Characteristics of fire resistant wire and cable
1, the introduction
Fire retardant (Flame proof) wire and cable for the fire prevention performance is the floorboard of the wire and cable, usually divided into two categories, Flame retardant cable and fire-resistant wire and cable. Starting from the fire security and its lifesaving, more and more demand for wire and cable fire prevention performance, such as:
Flame retardant (Flame retardancy) - block and delay the spread of Flame along the wire and cable, fire not to expand.
Refractory (Fire hold) - in the case of flame can keep a certain time of running, that maintain integrity of Circuit (Circuit integrity).
Halogen halogen Free (Free) - a wire and cable materials do not contain halogen, its low corrosive products of combustion.
Low halogen (Low halogen) - a wire and cable materials can contain halogen, but the content is Low.
Low smoke, Low smoke), wire and cable produce less smoke when burning, the light transmittance is higher.
LOW toxicity, LOW toxicity), wire and cable materials produced by the burning gas LOW toxicity.
The research and development of flame-retardant and fire-resistant wire and cable in China began in 1982. After five years of time, i.e., in 1987, many cable manufacturers have been put into production and for the user. For the naming and the characteristics of the combustion model was more chaotic situation, the author puts forward to burning combustion test method for wire and cable, the classifying fire retardant wire and cable, use the first letters to Chinese pinyin as corresponding prefix of ordinary wire and cable type. Flame retardant wire and cable type of model of ZR and fire-resistant wire and cable model NH has been in use today.
As fire retardant wire and cable in the development, many new advances in the study of the original model has not apply. Combined with production manufacturers more and more, in formulating enterprise standards, about the model, to get new confusion again. Is the most outstanding performance, the combustion characteristic of wire and cable are the same, but different name and model number. The industry and user demand change this situation, hope to unified model of them. To this end, the paper put forward the fire wire and cable model establishment method, reference for compiling enterprise standards or industry standards in the future.
2, fire prevention principle of wire and cable model's establishment
(1) a model corresponds to a combustion characteristic, has the corresponding test methods and specific indicators can examination, and the first Chinese pinyin letters, simplified as much as possible.
(2) model with prefix method in ordinary wire and cable model before.
(3) the combustion characteristic of ordinary wire and cable inherent, not to other models.
(4) supplement for the development of leeway.
At present our country standard and IEC international standard is still some difference, because some of the standard, issued by IEC standards in our country, based on the principle of equivalent to adopt international standards, the difference will be eliminate in the future.
3, model and method of use
3.1 about flame retardant (ZURAN)
According to IEC 332, flame retardant with single or fascicles. More than a decade ago, China's main wire and cable for polyvinyl chloride (PVC), chloroprene rubber contain LuZhiPin, such as through a single vertical burning test is the basic requirements in the product standard, so there is no need to give model of single flame retardant. The bundle C as the basic requirement of the flame retardant wire and cable, the class B and class A as A flame retardant user must be specified requirements. Therefore, the flame retardant (ZURAN) the first letter of ZR as model is prevalent.
Now the situation is different. Polyolefin, such as polyethylene, polypropylene, ethylene propylene, natural yiding benzene is flammable material, such as when its flame retardant products can pass the single vertical burning test will be given, to phase difference with the original flammable characteristics. This model with Z. Into A bundle of burning with A flame retardant, flame retardant, flame retardant C B, flame retardant class D, therefore with ZA and ZB, ZC, lh-zd models to distinguish. Flame retardant of class D new proposals for IEC, suitable for outer diameter 12 mm and the wire and cable. The nonmetal material of the sample used to volume was only about a third of the class C is 0.5 L/m. Time to 20 min and requirement for fire burning height less than 2.5 m is the same as the class C. Because the proposal is yet to be adopted by a vote.
In addition, IEC332-3 has A regulation, namely when making class A test, if the sample get interval arrangement (there is A core of conductor is greater than 35 was occasion) in front of the standard ladder arrangement not bottom, can be arranged at the back, and expressed in AF/R. Or use wide type of ladder (0.8 m wide) all rows in front of the ladder (AF), and with double burner for the fire. But if large size in the standard cable ladder front row, with a single burner for the fire, still write for AF. To simplify the model, for this kind of situation both for ZA.
