原文：
随着中国环境意识的加强和能源结构的改变，我国城市燃气事业有了长足的发展，燃气种类从单纯煤制发展到多种气源并举，九十年代后期，中国天然气资源的连续开发、建设和利用，促使中国城镇天然气发展进入了一个新的时期。 天然气输配储存的压力相对人工制燃气高，在人口密集的城镇中安全储存和输送是极为重要的。试想如果因燃气阀门选型不当或质量不佳，以至引发的泄漏、停产事故，轻者影响社会正常生活、生产，重者给国家、人民生命财产带来重大损失。因此笔者认为：阀门是燃气输配、存储系统安全运行和检修、改造、发展必不可少的重要设备，从事燃气行业的领导和技术人员对燃气阀门的选用必须引起足够的重视。本文将对燃气阀门的材质选用、结构造型、工况选型和有关标准提出看法，仅供燃气行业工程选型参考。 一、中国燃气阀门现状 上世纪八十年代以前，没有燃气专用阀门，只能沿用水阀门。改革开放以来，经济建设的发展促进了燃气制造业的发展，阀门生产厂家注重了研伟燃气专用阀门，当时主要从结构的设计上来克服煤制气中含有较多的杂质，尤其是焦油、芳香烃和粉尘混合形成的"煤气胶"影响阀门密封或"咬死"阀杆的问题。天然气的开发和应用，使燃气的性质发生了变化。天然气较煤制气洁净干燥，但含有砂粒质粉尘，压力也较煤制气高(煤制气压力一般在0.05～0.3MPa，天然气一般在0.4～1.6MPa甚至更高)在高压力作用下砂粒粉尘将对阀门内腔形成较强的冲刷作用，多种气源工况条件下，因此如何在城镇市区、门站、储存设备、地下管道上选用燃气阀门是摆在我们面前的新课题。 二、安装在地下管网上的阀门应满足的要求 要有足够的"强度"和"刚度"--"强度"是阀门应能承受管线内输配燃气的{zg}压力，更重要的是必须具备足够的"刚度"即在承受地下管网受到各种外力情况下仍能保持阀门不发生变形，可靠保证阀门的密封性能： 1、尽可能降低阀门的结构高度(指阀门流通断面中心线到阀顶的高度)以减少埋管深度； 　 2、阀门顶部应装有全封闭的启闭指示器，便于操作者随时看清阀门所处状态，是安全操作的重要条件； 3、全通径设计，降低流阻，便于通过管道清扫器或管道探测器，还应满足不停输封闭式开孔机在管道上开孔； 4、可靠的密封性能，CJ3055-95《城镇燃气阀门的实验与检验》标准规定：软密封阀门在1.1倍公称额定使用压力下不允许有任何察觉的内泄漏、硬密封阀门在1.1倍公称额定使用压力下允许的内泄漏量小于0.3DNmm3/s，这个要求是比较严格的，例如：500mm公称通径的燃气阀门每分钟的内泄漏量不能大于9毫升(普通饮水杯的容量是200毫升)至于外泄漏是{jd1}不允许的； 5、使用于地下管网的燃气阀门的壳体要耐腐蚀，建议根据管线的输送介质和使用压力采用不同的壳体材质； 6、阀门的零部件设计应考虑采用少维护、免维护结构，尽可能减少检修保养的工作量，减少因阀门检修保养而封闭道路，影响交通； 7、地下管线阀门绝大多数为人力启闭，要求阀门的启闭扭矩小，全程转圈数不能太多，事故发生后能够尽快切断气源； 8、我国城市道路地下各种管线拥挤，错综复杂，不宜开挖地下室窨井，因此推荐直埋式阀门。 三、燃气阀门的阀体材质选用 根据燃气管线的使用压力合理选用阀门壳体材质，既宫满足管线的安全运行又能达到减少造价，物尽其用的目的。 1、中压B级(0.2MPa)以下的输配管线，建议采用灰铸铁制阀门，其{zd0}的优点是防腐蚀性能好，而且价格便宜，非常适用于地下管线； 2、中压A级(0.4MPa)以下，甚至于高压B级(0.8MPa)以下，建议选用球墨铸铁或铸钢制造，侧重推荐选用球墨铸铁。例如：球墨铸铁牌号QT400--18与铸钢牌号WCB相比较，前者的机械性能不亚于后者，而防腐蚀性能和铸造工艺都优于铸钢，价格也低于铸钢(一般是铸钢的70%左右)因此球墨铸铁阀门的整体性能和价格都优于铸钢阀门，在上述压力范围内尽可选用球墨铸铁阀门，但是特别要注意对球墨铸铁材质质量的监控； 3、在高压A级(1.6MPa)或压力级别更高的地方，建议选用铸钢制阀门，制造4MPa压力级别以下的阀门一般选用WCB牌号； 4、最近几年，各地煤气公司开始使用PE管，PE管目前使用于0.4MPa压力级别以下。 PE球阀也已问世，该系列球阀可直埋，密封性能较好。但是目前PE球阀价格较高，尤其是大于100mm通径以上的球阀，PE球阀目前处于推广试用阶段。 四、中国燃气行业目前使用的几种燃气阀门简介 1、RX系列油密封式旋塞阀 上世纪八十年代，我国燃气主要是人工煤制气，人工煤制气中有较多的杂质和"煤气胶"，原来传统使用的单闸板契式水闸阀越来越不能适应燃气工况的需要，这类阀门普遍存在"关不严"和阀杆咬死的问题，我们参考日本技术研制而成的RX系列燃气用油密封式旋塞阀，解决了关不严和阀杆咬死的问题。其主要技术特点： 采用硬密封结构，使其具有刮胶作用；密封面与煤气杂质不接触，腔内无阀杆，不存在阀杆咬死的问题：专门研制了抗煤气介质侵蚀的密封油脂和O型圈，提高了旋塞阀性能，适应我国燃气工况，得到了同行们的好评。但是，油密封式旋塞阀也有其弱点，{dy}、不与管线同通径，是管线流通面积的75%左右，增加了流阻和涡流，也无法通过清管器；第二、启闭阀门前需加注油脂，给使用者带来不便；第三、公称通径一般为DN300以下，DN400以制造难度较大，DN600以上太重用户不欢迎； 2、RZ系列燃气用平行双闸板闸阀 随着燃气事业的发展和煤气厂的纷纷建立，需要较大甚至特大公称通径的燃气专用阀门，RZ系列燃气用平行双闸板闸阀针对人工煤气形成的问题给予一一解决，{zd0}通径达1600mm。 {dy}、平行双闸板闸阀在启闭过程中能刮去密封面上的"煤气胶"，解决了煤气杂质黏附在密封面上影响阀门密封的大问题； 第二、装有阀杆保护套，使阀杆不受"煤气胶"的侵蚀； 第三、阀门下部带有排污孔侧盖，可以清扫落在阀腔底部的 ； 第四、全通径设计流阻小，又能通清管器； 第五、阀体采用特殊设计的"鼠笼框架式加强筋"减轻了阀门总体重量，增强了壳体强度和刚度； 第六、RZ系列燃气闸阀壳体选用灰铸铁制造，价格低廉；第七、该系列闸阀带有全封闭的启闭指示器，使操作者清楚了解阀门所处状态。 该系列闸阀问世以来，迅速在全国煤气行业推广使用，得到了较好的评价，至今仍在各地煤气公司中压管线上使用； 3、RQZ系列球墨铸铁制燃气用平行双闸板闸阀 随着我国天然气进入城镇，笔者与上海煤气总公司、苏州市燃气设备阀门制造有限公司根据天然气的特点又研制了RQZ球墨铸铁制燃气用平行双闸板闸阀，该闸阀除保留了RZ系列闸阀的特点外，选用的材质增强了阀门的耐磨性，同时将压力等级提高到了高压B级； 4、蝶阀 蝶阀相比上述几种阀门轻便，口径大，价格较低，八十年代初期部分煤气公司曾-度采用蝶阀，经过十年左右的使用，普遍认为效果不好。{dy}、蝶阀的密封付隔离宽度太窄，容易造成阀瓣关闭过程中过头或不到位，影响密封；第二、阀瓣在阀腔中部，流阻大，不能通过清扫器；第三、由于密封付中-部分是橡胶或聚四氟乙烯，在气体冲刷中易损坏或脱落，使用年限短。实践证明除特殊位置，燃气管线上不宜采用蝶阀，一些已经使用蝶阀的煤气公司正在(或考虑)更换其他阀门； 5、平板闸阀 平板闸阀是燃气管道近年来才开始使用的通用阀门，全通径时流阻小，两边的密封由聚四氟乙烯或橡胶O型环压紧在闸板上形成，这种阀门在全关或全开时不能做到中腔无气，不便于用户抢修时迅速判断阀门是否关严，要达到中腔无气则启闭扭矩会迅速增加；有些厂家制成缩径的，列如DN200口径，内径只有150mm，用户特别要注意。因此这种平板闸阀适用于压力级制较低，公称通径较小的场合。 6、TRZ系列弹性密封燃气闸阀 TRZ系列弹性密封燃气闸阀是区别于平板闸阀的一种燃气专用阀门。该阀的特点与固定球球阀的弹性阀座结构相似，闸板两边密封座圈采用弹性浮动式结构，密封面在启闭及启闭过程中始终紧贴在一起，而且能补偿密封付的磨损，适用于高压力级制的场合；该阀在全开、全关时阀腔内可达到无气，即使放散完阀腔中剩余的燃气，阀腔内仍无压力，使用者可放心在阀门下游管道施工，大大缩短了施工前的停气准备工时，得到了用户的首肯。 TRZ系列弹性密封燃气闸阀的连接形式有法兰式和焊接式两种，法兰式是传统的连接方式，焊接式可将阀门与管道直接焊接，节约铺管费用；两种阀门均可直埋，避免了不必要的窨井，给施工带来了方便。 TRZ系列弹性密封燃气闸阀全开时，似管线同通径的一段管道，流阻极小；且所有密封面暗藏，不与介质接触，对人工煤制气来讲，"煤气胶"不可能黏附在密封面上，对天然气来讲粉尘砂砾冲刷不到零部件上。 总而言之，TRZ系列弹性密封燃气闸阀适用于燃气管线，特别适用于地下燃气管线，从国外考察的情况来看，许多国家的天然气管线上都采用弹性平板闸阀，同公称通径弹性平板闸阀与球阀相比，都有防火功能，而价格比球阀低30%左右，使用效果相同。TRZ系列弹性密封燃气闸阀的缺点是结构高度较大，有4个公称通径的高度，因为埋在地下，管线中轴线上面的高度与通常闸阀相同，其缺点还不明显，主要是下半部高度较通常闸阀大-些，施工时埋设深度大些，但-般不影响管线铺设； 7、RQ系列球阀 球阀是因其流阻小、结构高度小、密封性能好等优点而得到广泛应用，近年来得到迅速发展。 