【 Weak current College 】 sprinkler system functional analysis of the fire water tank---Power By 【 China power house network 】

Outline for the automatic sprinkler system fire water tank features mainly boot system and associate work State provide detection system components on the needs of water pressure. According to the system of different type, for the different requirements of water features, reasonable to determine the height of setting fire water tank.
Keywords for automatic sprinkler systems, fire water tank function sets the height of 1 to the relevant provisions of the specification's understanding of the sprinkler system (hereinafter referred to as sprinkling system) of the fire water tank is a system of water supply facilities. Its main role is sprinkler system in the initial phase (or maintenance) to the water filling system, when in prospective work State supplementary piping water leakage, fire sprinkler system ensure the timely start and control the fire or fire fighting. Fire water tank design's main job is to make sure it's valid storage volume and set the height. The automatic sprinkler system design code (GB50084-2001) (hereinafter referred to as the "Jet-discipline) section 10.3.1 on this issue as a mandatory requirement:" a temporary high pressure water supply system of automatic sprinkler system, should be set to high fire water tank, the water should be in line with existing provisions of the relevant national standards. Fire water tank water supply, should satisfy the system is the most disadvantageous point minimum working pressure sprinkler and water jet strength. "The first sentence of the said provisions when setting fire water tank and its effective volume, after the Word provides the set height of fire water tank, water supply systems in overcoming resistance losses after meet the minimum working pressure and spray intensity. Tank height requirement is new content, as it's understood differently, coupled with the implementation of very difficult, and response to comments. The reason, the author believes that the following aspects: (1) excessive stresses the high water in fire-extinguishing fire control in the early days, for that purpose "should be provided for the system most unfavourable point minimum working pressure sprinkler and water jet strength" requirements. Here the water jet strength is the strength of the fire-fighting needs, or nozzle orifice minimum working pressure strength? Standard provisions and provisions are ambiguous, instructions to design difficult. (2) the provisions for cancellation before the implementation of the 2001 edition of the publication of the storage of low height and are often adopted effective water O pressure water sharing (or voltage pump) pressurized water supply. Only requires building height not exceeding 24 m, and press lightly, the risk-level settings in the wet, dry, preaction system, such as difficulty high fire water tank, with 5 L/s flow-pressure water sharing equipment supply 10 min initial water (this is possible will be discussed separately). (3) water tank height requirements ignored for different type of sprinkler systems, different kinds of nozzle exists different functionality needs. (4) fire water tank in the sprinkler system is to boot the system, or charged with fire or fire fighting. The following are on a comprehensive analysis of these issues, and to make modifications to the specification section. 2 start sprinkling system is the primary function of the fire water tank under fire load, indoor space conditions, personnel are crowded, and the evacuation of ease and external reinforcements Division set criteria such as place of fire danger rating, select the type of sprinkler system. Different fire danger levels have different spray intensity and effects of area, this is a fire sprinkler system to efficiently. To meet the requirements of the water-jet strength use different types of sprinklers, and according to certain layout in the settings of gap. We use wet system for analysis, in accordance with the regulatory requirements, spraying in the nozzle to a square layout, different risk levels and different types of sprinkler calculated data are summarized in table 1. 2.1 fire water tank fire extinguishing capability analysis from table 1 we can see that: (1) in the light, medium risk level places with standard nozzle (flow coefficient K = 80, nozzle function head 0.1 MPa, when using different spacing layout design water spray nozzles are able to meet the strength 4, 6, 8 L/(min · m2). (2) in grave danger level I (warehouse dangerous I grade) with standard nozzle and maintain 0.1 MPa pressure of work, the nozzle spacing 2.6 m. A sprinkler head protection areas to 6.75 m2. In the function area 260 m2 (200), generally to layout 39 (30), which apparently only nozzle is not economical. If changed to large diameter nozzle (K = 115, working pressure 0.1 MPa), in grave danger I-level's role in the area just layout 27 only nozzle, I-level layout warehouse dangerous 21 you can only print head, respectively, reduced by 12 and 9 only nozzle. (3) for serious danger dangerous ⅱ and warehouse ⅱ to continue with standard nozzle, you must increase the nozzle pressure to increase water MPa 0.2 quantity to meet the 12 L/(min · m2) sprinkling strength needs. To continue the work pressure 0.1MPa unchanged, the nozzle spacing is less than 2.4 m. Spacing is too thick will affect adjacent nozzle open, on the fire. Therefore, the first of the "Jet-discipline 7.1.2 stipulates that the spacing should not be less than 2.4 m (mandatory provisions). Even with large diameter nozzle, pressure is