March is a tumultuous month for China's explosion-proof industry, with explosions and explosions occurring in Yancheng, Jiangsu on March 21, Qingzhou, Shandong on March 30, and Kunshan, Jiangsu on March 31. In today's rapidly developing explosion-proof industry in China, bloody cases point out a basic fact that there is a risk of overall loss of control in the national explosion-proof field.
So what are the reasons for losing control?
1、 Explosion proof standard lag
In July 1948, the International Electrotechnical Commission TC31 began to develop international explosion-proof technical standards. China started relatively late and officially began the standardization of explosion-proof technology in 1977. Over the past 40 years, although China's explosion-proof technology and explosion-proof market have undergone earth shaking changes, China's explosion-proof standards still seriously lag behind international explosion-proof standards, especially the standard GB3836.1-2010 for general explosion-proof requirements, which only compares to the IEC60079-0:2007 version. However, the current international explosion-proof standard is already IEC60079-0:2017, which is a full 10 years behind the two versions.
The lag of explosion-proof standards directly leads to the backwardness of design specifications for explosion-proof products in China. Therefore, in the subsequent verification, production, and selection application process, we can only stick to the old ways of thinking and methods.
As stated in IEC60079-14:2014 "Design, Selection, and Installation Standards for Electrical Equipment", significant changes have been made to the selection and application of cable entry devices, especially for Class IIC explosion-proof cable entry devices with sealing rings. The limitation and requirement on the volume of the applied equipment are no longer pursued, and the core wire of the cable is peeled off and filled with filler on site. Instead, detailed regulations are provided for the applicable cable, whether from the perspective of on-site operation technology or explosion-proof safety, The new standard regulations are more mature and rigorous.
However, the latest GB/T 3836.15-2017 (compared to IEC60079-14:2007) released in 2018 still adopts the old regulations. When the IIC level explosion-proof cable entry device is used on equipment with a volume exceeding 2 liters, it can only be used by construction personnel to strip the wire and fill the stuffing box at the equipment installation site. This method is very cumbersome in terms of operation skills and requires high professional skills and qualities of construction personnel, Any improper operation can bring safety hazards.
As the most basic and commonly used basic component of explosion-proof electrical equipment, cable entry devices are almost applied to every explosion-proof product. The lag in design, selection, and installation standards not only restricts the breakthroughs in design and innovation in application of Chinese explosion-proof products from the source, but also causes real safety risks for explosion-proof products.
2、 Explosion proof technology is fixed and self sealing
In recent decades, with the rapid development of the petrochemical industry, explosion-proof technology has also changed rapidly. The safety of explosion-proof products depends not only on the protection of ignition sources, but also more on the consideration of environmental or human factors. In the international explosion-proof field, according to the characteristics of various electrical equipment, application environments, and customer application needs, a composite explosion-proof mode consisting of a lightweight "Ex e" increased safety shell and internal "Ex d" or "Ex m" encapsulated components is gradually replacing the traditional single explosion-proof mode, becoming a consensus. For example, in addition to the protection of common elements such as shell strength, electrostatic protection, and hot spot ignition, the core requirement of increased safety for explosion-proof is to ensure the IP protection of the increased safety shell and configure independent explosion-proof components. Each key explosion-proof element is completed by professional and skilled workers in the explosion-proof equipment factory, which is safe and easy to control, greatly facilitating on-site installation and later maintenance; The core requirement for explosion-proof type is to ensure the surface quality and explosion-proof clearance of the explosion-proof surface of the explosion-proof shell. During on-site installation and maintenance, errors are prone to occur. It is required that on-site construction or operation personnel must have corresponding professional skills and high professional ethics. Any slight negligence can bring safety risks. Moreover, in chemical areas where explosion-proof products are applied, there is often a corrosive environment. The explosion-proof surface of aluminum alloy materials is prone to failure under on-site corrosion, and the corrosion resistance of plastic shells is much better than that of metal materials, resulting in higher overall safety. (Note: Analysis of unqualified items in the national supervision and inspection of explosion-proof lamps in 2018, the non-compliance rate of explosion-proof surface elements reached 61.5%)
However, in the Chinese explosion-proof industry, many professional explosion-proof design institutions still adhere to tradition. There are differences in understanding of advanced explosion-proof concepts and new technological applications among mainstream domestic design institutes used to undertake user projects. A considerable number of people still do not use non explosion-proof explosion-proof types. This outdated top-down explosion-proof concept hinders the development of Chinese explosion-proof technology and enterprises, and also lays many hidden dangers for Chinese explosion-proof safety.