球阀有两种，一种是浮动球阀，即球体在阀腔内可浮动，依靠两端的密封座压紧球体而稳定。这种球阀只能用于公称通径较小(150mm以下)或压力级制较低(0.8MPa以下)的场合，否则启闭扭矩会很大，给使用者带来困难。 在公称通径大于DN200或压力级制较高的场合，需用固定球结构，固定球阀在阀门全关时，压在球体上的作用力传递到上下两个球体支撑轴上，大大减少操作力矩，压力增加而扔矩不会明显增加，便于操作者使用。 RQ系列固定球球阀是专门为燃气行业设计制造的，该阀结合了国内外各类球阀的特点，再根据中国国情开发研制，适用于燃气长输干线、城市燃气设施。该阀除具有一般球阀的优点外还有明显的特点。{dy}、耐火性，火灾高温烧毁密封座上的聚四氟乙烯材料后，金属密封座及各个密封部位均能形成金属对金属的密封结构，阻止燃气介质扩散，防止灾情继续扩大；第二、防静电，球阀在启闭过程中形成的静电极易点燃燃气，该球阀将静电导入地下，确保设备安全；第三、限位加锁，球阀是旋转机构，容易造成360度旋转，除了有限位机构外再可加锁，防止操作人员误操作或非操作人员擅自操作而引发的事故；第四、球阀阀杆密封设计有防阀杆冲击装置，并采用特殊O型圈密封，力矩比同类球阀小，操作轻便，启闭快速。 五、几种特殊用途的燃气阀门介绍 1、调压器用紧急切断阀 调压器用紧急切断阀是燃气输配系统中的重要安全保护装置。紧急切断阀是在截止阀上位或侧位安装紧急脱扣机构，也有与调压器本体连成一个整体，也有与过滤器连成一个整体，其作用是在调压器失灵，造成超压或失压后紧急关闭气源，保证安全。天然气在城市中的大量使用，提高了管网压力级制，调压器的失灵将给城市带来灾难性的后果，国内燃气行业对此越来越重视。国内选用的产品还没有形成一定的趋向，进口的、合资的、国产的，良莠难分，选用需谨慎。RAQ系列燃气紧急切断阀是与过滤器连为一体，结构新颖紧凑，灵敏度高，能在设定的超压(300mm/H2O)和失压(180mm/H2O)迅速切断调压器气源，确保用户安全； 2、燃气紧急切断阀 燃气锅炉、燃气空调、燃气设备在发生燃气泄漏或其他灾情时，紧急切断阀快速切断燃气来源，防止灾情扩大。目前燃气紧急切断阀在国内还没有普及，随着环保意识和安全意识的加强，以及燃气事业的发展，燃气紧急切断阀必定会得到人们的重视。燃气紧急切断阀是保障安全性质的阀门，与自动化监控设备连机，执行关阀指令，因此燃气紧急切断阀都是电动阀门，据现有资料反映该类阀门有两大类型，一类是电磁阀，一类是电动阀。由于燃气紧急切断阀要求高，主要是快速、密封、流阻小、口径规格安等，现有的电磁阀、电动阀都有一定的缺陷，不能满足其所有要求。下面对这些阀门逐一进行分析： {dy}、电磁阀，目前大多选用进口电磁阀，电磁阀速度快，但是流阻大，是截止阀中流阻{zd0}的，压力损失大，而且口径小，大口径的电磁阀制造困难，一般只能做到DN150以下，价格昂贵，如配备大口径的电磁阀以满足通径要求，技术经济比指标就很差。有些电磁阀是靠电磁场吸住开阀，一旦失电，哪怕瞬间失电阀门就关闭，不符合工况实际。脱钩式电磁阀，通电脱钩关阀，灵敏度很高，速度很快，因为用直流低电压，有一点干扰或电源"晃动"就会产生误动作，影响正常生活和生产； 第二、电动蝶阀，价格较低，容易做成大口径，启闭速度较闸阀快，较电磁阀慢；流阴较电磁阀小，较闸阀大；密封性较电磁阀和闸阀都差，而且由于密封隔离宽度小，快速启闭的速度冲击容易造成启闭不足或过头的现象； 第三、电动闸阀，价格较电动蝶阀高，流阻小，密封性好，但是速度慢，达不到紧急切断的要求； 第四、球阀，流阻小，密封性好，但是市场上国产或进口的电动球阀，启闭速度一般在15～30秒，还不能满足快速的要求，用户对紧急切断阀启闭速度要求一般在10秒以内，电动球阀有许多优点，只要在启闭速度上改进提高就能成为理想的紧急切断阀。 RKQ紧急切断电动球阀集合了球阀的优点，启闭速度达到3.75秒，填补了国内外空白，而且在结构上设计有防静电和防火功能，电器设备可与燃气泄漏xxx、灾情控制设备连机，又可与风机等辅助设备连控，整体设计符合DBJ08--65--97《城市天然气管道工程技术规范》价格比同类进口产品低得多。一经问世即被燃气用户所接受，并得到好评。 3、燃气止回阀 燃气储配站的压缩机往往需要配置止回阀，防止燃气回流进压缩机。水用止回阀在燃气行业已经淘汰，一般燃气止回阀的主要缺点是阀板随着压缩机往复运动而颤动，与阀体碰撞发生很大的响声，容易损坏阀板；第二是密封性差。R型系列燃气止回阀较好地解决了这些问题。该系列止回阀的密封付将其他止回阀的90度改为75度，使阀板向阀座形成-个自然压力，同时阀板外结构再加上可调节平衡锤，解决了声响问题；密封付改用聚四氟乙烯改善了密封性能，杜绝了"回气"现象，R型燃气止回阀问世以来已逾十年，使用效果很好。 六、燃气阀门有关标准 燃气阀门在燃气行业中占有重要的地位，建设部十分重视对燃气阀门的规范性建设，燃气阀门的行业标准有CJ3005-1992《城镇燃气用灰铸铁阀门的通用技术要求》、CJ3055-1995《城镇燃气用阀门的试验与检验》、CJ3056--1995《城镇燃气用球墨铸铁和铸钢制阀门的通用技术条件》、2002年6月又通过了《家用手动燃气阀门》的行业标准。这些标准的制订和颁布规范了阀门行业、推动了燃气阀门的进步和发展、促进了燃气事业的发展；为研制、生产、使用单位提供了参考依据；提高了对燃气阀门与通用阀门区别的认识，保证了燃气阀门的安全裕度；受到了燃气同行们的欢迎。 燃气阀门结论 根据我国国情和燃气阀门现状的分析，可以得出以下基本结论。 1、地下管网中压B级以下压力级制，推荐使用直埋式RZ系列灰铸铁平行双闸板闸阀； 2、地下管网中压A级以下压力级制，推荐使用直埋式RZ、RQZ系列平行双闸板闸阀或TRZ系列弹性平板闸阀； 3、地下管网高压B级以下或高压A级压力级制，推荐使用直埋式TRZ系列弹性平板闸阀和固定球燃气球阀； 4、地下管网高压A级以上压力级制，推荐使用固定球燃气球阀； 5、储配站或地面设备上由于压力在0.4MPa以下，大于DN500口径的，尽量使用闸阀，可降低价格。 6、在调压器或调压站内，压力级制较低(0.4MPa以下)建议采用RZ或RQZ平行双闸板闸阀，燃气球阀可采用浮动型燃气球阀，如压力级制低于1.6MPa，可用固定型燃气球阀和TRZ弹性平板闸阀。 7、在调压箱内，因空间条件限制，必须选用蝶阀时，应选用多偏心优质蝶阀，密封材料选用聚四氟乙烯或硬密封，调试时必须准确调整到关闭位置。 我国的燃气事业，尤其是天然气的快速发展和普及，带动了燃气阀门制造业的进步和发展。随着西气东输、海洋天然气上岸、俄罗斯气源的引进，新型的燃气阀门将会问世，以适应广大燃气用户的需要。

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译文：
With the strengthening of environmental awareness and change the energy structure, China's city gas utilities have made great progress, coal-gas type of development from simple to multiple gas sources simultaneously, in the late nineties, the continuous development of China's natural gas resources, construction, and use of natural gas to promote the development of China's cities and towns have entered a new period. Transmission and distribution of natural gas storage system gas pressure is relatively high labor, in densely populated cities and towns in the safe storage and transport is extremely important. Imagine if the gas valve for selection of inappropriate or poor quality, and even lead to leakage, cut-off accident, the light affect normal social life, production, and in serious cases to the state, significant loss of life and property. So I think that: the valve is gas transmission, storage