欧美激情视频网址I狠狠色依依成人婷婷九月I久久综合站Iav青草I日本黄色xxxxI丰满放荡岳乱妇91wwI日韩激情中文字幕I国产精品,I成人高清I20日本xxxxxxxxx46I国产精品9191I日韩熟妻I91精品人妻一区二区三区蜜桃2I国产黄色一级片I欧美色涩I69福利视频Ihd国产人妖ts另类视频I亚色网站I青青草手机在线视频I国产精品手机在线Iwww.色午夜.comI亚洲国产精品久久久久制服I色射网I寡妇avI亚洲激情图

The classification of rubber insulation cotton grades is mainly based on the following aspects:

1、 Fire resistance performance

Oxygen index

The oxygen index is one of the key indicators for determining the grade of rubber insulation cotton. It refers to the minimum oxygen concentration required to maintain stable combustion of rubber insulation cotton under specified conditions, expressed as the volume percentage of oxygen. There are clear requirements for the oxygen index of different grades of rubber insulation cotton, such as zero grade ≥ 39, B1 grade ≥ 32, B2 grade ≥ 26. The higher the oxygen index, the stronger its fire resistance.

combustion characteristic 

A-class materials are non combustible and will not burn in air, such as some inorganic insulation materials. A1 level is also non flammable and does not ignite open flames, and A2 level is also non flammable. It has undergone professional performance testing and has a qualified attribute certificate.

B1 grade belongs to fire-resistant building materials, which are difficult to ignite when exposed to open flames or high temperatures in the air, and are not easily spread quickly. The combustion will immediately stop when the fire source is moved away.

B2 level has a certain degree of flammability, but it has a certain flame retardant effect. When exposed to open flames or high temperatures in the air, it will immediately ignite and burn, which can easily lead to the spread of fire.

B3 grade is a flammable building material with almost no flame retardant effect, extremely flammable, and high danger. However, B3 grade has gradually been phased out in the market.

2、 National standards and dimensional specifications

national standard

According to the old national standard GB8624, the fire resistance level of rubber insulation cotton is divided into four levels: Class A, B1 flame retardant, B2 flame retardant, and B3 flame retardant.

Size specifications

In terms of product specifications and dimensions, B2 grade is a non-standard material, with deviations in the wall thickness and length of its pipes, as well as the length, width, and thickness of its plates; Grade B1, Grade A, and Grade 0 are national standard materials with regular dimensions, including length, width, thickness, pipe diameter, and wall thickness.

3、 Appearance identification and packaging

Appearance identification

For rubber insulation boards or pipes, grades can be distinguished based on their appearance. There may be slight protrusions on the surface of B1 grade products. After opening the product, the pipe or board will be printed with the words' B1 grade product '; The surface of B2 grade products is relatively smooth and soft to the touch.

Packaging difference

The packaging of B1 level products is printed with the company name and affixed with a certificate of conformity; B2 level products are packaged in green packaging.

The classification of rubber insulation cotton grades is the result of comprehensive factors, which helps consumers choose suitable products according to their needs, optimize insulation and other functions while ensuring safety.