原文：
供水管网把从水厂送出的自来水输配到千家万户，因此供水管网分布于城市的每个角落，其长度少则上百公里，多至数千公里。 　　水的不可替代性和人们生存的必需性，决定了供水管网安全运行的重要性。但是由于主客观多方面的原因，管道往往会出现一些故障，管网总是要不断更新改造，用水户经常要有增减，因此局部管段的停水现象难以避免。为了缩小停水范围，在管网内适当地安装控制阀门是十分必要的。因此在一座城市的供水管网中，阀门数量成千上万，并无规则地分布于城市街道下面。 　　供水管网上的阀门操作并不频繁，长期待命，一旦需要，阀门应能关闭迅速，截流可靠；平时要求阀门开启要到位，减少管段的水头损失，所以 阀门是一种“养兵千日，用兵一时”的控制设备；阀门的完好率，关系到阀门的选型、阀门的制造、管路的设计、阀门的组装、阀门的启闭及阀门的管理，当然最主要的原因还是阀门的质量。 　　阀门在供水管网中数量多、分布广、作用大。因此，在阀门选型、检验、性能和管理上均有许多问题值得研讨。 一、阀门的选型 阀门有蝶阀、闸阀、球阀及旋塞阀等几种，在供水管网中使用的范围不同。为了降低管道覆土深度，一般口径较大管道选配蝶阀；对覆土深度影响不大的，力求选配闸阀；球阀及旋塞阀铸造及加工难度大，价格较贵，一般适用于中小口径管道上。近几年由于铸造技术的改进，采用树脂砂法铸造，可避免或减少机械加工，从而降低了成本，因此球阀用于大口径管道上的可行性值得探索。至于口径大小的分界线应各地按具体情况考虑划分。 　　蝶阀的主要缺点是蝶板占据一定的过水断面，增加一定的水头损失；闸阀虽无此问题，但大口径立式闸阀的高度影响管道的覆土深度，大口径卧式闸阀的长度增大了管道占据横向面积，影响其他管线的安排；球阀及旋塞阀则保持了闸阀单、水流阻力小、密封可靠、动作灵活、操作及维修方便等优点。旋塞阀亦具有类似优点，惟过水断面不是正圆形。 　　近年来，国内不少阀门生产厂家研制软密封闸阀，这种闸阀和传统的锲式或平行式双闸板式闸阀相比有如下特点： 　　１．软密封闸阀的阀体、阀盖采用精密铸造法铸造，一次成型，根本不再机械加工，不使用密封铜环，节约有色金属； 　　２．软密封闸阀底部无凹坑，不积存渣物，闸阀启闭的故障率低； 　　３．软密封衬胶阀板尺寸统一，互换性强。 　　因此软密封闸阀将是闸阀的发展方向，也是供水行业乐意采用的一种阀门。启闭软密封闸阀时，千万不要关闭过死，只要达到止水效果即可，否则不易开启或衬胶剥离。 　　供水行业使用的蝶阀多数是软密封蝶阀，针对蝶阀在安装过程中胶圈易受损影响密封性，不少厂家推出金属密封蝶阀代替胶圈密封蝶阀。金属密封蝶阀由于密封件的弹性较小，一般采用偏心结构，特别是用三维偏心结构较为合理。 二、阀门的性能与测试 　　阀门的特殊性要求其质量可靠、性能优异。评价阀门的性能与性能测试时，应注意以下几点： 　　１．阀门在工作水压下启闭灵活、轻便，在工作水压下用扭矩扳手检测开启力矩。 　　２．阀门关闭严密，在１．１倍工作水压下不渗漏或渗漏符合标准要求（金属密封的蝶阀），这要求阀门的两侧轮流承压、分别检测，且多次启闭达到同样效果。要求各种口径、不同类型的阀门均应在生产厂家和有检测资格的单位进行带负荷启闭的寿命检测。这种检测也包括对阀轴密封效果的评价。 　　３．阀门过流能力要强，特别是蝶阀，蝶板的过流阻力要小，过流有效面积要大。这要求各种口径、不同类型的阀门都应进行流阻系数的测定。 　　４．阀体承受水压的能力应与管道一致，也就是阀门开启状态下，阀门能承受管道试验压力的要求。 三、阀门的内衬与外防腐 　　阀门是输送饮用水的设备，阀体内衬一定要xx、耐腐蚀、耐磨、光洁，使水流阻力尽可能小。如阀门的压板、螺栓和蝶板材质不同，很容易发生电化学腐蚀，腐蚀生成的铁锈延伸至密封面，影响阀门的密封效果，另外阀门安装在阀井内，浸泡在水中，防止锈蚀是很重要的，因此内衬要覆盖完善，防止产生锈蚀造成供水的二次污染。 　　阀门的外防腐可采取抛光清砂后，再作静电喷涂xx环氧树脂防腐，也可以先刷１－２遍红丹漆，于后再刷两遍防锈漆。 四、阀门的运行管理 　　阀门能否启闭良好，不仅要阀门选型恰当、产品质量好、精心施工安装，而且还要周到地管理，才能起到“养兵千日，用兵一时”的效果。良好的运行管理体现在以下三个方面： １．技术资料齐备 　　阀门的技术资料包括阀门出厂说明书，阀门购进后的检验合格单，阀门的组装及位置卡，阀门的检修记录。对于街道的变迁，阀门卡片应及时更新，力求建立ＧＩＳ管理系统。 　　２．阀门运行管理周到 阀门运行管理的质量要求包括阀门应关闭严密，阀门轴杆密封填料处不串漏，阀门启闭轻便、指示完好。阀门运行管理日常工作包括阀门历次启闭操作单的报批记录及操作记录的完善，阀门定期检测的启闭记录等。对于长期没有操作过的阀门，根据口径的大小，定出不同的检测周期是必要的。对于发现的故障应提出维修方案，及时处理，特别是关闭后无法开启的阀门应像抢修爆管一样进行紧急处理。 　　３．阀井状况良好 　　阀井状况包括阀井砌筑符合行业标准和设计规范，井盖与路面衔接完好，操作阀门的孔位准确，井内无杂物及污水，阀门表面无锈斑。在条件许可的情况下，大口径阀门井应考虑井内空气可长期对流的技术措施。对阀门井应定期巡视，对井盖的丢失和损坏应及时处理。

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译文：
Water supply network to send the water from the transmission and distribution to millions of households, so the water supply pipeline network located in every corner of the city, the length of anywhere from several hundred kilometers up to several thousand kilometers. Water is irreplaceable and the people the necessity of survival, the decision of the water supply network the importance of safe operation. However, due to various objective and subjective reasons, tend to be some trouble pipeline, pipeline network, must constantly update the transformation of water users must change often, so the phenomenon of partial disruption of water supply pipe is difficult to avoid. In order to narrow the scope without water in the pipe network within the proper installation of control valves is necessary. So in a city water supply network, the number of tens of thousands of valves, there is no regularly distributed in the city streets below. Water supply line valve operation is not frequent, long-term stand-by, if necessary, the valve should be closed quickly, closure and reliable; usually required to open the valve to be in place to reduce the pipe head loss, so the valve is a kind of "the idea that Japan, used for one day, "the control equipment; valve