外文翻译-阀体和水龙头大学论文

水龙头和阀门看完本章的读者应该能：1.简述家庭热、冷水供应的水龙头和阀门的工作原理。2.简述用于修理、维护水龙头和阀门并使其处于优良工作状态的方法。3.认识不同类型的悬浮阀门的工作原理。4.为特殊用途指定适当的类型的阀门。5.简述冷水系统的噪声问题。水龙头和阀门的一般规定水力规章条例要求所有配件必须与他们的用途相吻合，用抗腐蚀材料足以抵抗正常水流的压力。他们也能在适当的温度下工作。密封垫圈一定是最易受影响的部分。用于供应热水和冷水水龙头的配件的应该遵照BS1010第1部分和BS5412第2部分。高阻力水龙头应该遵照BSEN200和BS6920，极小的入口的压力不应超过0.5MPa。漂浮操作的阀门应该遵照BS1212的第1，2，3，4部分。所有水龙头和阀门通常由黄铜压制或铸造做成，一些水龙头用镀铬的方法改进外观，并使其容易清洗。叫乙缩醛二乙醇的热固性塑料最近用于水龙头的制造变得越来越普遍。在市场上有多种商标销售的是一种耐用并能够能用机器批量生产制造的金属化的工程学塑料。它比金属更容易损坏，抗压性业也相对较低而且并不像黄铜那样耐磨。这是作为金属材料有力竞争者的最主要的不利因素。现代水龙头、喷头和阀门的某些部分使用综合性塑料，特别是尼龙有很好的耐磨性且耐高温。聚丙烯是另一种被成功的用于制造悬浮操作阀门可朔性材料，但由于它材料的特殊性也导致他在设计方面有一定的缺陷。螺旋拧紧式水龙头在1986之前只有螺旋拧紧式水龙头被允许使用通过管道直接从水系统中取水，与这种设计一样，由于这种水龙头不能很快的关闭，从而避免了水锤。这是一个用于形容噪声的术语，通常当高压水流突然遇阻时出现重击声或吵杂的振动声。这不仅是产生了噪声，而且水锤可能损坏管道，特别是暴露出来的粗糙部分。然而从1986年水力规章条例，可以快速关闭的直角转弯水龙头被允许使用，但读者应该知道安装他们的后果是会导致水锤。要避免此，特别是在供水水压非常高的区域，也许提供减压阀或水锤消除器是必不可少的。在各种各样的螺旋拧紧式水龙头中如何来选者最合适的。然而，所有螺旋拧紧式水龙头阀门的工作原理基本上是相同，一体化的螺纹轴必须通过几次旋转才能使其关闭。许多调制解调器水龙头被做成非上升的纺锤状。这有利于减少通过密封管的轴垫水流压力。这也使得制造商在水龙头的美学设计上有更多的自由(参见6.1)图6.1小水龙头小水龙头是螺旋拧紧式水龙头的一个典型的例子，此设计是适合安装在像厨房或卫生间的水池上的。螺旋水龙头也用软管连接在水箱上。当小水龙头安在水池上时，一定注意到保留图6.2足够的高度使得能够把桶或碗轻松地放在下面。小水龙头的剖视图显示在。6.2(a)。一种叫做易洁罩的覆盖物涂于水龙头上用来防止污垢堵塞和尖端的腐蚀。在图中小水龙头的锭子、套管和跳垫是普通的螺旋拧紧式阀门类型。当转动转把时，锭子上的螺纹啮合龙头内部的螺纹，使锭子向上或向下移动，从而打开或者关闭给水。小水龙头的另一个类型显示在6.2(b)。通常这些水龙头的外形适合于与直接连接的水管管口。对于这些水龙头，所有供水系统带有合并复核阀门。最好安装在他们二者之间最容易生产磨损的地方，或者在水龙头末端。由于不可能有效地排水，他们在寒冷的天气非常易受损伤。遵照BS1010所有螺旋拧紧式水龙头都有固定的套垫。这是，因为压力在一些间接系统是不足以来顶起套垫。唯一的例外是遵照BS5433的停止阀.梁式水龙头这些也是螺旋拧紧式，但不同于小水龙头的是他们被设计成适合直接地用螺帽接入清洁器具上。第7章涉及到如何维护和修理这些小水龙头。梁式水龙头的调制解调器的设计是比较复杂的，外端同样需要易洁罩，在这种情况下也打开或关闭水龙头。