3.2 about refractory (NAIHUO)
According to the standard GB 12666.6 90, refractory divided into class A and class B two levels. The offering of class A fire temperature is 950 ℃ ~ 1000 ℃, B type for the fire temperature is 750 ℃ ~ 800 ℃. Fire-resistant wire and cable are had earlier expressed in NH model according to the requirements of IEC 331-331 standard, equivalent to the standard class B. Because some users require A kind of fire-resistant wire and cable, so the expanded model for NA and NB, to show the difference. But, in a recent new standard IEC60331-1999, published by IEC for fire temperature is 750 c ~ 750 ℃, and the Suggestions for the improvement of test temperature is still under consideration. As A result, such as equivalent to the preparation of the new national standard, the fire resistance rating is not A class B class distinction. The fire-resistant wire and cable model can be simplified as team if IEC separate category to the test temperature again in the future, we have room for the development of models.
It is important to note that the figure up to the requirement of fireproof cables, so there are many models. Considering the influence on IEC, IEC to improve the test temperature, hydraulic and mechanical shock has been under consideration, therefore, additional impact (CHONGJI) using model C, additional water (PENSHUI) with the model S, for later use.
Note: refractory, refractory and impact when fire test was conducted respectively. Such as through the refractory, 950 ℃ for 3 h and 950 ℃ impact for CY cable type through the refractory, 950 ℃, 650 ℃ 3 h 20 min refractory, water 650 ℃ and 650 ℃, the cable type for ASWX impact requirements, etc. Models for CwZ their highest levels.
3.3 about low halogen (DILU), (WULU) low smoke zero halogen (DIYAN), low capacity (DIDU)
About the low halogen (DILU), represented by D. Use IEC60754 - "94 (national standard of GB/T 17650.1 1998) method for determining content of HCI. Stipulated in the standard indicators, it is recommended that the HCI acuities were 100 mg/g.
About the halogen free (WULU) or low corrosive, expressed in W: use IEC60754 21-91 (1997 revision), China's equivalent to the national standard of GB/T17650.2-1998 method for determining, wipe labeled PH 4.3 or higher, r (conductivity) ps / 10 mm or less. Foreign many countries or companies have no halogen standards as HCI acuities were 5 mg/g, people also have to follow, it is not appropriate. Because of IEC 60754 - l have made clear that this method cannot be used for determination of HCI material content is less than 5 mg/g, namely can't decide "halogen free". Second, when the content of HCI > 2 mg/g, its aqueous solution PH value is less than 4.3, which does not conform to IEC60754-2 requirements. In addition, some people think that the IEC indicators of PH 4.3 or higher, and the index of Germany is PH 3.5 or higher, so the requirements of the IEC is higher than in Germany. This is only superficial. In fact the effect is completely the same. Have the opportunity to I will article introduce again.
About the low smoke (DIYAN), also expressed in D. Although with low halogen D repeat, but has been established, when model combination from misunderstandings. Low smoke international standards for the light transmittance of 60% or higher. It must be pointed out that our country with PVC as the base of the so-called low halogen low smoke material made of wire and cable, its low smoke can not meet the above requirements, should not be using the low smoke model. Unless otherwise specified in the product standard, reduce the light transmittance of the index, for example, and explains the index is lower than international standards or the requirements of national standard, in order to avoid the user misunderstanding.
On low toxicity (DIDU), can no longer use D said that with U. Relevant standards of IEC is still under consideration. Currently in use is more British naval engineering standard NES713, expressed with toxic refers to (TI), such as toxicity index of the insulating material is less than
3, sheathed toxicity index of less than 5. Said of domestic some manufacturer is available, low smoke, zero halogen non-toxic cable, non-toxic referred here is not appropriate, should be low toxicity. Because, low smoke zero halogen material combustion would produce toxic CO, such as material containing P, N, S, generate more toxic gases.
