建筑给排水文档翻译

1、 自动喷水灭火系统设计中的几个重要问题1 喷头布置合理布置喷头是自动喷水灭火系统设计安全与经济的关键。喷规比较强调的是作用面积内的喷水强度和喷水的均匀性及喷头的适时开放。对于每个喷头的半径，一是和生产厂家的产品及其技术参数有关，二是和喷头所在位置的水压有关，三是和喷头的布置位置有关。喷规规定的喷头间距只是一个"限"，目的是为了更好地保证喷水强度和喷水的均匀性及适时开放。 1.1 喷头布置原则与要求(1) 满足作用面积内的喷水强度、喷水的均匀性及喷头的适时开放(喷头的受热条件和开放时间)；(2) 喷头在喷水半径内灵活布置，不出现未被覆盖的空白，也不出现过多的重要覆盖面积；(3

2、)保证喷湿墙根及一定范围内的墙面； (4)喷间之间不应互相影响；(5)按规范和实际处理障碍物的遮挡，并积极与相关专业协调；(6)应满足其它相关规范对喷头布置的要求；(7)考虑火灾时烟羽流对喷头动作的影响；1.2 喷水半径与喷头布置喷水半径是喷头布置的主要依据，它代表一个经济数值，在喷头工作时不致出现未被覆盖的空白，也不出现过多的重要覆盖面积。它与危险等级的喷水强度、喷头特性和工作压力有关。工程设计中喷头布置视建筑平面，在喷水半径范围内，可灵活采用正方形、矩形或平形四边形。喷水半径不同于喷头的计算半径，它是在计算半径的基础上，考虑喷水强度、喷水均匀性、喷头受热条件与适时开放，根据规范的规定而得出

3、的数值。由于喷头的布置受其它因素影响较大，实际上常常出现喷头不能按一个固定的距离来布置，别说同一建筑中往往不会按一个间距布，就是同一层、同一防火分区也常常如此。此外，作为土建设计，不同于装修设计，需要给二次装修留下有余地，喷头间距不宜按规范规定的最大距离要求设置，而且实际上这么做也不易达到规范要求的喷水强度和喷水的均匀性。设计时必须根据工程实际情况，按设计选定的喷水强度、喷头的流量系数、工作压力确定，并考虑喷头的受热条件和开放时间，在满足规范要求的喷头强度条件下，按喷头的实际工作压力，结合建筑分隔与结构柱网灵活布置。在布置中，喷头间距不应是个定数，应根据所在位置的条件来定，最终目的还是保证喷水

4、强度和喷水的均匀性及适时开放。2 水力计算水力计算将决定系统投入灭火的水量及对灭火水量的分配，是关系系统可靠性、合理性和经济性的一项重要设计内容。根据对喷规的理解和大量相关资料及部分工程实例的分析，觉得水力计算应采用"矩形面积-逐点法"，也就是首先确定最不利作用面积在管网中的位置，作用面积的形状宜为矩形，仅在作用面积内所包含的喷头计算其喷头量；之后选定最不利计算路线，采用节点流量法将最不利作用面积内的每个喷头的压力值和出流是一一求出，当两个分支交汇时，根据两分支的压力差对压力较高的分支进行流量修正，然后将作用面积内经过流量修正之后的所有喷头出流量的总和作为整个自动喷水灭火系

5、统的设计流量，在此以后的管段流量不再增加，仅计算沿程和局部水头损失，一直算到管网起点。实际火灾发生时，一般都是火源点呈辐射状向四周扩大蔓延，而只有失火区上方的喷头才会开启喷水。因此采用作用面积保护方法及仅在作用面积内的喷头才计算喷水量是合理的。同时由于火灾时对流及风的影响，作用面积的形状以呈矩更为合理，且矩形面积在管道水力计算时也是最不利的。因而这种"矩形面积-逐点法"符合火场实际，科学严谨，并与欧美等国接轨，是合理的、安全的，也是喷规的推荐作法。(1) 矩形面积的确定：作用面积的形状宜为矩形，其长边平行于配水支管，其长度不小于作用面积平方根的1.2倍，喷头数若有小数就进位

