标题: BS 476 Part 6 [打印本页] 作者: robinchen 时间: 2010-5-19 15:24 标题: BS 476 Part 6 Information Sheet – BS 476: Part 6 Fire Propagation Test
Heat release is a measure of the contribution that a burning material makes to a fire in progress, for example, a high rate of heat release will produce a high rate of rise of temperature in surrounding unburnt material and accelerate fire spread. At present, the only standard method of test which exists for determining the contribution of materials to fire is BS 476: Part 6 which utilises apparatus commonly known as the Fire Propagation Box. This method gives a rough indication of the heat output of the material under test so that an assessment of its possible performance in a real fire situation can be made.
放热是易燃材料在燃烧过程中所起作用的衡量尺度。打个比方，高速率的放热将对不完全燃烧的材料产生了高速率的升温并且加速了火焰的蔓延。目前，唯一能决定材料对燃烧起的作用的标准测试方法是BS 476: Part 6，BS 476: Part 6采用了大家所熟知的火焰传播盒。这个测试方法提供了在测试过程中的材料是释放出的大概热量，因此能对材料在真实的燃烧情况下的可能的反应作出评估。
This method of test, the result being expressed as a fire propagation index, provides a comparative measure of the contribution to the growth of fire made by an essentially flat material, composite or assembly. It is used primarily for the assessment of the performance of wall and ceiling linings. A diagram of the equipment is given below:-
Fire propagation is determined by exposing the specimen to the 14 jets of a gas pipe burner at a distance of 3 mm. The heat evolved is 530 J/s. The two electric elements with a total output of 1800 W are switched on after 2 min 45 s. Their output is reduced to 1500 W after 5 minutes and maintained constant until the end of the test (20 min).
To evaluate a material, the difference between ambient temperature and that in the chimney is recorded continuously using thermocouples and compared with a calibration curve derived in a similar manner using asbestos cement board of a specific density. The two curves are evaluated by establishing the temperatures from the calibration curve and test curve at 30 s intervals from the start of the test to 3 min, at 1 min intervals from 4 to 10 min and at 2 min intervals from 12 to 20 min.
The individual indices are calculated as follows from these values:
单个指数用这些数值计算，计算方式如下：
The total index I = i1 + i2 + i3
总指数I= i1 + i2 + i3
where i1, i2 and i3 are the sub-indices at 3 min, 10 min and 20 min respectively
i1 i2 和 i3分别是在3分钟，10分钟和20分钟的副指数
t time in minutes from the origin at which the reading is taken
从开始计数的时间（分钟）
m temperature in C of the test curve at time t
在时间t时测试曲线所显示的温度
c temperature in C of the calibration curve at time t
在时间t时校准曲线所显示的温度（C）
If four or five specimens are needed to obtain three valid results, a suffix `R' is added.
如果4个或5个样品需要得到三个有效的测试结果，添加一个`R'后缀
The fire propagation test serves mainly to investigate whether materials which have achieved Class 1 according to BS 476: Part 7 conform to Class 0. To achieve Class 0, a material must be wholly non-combustible or must meet the requirements of Class 1 to BS 476: Part 7 and have a subindex i1 < 6 and a total index I < 12 using BS 476: Part 6.
火焰传播测试主要用来研究已经通过BS 476: Part 7的Class 1的材料是否符合Class 0的要求。为了达到CLASS 0，材料必须是不可燃的，或者必须达到BS 476: Part 7的Class 1的要求且BS 476: Part 6的第一个副指数i1 < 6，总指数index I < 12。
The requirements of Class 0 make increased demands on the fire performance of Class 1 building products and differentiate between them as regards fire hazard. This test method is also used to examine the suitability of building materials for certain applications.
Class 0的要求比通过Class 1的建筑产品的防火性能的要求要高，并且把它们在火灾方面区分开。这个测试方法也用来检查特定应用的建筑材料的适用性。
Specimen requirements:
5 specimens each 225mm x 225mm. Thickness as in practice but no greater than 50mm. Specimens must be essentially flat and free from holes, cracks or fissures。