systems, safe operation and maintenance, transformation, essential for the development of important equipment in gas industry leaders and technical staff on the selection of gas valve must be taken seriously enough. This paper will use the material gas valve, structure modeling, working conditions and the criteria for selection of views, only for selection of reference gas industry works. I. Current Situation of China Gas Valve Before the eighties of the last century, no special gas valve, water valves can only follow. Since the reform and opening up, economic development and promote the development of gas industry, valve manufacturers pay attention to the research dedicated Wei gas valve, which was mainly come from the structural design overcome the coal gas contains more impurities, especially tar , aromatic hydrocarbons and dust mixed to form a "gas glue" affecting the valve seal or "killed" stem the problem. Development and application of natural gas to make a change in the nature of gas. Natural gas than coal-gas clean dry, but with the quality of sand dust, gas pressure higher than coal (coal-gas pressure is generally in the 0.05 ~ 0.3MPa, natural gas is generally 0.4 ~ 1.6MPa or higher) in the sand under high pressure Dust will form a strong scour valve cavity effect, a variety of gas source working condition, so how in the urban cities and towns, gate stations, storage facilities, underground gas pipe valve is used in front of us new subject. Second, the installation of underground pipe-line valves shall meet the requirements of Have enough "strength" and "rigidity" - "Strength" is the valve inside the transmission and distribution lines should be able to withstand the maximum pressure of gas, more importantly, must have sufficient "stiffness" that is affordable by the underground pipe network kind of external circumstances remain the valve is not deformed and reliable valve sealing performance guarantee: 1, to minimize the structural height of the valve (refer to the centerline of the valve flow to the valve top section height) to reduce the buried depth; 2, closed the valve at the top of the hoist should be fitted with all indicators, to facilitate the operator at any time see the state in which the valve is an important condition for safe operation; 3, the whole path design to reduce flow resistance, easy cleaning, or pipe through the pipe detectors, closed-end opening should also meet the continually lose opening machine in the pipeline; 4, a reliable sealing performance, CJ3055-95 "town gas valve experiment and test the" standard provides: Soft sealing valve rated at 1.1 times the nominal pressure does not allow the use of any detection of internal leakage, seal the valve in the 1.1 times the nominal rated using the pressure within the allowable leakage rate is less than 0.3DNmm3 / s, this requirement is more stringent, for example: 500mm nominal diameter of the gas valve within the leakage per minute can not be greater than 9 ml (normal drinking cup The capacity is 200 ml) For the external leakage is not permitted; 5, for use in underground gas pipe valves of the shell to corrosion, the proposed pipeline transportation under the pressure medium and the use of different shell material; 6, valve components should be considered low-maintenance design, maintenance-free structure, repair and maintenance to minimize the workload, reduce maintenance and road closure valve maintenance, impact on traffic; 7, most of the human underground pipeline valves open and close, open and close the valve torque requirement is small, not too many full revolutions, as soon as possible after the accident cut off gas supply; 8, a variety of urban roads underground pipelines crowded, complicated, not digging the basement cellar well, so recommend directly buried valve. 