6、成整数。当配水支管的实际长度小于边长的计算值时，作用面积要扩展到该配水管邻近支管上的喷头。(2) 经济流速和最不利点处水压 经济流速：自动喷水灭火系统最主要的组成部分是配水管道，而配水管道管径的确定，不仅影响到整个系统的造价，更关系到系统消防的安全性。在流量确定的条件下，流速是确定管径的重要参数。采用经济流速是给水系统设计的基础要素，生产、生活给水管道的流速一般采用经济流速，以使管道的基建投资与经常性的运行能耗得到优化匹配。所谓经济流速是一次投资与经常费用之和最小时的流速为经济流速，而相应的管径即为经济管径。所以选择输配水管管径的大小涉及投资与耗电的大小，管径大基建费用高，电费却省，管径小一次

7、投资省，但水头损失大，水泵扬程高，电费高。喷规在管道水力计算9.2.1条也规定"管道内的水流速度宜采用经济流速，必要时可超过5m/s，但不应大于10m/s。然而，自喷给水管道只是在火灾时短时间运行，不同于生产、生活给水管道始终处支运行状态，故可以提高流速，减小管径以降低基建投资，这同样是经济的。但同时如果自喷系统管内水流速度较高，水头损失就较大，配水管支管管径往往就会偏小，造成在设计流量下，喷头实际保护面积可能满足不了规范有关作用面积的要求。此时尽管作用面积内喷头动作时，其平均喷水强度符合规范，但上下游喷头因压力不同而流量有差异，此外，由于管径小，管网水头损失大，消防水泵扬程高，喷头

8、喷水极不均匀，其出水量必然过大，将过早地用完消防贮水。因而管道流速宜采用较低值，管径小时尤宜采用低值。同时，从上述分析中也不难看出，喷规中提到的经济流速应是经济性、合理性、可靠性与安全性的统一，并非能常意义上的经济流速。结合工程算例分析有关手册与文献介绍3-6，配水干管和配水支管设计流速一般不宜超过3.5m/s，常用1.8-2.8m/s。这种做法能够较好地满足喷规表5.0.1、表5.0.5及9.1.4条的有关作用面积和喷水强度的规定，且配水管网水头损失较小，消防水泵的扬程较小，喷头出水不均匀性较小，消防贮水量可得到合理使用，是比较安全、经济、合理的。 最不利点处水压：最不利点水压一般为0.1M

9、Pa，最小不应小于0.05MPa。过去大家习惯认为0.05MPa是针对屋顶水箱高度往往难以满足最不利喷头压力值而提出的，在消防泵、增压设施扬程计算时，不存在这个问题，都得取0.1MPa，但实际上情况并非如此，甚至可以说对于某种类型的自动喷水灭火系统，按现行规范，一般应取0.05MPa，而非0.1MPa。 (3) 减压与减压措施喷规第8.0.5条规定"配水管道的布置，应使配水管入口的压力均衡。轻危险级、中危险级场所所各配水管入口的压力均不宜大于0.4MPa"而自动喷水灭火系统中，不但存在着低层管道系统中水压不平衡，即使在同层中，当保护面积较大时，由于设计是按最不利工作面积计算

10、，同层中有利工作面积内喷头的水压也有剩余，所以习惯是对连接有利工作面积的配水管或配水干管予以减压，减压的方法可以采用设置减压阀、减压孔板、节流管以及缩小有利工作面配水支管的管径等方法增加沿途水头员失达到减压目的。3 消防水箱供水矛盾主要在动力源的可靠性，矛盾的暴露表现在水系统，但涉及面较宽。按建筑分类分别采用一级供电或二级供电加柴油机，临时高压给不系统应设消防水箱等规定。我国现行水防技术规范对消防水箱的规定，存在顶层、远端等不利部位欠压的问题，使消防水箱对这些不利部位不能发挥应有的作用，而按高规规定设置的增压设施，由于水量偏小同样未能妥善解决这个问题。自动喷水灭火系统用于扑救初期火灾，在喷头动