intact rate, related to the valve selection, valve manufacturing, pipeline design, the valve assembly, valve and valve opening and closing of the management, of course, The main reason is the quality of the valve. Valve in the water supply pipe network number, widely distributed in function. Therefore, valve selection, testing, performance and management are many issues worthy of discussion. First, the selection valve Valves are butterfly valves, gate valves, ball valves and plug valves, etc. Some, in the water supply pipe network used in the coverage is different. To reduce pipeline overburden depth, large diameter pipes generally matching butterfly; little impact on the overburden depth, and seek matching valve; ball valve and plug casting and machining difficult, more expensive, generally applies to small and medium caliber pipe. In recent years, improvements in technology as casting, resin sand casting method can avoid or reduce the mechanical processing, which reduces costs, ball valve used for the feasibility of large-diameter pipe is worth exploring. The aperture size of the dividing line should be considered around the divide-by. The main disadvantage is the butterfly valve plate occupy a certain cross section, that the additional head loss; valve substance though not in this issue, but the large-diameter vertical pipe valve of the high impact of overburden depth, large diameter horizontal gate valve increased the length of horizontal pipe occupied area, affecting other pipeline arrangement; ball and plug valves are maintained single valve, water resistance, reliable sealing, flexible movement, operation and convenient maintenance. Plug valves also have similar advantages, but not being circular cross section. In recent years, many domestic manufacturers developed soft-sealing valve gate valve, this valve and the traditional style or Parallel Double Figure valve plate than the following characteristics: 1. Soft sealing gate valve body, valve cover using precision casting in metal, a shape, there is no longer machining, do not use sealed copper ring, saving non-ferrous metals; 2. Soft sealing gate valve at the bottom of no pit, no accumulation of slag material, valve opening and closing of the failure rate is low; 3. Soft seal with rubber valve plate size uniform and interchangeable. So soft sealing gate valve will be the development direction of the industry is willing to adopt a water supply valve. Soft sealing gate valve open and close, do not close off dead, as long as you can achieve the sealing effect, or difficult to open or with rubber stripping. Most of the water supply industry is using the soft seal butterfly valve, butterfly valve in the installation process for the apron easily damaged sealing effect, many manufacturers have introduced instead of rubber ring seal metal seal butterfly valve. Metal sealing butterfly valve seals less flexibility because, generally eccentric structure, especially the use of three-dimensional asymmetric structure is more reasonable. Second, performance and test valve The special requirements of its quality valve reliability, excellent performance. Performance evaluation of valve performance testing and should note the following: 1. Open and close the valve under pressure at work a flexible, lightweight, water pressure at work to open the next moment with torque wrench testing. 