also a need to adopt 0.15 MPa. (4) dangerous for the warehouse of class to meet water jet strength 20 L/(min · m2), with standard nozzle pressure to increase when working to 0.3 MPa, with large diameter nozzle pressure also need 0.15 MPa. You can see from the above data, for different hazard class settings sites should use different types of sprinklers, their working pressure is different. "The first jet-discipline 5.0.1 and 5.0.5 on water jet strength, function area and nozzle pressure for a mandatory requirement is correct. To have the effect of nozzle area according to the rules of strength within 1 h continuously sprinkler can only rely on fire pump water supply. From table 1 we can see that, when the (use of fire water tank water supply) nozzle working pressure 0.05 MPa, its water jet strength ratio requirements were reduced by 30% to 60%, thisFire sprinkler strength is very unreliable. If you want to achieve the required strength of water spray nozzle spacing must be reduced, increasing the role of the head area. Light hazard level nozzle spacing 3.7 m, I-level 3 in danger, the danger in m Ⅱ-level reduced to 2.6 m, grave danger and risk level nozzle spacing warehouse is reduced to the following, this m 2.4 approach is not feasible. In order to emphasize the fire water tank fire extinguishing capability and reduce the number of nozzle spacing increase nozzle is not desirable, and increases the water tank set height to spray intensity approach works hard to achieve. 2.2 fire water tank boot capability analysis for sprinkling system boot functionality requirements, we are still the most widely used wet system as an example for analysis. Nozzle open decision by the fire temperature, pressure, water-related mainly to the flow meter and wet alarm valve Group (including hydraulic alarm and pressure switch). The Ministry of public security standard GA32-92 the sprinkler system flow indicator of performance requirements and test methods "in the section 5.8.1, when the required sensitivity test pressure in 0.14 ~ 1.2MPa: flow is less than or equal to 15 L/min, flow indicator should not be alert; alarm flow should be in the 15 L/min to 37.5 L/min to any value between, to 37.5 L/min, you must alert; alarm flow should not be greater than 37.5 L/min. From the product requirements of the standard view: fire water tank water supply, most unfavorable nozzle opening, when its working pressure 0.05 MPa, standard nozzle flow to 56 L/min, to meet the current requirements of the indicator work flow, pressure can meet the requirements will be difficult to guarantee.　89 the national standard GB797-sprinker system wet alarm valve performance requirements and test methods "in the alarm valve of functional requirements as follows: 4.14.2 with attachments wet alarm valve, inlet pressure respectively 0.14, 0.7, 1.2 MPa, system side the corresponding to 60, 80, 170L/min flow continuous discharge, shall issue a warning signal. 4.14.5 wet alarm valve inlet pressure 0.14 MPa, valve's alarm or delayer top pressure must not be less than the 0.05 MPa. 4.14.7 wet alarm valve pressure in 0.14 ~ 1.2MPa between velocity at 6 m/s, no adjustment should be accurate. From the alarm valve standards, alarm valve for accurate alarm function of inlet pressure 0.14 MPa, flow rate 60 L/min. And fire water tank water supply, shower working pressure is when you open the spray 0.05 MPa, the system of flow rate and pressure are not able to make reliable work alarm valve, start the system role cannot be guaranteed 100%. 2.3 conclusions and recommendations from the above analysis we can conclude that: for wet systems, fire water tank water supply in meeting system most unfavourable point the nozzle orifice minimum working pressure strength, neither effective fire suppression, cannot reliably boot the system. If you want to make a fire water tank water supply to meet the firefighting and start the wet system function, for light, medium risk level tank height should be set in the most adverse nozzle position 15 m and above, the use of large-diameter nozzle of Ⅱ-level and the use of large-diameter nozzle warehouse of class establishments in more than 20 m, the height except in rare conditions, the vast majority of engineering outsourcing is impossible. Therefore, the role of the fire water tank should be starting the system in the first place, fire fighting and fire control on the second place. Fire water tank to work together with booster facilities is to solve the problem of effective approaches, this approach also for the numerous projects in the past, some projects have also been effective in extinguishing the practice test. Hope when revising the specification can be provided in the sprinkling system fire water tank of setting more rationality and feasibility. 3 fire water tank set height of sprinkler system design should be based on the setting of the different situations select venues system type. Fire water tank in a different type of sprinkler system function, so it's effective volume and set the height of the inevitable. This section only on fire water tank of the set height, for its effective volume not involved. 