11、作的时间段，火势将以每秒几千瓦至十几千瓦的速率增长，此时开放喷头如不能按规定强度连续喷水，系统效能将显著降低，甚至给火灾入迅猛燃烧阶段以可乘之机，其结果将导致灭火的难度增大使火灾超出系统的控灭火能力。为保证喷头开放后连续喷水，并保证对不利部位火灾的及时有效扑救，喷规第10.3.1、10.3.2规定："采用临时高压给水系统的自动喷水灭火系统，就设高位消防水箱，其储水量应符合现行有关国家标准的规定。消防水箱的供水，应满足系统最不利点处喷头的最低工作压力和喷水强度。建筑高度不超过24m、并按轻危险级或中危险级场所设置湿式系统、干式系统或预作用系统时，如设置高位水箱确有困难，应采用5L/s流

12、量的气压给水设备供给10min初期水量。对此可作如下考虑：(1)设置消防水箱(气压给水设备)的目的在于：一是利用位差为系统提供准工作状态下所需要的水压，达到使管道内的充水保持一定压力的目的；二是提供系统启动初期的用水量和水压，在供水泵因动力或机械故障不能正常投入运行的紧急情况下应急供水，确保喷头开放后立即喷水，并为首批开放的喷头扑救初期火灾，提供维持10min喷水的用水量，控制初期火军和为消防队增援灭火争取时间。(2)采用临时高压给水系统的自动喷水灭火系统，凡超过24m的高层建筑或其它严重危险级和仓库危险级的建筑均应设高位水箱，且不可用气压给水设备替代。由于位差的水箱供水期间，系统的喷水强度不

13、足，因此将削弱系统的控灭火能力。为此，要求消防水箱满足供水不利楼层和部位喷头的最低工作压力和喷头强度。但单独设置稳压泵，仅能为系统稳压而不能提供灭火初期的用水量。高规在条文说明里指出，设置增压设施的目的主要是在火灾初起时，消防水泵启动前、满足自动喷水灭火系统的水压要求。对增压水泵，其出水量应满足一个自动喷水灭火系统喷头的用水量。对气压罐其调节水容量为5个喷头30s的用水量，即5×1×30150L。现行国标图集-消防增压稳压设备选用与安装(98S176)是按高规编制的，其功能只是解决火灾初期时，即消防主泵启动前，确保具有足够消防压力的30s储水量进行初期火灾扑救，直至消防主泵

14、全负荷启动运行。对于合用消防水箱的增压设施，450L容量也仅能在紧急情况下向3只喷头供给不足2min水量(3×1.33×120479L)。可见以前的屋顶水箱和稳压设备联合工作方式已不能满足喷规的要求，而架高水箱在建筑设计中由于多种因素的影响又很难实现。为此喷规规定了最低工作压力0.05MPa的要求。但到底是动压还是静压，规范没有强制限定，这就给设计带来了难度的同进也有了一定的灵活性。实际上，0.05Mpa应是动压而非静压。0.05Mpa是指系统最不利点处喷头最低工作压力，同时规范在条文说明中指出;如果顶层最不利点处喷头的水压要求为0.1Mpa，则屋顶水箱必须比顶层喷头高出1

15、0m以上，将会给建筑造型和结构处理带来很大困难。根据上述情况和参考国外有关规范，将最不利喷头的工作压力确定为0.05Mpa。(3) 高位水箱的高度，建规规定设在建筑物的最高处(建规送稿也有静压0.07Mpa的要求)，高规要求保证顶层消火栓0.07Mpa的静水压力。若按建筑层高3m考虑，最不利消火栓上0.07Mpa，对自喷静水压刚好在0.05Mpa左右。为与相关规范达到协调一致，实际工程设计中，当水箱难以满足0.05Mpa动压要求，在动力可靠、管理到位的情况下，以0.05Mpa静压考虑也是可行的。(4) 高位水箱的设置保证0.05Mpa动压，在不宜采用增压稳压装置的情况下，就得将水箱架高。由于水