2. Close the valve tightly under 1.1 times the working pressure without leakage or seepage standard requirements (metal sealed butterfly valve), which in turn required pressure on both sides of the valve were detected, and repeated opening and closing achieve the same effect. Requirements of various calibres, different types of valves should be testing at the manufacturer and qualified units open and close with a load life test. This testing also includes evaluation of the valve shaft seal. 3. Stronger than the valve flow capacity, in particular butterfly, butterfly board over-current resistance to be small, over-current effective area larger. This requires a variety of caliber, different types of valves should be flow resistance coefficient. 4. The ability to withstand water pressure valve should be consistent with the pipeline, which is the valve open state, the valve can withstand the test pressure piping requirements. 3, valves lining and external corrosion Valve, the transportation of drinking water equipment, body lining must be non-toxic, corrosion, wear, bright and clean, so water resistance as small as possible. If the valve plate, bolts and disc material difference, it is prone to electrochemical corrosion, rust and corrosion generated extending sealing surface, affecting the sealing effect of the valve, another valve installed in the valve wells, soaked in water to prevent corrosion is very important, so perfect liner to cover, preventing secondary pollution of water supply caused by corrosion. Corrosion can be taken outside the valve polished sand, then for electrostatic spraying non-toxic anti-corrosion epoxy resin can also be 1-2 times the first red lead paint brush, then brush on twice rust. 4, valve operation and management Valve can open and close well, not only to proper valve selection, product quality, well construction and installation, but also thoughtful management can play a role, "the idea that Japan, used for one day" effect. Good operational management in the following three aspects: 1. Technical details are available Valve valve factory technical information including specifications, valve quality certification after purchase, the valve assembly and the location of cards, valve maintenance record. The street changes, the valve should be to update the card, and strive to build GIS management system. 2. Valve operation and management thoughtful Valve operation and management of quality requirements, including the valve should be closed tightly, the valve shaft seal is not padding string leak, the valve opening and closing light, indicating intact. Valve operation and management daily operations, including opening and closing valves previous approval the list of records and operational records of the perfect valve opening and closing records of periodic inspection. Not operate for long-term off valve, according to the size of caliber, set different testing period is necessary. The failure to discover the maintenance program should be put forward, in time, particularly after the closure of the valve can not open pipe explosion should be the same as the repairs were urgently addressed. 3. Valve shaft in good condition Well conditions, including valve shaft valve masonry industry standard and design, covers well and the road link, operation of the valve hole position accuracy, wells and sewage debris-free, valve surface without rust. Under the conditions permit, large caliber air valve well to consider the well can be a long-term flow of technical measures. Should be regular inspections of the valve well, and covers the loss and damage should be processed.