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Common safety hazards of explosion-proof equipment in explosive hazardous areas

SINO Testing Services

| 2020-07-24|Return

To do a good job in safety, 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 safety hazards in equipment selection

1. Select ordinary electrical products in explosive hazardous areas.

2. Select electrical equipment for coal mine underground use 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 do not have product nameplates, explosion-proof labels, or product certification information (such as explosion-proof certificate numbers). At the same time, it is not possible to provide the explosion-proof qualification certificate for the three no products.

5. From the appearance and structure of the product, it is suspected to be an explosion-proof product. However, the brand names of these products only have the "Ex" universal identification and explosion-proof mark, but there is no product certification information (such as explosion-proof certificate number). Unable to query, confirm if the product has been inspected and certified by a nationally authorized testing agency.

6. Counterfeit and inferior products that have been determined by professional inspectors to be ordinary products but are labeled with explosion-proof information labels.

7. In hazardous areas with IIC substances, choose IIB explosion-proof products.

8. The equipment selection requires a T4 temperature group, but in reality, explosion-proof products with a temperature group of T1 are selected.

2、 Explosion proof electrical products themselves have safety hazards

1. Explosion proof electrical product casing damaged.

2. The nameplate of explosion-proof electrical products is missing or unclear.

3. The isolation sealing fillers for the explosion-proof and safety enhancing composite products in the explosion-proof and wiring chambers do not meet the requirements.

3、 Explosion safety hazards in the installation of electrical equipment

1. The cable introduction does not meet the requirements.

2. Excess inlet holes are sealed with adhesive/plastic sealing parts/not sealed.

3. Inconsistent, missing, loose, corroded, lacking springs, flat washers in fastening bolts.

4. Explosion proof electrical equipment cables or wire entry points are directly connected to steel pipes.

5. Flexible pipes are directly connected to the equipment without cable entry devices installed.

6. The cable entry device installed on 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. Rust on the explosion-proof joint surface.

9. The explosion-proof joint surface between the cover and the box body is coated with material or padded.

10. Independent explosion-proof chambers are mutually conductive without isolation and sealing measures.

11. The distance between the explosion-proof joint surface and solid obstacles is too small.

12. The aging of the box or the aging of the sealing gasket, as well as the widening of the gap, result in the protection level not meeting the requirements and internal water ingress.

13. The increased safety equipment replaces or adds electrical components without approval.

14. The bending of the explosion-proof disturbance tube is too small, the disturbance tube is aging, and the rubber protective layer is damaged.

4、 Problems in cable laying

1. Cable changes, damage.

2. Cable lines are directly connected in hazardous areas.

3. The wires are twisted inside the increased safety wiring.

4. Connect wires inside the wiring box.

5. No isolation and sealing measures were taken when cables passed through different areas.

6. Armored cables are not equipped with armored cable entry devices.

7. The armor layer of armored cables is exposed.

8. Idle cable heads should be disposed of in hazardous areas, and excess bare copper wires should be placed in increased safety junction boxes without proper fixation or insulation treatment.

5、 Grounding and equipotential connection issues

1. External grounding not connected.

2. External grounding wire series connection, cable tray and liquid conveying pipeline equipotential connection issues.

3. External grounding wire less than 4mm ²。

4. The external grounding bolt is corroded.

6、 Inspection and maintenance

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 it is found during inspection and maintenance that explosion-proof electrical equipment has decreased or failed in explosion-proof performance due to external force damage, atmospheric corrosion, chemical corrosion, mechanical wear, natural aging, and other reasons. Should be repaired. The maintenance of explosion-proof electrical equipment should be carried out in accordance with GB3836.13-2013. If the original explosion-proof performance cannot be restored after maintenance, the following principles can be applied based on actual technical performance:

a. Reduce the explosion-proof level for use;

b. Reduced to non explosion-proof electrical equipment use.

2. Failure of explosion-proof performance of explosion-proof electrical equipment

If it is found during maintenance that the structure and parameters of explosion-proof electrical equipment have changed 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, such as:

a. The shell of explosion-proof electrical equipment is severely deformed and cannot be repaired;

b. Serious damage to the explosion-proof surface that cannot be repaired;

c. The explosion-proof gap exceeds the national standard and cannot be restored;

d. The shell of explosion-proof electrical equipment is cracked and does not meet the requirements of the original explosion-proof type.


Conclusion

1. The appeal issue is only a typical example of common explosion-proof safety hazards in equipment in explosive hazardous areas.

2. For a long time in the past, people mainly focused on hazardous chemicals or explosive gas environments for explosion hazards; For combustible dust, there is less attention paid to the explosion danger of fiber materials. In fact, once combustible dust and fiber materials explode, their harm is no less than gas explosion. For example, accidents such as the linen 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. For example, the use of ordinary electrical equipment in dust explosion hazardous areas, the use of gas explosion-proof electrical equipment, or the use of dust explosion-proof electrical equipment that does not match the operating environment are very common phenomena.

4. Due to different industries and situations, the explosion safety hazards in hazardous areas are diverse and varied.

5. What should we do if there is a hidden danger and an explosion accident can occur at any time?

a. Before thoroughly rectifying explosion-proof electrical equipment with severe safety performance failure, it is necessary to strictly monitor the working 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 the valid measurement period. If they exceed the standard or alarm, all devices should be immediately stopped for inspection and disposal.

c. According to the safety production industry standard AQ3009-2007 "Electrical Explosion Protection Safety Code for Hazardous Areas" issued by the State Administration of Work Safety, Article 7.1.3.2, it is necessary to commission a safety production testing and inspection institution with professional explosion-proof qualifications 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 management systems for the procurement, installation, acceptance, use, maintenance, repair, and scrapping of electrical equipment in explosive hazardous areas, and strictly inspect and implement them.

f. In the entire process of equipment engineering design, selection, procurement, installation, commissioning, acceptance, acceptance, and operation in explosive environments, 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 in the embryonic stage and minimize economic losses and personal injuries.


 

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