16、箱中的水要经报警阀、水流指示器后才到达最不利喷头，加上管钱较长，即使火灾初期，自喷用水量很小，也是有一定的水头损失的，具体可详细计算后确定。但一般在高出7m(这个高度在建筑上稍微处理一下是能满足的：跃层电梯机房水箱垫高)以上的话，可以满足规范的要求。(喷规按照相关的现行标准，规定湿式报警阀、水流指示器局部水头损失取值为0.02MPa，明显偏高，至少在校核水箱高度时要比这小得多!)。另外，可通过采用缩小喷头间距、增大管径减少损失等其它措施来满足最不利点喷头在最低工作压力(0.05Mpa)下的喷水强度。 (5)喷规10.3.2规定的5L/s、10min的消防贮量的气压给水设备，若采用隔膜式气压罐，

17、由一般需2个立式或1个卧式。立式的可选用91SB3-132中SBQL1600×1.5的两个就可以了。系统占地约35m2，价格约3.2万元左右。部分人对此规定有此争议，但考虑到新规范比较强调火灾的初期灭火，强调系统能在尽量快的时间里出水，和火灾发生后人们习惯于断电的思维，为增加安全性，减少部分使用面积，增加一些造价是合理的、值得的，相信随着经济条件的不断提高安全问题会越来越得到重视，同时，随着经济条件的不断提高，设施也会越来越有利于工程。此外，考虑到建规第8.8.5条"消防水泵应在火警后5min内启动，并在火场断电时仍能正常运转。及"建规"送审稿等8.7.

18、9条"消防水泵应保证在火警后自动启泵，并在火场断电时仍能正常运转"的规定，水罐的贮水是否可以根据建规按5min考虑，也值探讨。但个人认为，尽管水泵的启动时间可以很快，考虑到与相关规范的协调一致，以及喷水的不均匀性和其它因素，作为保障措施，气压罐还是应贮存10min用水。Design For Sprinkler Systems And Important Problems Within Syste Design1 Arrange of the sprinkler headThe reasonable arranges to spray a sprays automatical

19、ly the water extinguishes fire the system design the safety and economic key.The Code of design for sprinkler systems compares to emphasize of is a function area inside to spray the strength of water with spray the aqueous and even and spray the head open in good time.For the radius sprayed every, o

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37、ire system discharge that a havings for of pressure badly to higher branches in pressures proceeding discharge revising, then function area inside passing by discharge revising after spray an a discharge, here later on of the tube a discharge no longer increases, computing only to lose along the dis

38、tance tie a water head, hading been calculating till the tube net the point of departure.When the actual a fire take place, is a fire source to light to report the radiate direction generally and all the on all sides extending spread, but only have the accidental fire area above spray the head would

39、 open to spray the water .Therefore adopt the function area protection method and spray in function area only a just compute to spray the amount of water is reasonable of.At the same time because of a fire hour the influence between convection and breeze, the shape of the function area to report the

40、 is more reasonable, and rectangle area when the piping water power computes also is the most disadvantageous.As a result this kind of" the rectangle area- orders the method" match the fire field is actual, science is careful, and wait with Europe and America the country connect the , isin

41、g reasonable and safe, ising also a Code of design for sprinkler systems recommend the method.(1) The rectangle area really settles:The shape of the function area is proper for rectangle, its long side runs parallel with to go together with the water a tube, not smaller function in its length area s

42、quare root of 1.2 times, spray the number if have the fraction and then enter integral.When go together with an actual length for taking care of the smaller the calculation value that side grow, the function area want to expand to and should go together with pipe line the close by a tube ascends of

43、spray head.(2) Economic current velocity with a little bit the most disadvantageous water pressure Economic current velocity in :Spray automatically the water extinguish fire the system most constitutes the part is a safety to goes together with pipe line way, but goes together with the pipe line a

