year have all caused very serious consequences.
3. For most powder related enterprises in China, the safety situation is still not optimistic, and there are still a large number of explosion-proof safety hazards, such as using ordinary electrical equipment in dust explosion hazardous areas, selecting gas explosion-proof electrical equipment, or using dust explosion-proof electrical equipment that does not match the usage environment, which is very common.
4. Due to different industries and situations, there are various explosion-proof safety hazards in explosive hazardous areas.
5. Since there are hidden dangers and explosion accidents can happen at any time, what should we do?
a、 Before thoroughly rectifying explosion-proof electrical equipment with serious failure of explosion-proof safety performance, it is necessary to strictly monitor the working and operating status of the main device to prevent the leakage of flammable gases, liquids, and dust in large quantities. Create an explosive hazardous environment.
b、 Ensure that combustible gas detection alarms and dust detectors installed in explosive hazardous areas are used within their valid measurement period. Once they exceed the standard or sound an alarm, all devices should be immediately shut down for inspection and disposal.
c、 According to Article 7.1.3.2 of the safety production industry standard AQ3009-2007 "Safety Specification for Electrical Explosion Protection in Hazardous Areas" issued by the State Administration of Work Safety, it is necessary to entrust a safety production testing and inspection institution with professional qualifications for explosion protection to conduct regular inspections as soon as possible.
d、 Based on the results of regular inspections and corresponding rectification suggestions, timely take rectification measures according to standards, and carry out comprehensive and positive rectification.
e、 Establish and improve the management system for the procurement, installation, acceptance, use, maintenance, inspection, and scrapping of electrical equipment in explosive hazardous areas, and strictly inspect and implement it.
f、 In the entire process of explosive environment equipment engineering design, selection, procurement, installation, commissioning, acceptance, acceptance, and operation, explosion-proof professional inspection/control units are introduced, and professional institutions are responsible for explosion-proof professional control work. Fire and explosion hazards are detected early, and scientific treatment is carried out early to eliminate accident hazards at the embryonic stage, minimizing economic losses and personal injuries.
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