How to improve the building exterior wall thermal insulation material burning level of fire safety
Beijing CCTV fire in a row this year, nanjing international square, central fire, let building exterior wall thermal insulation material such as plastic extruded board become the focus of attention. In our country, the requirement of the safety of the external wall thermal insulation material on the standards and specifications have not been fully reflected, especially in the aspect of fire safety, there have been various hidden dangers. How to improve the domestic all kinds of building external wall thermal insulation material of fire safety has become an important issue relates to the safety of the people's livelihood.
One, the fire risk of exterior wall thermal insulation system
1, the type of exterior wall thermal insulation material
From the perspective of the burning material currently used for the insulation of external thermal insulation system mainly includes three categories.
Inorganic thermal insulation material: rock wool, glass wool, expanded vitrified beads insulation slurry, etc., incombustible material, its no fire safety problems. But the other can't fully meet the requirements of external thermal insulation performance, widely used at present are not possessed of technical conditions.
Organic inorganic composite thermal insulation material: give priority to with powder polystyrene particles insulation pulp, flame retardant materials, and flame propagation resistance, not their own there is no fire safety problems.
Organic polymer insulation materials: in order to satisfied with polystyrene foam plastic and rigid polyurethane vinegar is given priority to, the combustible material, has the danger of fire.
2, exterior wall thermal insulation fire risk
Civil architecture, especially in high-rise building fire tend to form a vertical spread, this is because the window glass, though not melt at about 900 ℃, but under the condition of the fire, because the glass is heated uneven expansion deformation is limited by a window, and inside and outside surface temperature difference is too big, often in 250 ℃ or so, cracking and broken. Door window glass when the building was on fire in the role of fire or high temperature, quickly broken off, fire out from the broken door window, it is for this reason. Flametongue basic way of spreading to the outside through a window outside doors have two: one is the flame of the radiant heat through the door opposite the window roast burning buildings; Second, the fire out from the window up, bake the upper window of fuel combustion, resulto spread, causing the building caught fire. Especially after fire wall, due to the stack effect of fire spread quickly. In the current "code for fire protection design of buildings" and "code for fire protection design of tall buildings are not contained in the external wall thermal insulation of the fire protection design requirements, the external wall thermal insulation material no clear requirements on the fire resistance of fire due to the effect of high temperature, wall thermal insulation surface mortar crack, fall off, will soon be ignited insulation materials, fire quickly spread to a wide range. At the same time, external wall after fire, automatic fire control facilities due to indoor fails to cover walls, especially after the high-rise building external wall thermal insulation material is on fire, but also can.
Second, the exterior wall thermal insulation system fire prevention technology status at home and abroad
1, the exterior wall insulation fire prevention technology abroad
The development history of exterior wall thermal insulation system can be seen from abroad, the external wall thermal insulation material as the fire safety requirements has been the preferred condition in application of this technology. Exterior wall thermal insulation technology advanced countries such as Europe and the United States, the external wall thermal insulation system has strict level of fire safety requirements, the exterior wall thermal insulation system and thermal insulation material with different fire test method and classification standard (considering combustion flue gas and toxic release), and the fire rating of exterior wall thermal insulation system has strict rules in the use of the building.
In the European standards ETAG004 with plaster layer of external thermal insulation composite systems European technology standard authentication, for insulation fire retardancy test methods should be according to the CEN hierarchical file EN13501-1 combustion performance classification of building products or components for flame retardant grade A1 - E test. Fire rating determination and the relevant tests require twice: once for the entire system, and another only for thermal insulation material. Need to consider when testing the possibility of flame spread in the thermal insulation material and system suppliers should recommend a fire isolation to prevent the fire spreading, as part of the system, you may refer to the fireproofing performance product performance list or the results of the large scale test. At the same time, the external wall thermal insulation fireproof requirements will be applied according to laws, regulations, and eventually use the regulations of the building. In Germany have caused by the fire safety of polystyrene board thin plastering system can not meet the requirements and cannot be used in more than 22 meters building regulations; In Britain there are more than 18 m building are not allowed to use polystyrene board thin plastering exterior insulation system; In the United States in New York state building instructions specified refractory limit of less than two hours of polystyrene board thin plastering exterior insulation system are not allowed to use in more than 75 feet or 22.86 meters of residential buildings. Non-combustible material such as rock wool and made of exterior wall thermal insulation system can be widely used in various types of buildings, the system has become the world's most widely used one of the outer wall heat preservation practices.
2, the domestic current situation of the exterior wall insulation fire prevention technology
At present, the domestic external wall thermal insulation system fire prevention technology research and the emphasis is not enough, almost all mention of the content is about system adopted by the combustion performance of insulating material, even in the outer wall heat preservation industry standards for organic heat preservation material requirement is only oxygen index and the flammability test index. At present, the current "code for fire protection design of tall buildings" in no of exterior wall thermal insulation material for fire protection design content, lack of external wall insulation system classification standard and using scope, exterior wall insulation fire prevention technology also has no national or industry standards and specifications, production enterprise product manuals in general lack of fire prevention performance indicators.
