Knowledge of fireproof cables 1 Introduction Fire proof (Flame proof) wire and cable is a general term for wire and cable with fire resistance performance, usually divided into two types of flame-retardant wire and cable and fire-resistant wire and cable. Starting from fire safety and fire rescue, more and more requirements are placed on the fire performance of wires and cables, for example: Flame retardancy-retards and delays the spread of flames along wires and cables so that the fire does not expand. Fire resistance (Fire resistance)-can maintain a certain period of operation in the case of flame combustion, that is, to maintain the integrity of the circuit (Circuit integrity). Free halogen-The materials that make up wires and cables are free of halogens, and the combustion products are less corrosive. Low halogen-The materials that make up wire and cable may contain halogen, but the content is low. Low smoke (low smoke)-less smoke and dust generated when the wires and cables burn, that is, higher light transmittance. Low toxicity (low toxicity)-the gas toxicity of wire and cable materials when burning is low. The research and development of flame-retardant and fire-resistant wire and cable in China began in 1982. After 5 years, in 1987, many cable manufacturers have put into production and recognized by users. In view of the confusing naming and model of combustion characteristics at that time, the author proposed to classify the fire-resistant wires and cables according to the combustion characteristics of the wire and cable corresponding to the combustion test method, and use the first letter of Chinese pinyin as the prefix of the corresponding ordinary wire and cable model . Among them, the flame retardant wire and cable type ZR and the fire-resistant wire and cable type NH have been used until now. With many new developments made in the development and research of fireproof wires and cables, the original models are no longer sufficient. In addition, more and more manufacturers have put into production, and when formulating enterprise standards, the need for each type of related models has caused new confusion. The most prominent performance is that the burning characteristics of wire and cable are the same, but the name and model are different. The industry and users strongly demand to change this situation, hoping to unify the models. To this end, this article proposes a method of compiling fire-resistant wire and cable models for future reference in compiling corporate standards or industry standards. (2) The model number is added before the ordinary wire and cable model by the prefix method. (3) The inherent combustion characteristics of ordinary wires and cables are not given separately. (4) There is room for supplementary development. When a certain wire and cable has a variety of burning characteristics, according to international practice, a certain model and title are in the following order (no items should be omitted); No (low) halogen-low smoke-low toxicity-flame retardant-fire resistant E.g: (1) Flame-retardant (A) type PVC insulated PVC sheathed power cable, model: ZA-VV (3) Flame retardant should not be called flame retardant flame retardant. It is in line with internationally accepted FLAME RETARDANT, because RETARDANT is meant to delay and prevent. The Japanese call it flame retardant; and the flame retardant is called flame retardant. For unified appellation, good flame retardancy, Z is used instead of N. (4) Do not use Pg fireproof cable for mineral insulated (MI) cables. Mineral insulated (MI) cables are different types of cables from organic insulated cables. Flame retardancy and fire resistance are one of its inherent characteristics. MI cable can be recommended. But it is not necessary to call it fireproof cable again, so as not to be confused with organic insulated flame retardant cable and fire resistant cable. Do not add another model. The MI cable is called a fireproof cable in China. Some people think that its flame retardant and fire resistance performance is better. In fact, the test methods and assessment indicators are the same. The combustion characteristics of the cable are always aggregated, and the individual characteristics of each component are not taken into account, which not only makes the cable design useful, but also provides favorable conditions for the simplification of the model and appellation. The above method of compiling fire-proof wire and cable model is based on the above, and conforms to the domestic custom Gu Cheng habit. Hope to be accepted or put forward by everyone.
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2 Principles for the preparation of fire-resistant wire and cable models (1) A model corresponds to a combustion characteristic. There are corresponding test methods and specific indicators that can be evaluated, and the first letter of Chinese Pinyin is used to simplify it.
At present, there are some differences between China's standards and IEC international standards, because some standards, IEC issued after China's standards, according to the principle of equivalent use of international standards, this difference will be eliminated in the future.
3 Description of model and usage
3.1 About flame retardant (ZURAN)
According to IEC 332, flame retardant is divided into single and bundled. More than ten years ago, China's wire and cable were mainly halogen-containing products such as polyvinyl chloride and neoprene. Passing a single vertical burning test is a basic requirement in the product standard, so no single flame retardant model is required. Bundle C is the basic requirement for flame-retardant wire and cable, and Class B and A are flame-retardant requirements that users must specify. Therefore, it is popular to use the first letter of flame retardant (ZURAN) ZR as the model.