3、 There are loopholes in the explosion-proof system
1) The international explosion-proof system adopts a combination of "sample certification" and "factory audit". On the one hand, strict verification of samples is carried out according to the requirements of explosion-proof standards. On the other hand, by regularly reviewing the qualifications, management responsibilities, production inspection facilities and equipment calibration, product design and development, procurement, production process control, monitoring and measurement of explosion-proof production enterprises, as well as the control of non-conforming products, all elements that affect the quality of explosion-proof products are comprehensively controlled from an overall perspective. This method has been fully tested by the market and is recognized and adopted by most countries and regions around the world. However, the domestic explosion-proof system adopts the management methods of "explosion-proof qualification certificate" and "production license". The production license only reviews the factory system every 5 years when the certificate is renewed, and there is no monitoring of the entire production process of the enterprise. There is no effective supervision link for the quality control of production links that are crucial to the quality of explosion-proof products. Especially for explosion-proof lamps, even the lack of a production license has left endless hidden dangers for the quality and safety of explosion-proof products. The results of the national supervision and spot check on the quality of explosion-proof lighting products in 2018 showed that out of 26 batches of explosion-proof lighting products from 26 enterprises, 13 batches were found to be unqualified. This sampling was only conducted on enterprises above a certain scale. If the mobile market products were sampled and evaluated, the qualification rate is expected to be even lower. For explosion-proof products that are related to the safety of people's lives and property, the unqualified rate reaches an astonishing 50%, From a factual perspective, it is evident that there are significant loopholes in the regulatory system for explosion-proof products.
2) The explosion-proof certificates issued by most explosion-proof organizations do not clearly specify the manufacturing conditions of the products according to standard requirements and product characteristics, especially the factory routine tests for determining the quality of explosion-proof products, such as power frequency withstand voltage and overvoltage tests, which are crucial. Furthermore, the production license for explosion-proof products is only responsible for sampling samples, and there are no requirements for the production control process that affects the quality of explosion-proof products. There are obvious loopholes in the regulatory system, which not only violate the original intention of strict control over safety products, but also leave room for some explosion-proof equipment manufacturers to not or less implement the standard terms, which will inevitably lead to significant safety hazards in the explosion-proof products put on the market.
3) Internationally, there is no specific recall measure for products that fail spot checks, and knowing that the unqualified products are still being used in potentially explosive places makes it impossible to guarantee explosion-proof safety. In addition, the imitation and imitation of explosion-proof products from well-known brand enterprises have been rampant in the market, relying solely on the rights of the counterfeited enterprises themselves, and the lack of national quality supervision is severe;
4、 Lack of self-discipline in production enterprises
The self-discipline of enterprises is the cornerstone of ensuring product quality, and the self-discipline of production enterprises of explosion-proof products is also related to the life safety of thousands of households. However, some explosion-proof enterprises, due to inadequate supervision, market competition and other reasons, neglect their responsibilities and bring safety risks to users.
1) Not implementing standards;
According to the explosion-proof standard (Article 15.2 of GB3836.2-2010), unless the volume is less than 10 cubic centimeters or has passed four times the overvoltage test in the type test, every explosion-proof product must undergo an overvoltage test before leaving the factory, and the shell of the welded structure should undergo an overvoltage test in any case. However, many explosion-proof enterprises, knowing the requirements of standard specifications, refuse to comply due to cost savings or lack of confidence in product performance.
Most explosion-proof products are made of aluminum alloy material through die casting. Due to the characteristics of aluminum alloy die casting technology, a certain amount of process defects are inevitable. Especially for explosion-proof lamps with transparent glass, the glass components are bonded to the explosion-proof shell through pouring and sealing process to form a whole. The pouring and sealing process is very sensitive to curing parameters and process environment, and has high requirements for the surface of the aluminum alloy shell that is adhered to the glass. It cannot guarantee that every poured product is qualified. At this time, as the last control gate of explosion-proof safety, the overpressure test is very important. Based on the analysis results of relevant data, Out of every 100 explosion-proof products, there are always 1 to 2 that cannot pass the overvoltage test. Unlike civilian products, if these one or two unqualified products are used in potentially explosive places, it undoubtedly brings great safety risks to the place.
2) The claim does not match the reality
The national explosion-proof standard (GB3836.2-2010, Article 5.2.7) clearly stipulates that the IIC level (typical gas acetylene) square explosion-proof box with a flat joint surface is not allowed to exceed 500 milliliters in volume.
Opening the samples or promotional materials of various explosion-proof enterprises, there are many explosion-proof box products with a volume exceeding 500 milliliters, or even 50 liters. In the sales process of this type of explosion-proof box product, some enterprises have expanded or falsely promoted the explosion-proof performance and consistency requirements of the product. Due to the lack of corresponding professional identification ability by customers, it poses great risks to the explosion-proof safety of users.
3) Production without control
The quality control of the production process of explosion-proof products is closely related to the final performance of explosion-proof products. The international explosion-proof quality system standard IEC 80079 provides detailed procedures for controlling the consistency of explosion-proof product production and certification. Clear regulations have been established for raw material procurement, inspection and testing, equipment calibration, process control, routine inspection, and non-conforming management, as well as certificate validity control. Regular review of the above control measures and records is required to identify and improve problems, continuously improve the quality control and management level of the enterprise, fully ensure the consistency between the verified samples and the produced products, and thus ensure the explosion-proof performance of the produced products.
This quality management system has very high requirements for explosion-proof enterprises in both product and management aspects. From feeding to shipping, they are interconnected. If any link does not meet the requirements, it will cause the subsequent process to be unable to proceed. Enterprises must strictly control the process to meet the management requirements of the quality system. However, many domestic enterprises do not have the necessary conditions for systematic control. Some products have defects from the source of product design, which cannot meet the control requirements of the quality system in the subsequent production process, resulting in the quality and performance of explosion-proof products produced not matching those of verified samples, leaving infinite hidden dangers for explosion-proof safety.
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