3, gas valve body material selection Pressure gas pipeline under the reasonable use of the valve housing material selection, not only palace to meet the safe operation of pipeline and is able to reduce the cost and make the best use for the purpose. 1, medium B level (0.2MPa) the following transmission and distribution pipelines, the proposed system of gray cast iron valve, its biggest advantage is a good corrosion resistance, and low price, very suitable for underground pipeline; 2, medium A-level (0.4MPa) below, and even B-level high pressure (0.8MPa) the following, suggested the use of ductile iron or cast steel manufacturing, focusing on recommended use ductile iron. For example: ductile iron grade QT400 - 18 compared with the WCB cast steel grades, as much as the mechanical properties of the former to the latter, while the anti-corrosion and the casting process are superior to steel, prices are lower than the cast (usually cast 70% of the steel) so the overall performance of ductile iron valve cast steel valve and the prices are better than, the pressure in the range of ductile iron valve used where possible, but with particular attention to monitoring the quality of the cast iron material; 3, A-level high pressure (1.6MPa) or a pressure level higher, the system suggested the use of cast steel valve manufacture 4MPa pressure valve below the level of general use WCB grade; 4, in recent years, local gas companies began to use PE pipe, PE pipe pressure levels currently used in the following 0.4MPa. PE ball has come out, the ball valve can be directly buried, good sealing performance. But the current PE ball higher prices, especially in larger than 100mm diameter or more of the ball valve, PE ball is now in trial stage of the promotion. Fourth, China's gas industry currently uses some gas valves Introduction 1, RX Series Oil sealed plug Eighties of last century, our gas is mainly artificial coal gas, artificial coal gas has more impurities and the "gas glue", the original traditional use of single-gate type water valve more and can not meet the lease conditions gas needs, such valves widespread "off loose" and the issue of stem killed, we draw on technology developed from the RX series of gas oil sealed plug solve the lack of strict and stem killed off problems. The main technical characteristics: With seal structure, it has the role of scraping gum; sealing surface and gas impurities in non-contact, no stem cavity, there is no issue of stem killed: specially developed anti-corrosion medium gas oil, and O-ring seal, improved plug performance, adapt to our gas conditions, have been colleagues at home. However, the oil seal type plug has its weaknesses, first, not with the same diameter pipeline, pipeline flow area is about 75%, an increase of flow resistance and eddy current, it can not Pig; second, open and close valves aquifers in front of oil, the inconvenience to users; Third, nominal diameter less usually DN300, DN400 to create difficult, DN600 more heavy users are not welcome; 2, RZ series gas with parallel Gate Valve With the development of gas and gas plant's have established a larger and even large nominal diameter of the gas special valve, RZ Series Gas Gate Valve with parallel formation of artificial gas for 11 to solve the problem, maximum diameter up to 1600mm. First, the parallel Gate Valve opening and closing process to scrape the surface of the seal "Gas glue" to solve the gas impurities affect the adhesion of the valve sealing surface in sealing a major issue; Second, with stem protection cover, so that stem from "the Gas glue" of erosion; Third, the valve cover side of the bottom hole with sewage, you can clean the bottom of the rubbish fell valve chamber; Fourth, the whole design flow path resistance is small, but