In order to solve the long-standing problem of the lack of flame retardant classification standards in the AAC Cable industry and the imperfection of the evaluation index dimension in the original flame retardant standard system, the former Sichuan Fire Protection Research Institute of the Ministry of public security organized relevant units to take the lead in formulating the national mandatory standard GB 31247-2014 “classification of burning performance of cables and optical cables”, which was issued on December 5, 2014 and officially implemented from September 1, 2015. On the basis of full investigation and verification test, combined with the relevant requirements of EN 13501-6:2014 and the actual grading assessment needs of domestic cables and optical cables, GB 31247-2014 finally forms four grades A, B1, B2 and B3. The assessment dimensions include the main grading indexes such as combustion calorific value, flame spread, heat release, smoke production characteristics and smoke density, and the main grading indexes such as combustion droplet / particle, smoke emission and so on The toxicity and corrosivity of flue gas are three additional classification indexes. Generally speaking, these assessment indexes can more truly reflect the combustion characteristics of cables under actual fire conditions, and the evaluation of cable combustion performance grade will be more scientific, reasonable and practical.
In order to promote the flame retardant cable classification standard and link up the related testing and certification work, China Quality Certification Center and National Center for quality supervision and inspection of fire resistant building materials (nftc) have cooperated closely since the standard drafting stage to develop cqc17-463416-2015 “implementation rules for classification certification of burning performance of cables for construction Engineering”, Since 2015, we have held publicity and implementation meetings on standards and certification in Nanjing, Yixing, Guangzhou, Jinan, Chengdu and other places, actively promoting the application and acceptance of standards to relevant architectural design units and architectural design specifications, and achieved good promotion results. This work also lays a foundation for the domestic flame retardant cable export to meet the relevant technical requirements of the European Union CPR building product regulations.
Considering the identification and type selection requirements of cables with different flame retardant grades, the new version of the implementation rules (cqc17-463416-2020) in 2020 adds the model naming provisions of cables with flame retardant grades, and adds some products with flame retardant grades B1 and B2, such as wdzb1-yjy, zb2-bv, etc., and provides the new products to Jiangsu Shangshang, Wuxi Jiangnan, Wuxi Jiangnan, etc Some excellent cable enterprises such as Jiangsu Zhongmei and Sichuan Xinshiji have issued the first batch of new CQC fire prevention certificates.
The new version of CQC fire prevention Certification Implementation Rules includes power cable, wiring, control cable, computer cable, flexible cable, communication cable, optical cable and other construction cable products. The CQC fire prevention certification mark shown in Figure 1 can be applied to the certified products to prove that the products meet the relevant requirements of each flame retardant grade. After the implementation and promotion of flame retardant classification standards and certification, many laboratories including the National Center for quality supervision and inspection of fire resistant building materials, the National Center for quality supervision and inspection of wire and cable products (Yixing) and Shanghai ABC Cable wisdom Testing Technology Co., Ltd. (istcw) have obtained the relevant recognition of the flame retardant classification certification.
3、 Some misunderstandings and development prospects of flame retardant graded cables
In recent years, with the popularization and application of GB / T 19666 “general rules for flame retardant and fire resistant wires, cables or optical cables” and the flame retardant categories of ZA, ZB, ZC and ZD, due to the common sense tendency to code a-b-c-d level arrangement and the non-metallic content from high to low in the test, there are a large number of manufacturers, users and technical institutions in the industry that bundle flame retardant ZA, ZB, ZC and ZD are flame retardant levels, It is also understood that flame retardant class A is superior to (covering) class B, class C, and then to class D.
However, the standard analysis shows that the main difference of bunched flame retardant (ZA, ZB, ZC, ZD) categories lies in the different application and evaluation occasions, and the grade relationship or classification concept is not mentioned in the relevant standards. In particular, in the article “understanding and suggestions on the requirements of Flame Retardancy for wiring bundles” recently received in the Journal of quality and certification, verification tests were carried out on five groups of samples of typical wiring products from different manufacturers: za-bv 450 / 750V 2.5 and wdza-byj 450 / 750V 2.5, and the above ten groups of samples were tested in accordance with GB / T 18380 series standards Class C and class D combustion tests. By analyzing the carbonization height of the samples before and behind the steel ladder after the combustion test, the results show that the carbonization height of most of the bundles of this kind of wire products is higher than that of class A, and even some of the samples have passed the flame retardant class a test, and the flame retardant class D is unqualified. The bundle combustion verification test of this cloth and wire product also proves that the traditional bundle flame retardant ZA, ZB, ZC and ZD do not belong to the classification of flame retardant performance, and there is no relationship between high and low levels.
In contrast, GB 31247-2014 “classification of burning performance of cables and optical cables” scientifically and systematically classifies the burning performance of cables used in construction projects through multi-dimensional index assessment and evaluation, which is close to the requirements of actual building fire safety scenarios, and gives a clear description of the performance grade in the standard, for example, the burning performance B1 is flame retardant 1 cable (optical cable), The combustion performance of grade B2 is flame retardant grade 2 cable (optical cable), etc（ This also lays a solid foundation for the reference and acceptance of GB 31247-2014 flame retardant classification in GB 51348 standard for electrical design of civil buildings.
It is believed that with the promulgation and heavy implementation of GB 51348 “standard for electrical design of civil buildings” and subsequent relevant design specifications, a more unified and clear understanding and application of the classification of combustion performance of cables and optical cables will be formed from user units, design units, supervision units, testing and certification Institutions to manufacturers and other relevant policies, The flame retardant cables and optical cables used in domestic construction projects will also usher in a brighter development prospect.
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