44、tube path to really settles, not only affect to whole system build the price, but also relate to the system fire fight.Under the term that discharge is certain, the current velocity is the important parameter of the certain tube path.Adopting the economic current velocity is economic current velocit

45、y in general adoption in current velocity that the foundation main factor that the water supply system design, produce, life water supply piping, to make the of the piping set up the investment to can consume to get with usually sexual movement the excellent turning match.The so-called and economic

46、current velocity invests once with the recurrent expenditure it with minimum hour of current velocity is economic current velocity, but homologous tube path namely take care of the path for the economy.So the choice loses the pipe line that go together with the size takes care of the path involve th

47、e investment with the size that consume the electricity, taking care of the big in path set up the expenses high, electricity charges however province, tube the path is small an investing the province, but the water head loses big, water pump the distance is high, the electricity charges is high.The

48、 Code of design for sprinkler systems to compute in the piping water power 9.2.1 also rule" economic current velocity in flat-out proper adoption in water current in the piping, necessity hour can over 5 m/ s, but shouldn't over and above 10 m/ s.However, from just spray the water supply pi

49、ping at a fire hour short time circulates, different from produce, life water supply piping always a circulate appearance, so can increase current velocity, let up to take care of the since low inpath sets up the investment, this similarly economic.But at the same time if from spray the system tube

50、internal water current velocity a request for higherly, water head losing biggerly, going together with pipe line a tube tube path would usually being partial to smallly, resulting in while designing the discharge, spraying a the actual protection area may can not satisfy the norm the concerning fun

51、ction area.This time though the function area inside sprays an action, its average sprays the strength of water matches the norm, swims to spray up and down head discharge contain difference because the pressure is different, in addition, is small because of the tube path, tube the net water head lo

52、ses big, fire fight water pump the distance is high, spraying the head sprays the water the pole the asymmetry, its a water measures inevitable over big, will over use up the fire fight water early.As a result lower value in proper adoption in current velocity in piping, take care of the hour in pat

53、h is particularly proper to adopt the low value.At the same time, from the above analysis inside too not difficult see, the Code of design for sprinkler systems should be an economic current velocity that economic, rationality, dependable unify with safety sexually, not can often meaning( but involv

54、e all and not in its ruling and its elucidations!).Combination the engineering an analysis is relevant the manual introduces with cultural heritage the 3-6 , go together with the water fuck the tube with go together with a tube design current velocity general not proper over 3.5 ms/ s, in common use

55、 1.8-2.8 ms/ s.This kind of way of doing can than satisfy goodly the Code of design for sprinkler systems table 5.0.1, table 5.0.5 and 9.1.4 of relevant functions area with provision that spray the strength of water, and go together with the pipe line net water a the distance of for losing smallerly

56、, fire fight water pump smaller, spray an a water asymmetry is smaller, the fire fight amount of water can get the reasonable usage, is a comparison safety, economy, Reasonable.A little bit the most disadvantageous water pressure in A little bit the most disadvantageous water pressure is general for

57、 0.1 MPa, least shouldn't smaller 0.05 MPa.Past everybody's habit thinks a the 0.05 MPa are to aim at the roof water tank high degree the usually hard satisfying most the disadvantage sprays a pressure value but put forward of, when the fire fight pump, increases to press the facilities dist

58、ance calculation, nonexistent this problem, have to take a 0.1 MPas, but in reality the circumstance is really not so, even can say that spray automatically for the some category type the water extinguish fire the system, pressing current norm, shoulding take generally 0.05 MPas, rather than 0.1 MPa

59、s.Everybody knows, spraying because of the underground garage an arrange, on toing press the Code of design for sprinkler systems the inside the dangerous class, two is should in the parking lot above establish, three is to is limited by construction pillar net to cover with other and its processed influence, make its spray a general arrange than , this time and compute by one more, on ising to design the discharge be partial to big, can amount to a 40 Ls/ s( do not include the protection cool off the