The situation is different now. Polyolefins such as polyethylene, polypropylene, ethylene propylene, and natural butylbenzene are flammable materials. When their flame retardant products can pass a single vertical combustion test, they must be given a model to match the original flammability characteristics. the difference. This model uses Z. Bundle combustion is classified as flame retardant A, flame retardant B, flame retardant C, and flame retardant D, so it is distinguished by ZA, ZB, ZC, ZD models. Among them, the flame retardant Class D is a new proposal of IEC, which is suitable for wire and cable with an outer diameter of 12mm and below. The total volume of non-metallic materials used in the sample is only 1/3 of Class C, or 0.5L / m. It is the same as Class C if the fire supply time is 20min and the scorch height is less than 2.5m. Because this proposal has yet to be voted through.
In addition, IEC 332-3 has a provision that when doing A-type tests, if the samples are arranged at intervals (in the case where a core conductor is greater than 35mm2) can not be arranged in front of the standard ladder, they can be arranged at the rear, and AF / R Said. Or use a wide ladder (0.8m wide) all in front of the ladder (indicated by AF), and use double blowtorch for fire. However, if a large-sized cable can be run down in front of a standard ladder, a single blowtorch is used for fire, which is still recorded as AF. In order to simplify the model, for this type of situation are recorded as ZA.
3.2 About fire resistance (NAIHUO)
According to the national standard GB 12666.6-90, fire resistance is divided into two grades, A and B. The fire supply temperature of Class A is 950 ℃ ～ 1000 ℃, and the fire supply temperature of Class B is 750 ℃ ​​～ 800 ℃. Earlier, the NH model was used to indicate fire-resistant wire and cable, which is equivalent to the Class B of China's standard according to the requirements of the IEC 331-1970 standard. Because some users require Class A refractory wire and cable, the model is expanded to NA and NB to show the difference. However, in the recently published standard IEC60331-1999 by the IEC, the fire supply temperature is still 750C to 800 ° C, and suggestions for increasing the test temperature are still under consideration. Therefore, if the new national standards are used in the same way, there is no distinction between Class A and Class B fire resistance. At that time, the model of refractory wire and cable can be simplified as the team. If the IEC classifies the test temperature in the future, our model has room for development.
It is worth noting that the UK has the most requirements for fire-resistant cables, so there are many models. Considering the impact of the United Kingdom on IEC, IEC has been considering increasing the test temperature, water spray and mechanical impact. Therefore, model C for additional impact (CHONGJI) and model S for additional water spray (PENSHUI) for future use .
Note: The fire resistance, water spray resistance and impact fire tests are carried out separately. For example, the cable type that passed the fire resistance at 950 ℃ 3h and 750 ℃ ​​is CY; the cable type that passed the 650 ℃ 3h fire resistance, 950 ℃ 20min fire resistance, 650 ℃ water spray and 650 ℃ impact requirements is ASWX, and so on. The highest level model is CwZ.
3.3 About Low Halogen (DILU), Halogen Free (WULU), Low Smoke (DIYAN), Low Capacity (DIDU)
Regarding low halogen (DILU), it is represented by D. The method of IEC60754-1: 1994 (GB / T 17650.1-1998 national standard) was used to determine the HCI content. There is no index in the standard, it is recommended that HCI ≤100 mg / g.
Regarding halogen-free (WULU), that is, low corrosivity, it is represented by W: IEC 60754-2: 1991 (revised in 1997), the national standard equivalently adopted in China is determined by the method of GB / T17650.2-1998, and the standard is PH≥4.3 r (conductivity) ≤10ps / mm. Many countries or companies abroad set the halogen-free standard as HCI≤5mg / g, and the Chinese have followed suit, which is inappropriate. Because IEC 60754-1 has clearly stated that this method cannot be used to determine materials with an HCI content of less than 5 mg / g, that is, "halogen-free" cannot be determined. Secondly, when the HCI content is> 2 mg / g, the PH value of its aqueous solution is less than 4.3, which does not meet the requirements of IEC60754-2. In addition, some people think that the index set by the IEC is PH≥4.3, while the index of Germany is PH≥3.5, so the requirements of the IEC are higher than that of Germany. This is only a superficial phenomenon. In fact, the effect of the two is exactly the same. I have the opportunity to introduce another article.