Dominant in domestic external wall thermal insulation system of polystyrene board thin plastering systems exist the following problems. Polystyrene board thin plastering system in developed countries because of its poor fireproof performance, and have strict limits on the scope of its use, but there is no standard in China have made stipulations. Almost all polystyrene board thin plastering exterior insulation of production units of the polystyrene board thin plastering system fire hazards are turning a blind eye, some international famous exterior insulation company after entering the Chinese market has shown to society, attitude towards people's life and property shall bear the responsibility, to hide their products because of fire safety in their own country can not meet the requirements for the use of its products to limit the scope of regulation, they used the present situation of the external wall thermal insulation market in China is not standard, at the top even in the building height of 170 meters, central such super-tall building still using this product. Domestic high-level, high-rise building with polystyrene board thin plastering grid cloth paste brick exterior insulation is also quite common, the danger of this approach is that once the fire, not only toxic gases from the burning of the organic insulation board and flame can bring huge to escape the danger, at the same time due to the thermal shrinkage deformation of polystyrene heat and falling caused by overheating broken tile grid cloth, the potential risk of escape and rescue personnel is fatal. It is because in the external insulation design, construction process and construction after the completion of neglect and fluky psychology problems of fire prevention, fire caused by combustible exterior wall thermal insulation material or accelerated the spread of shocking cases. In our country, is currently promoting energy-saving building, but the present condition of the external wall thermal insulation system is that about 80% of the body of the heat preservation material in the system for organic combustible materials, and systems and to poor fireproof performance of polystyrene board thin plastering system primarily.
Three, exterior wall thermal insulation fire safety measures
The author thinks that, solve the problem of exterior wall thermal insulation fire safety, on the one hand to take measures on technology, make the exterior wall insulation, heat preservation system has the ability of state security, must strengthen the management on the other hand, fire management measures to strengthen the construction site, reach the harmony of system, in order to realize the security of the whole system.
One of the measures: strict external wall thermal insulation technology of fire prevention safety
When building external wall thermal insulation engineering design and construction should comply with the relevant provisions in the external wall thermal insulation engineering technical regulations. Construction, the construction unit must use flame retardant or non-combustible building external wall thermal insulation material, or treated with flame retardant insulation material selection (combustion performance level indicators should meet the national standard in building materials and products of combustion performance classification rules of monomer combustion performance grading test).
The exterior wall thermal insulation technology of fire prevention safety problem is divided into four levels:
(1) the proposal is in the revision of the standard, making the combustion performance of insulating material grade shall not be lower than the rules of the B1 level.
External thermal insulation system of combustion performance rating can not make the request or not as a mandatory requirement, shall require external thermal insulation system has the ability to prevent the spread of flames. The appropriate fire isolation structural measures as part of the external thermal insulation system. This is a matter of guidance, encouraging external thermal insulation production enterprise for its reasonable improvement to the original system, meet the fire safety requirements.
(2) advice explicitly stipulated in the laws and regulations construction of more than 24 m it is forbidden to use organic combustible insulation material, so the polystyrene board exterior insulation system construction can only be used for less than 24 m, 24 m higher than most buildings use noncombustible or external thermal insulation system fire rock wool. Non-combustible material such as rock wool and made of exterior insulation system can be widely used in various types of construction, has now become the world's one of the most widely application scope exterior insulation of practice.
(3) the determination of fire rating and related tests require twice: once for the entire system, and another only for thermal insulation material. Need to consider when testing the possibility of flame spread in the system heat preservation material, system supplier shall recommend a fire isolation to prevent the fire spreading.
(4) to meet the premise (2), use the paste of polystyrene board thin plastering exterior insulation system, usually two questions to consider is to maintain the stability of the system under the condition of fire ability and system ability to prevent the spread of flames. The following measures should be taken.
Set fire belt: level in building or vertical set fire partition between layer and layer, generally USES non-combustible or difficult to heat preservation material, system is not space between any of the material, has a certain width. In every one eye brow and signage (non-combustible high mineral wool fire belt, thickness with polystyrene board, up width is greater than 200 mm; More than 300 mm length of Windows on both sides of the extending outward, with full of sticky post. Mainly to prevent the indoor fire, the fire area from the window light exterior insulation system and lead to the spread of fire.
Fire damper beam: a way of fire insulation of Windows and doors hole structure, similar to fire belt, level set on the edge of the doors and Windows on the mouth of the cave, and the length of the vertical edge of the hole out of doors and Windows must be.
In order to maintain the stability of system, under the condition of fire protection system not flame propagation resistance, can consider to use metal firmware.
Measure 2: strict external wall thermal insulation fire safety management
To strengthen the management, according to the existing and thermal insulation engineering construction fire safety management of fire protection regulations and other relevant rules and regulations, combined with the actual situation, thermal insulation engineering construction safety management measures are put forward, and carefully carried out. To correspond to the structure of external thermal insulation system of the reasonable technical method, such as considering the combustible insulation board before entering the construction site fire-proof interface agent, etc, in order to satisfy the requirement of the construction process of fire safety.
Measure 3: strict construction engineering construction site management
To strictly implement the provincial construction department issued the construction engineering construction site fire safety standards, strengthening the fire safety management of construction engineering construction site. Especially for the use of open flame must be strict fire safety management. Need, the open flame, hot departments and personnel shall, in accordance with the use of fire management system for examination and approval formalities, to carry out the on-site guardian, after the confirmation no fire and explosion danger when hot construction; When hot construction personnel shall abide by the fire safety regulation, and to carry out the corresponding fire control safety measures, especially closely overhead welding special welding such as environment protection requirements; Electric welding, gas welding, electricians and other special type of work personnel must hold relevant certificates; Will be easy to fire, severe consequences when a fire breaks out areas identified as key fire prevention area, strict management.
