Abstract: Dennis Logistics Center is a large-scale warehousing and logistics center designed and built according to the super high-rise building, with a high floor (> 12? M) Features of large space, dense shelf layout and high cargo placement. Combined with the water fire protection design of this project, the calculation of indoor fire water consumption, scheme selection and system design of automatic sprinkler system in ultra-high warehouse building are discussed, and some unclear problems in the code are put forward, which are willing to be discussed with colleagues. ?
Keywords: large warehouse logistics building? Fire hydrant? Automatic sprinkler? Design? Discuss the project overview?
1? Project overview
Dennis Logistics Center was built by Zhengzhou Dennis Department Store Co., Ltd. With the continuous expansion of Zhengzhou Dennis Department Store, in a few years, the original Renmin Road store gradually developed into a chain operation of several stores. The project is located at the intersection of Hanghai East Road and First Street in Zhengdong New District. The plot is adjacent to Beijing-Zhuhai Expressway in the east and National Highway 107 in the west, with convenient traffic conditions. The building structure of this project is a light sloping roof steel frame structure, with a building area of 2 1800m2 and a maximum story height of 1.5? M, there are elevated area, low shelf area and cargo sorting area. The goods stored in the logistics center are classified as Class C ... This project is divided into four fire zones according to the difference of building area and floor height, and the area of each fire zone is controlled within the scope permitted by the Code for Fire Protection Design of Buildings (hereinafter referred to as "Building Code") (that is, it does not exceed 6000m2). The first, second and third fire zones include part of the elevated shelf zone and part of the goods sorting zone, and the fourth fire zone is the mezzanine low shelf warehouse zone. The fire resistance rating used between fire zones is not less than 3? Fire shutter, firewall separation. Roof steel beams, purlins and shelves shall be coated with fire retardant coating, and the fire resistance rating shall be no less than 3h.
2? Design of fire hydrant system
2. 1? Fire water source
There are two water sources in this building, and two DN300 water supply pipes are introduced from different municipal roads, forming a DN300 circular water supply pipe network in the park. The water pressure at the project site is about 0.30MPa, and a 250m3 fire pool is set outdoors. The insufficient fire water is supplemented by the municipal water supply network.
2.2? Outdoor fire hydrant system
According to the provisions of the Building Code, the outdoor fire-fighting water consumption of Class C warehouse with fire resistance grade I and II is 45? Letter of credit. According to the water pressure and water supply of the water supply network, outdoor fire fighting adopts atmospheric pressure and high pressure water supply system. There are two other buildings in the base, because the site length is 380? M, north-south width 120? M, considering the safety of the water intake of nearby fire engines and the project, * * * has set up six fire hydrants on the ground, which are evenly arranged along the circular fire lane and combined with the layout of single building.
2.3? Indoor fire hydrant system
According to Article 8.5.2 of Building Code, the water consumption of indoor fire hydrants is 10L/s, and the number of water guns used at the same time is 2, and the minimum water output of each water gun is 5l/s. As the maximum height of goods on the overhead shelf is 1 1.5? M, when putting out a fire, in order to prevent firefighters from being burned by flame radiation or injured by collapsed burning objects, the tilt angle of the water gun should generally not exceed 45 degrees. The schematic diagram of fire extinguishing with inclined water gun injection is shown in figure 1 ..
According to the calculation, the required length of DC water gun is sk = (h1-H2)/sin45 =1.41(h1-H2) =1.41(65438 When the caliber of the water gun is 19mm, the pressure at the hydrant orifice is 0.265? MPa, flow 6.44? Letter of credit. Therefore, the design water consumption for indoor fire protection in this building should be 12.88L/s, and for safety reasons, the design water consumption for indoor fire protection is15L/s.
3? Scheme selection of automatic sprinkler system
According to the specific conditions of this project, the following three design schemes are considered in the design of automatic sprinkler system of this project:
3. 1? Adopt rainwater system
According to 4.2.5 of Code for Design of Automatic Sprinkler Fire Extinguishing System (hereinafter referred to as "Sprinkler Meter"), if the indoor clearance height exceeds 6. 1. 1 (that is, the maximum indoor clearance height of the warehouse with quick response and early suppression of sprinklers is 12m), but the initial fire must be put out quickly, the rain system should be adopted. The design parameters of the deluge system are only mentioned in "Spray Meter" 9. 1.8 (the design flow of deluge system and water curtain system shall be determined according to the sum of nozzle flow controlled by deluge valve; For parallel systems controlled by multiple deluge valve, the design flow of the system shall be determined according to the maximum sum of the flows with deluge valve enabled at the same time. According to specification 5.0. 1, the action area of a single deluge valve control is 180m2, and the fire zone area of this building is 6000m2. According to the specification, 34 deluge valve should be installed. How many factors should be considered at the same time if the fire occurs at any point in the fire zone? In addition, whether the warehouse building belongs to the building that must quickly put out the initial fire is not clearly defined in the specification. At the same time, we consider that several sprinklers can put out the fire in the initial fire, and once the rain system is turned on, a large number of sprinklers will act at the same time, which is bound to cause floods. Therefore, it is a bit inappropriate to adopt the rainwater system in this project. ?