also through Pig; Fifth, the body uses a specially designed "frame rib cage" to reduce the overall weight of the valve, and enhance strength and stiffness of the shell; Sixth, RZ series gas valve used gray cast iron shell, low price; seventh in the series with a completely closed valve open and close indicator to the operator a clear understanding of the state in which the valve. Inception of the series gate quickly in the national gas industry to promote the use, get a better evaluation, it is still pressure around the gas pipeline companies to use; 3, RQZ gas system with a parallel series of iron Gate Valve As China's natural gas into the town, the author and the Shanghai Gas Company, Gas Equipment Suzhou Valve Manufacturing Co., Ltd. According to the characteristics of natural gas, has developed a system of gas cast iron RQZ Parallel Gate Valve with the valve, while retaining the RZ Series valve features, the use of the material enhances wear resistance of the valve, while pressure levels up to the high-pressure B; 4, Butterfly Light compared to the several valves butterfly valves, large diameter, low price, 80 in the early part of the Gas Company has - degree with butterfly, after about ten years use, generally considered ineffective. First, pay the isolation valve seal width is too narrow, making it easy valve valve in place the process too far or not, affect the seal; second valve flap valve chamber in the middle of a large flow resistance, can not sweepers; third, As the seal to pay in - part of rubber or PTFE, in the gas are easily damaged or washed off, short service life. Practice shows that except in special position, gas pipeline should not use butterfly valves, butterfly valves have been used a number of gas companies are (or consider) the replacement of other valves; 5, flat gate valve Flat gate valve is the gas pipeline in recent years begun to use the common valve, full bore when the flow resistance is small, both sides sealed by a PTFE or rubber O-ring compression to form the gate, this valve in when fully closed or fully open in the cavity can not do without gas, do not react quickly to user-friendly repair the valve is locked, no gas to reach the cavity opening and closing torque is rapidly increasing; some manufacturers made of reduced diameter, out as DN200 diameter, inside diameter is only 150mm, the user should pay special attention. So the pressure plate valve suitable for low-level system, nominal diameter smaller occasions. 6, TRZ series elastic sealing gas valve TRZ series elastic sealing gas valve is different from a gas valve plate special valve. The characteristics of the valve fixed ball valve with the flexibility of the valve seat structure similar to ram both sides of the seal seat with flexible floating structure, the sealing surface in the opening and closing and opening and closing process is always close together, but also pay compensation for seal wear, suitable for high-pressure-level system of the occasion; the valve is fully open when the valve is fully closed chamber can be achieved without gas, even if the elution complete the remaining gas in the valve chamber, valve chamber still no pressure, users can rest assured that the valve downstream pipeline construction, greatly reducing the air ready to stop pre-construction work hours, receive the user's consent. TRZ series elastic sealing gas valve connection in the form of welded flange-type and two, the traditional flange connection, welding can be welded directly to the valve and pipe, pipe-laying cost savings; two valves are can be buried, to avoid unnecessary scenting well, to bring the convenience of construction. TRZ series elastic sealing gas valve fully open, like a section of pipeline with pipe diameter, flow resistance, minimal; and all the sealing