许多这些调制解调器水龙头使用丙烯酸酯这种塑料来做水龙头的手轮。截止阀螺旋式阀的另一种家庭成员是截止阀(参见图6.3(a))。这种阀一般安装在连续运行的管道上，其目的是要控制一幢建筑物里，或控制在同一建筑物里的1个或几个独立的水供应。这种阀适合平直的管道，他们的目的是控制进入建筑物的供水，或者独立同一个建筑物里其他控制配件或一个小组配件。这种截止阀主要用在建筑物的供水系统的控制，并且精良避免让截止阀直接和外面的冷空气直图6.3接接触，在通天天气寒冷的时候，要把管道里的水排净。截止阀在地下使用时必须符合BS5433里的要求。他们一般是由抗腐蚀材料制成例如青铜或古铜，有一个套垫并且重量要遵从BS1010。还有一种阀门是按照BS5433自造的，这种阀的工作原理相似于那些球形阀的直角转弯阀门如图。因为这种阀门只是用来控制水流，他们不会加重水锤。另外的好处是这用法没有或者说是很少有压降，这种阀不同于那些螺旋拧紧式阀门，当他们被称为‘完美的’阀门。螺旋拧紧式节止阀上有盖印与表明水流量的方向的箭头，这能使得截止阀用在正确的管道中，并不能够保证水流方向不会出错.阀锁阀锁一般用在学校、医院和公共厕等暴露在公开区域的阀上以防止这些阀在没有被允许的情况下擅自被他人打开或关闭。图6.4(a)显示水龙头的头符合保护闸门。终止锭终止作为正方形在被拧紧在水龙头并且用固定螺钉巩固锁盾的上缘之下。这些水龙头拥有活动键，用于在水龙头安装时保证负责人的安全。三通头有时也叫它马恩导管(图6.4(b))，这是进行公共区域阀体维护的一个基本的工具。在他每个头上都有一个正方形的凹槽，这个凹槽是用来锁定和打开阀锁。圆盘式水龙头这种类型的水龙头兴起于维多利亚女王时代时期，他用塞嘴式拧紧的设计的替换了原来螺旋拧紧封闭的那种阀门。图6.5是以图解方式说明这这个简单的圆盘阀门的工作原理。不同于螺旋拧紧式阀门他们没有座套或垫圈。这些被一端静止的二个陶瓷圆盘固定住阀门，因此它不可能转动，其他可以转动90°，通常是利用杠杆原理。圆盘带有的排水沟，当水龙头打开时。像多数调制解调器水龙头一样从封垫漏出，并且它被要求的非上升的纺锤圆盘，不同于橡胶垫圈，将延续水龙头的寿命。这种陶瓷圆盘的原则是确保感到一直是出于畅通无阻的状态。进而保证整个阀体一直维持一个良好健康的运行状态。抗震水龙头这些是为公共建筑而设计为保存水和经营的特别水龙头，只有当向下压力在头的顶端被施加时，震荡开关才会被打开。调制解调器抗震水龙头是更加复杂的，它是通过一个水力阀门里面的一个内置开关来调节的。安全阀安全阀是根据压力系统的工作压力自动启闭，一般安装于封闭系统的设备或管路上保护系统安全。当设备或管道内压力超过安全阀设定压力时，自动开启泄压，保证设备和管道内介质压力在设定压力之下，保护设备和管道正常工作，防止发生意外，减少损失。安全阀的作用：安全阀在系统中起安全保护作用。当系统压力超过规定值时，安全阀打开，将系统中的一部分气体排入大气，使系统压力不超过允许值，从而保证系统不因压力过高而发生事故。安全阀又称溢流阀。图示为安全阀的几种典型结构形式。图a为活塞式安全阀，阀芯是一平板。气源压力作用在活塞A上，当压力超过由弹簧力确定的安全值时，活塞A被顶开，一部分压缩空气即从阀口排入大气；当气源压力低于安全值时，弹簧驱动活塞下移，关闭阀口。此阀密封面要干净安全阀结构主要有两大类：弹簧式和杠杆式。弹簧式是指阀瓣与阀座的密封靠弹簧的作用力。杠杆式是靠杠杆和重锤的作用力。随着大容量的需要，又有一种脉冲式安全阀，也称为先导式安全阀，由主安全阀和辅助阀组成。