3.4 about the type of combination
When a ~ combustion of wire and cable has many features, according to international practice, a type and name in the following order (no project should be slightly);
No (low) low smoke, low toxic one flame retardant a refractory
(1) flame retardant (A) kind of PVC insulated PVC sheathed power cable, model is: the ZA - VV
(2) low halogen flame retardant (class B) PVC insulated PVC sheathed power cable, models for: DZB - VV
(3) low smoke low halogen flame retardant (class C) PVC insulated PVC sheathed power cable, models for: DDZC - VV
(4) low smoke zero halogen flame retardant (class A) crosslinked polyethylene insulation steel pin polyolefin sheathed power cable, models for: WDZA - YJY23 (outer sheath of polyolefin to figure 3)
(5) low smoke zero halogen flame retardant (class B) crosslinked polyethylene insulation polyolefine sheathed power cable, models for: WDZB YJY
(type of polyolefin with no X, E, Y O or P, according to GB/T13849-1993)
(6) low smoke zero halogen fire (class A) crosslinked polyethylene insulation polyolefine sheathed power cable, models for: WDNA - YJY
(7) refractory (class B) PVC insulated PVC sheathed power cable, models for: NB - VV
3.5 must pay attention to the problem
Above put forward according to the combustion characteristic of wire and cable to determine the corresponding model and the method of appellation. Regarding the current problems and shows how to deal with the following:
(1) not to wear a top hat in order to make flame retardant wire and cable as to meet the requirement of flame retardant, there are all kinds of methods. , for example, USES the inorganic flame retardants as the base of cement filling (so-called "oxygen insulation layer", "" fire insulation layer, etc.) or with inorganic flame retardants as the base city of paint coating of the flame retardant belt (the so-called" high flame retardant belt ", "isolate HuoDai oxygen", etc.) bag, in dealing with cross-linked polyethylene insulation composed of flammable materials such as flame retardant cable problem plays A very important role, even can achieve the level of the flame retardant class A.
But don't give it put on "high flame retardant", "high" fire retardant, "high flame retardant" hat, do not use GZR models. This is because, on the basis of fire test methods and indexes, the same is IEC 332-3 or GB12666.5, so regardless of the means and methods to implement the flame retardant, the type and name should be the same. The highest level in the flame retardant is ZA. Is worth pointing out, don't give new name flame retardant cable, such as oxygen insulation layer cable, fire cable, etc., otherwise, in the international bidding let people hard to understand.
(2) title jolted its passengers badly as it went over don't you call "low smoke zero halogen", his name is "low smoke zero halogen" and essentially no difference, but the title is not unified. And lead to models can be a WD, also can be DW, turned it also not uniform. Abroad, appellation is after smoke first. France, for example, alcatel company said HALOGEN FREE LOW SMOKE CABLES (LOW SMOKE zero HALOGEN CABLES), model as the XLS; British delta company said ZERO HALOGEN LOW SMOKECABLES (should be LOW smoke ZERO HALOGEN cables, LOW smoke ZERO HALOGEN cables, not in order to avoid the build confusion), models for OHLS, and so on. Visible or call "low smoke zero halogen". By the same token, the "low low smoke" don't be called "low smoke low halogen.
(3) don't referred to as the FLAME RETARDANT FLAME RETARDANT FLAME RETARDANT and international general FLAME RETARDANT suit, because RETARDANT is delay and stop. Japan said embarrassed; And called the flame retardant flame retardant agent. Call unified appellation, good flame retardant, model with Z without N.
(4) the mineral insulated (MI) cables don't Pg fire-resistant cable mineral insulated (MI) cables are different from the organic insulated cable alternative cable, flame retardant and refractory is one of its inherent characteristics, therefore, in the fire place, can be recommended to choose the MI cable. But don't call it fire cable, in order to avoid and organic flame retardant cables and fireproof cables of the insulation confused. Don't add a model. Domestic called MI cable fireproof cables, it is some people think that its flame retardant and fireproof performance better. In fact, the test methods and evaluation indexes are the same.
(5) flame retardant grade of fire-resistant cable according to the newly published by the British standard and BS6387 BS7629-1997-1994, are the requirements for flame retardant properties of fire-resistant cable through single vertical burning test. So if our country to follow, in formulating standards can also be uniform fire-resistant cable single flame retardant, flame retardant level for the flame retardant in the fire-resistant cable model code save. Of course, such as user's request to improve the flame retardant grade, flame retardant in the model code in again can.
The combustion characteristic of the cable is in view of the overall, does not care about all the members of individual characteristics, which not only make the cable design do have a brain, but also for simplified model and terms provided favorable conditions.