surface hidden and not with the media exposure, in terms of artificial coal gas, "gas plastic" can not adhesion in a sealed surface, erosion of natural gas in terms of less than parts of dust on the gravel. All in all, TRZ series elastic sealing gas valve suitable for gas pipelines, particularly suitable for underground gas pipeline, from the study of the situation abroad, many countries have adopted flexible natural gas pipeline valve plate, the same nominal diameter flexible valve plate Compared with the ball, have fire protection features, the price is about 30% lower than the ball, use the same effect. TRZ series elastic sealing gas valve weakness is structural height is greater and four nominal diameter of the height, because buried in the ground, the height above the pipeline axis and the valve is usually the same, the drawback is not clear, mainly under half height than the gate usually large - more, the construction of burial depth, a little bigger, but - generally does not affect the pipeline laying; 7, RQ series ball valve Valve is its flow resistance is small, the structure height is small, and good sealing performance is widely applied in recent years, rapid development. Ball two, one is a floating ball valve, which can be a floating ball in the valve chamber, relying on both ends of the compression ball and stable sealing seat. This valve can only be used for smaller nominal diameter (150mm below) or system-level low pressure (0.8MPa or less) occasions, or open and close torque will be great for users difficult. Greater than the nominal diameter or pressure-level system of higher DN200 occasions, needed the ball structure of fixed, fixed ball valve in the valve fully closed, the pressure force on the ball passed to the upper and lower ball support shaft, greatly reduce operating torque, pressure drop increase will not significantly increase the moment for easy operator use. RQ series fixed ball valve is designed and manufactured specifically for the gas industry, and the ball valve combines the characteristics of both domestic and overseas, and then developed according to China's conditions for long-distance trunk gas, city gas facilities. The ball valve addition to the general strengths of the characteristics are obvious. First, fire resistance, fire burned hot seat PTFE seal material, the metal sealing seat and can form part of each sealing metal to metal sealing structure to prevent gas diffusion media to prevent the disaster continue to expand; second, anti-static, ball valve in the open and close easily formed in the process of electrostatic ignition of gas, the valve will be static into the ground to ensure the safety of equipment; third, limit lock, ball is rotating bodies, likely to cause 360-degree rotation, In addition to limited spaces outside the re-organization can be locked to prevent operator misuse or unauthorized operation of the operator caused the accident; the fourth, the ball valve stem seal design of the anti-stem shock device, and the use of special O-ring seal, torque than the same ball is small, easy to operate, open and close quickly. 5, several special-purpose description of gas valve 1 Used for emergency shut-off valve regulator Used for emergency shut-off valve regulator gas transmission and distribution system is an important safety device. Emergency shut-off valve in the valve upper body or lateral installation of emergency release, also connected with the regulator body as a whole, but also connected with the filter as a whole, its role in the voltage regulator failure, causing excess pressure or emergency shut down after loss of pressure gas source, and ensure safety. Large number of natural gas used in cities, improve the pipe network pressure level system, voltage regulator failure would have