Regarding low smoke (DIYAN), it is also indicated by D. Although it repeats with the low halogen D, it has been agreed, and it should not be misunderstood when the model is combined. The international standard for low smoke requires light transmittance ≥60%. It must be pointed out that the low-smoke of the wire and cable made by the so-called low-halogen and low-smoke materials based on PVC in China does not meet the above requirements, and low-smoke models should not be used. Unless otherwise stated in the product standard, such as the index for reducing the light transmittance, and indicating that the index is lower than the requirements of international standards or national standards, so as not to misunderstand users.
Regarding low toxicity (DIDU), D can no longer be expressed, but U. The relevant standard IEC is still under consideration. Currently used more is the British Navy Engineering Standard NES713, which is expressed by the toxicity index (TI). For example, the toxicity index of insulating materials is required to be less than 3, and the toxicity index of the sheath is less than 5. Some domestic manufacturers claim that they can provide halogen-free, low-smoke, and non-toxic cables. The non-toxic mentioned here is inappropriate and should be low-toxic. Because halogen-free and low-smoke materials burn, they produce toxic CO. If the materials contain P, N, and S, more toxic gases are generated.
3.4 About the combination of models
(2) Low halogen flame retardant (Class B) PVC insulated PVC sheathed power cable, model: DZB-VV
(3) Low halogen low smoke flame retardant (Class C) PVC insulated PVC sheathed power cable, model: DDZC-VV
(4) Halogen-free and low-smoke flame retardant (Class A) XLPE insulated steel tape pin-mounted polyolefin sheathed power cable, model: WDZA-YJY23 (number 3 for polyolefin sheath of outer sheath)
(5) Halogen-free low-smoke flame retardant (Class B) XLPE insulated polyolefin sheathed power cable, model: WDZB-YJY (polyolefin model Y does not use X, E, O or P, according to GB / T13849 ï¼1993)
(6) Halogen-free, low-smoke, fire-resistant (Class A) XLPE insulated polyolefin sheathed power cable, model: WDNA-YJY
(7) Fire-resistant (Class B) PVC insulated and PVC sheathed power cable, model: NB-VV
3.5 Problems that must be noted The method for determining the corresponding model and appellation based on the combustion characteristics of wires and cables is proposed above. The following are some of the current problems and how to deal with them as follows: (1) Do not wear high hats for flame retardant In order to achieve the flame retardant requirements of wire and cable, there are various methods. For example, the use of inorganic flame retardant-based cement filling (so-called "oxygen barrier", "fire barrier", etc.) or inorganic flame retardant-based paint coating flame retardant city (so-called " High flame retardant tape "," oxygen and fire barrier ", etc.), it plays a very important role in solving the flame retardant problem of cables composed of flammable materials such as cross-linked polyethylene insulation, and can even reach flame retardant class A s level. But don't wear it with "high flame retardant", "ultra high flame retardant", "ultra high flame retardant" hats, do not use GZR models. This is because, based on the same combustion test methods and indicators, they are all IEC 332-3 or GB 12666.5, so no matter what means and method is used to achieve flame retardancy, the model and title should be the same. The highest level of flame retardancy is currently ZA. It is worth noting that do not give fire-retardant cables new names, such as oxygen-barrier cables, fire-barrier cables, etc., otherwise, it will be difficult to understand in international bidding.
(2) Don't call it upside down. Your name is "halogen-free and low-smoke". His name is "low-smoke and halogen-free". There is no difference in substance, but the titles are not uniform. And the model can be WD or DW, and it is not unified upside down. In foreign countries, the titles are first halogen and then smoke. For example, the French Alcatel company called HALOGEN FREE LOW SMOKE CABLES (halogen-free low-smoke cable), model XLS; British Delta company called ZERO HALOGEN LOW SMOKECABLES (halogen-free low-smoke cable should be translated, zero-halogen low-smoke cable should not be translated, To avoid self-made confusion), the model is OHLS, and so on. It can be seen that it is better to call it "halogen-free and low smoke". Similarly, "low smoke and low smoke" should not be called "low smoke and low smoke".
(5) Regarding the flame retardant rating of fire-resistant cables According to the newly published British Standards BS7629-1997 and BS6387-1994, the flame-retardant properties of fire-resistant cables are required to pass the single report vertical burning test. Therefore, if our country imitates it, the flame-retardant grade of the fire-resistant cable can be uniformly stipulated as a single flame-retardant when formulating the standard, and the flame-retardant code can be omitted in the model of the fire-resistant cable. Of course, if the user requests to increase the flame retardant level, then the flame retardant code can be inserted in the model.
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