3.2? Adopt large space intelligent fire extinguishing device
In recent years, in order to meet the requirements of automatic sprinkler fire extinguishing in large space, many domestic manufacturers have developed intelligent active sprinkler fire extinguishing systems in large space, and Guangdong Province has taken the lead in compiling the Code for Design of Intelligent Active Sprinkler Fire Extinguishing Systems in Large Space. The fire extinguishing device provides a new design concept and method for solving the problem of super high-rise building (H> 12m). Large space intelligent fire extinguishing device, suitable for the production and storage of Class A articles, with a maximum clearance height of 6 ~ 25? Warehouses, factories and other places. The device is always in an all-round monitoring state for the protected area, and organically combines infrared sensing technology, computer signal processing and communication technology to complete the whole process control from detecting and judging the fire to starting the device to extinguish the fire and stopping the water spraying. Compared with ordinary wet automatic sprinkler system, it has incomparable advantages in finding fires and extinguishing early fires. However, this code is only a local standard in Guangdong Province at present. Whether this specification can be used as the design basis in Henan Province has been reported to the Provincial Fire Corps for comments, but we have not received a reply. In addition, because the investment cost is particularly high, designers must consider comprehensively when choosing the scheme.
3.3? A system combining quick response early automatic sprinkler system and shelf automatic sprinkler system is adopted.
According to the different height of the inner layer of the building and the different shelf layout, different types of sprinklers are used for protection. For the height of building inner layer less than 12? M warehouse part (the maximum shelf height is 6m), according to 5.0.6 of the Spraying Regulation, quick response and early suppression nozzles are adopted; Is the height of the inner layer of the building greater than 12? M (maximum shelf height 1 1.5? M) According to Article 5.0.6 of the Sprinkler Code, if only quick response and early suppression sprinklers are installed under the roof, it will not meet the needs of effective fire fighting, but adding sprinklers on the shelf is a supplement to the fire fighting ability of the top sprinklers. Therefore, we adopted a quick response early fire sprinkler with flow coefficient k = 200 under the roof, and also installed a common sprinkler with flow coefficient k = 80 on the shelf. The scheme has the advantages of simple system form, few alarm valve groups, low investment cost and convenient management.
By comparing the above three schemes and consulting the local fire department, the author thinks that the third design scheme has the advantages of low cost and simple system, and it is more reasonable to adopt it.
4? Design of automatic sprinkler system
4. 1? According to the characteristics of storey height and fire zone, the pipe network system is divided into three parts.
(1) elevated warehouse (H> 12? M) This part is designed according to the risk level II of the warehouse, and a closed sprinkler with quick response and early fire extinguishing with flow coefficient k = 200 is set under the roof. The nozzle arrangement spacing is 3. omx？ 3.0m, the water consumption for spraying water is 90l/s, and the viaduct is divided into five floors, each with 2m height. If nozzles are installed on each shelf, the height of goods in the shelf is limited due to the requirements of nozzle installation, so it is easy for workers to accidentally touch the nozzles at work. Therefore, the nozzles are arranged in the middle of the 5m aisle of the side-by-side shelves, and a row of nozzles with flow coefficient k = 80 is arranged every two floors from bottom to top. In order to put out the initial fire more effectively, it is required that the shelf tray must adopt a tray with strong permeability, and the nozzle spacing is 3.0 mx3.0 mm.
(2) Under the first mezzanine, there is a cargo sorting area with a height of 6.9m Usually, goods are not piled up, but only used in the wharf for loading and unloading goods. Therefore, according to the warehouse risk level II, the sprinkler with flow coefficient k = 80 can meet the needs of water spraying intensity. The nozzle arrangement spacing is 2.0? mX？ 3.0? M (depending on the arrangement of structural beams), and the spraying strength is: 16? L/(min m2), the action area is 300m2, and the water consumption for automatic sprinkler is 80l/s.
(3) For the mezzanine of the elevated warehouse (the maximum height of mezzanine is 8m, and the maximum stacking height of goods is 5.5m), a closed sprinkler with rapid response and early suppression with flow coefficient of k: 200 should be set according to the risk level II of the warehouse. The nozzle spacing is 3.0mX3.0m, and the water consumption for spraying water is 90l/s.
