摘要:
钢结构具有强度大、自重轻、易加工、便安装等优点,在石油化工企业中得到了广泛应用。钢结构防火设计对结构的安全性及经济性的影响十分重大,涉外工程中设计人员有必要熟悉不同标准之间钢结构防火设计的差异。通过对中、美标准中石油化工钢结构防火设计的对比研究,发现中、美标准中火灾危险区划分、防火范围、耐火极限等明显不同。对于防火范围,国标中石油化工企业钢结构的防火范围主要依据的是爆炸危险区,而美标防火范围依据的是火灾危险区,中、美标准危险区域的划分均与设备的火灾危险分类密切相关。国标中爆炸危险区是由电气工程师划分,美标中火灾危险区是由管道工程师划分。对于耐火极限,国标的耐火极限严于美标。对于耐火层,国内石油化工钢结构装置一般选用耐火涂料防火,海外石油化工钢结构装置一般选用外包轻质混凝土防火。1)对比分析中、美标准中承重钢结构(透空钢格板,封闭式楼板,支撑中、高危险设备等)的防火范围和防火高度,表明中、美标准中钢结构防火范围均考虑了楼板形式、空冷器布置等因素,但国标防火高度是具体到某一标高点,美标防火高度是具体到某一层,并且美标防火范围要做到中、高风险设备的支撑层。2)对比分析中、美标准中钢管架的防火范围,表明对于普通钢管架,当底层层高低于4.5 m时,国标防火高度大于美标,当底层层高不低于4.5 m时,中、美标准防火高度要求一致。3)对比分析中、美标准中下部设有可燃液体泵钢管架的防火范围,中、美标准中钢管架(下部设有可燃液体泵)的防火范围是不同的,国标的防火范围是具体到某一标高点,而美标是具体到某一层。4)对比分析中、美标准中耐火层的位置,表明中、美标准承重钢构架、支架及管架的下列部位,可不覆盖耐火层:a.不直接承受或传递设备、管道垂直荷载的次梁;b.仅用于支持楼板、钢格板的梁;c.仅用于抵抗风和地震作用的非承重支撑;d.卧式设备和换热器设备的鞍座。最后,给出了钢结构楼层缩进时的防火范围及柱间支撑的防火要求,采用框架支撑体系的钢结构装置,柱间支撑的防火要求应与钢柱相同。上部存在收进的钢结构防火宜按其平面投影范围内各楼层的楼板封闭情况、空冷器布置等因素确定防火范围。
Abstract:
Steel structure has advantages of high strength, light weight, easy processing and simple installation, and has been widely used in petrochemical enterprises. The fireproofing design is significant to the safety and economy of steel structures, and it is necessary for the designers to familiarize the differences between different standards in foreign projects. Through the comparative study on the fireproofing design of steel structures in petrochemical industry between Chinese and American standards, it is found that there are significant differences in the division of fire hazard zones, fireproofing scope, and fire-resistant time between Chinese and American standards. For the fireproofing scope of Chinese standard is mainly based on the explosion hazard zone, while the American standard is based on the fire hazard zone. And both the standards are highly related to the classification of fire hazards of the equipment. The explosion hazard zone in the Chinese standard is divided by electrical engineers, while the fire hazard zone in the American standard is divided by pipeline engineers. In addition, the fire-resistant time of the Chinese standard is stricter than that of the American standard. The fire resistance coating is generally used in the Chinese standard, while the external lightweight concrete is used in the American standard. For fire-resistant layer, domestic petrochemical steel structure devices generally use fire-resistant coatings for fire prevention, and overseas petrochemical steel structure devices generally use outsourced lightweight concrete for fire prevention. 1) The comparison of permeable steel grating, enclosed floor slabs, supporting medium and high hazard equipment indicates that the fireproofing scope of steel structures in both Chinese and American standards considers factors such as fire hazard zone, floor form, and air cooler layout. However, the Chinese standard fire protection height is specific to a certain elevation point, the American standard fire protection height is specific to a certain layer, and the American standard fire protection range should be the support layer of medium and highrisk equipment. 2) The comparison of steel pipe racks indicates that when the height of the first floor is lower than 4. 5 m, the fireproofing height of the Chinese standard is greater than that of the American standard, while the fireproofing height are the same when the height of the first floor is not lower than 4. 5 m. 3) Comparing the fireproofing scope of steel pipe racks with combustible liquid pumps in the lower floor, it is shown that the fireproofing height is specific to a certain point according to the Chinese standard, while fireproofing height is specific to a certain floor according to the American standard. 4) The following parts of load-bearing steel structures, supports and pipe racks in Chinese and American standards may not be covered with fire resistance layer:a. secondary beams that not directly bearing or transferring vertical load of equipment and pipelines; b. beams that only used to support floor slabs and steel grating; c. non-load-bearing supports that only used to resist wind loads and earthquake action; and d. the saddles of horizontal and heat-exchanger equipment. Finally, the fireproofing scope of the steel structure floors with set-back, and the fire protection requirements for column bracing are given. The fire resistance requirements of brace and column should be the same for the steel frame-braced structures. The fireproofing scope should be suitable to use the factors of floor format and the air cooler arrangement in the plane projection.