disastrous consequences for the city, the domestic gas industry, more and more attention to this. Domestic product has not yet selected a certain trend, imports, joint venture, made in China, is difficult to distinguish good and bad, use must be careful. RAQ series gas emergency shut-off valve is the filter as a single entity, new structure, compact, high sensitivity can be set overpressure (300mm/H2O) and loss of pressure (180mm/H2O) quickly cut off the gas supply regulator to ensure user safety; 2, gas emergency shut-off valve Gas boiler, gas conditioning, gas facilities in the event of gas leaks or other disaster, the emergency shut-off valve to cut off gas sources quickly to prevent the disaster to expand. Current gas emergency shut-off valve has not spread in the country, with environmental awareness and enhance safety awareness and the development of gas industry, gas emergency shut-off valve will get attention. Gas emergency shut-off valve is to protect the safety of the nature of the valve, and automatic monitoring equipment with machines, the implementation of the relevant valve command, so are electric gas valve emergency shut-off valve, according to available information, there are two types reflect the type of valve, a type of electromagnetic valve, one is electric valve. As the emergency shut-off valve for high gas main is fast, sealed, flow resistance is small, safety specifications such as diameter, the existing solenoid valve, electric valve has some defects, can not meet all the requirements. The following analysis of each of these valves: First, the electromagnetic valve, now mostly use imported electromagnetic valve, solenoid valve speed, but the flow resistance of which is the largest valve mid-stream resistance, the pressure loss of large and small caliber, large caliber of the solenoid valve manufacturing difficulties, the general can only do DN150 less expensive, such as solenoid valves with large-diameter path to meet the requirements of technical and economic indicators of the poor than. Some suck electromagnetic solenoid valve is opened by valve, once the loss of electricity, even if momentary loss of power valve is closed, does not meet the actual conditions. Decoupling-type solenoid valve, power decoupling off valve, high sensitivity, very fast, because of the low voltage DC, there is little interference or power "rock" will result malfunction, affecting normal life and production; Second, electric butterfly valve, lower prices, are likely to cause large-diameter, open and close gate faster than the speed, slower than the electromagnetic valve; stream shade smaller than the solenoid valve, gate valve than large; more solenoid valves and valve sealing are poor and isolated as the width of sealing small, fast opening and closing speed of the impact of inadequate or too far open and close easily lead to the phenomenon; Third, the electric valve, electric butterfly valve prices are high, small resistance, good sealing, but slowly, not reach the requirements for emergency cut off; Fourth, the ball valve, flow resistance is small, good sealing, but the market power of domestic or imported valve, opening and closing speed is generally 15 to 30 seconds, it can not meet the requirements of speed, users of emergency shut-off valve opening and closing speed requirements generally less than 10 seconds, the electric valve has many advantages, as long as the increase in the opening and closing speed can be ideal to improve the emergency shut-off valve. RKQ emergency cut off valve electric ball valve combines the advantages of opening and closing speed of 3.75 seconds, to fill the gaps at home and abroad, and structural design features anti-static and fire, electrical equipment, with gas leak alarm, disaster control equipment with machines, but also with fans and other auxiliary equipment with control, the overall design meets DBJ08 - 65 - 97 "Urban Natural Gas Pipeline Engineering" prices are much lower than similar imported products. Once accepted by the advent of Jibei gas users, and well received. 