4.2? Water consumption of automatic sprinkler system
According to 9. 1.5 and 9. 1.6 of the sprinkler code, when there are different types of systems or places with different risk levels in a building, the design flow of the system should be determined according to its maximum design flow. Therefore, the design water consumption of the automatic sprinkler system should be the maximum value of the sum of the initial water output of the sprinkler with 12 k = 200 and the water output of the four shelf sprinklers, that is, 95.32 l/s (12x7.5+4x1.33: 95.32).
4.3? Determination of pressure of automatic sprinkler system and setting of alarm valve group
Due to the rapid response of k = 200, the minimum working pressure of the early suppression nozzle is 0.50MPa, and the minimum working pressure of the nozzle in the shelf and the ordinary glass ball nozzle with k = 80 in the cargo sorting area is 0. 10MPa. Therefore, the water supply system needs to supply water according to the pressure and different areas of the fire protection zone, and alarm valve groups are set up respectively. The water supply pressure of the automatic sprinkler system is designed to suppress the nozzle pressure in the early response of the most unfavorable point, while the pipe network system with ordinary nozzles is depressurized by the pressure reducing valve group. Because the automatic sprinkler system is designed with large flow and long pipes, in order to reduce the pressure difference between the farthest and nearest working areas caused by the resistance of the pipe network, ensure the pressure to be constant, and appropriately increase the diameter of the main water supply pipe, seven groups of alarm valve groups are set according to different fire zones and different pressures. Considering that if the alarm valve group is concentrated in the fire pump room, the laying of seven water main pipes from the pump room to the four fire zones will not only occupy effective building space, but also increase the project cost due to excessive consumables, so the arrangement of alarm valve groups scattered in each fire zone is adopted.
5? Discussion on fire protection design of super high-rise building
5. 1? Problems of sprinkler spacing and minimum working pressure in heavy and super high-rise buildings
According to Article 5.0.6 of the Spraying Regulation, when the maximum gap is within the range specified in this table, the maximum spacing and minimum working pressure of sprinklers are given in the table, and when the gap exceeds this table, the spraying capacity of sprinklers installed on the shelf and roof sprinklers is compensated. This article does not give the spacing and minimum working pressure of roof sprinklers determined according to Table 5.0.6. Furthermore, the sprinklers on the shelves have not indicated which type of sprinklers should be selected. If the nozzle with flow coefficient K=80 is set, it can not meet the requirements of water spraying intensity specified in Table 5.0.6, and the nozzle with flow coefficient K=200 is not suitable to be set on the shelf.
5.2? Does the concept of action zone of super high-rise buildings exist?
Table 5.0.6 of the "Spray Gauge" shows that the design flow rate of nozzles with quick response and early suppression should be determined according to the water output of 12 nozzles in the action area. According to "Spray Gauge" and referring to American FM standard, the maximum arrangement spacing of early suppression nozzles for rapid reaction is 3.7? M, the minimum arrangement spacing is 2.4m, the maximum and minimum arrangement spacing is 12, and the difference of the nozzle protection area is 95. 16? m2L(3.7X？ 3.7) x12-(3.0x3.0) x12], since the distance between different protected areas and the sprinklers is 1.38 times, and the size of the action area is not clearly given, should the "number of sprinklers opened at the same time in the action area" in this table be modified?
5.3? Volume of fire water tank and water output of pressure stabilizing equipment
In the Spray Table 10.3. 1 and 10.3.2, it is stipulated that the water output of roof or gas water supply equipment is 5L/s and the water supply time is 10min, but it is not pointed out whether the above two parameters are the same when different nozzles are used, because the working pressure of an ordinary nozzle is 0.65433. Whether this parameter should be specified according to different nozzles.
6? Conclusion?
To sum up, adopting a reasonable fire protection design scheme can reduce the capital construction cost and cost of ultra-high logistics buildings, which is the key to fire control and effective fire protection design. Some unclear design parameters in the Spray Gauge are expected to be clarified in the revision of the new Spray Gauge.
References:
[ 1]? , Jiang,, etc. Design manual of automatic sprinkler system. China Industry Press.
[2]? Pan-Qin Zhen. Design and discussion of automatic sprinkler system for special buildings. Water supply and drainage, 2003. (8).
[3]? Ginger. Understanding of Code for Design of Intelligent Active Sprinkler System in Large Space. Paper on the Third Annual Meeting of Water Fire Protection Branch of National Building Water Supply and Drainage Committee and International Automatic Sprinkler Technology Exchange Conference); "> paper, April 2004.