3.1 wet wet system is allowed the system to work in full when the pipeline is used to start the system pressure water closed system (the "rules" section 2.1.2-1), shown in Figure 1. Fire water tank in this system's function is to provide water to start the system pressure. This pressure is the minimum requirement of water sprinkler opens the most disadvantageous, system of wet alarm valve inlet pressure group ≥ 0.14 MPa, Figure 1 wet system Schematic flow ¡ý 60 L/min. In this condition, alarm valve group retarder exit at the top of the pressure of not less than 0.05 MPa, setting where most of the pressure switch small pressure 0.02 MPa, and thus be able to start a fire pump to the fire-fighting water supply on an ongoing basis. Fire water tank set height H by type (1) calculation: H = h1 + h2 + h3 + h4 (1)-H-the height of the wet system tanks, m; H1 — the most negative pressure nozzle, should not small 10mH2O; H2 — wet alarm valve head loss, mH2O; H3 — flow indicator of head loss, mH2O; H4 — water tanks to the most disadvantaged nozzle pipe head loss, mH2O total. When tank height H does not meet the requirements of (1), should adopt pressure water sharing equipment to meet the needs of the wet system startup. Pressure tank water volume should be not less than 150 L; booster pump flow should 1 L/s, head of the pump set location determined by hydraulic calculation. Note: a booster pump flow under the tall buildings design fire protection standard (GB50045-95, 2001 Edition) the article determine 7.4.8.1, pressure tank water volume according to the Shanghai Municipal construction specification DGJ 08-94-2001 civil constructionWater fire extinguishing system design specifications for article 2 paragraph 6.1.5 of design parameters. 3.2 dry system dry system is prospective work status with water tubes filled with used to start the system pressure gases in closed system (the "rules" section 2.1.2 nozzle section 2), see Figure 2. Dry-type system in dry alarm valve group filled with pressurized air or nitrogen, fire sprinklers open Jet gas (or through accelerating the exhaust vent), pipe pressure drop allows alarm valve open, pressure water flow through the pipe reaches a sprinkler nozzles. Fire pump starts by inflatable devices at low air pressure pressure switch to instruction action, can also be accessed via alarm valve group Department by hydraulic pressure switch to directives make contact. The former than the latter pump startup time, enabling faster on fire. Fire water tank in the system's function is to provide a certain amount of hydraulic pressure, the prospective working state by alarm valve group at the hydraulic test water valve check alarm, pressure switches, and other conditions. Because dry alarm valve group of components: hydraulic alarm, pressure switches, filters, etc. of the structure and working principle and wet alarm valve group, therefore water pressure ≥ 0.14MPa. Fire water tank set height according to type (2) calculation: H = h1 + h2 + 14 (2) in the formula H-dry system tank set height, m; H1 — water tanks to dry alarm valve Department of total head loss, mH2O; H2 — dry alarm valve head loss, mH2O. 3.3 preaction system access preaction system is working with the water pipe is filled with water, by automatic fire alarm system automatically opened and rain alarm valve, converted to a wet system of closed-system (the "rules" section 2.1.2 nozzle section 3). Preaction systems generally use a combination configuration of preaction alarm valve set, rain water valve is located on the side, wet valve located on the system side, two valve overlap, while supporting setting the automatic fire alarm system. In double chain preaction system has two fire detector, with fire detectors and transmission pipe device to control preaction valve. Preaction system using fire detector perceived performance better than the characteristics of the closed-head, when the nozzle is not already open, by the fire detector pre-start rain valve, flow through rain and wet valve valve after opening fire pump water started to become wet pipe water filling system, once the nozzle open to rapid fire sprinkler. To strengthen preaction system preventing accidental spraying of performance, system piping is full of low-pressure air or nitrogen and set the low air pressure alarm device. And dry systems air pressure is low, do not need to use the gas pressure to confined alarm valve, pipe and sufficient water is adopted before the nozzle opening fire pump water supply has been completed. Fire water tank in the system and dry-type system similar to that set height can be a reference type (2). The calculation will dry valve head loss to preaction valve head loss. 3.4 deluge system deluge system consists of automatic fire alarm system or transmission control, the ventilatorautomatically opens rain alarm valve and pump, started to open type sprinkler water sprinkler system, also known as open system (the "rules" section 2.1.3 spray). Deluge system is open sprayer, the protection system once the action within the overall water spray area. Fire water tank was accurately state before the deluge valve pipe or transmission tube filled with water, in the rain when valve functions provided with the necessary water pressure, water. Thus, the deluge system tanks height in may reference type (2), the calculation will dry valve head loss to shower valve head loss. 4 the provisions of the specification for the revised proposal recommends that "the first jet-discipline 10.3.1 shall be revised as follows: using temporary high pressure water supply system of automatic sprinkler system, should be set to high fire water tank, the water should be in line with existing provisions of the relevant national standards. Fire cistern, should satisfy the system's startup and associate work State detection system components. When the fire water tank does not meet the above requirements, the water pressure should be set booster facilities. Booster pump for water production, L/s should be 1; pneumatic tank regulation should be 150 L water, when combined with the fire hydrant system up to 450 L.