3, gas valve Gas Storage and Distribution Station compressor often need to configure the check valve to prevent gas back into the compressor. Water with non-return valve in the gas industry has eliminated the major shortcomings of the general gas valve is reciprocating compressor valve plate movement with the quiver, and the body had great impact sound, easy to damage the valve plate; second sealed poor. R Series gas valve can solve these problems. The series of check valve check valve seal to pay the other 90 degrees to 75 degrees, the valve plate to the valve seat form - a natural pressure valve plate at the same time outside the structure together with a balanced hammer can be adjusted to solve the noise problem ; seal to pay to switch to improve the sealing performance of PTFE, to prevent the "return air" phenomenon, R-type gas valve more than a decade since the advent of the use of good results. 6, the standard gas valve Gas valve in the gas industry plays an important role, the Ministry of Construction paid great attention to the normative construction of gas valve, gas valve industry standards CJ3005-1992 "town gas valve with cast iron General technical requirements", CJ3055 -1995 "town gas valves of the test and test", CJ3056 - 1995 "urban gas system with ductile iron and cast steel valves general technical conditions", in June 2002, a "home manual gas valve" industry standards. The formulation and promulgation of these standards regulate the valve industry, promoted the gas valve to the progress and development, and promoting the development of gas; the development, production, and use of reference information; improved valve of the gas valve and the common understanding of different doors, to ensure the gas valve margin of safety; by gas counterparts welcome. Gas valve Conclusion According to China's national conditions and the gas valve on the analysis, the following basic conclusions can be drawn. 1, B underground pipe network pressure below the rank of the pressure-tier system, recommended RZ series of directly buried parallel Gate Valve Cast Iron; 2, underground pipe network pressure below the rank of A-level system pressure is recommended directly buried RZ, RQZ Series Parallel Gate Valve or TRZ series of flexible valve plate; 3, B underground pipe network below the rank of high pressure or high pressure A-pressure-level system, recommended directly buried TRZ series elastic plate and fixed ball valve gas ball valve; 4, A-level high pressure underground pipe network pressure level above the system, recommended a fixed gas ball valve; 5, storage and distribution station or ground equipment as pressure is 0.4MPa less than DN500 diameter, using the gate as far as possible, to reduce prices. 6, the regulator or the regulator station, system-level low pressure (0.4MPa below) recommended RZ or RQZ parallel Gate Valve, gas ball valve gas ball floating can be used, such as system-level low pressure at 1.6MPa, Gas Ball Valve can be fixed and TRZ flexible flat valve. 7, the regulator box, due to space constraints, must be selected valve should be used more eccentric quality butterfly valve, PTFE seal or seal material selection, testing must be accurately adjusted to the closed position. China's Gas Industry, in particular the rapid development and popularization of natural gas to drive a gas valve manufacturing progress and development. With natural gas, marine gas ashore, the introduction of Russian gas supply, new gas valve will come out to meet the needs of large gas users.