In industrial production, we often encounter sites with explosive gases or dust. For example, in high-risk industries such as petroleum, chemical industry, and coal mines, the production, transportation, and storage processes are often accompanied by the presence of flammable and explosive substances. Therefore, this requires the instrument devices used on site to have explosion-proof functions.
Explosion-proof instruments can maintain normal operation in flammable and explosive environments to prevent accidents caused by electrical sparks or high temperatures, thereby ensuring production safety. In order to ensure the effectiveness and safety of explosion-proof instruments, countries have formulated corresponding standards and requirements.
However, facing the dazzling array of explosion-proof instruments on the market, how to judge whether an instrument is really explosion-proof? Today, we take fixed gas detectors as an example to explain some common judgment methods.
1 Check product identification and certificates
Explosion-proof mark
The explosion-proof instrument shell generally has an explosion-proof mark in a prominent position, such as Ex d IIB T4 Gb, or Ex db IIB T4 Gb (GB/T3836.1-2021 standard). “Ex” means explosion-proof, “d” or “db” means explosion-proof type, “IIB” means gas group, “T4” means temperature group, and “Gb” means equipment protection level. You can check whether the mark is standardized and complete by comparing it with the relevant standards, and make a preliminary judgment on the authenticity of the instrument explosion-proof by the explosion-proof mark and the actual structure of the product.
Explosion-proof certificate
Regular explosion-proof instruments have explosion-proof certificates. You can log in to the official website of the issuing agency, enter the certificate number, check whether the certificate information is consistent with the information certified by the official website, and whether the product’s factory date is within the validity period of the certificate.
Other certification marks
In addition to the explosion-proof certificate, some instruments may have other related certifications, such as explosion-proof products in the CCC catalog must also have the CCC certificate of the product.
2 Check the appearance and structure of the product
The appearance of the instrument can also be used to preliminarily judge whether it meets the explosion-proof requirements.
Shell material and process
For example, the shell of explosion-proof explosion-proof instruments usually uses high-strength, flame-retardant, and impact-resistant materials, such as aluminum alloy, stainless steel, castings, etc. Check whether the shell has cracks, sand holes, pores and other defects, whether the surface is smooth, whether the connection parts are tight, and instruments with fine workmanship and flawless are more likely to be real explosion-proof products, but it is still necessary to make a comprehensive judgment based on the explosion-proof mark in the explosion-proof certificate.
Sealing structure
Good sealing is the key to explosion-proof. Check whether there are reliable sealing measures in the instrument’s line inlet, junction box, observation window and other parts, such as whether there are sealing rings, sealing pads, or explosion-proof glands. And observe whether the installation is in place, whether there are aging, deformation and other problems that affect the sealing performance at the seal.
Grounding device
Explosion-proof instruments with metal shells generally have a complete grounding device. Check whether the instrument shell has obvious grounding marks and grounding bolts, whether the grounding bolts are firm, whether the grounding wire meets the standard requirements, and whether the grounding is good.
3 Technical inspection
The core technology of explosion-proof instruments lies in the design and manufacture of their shells. Flameproof instruments are a common type of explosion-proof instruments. Their shells must be able to withstand the explosion pressure of the internal explosive gas mixture and prevent the internal explosion from spreading to the explosive mixture around the shell. Therefore, when checking the instrument, the basic definition of explosion-proof can be used to identify whether the instrument meets the explosion-proof requirements from the shell size and structure.
According to the requirements of the explosion-proof standard for industrial instruments, the basic definition of explosion-proof type is:
(1) Gap explosion-proof technology, relying on gap and meshing length to achieve cooling and flameout effects.
(2) Allowing dangerous gases to enter the explosion-proof shell, which may cause explosions inside the shell. However, the shell must have sufficient strength; and each shell joint surface must have a sufficiently long meshing length and a sufficiently small gap to ensure that the internal explosion will not pass through the explosion-proof joint surface and cause an explosion in the external environment.
(3) The shell of an electrical device that can withstand the explosion pressure of an internal explosive gas mixture and prevent the internal explosion from spreading to the explosive mixture around the shell.
Based on the above definition, it is not difficult to see that the explosion-proof requirements are mainly for the instrument shell. If the number of screw threads on the shell cover meets 5 and the total meshing length meets the requirements, then this instrument basically meets the explosion-proof requirements.
4 Understand the product source and manufacturer’s reputation
Purchase channels
Purchase instruments through formal and qualified channels, such as the manufacturer’s official website, authorized dealers, etc., to reduce the risk of buying counterfeit and shoddy products. Avoid purchasing from informal channels or unknown sources to prevent buying counterfeit or non-explosion-proof instruments.
Manufacturer qualifications and reputation
Understand the qualifications and reputation of the manufacturer, and check whether the manufacturer has the qualifications to produce explosion-proof instruments, whether it has a good reputation in the industry, and whether it has a bad record or violations. The quality of instruments produced by manufacturers with strength and reputation is more guaranteed.
5 Conduct actual tests (if conditions permit)
Gas environment test: Under the premise of complying with safety regulations, place the instrument in an environment containing a certain concentration of explosive gas and conduct actual tests to determine whether its explosion-proof performance is good, but this method is dangerous and belongs to destructive testing. It needs to be carried out by professionals in professional places.
Electrical performance test: Use professional instruments to test the electrical parameters of the instrument, such as insulation resistance, ground resistance, etc., to see whether it meets the corresponding requirements of the explosion-proof standard. If the electrical performance does not meet the standard, it may affect the explosion-proof performance.
Generally speaking, through the above methods, it is easy to identify whether the industrial instrument meets the explosion-proof requirements.
Daily maintenance methods for explosion-proof instruments
1 Inspection and maintenance should be carried out regularly. During the inspection, the appearance, environment (temperature, humidity, dust, corrosion), vibration, and whether the installation is firm should be checked.
2 When maintaining the explosion-proof instrument under power, the junction box and observation window must not be opened. When the cover needs to be opened for maintenance, the power must be cut off first. It is never allowed to open the cover for maintenance with power on.
3 Sparks should not be generated during maintenance. The test instrument used should be a flameproof or intrinsically safe instrument to avoid the test instrument causing induced sparks or directing excessive voltage to inappropriate parts.
4 When disassembling, care should be taken to protect the explosion-proof thread and the explosion-proof plane. No damage or scratches should be made, especially no longitudinal scratches are allowed on the explosion-proof plane.
5 When disassembling rubber sealing elements, sharp instruments should not be used to pry or smash hard, and there should not be any longitudinal scratches on the sealing surface.
6 When assembling, the assembly sequence should be followed, and no anti-loosening parts or fasteners should be missed.
7 Rusted and damaged components should be replaced in time, and aging, damaged and non-sealing rubber sealing components should also be replaced in time.
8 After the instrument is regularly inspected and repaired, it must be confirmed that the explosion-proof performance has been restored before it can be put into use again.
Installing explosion-proof instruments in explosive environments has important significance and positive effects such as ensuring the safety of personnel lives, protecting production equipment and facilities, complying with regulatory requirements and industry standards, enhancing corporate image and brand value, and promoting technological innovation and development.
Therefore, users must master the relevant knowledge and judgment methods of explosion-proof to ensure the safety and reliability of the instrument. Chicheng Electric will strictly follow international standards and industry specifications, strictly control product quality, and escort the safety of the gas environment!