当管道内介质压力超过规定压力值时，辅助阀先开启，介质沿着导管进入主安全阀，并将主安全阀打开，使增高的介质压力降低。蝶阀蝶阀又叫翻板阀,是一种结构简单的调节阀，同时也可用于低压管道介质的开关控制。蝶阀是指关闭件(阀瓣或蝶板)为圆盘，围绕阀轴旋转来达到开启与关闭的一种阀，在管道上主要起切断和节流用。蝶阀蝶阀启闭件是一个圆盘形的蝶板，在阀体内绕其自身的轴线旋转，从而达到启闭或调节的目的。蝶阀全开到全关通常是小于90°，蝶阀和蝶杆本身没有自锁能力，为了蝶板的定位，要在阀杆上加装蜗轮减速器。采用蜗轮减速器，不仅可以使蝶板具有自锁能力，使蝶板停止在任意位置上，还能改善阀门的操作性能。工业专用蝶阀的特点能耐高温，适用压力范围也较高，阀门公称通径大，阀体采用碳钢制造，阀板的密封圈采用金属环代替橡胶环。大型高温蝶阀采用钢板焊接制造，主要用于高温介质的烟风道和煤气管道。蝶阀的开度与流量之间的关系，基本上呈线性比例变化。如果用于控制流量，其流量特性与配管的流阻也有密切关系，如两条管道安装阀门口径、形式等全相同，而管道损失系数不同，阀门的流量差别也会很大如果阀门处于节流幅度较大状态，阀板的背面容易发生气蚀，有损坏阀门的可能，一般均在15°外使用。蝶阀处于中开度时，阀体与蝶板前端形成的开口形状以阀轴为中心，两侧形成完成不同的状态，一侧的蝶板前端顺流水方向而动，另一侧逆流水方向而动，因此，一侧阀体与阀板形成似喷嘴形开口，另一侧类似节流孔形开口，喷嘴侧比节流侧流速快的多，而节流侧阀门下面会产生负压，往往会出现橡胶密封件脱落。蝶阀操作力矩，因开度及阀门启闭方向不同其值各异，卧式蝶阀，特别是大口径阀，由于水深，阀轴上、下水头差所产生的力矩也不容忽视。另外，阀门进口侧装置弯头时，形成偏流，力矩会有增加。阀门处于中间开度时，由于水流动力矩起作用，操作机构需要自锁.闸阀闸阀的启闭件是闸板，闸板的运动方向与流体方向相垂直，闸阀只能作全开和全关,不能作调节和节流。闸板有两个密封面,最常用的模式闸板阀的两个密封面形成楔形、楔形角随阀门参数而异,通常为50,介质温度不高时为425℃。楔式闸阀的闸板可以做成一个整体，叫做刚性闸阀闸板；也可以做成能产生微量变闸阀形的闸板,以改善其工艺性,弥补密封面角度在加工过程中产生的偏差,这种闸板叫做弹性闸板。闸阀的种类,按密封面配置可分为楔式闸板式闸阀和平行闸板式闸阀,楔式闸板式闸阀又可分为:单闸极式、双闸板式和弹性闸板式；平行闸板式闸阀可分为单闸板式和双闸板式。按阀杆的螺纹位置划分，可分为明杆闸阀和暗杆闸阀两种。闸阀关闭时,密封面可以只依靠介质压力来密封,即只依靠介质压力将闸板的密封面压向另一侧的阀座来保证密封面的密封，这就是自密封。大部分闸阀是采用强制密封的,即阀门关闭时，要依靠外力强行将闸板压向阀座,以保证密封面的密封性。闸阀的闸板随阀杆一起作直线运动的。通常在升降杆上有梯形螺纹，通过阀门顶端的螺母以及阀体上的导槽，将旋转运动变为直线运动,也就是将操作转矩变为操作推力。插座水龙头有时也被人们称作为“回转水龙头”可能是最古老的水龙头了。直到1986条国际水组织章程也没有批准这种水龙头，然而他们发现一些情况，在这一段时期，几乎用于国内所有的工业电器，和供水系统都特别青睐于这种水龙头的使用。不久之后这种水龙头才得到水组织章程的认可。该水龙头是由锥形阀来带动相应的插件，使其到达圆形尖细的部位，来起到关闭和启动的作用。插座水龙头可以提供一个方形的头，有了这个方头就可以用扳手来改变调控水流的大小。疏水阀蒸汽疏水阀的基本作用是将蒸汽系统中的凝结水、空气和二氧化碳气体尽快排出；同时最大限度地自动防止蒸汽的泄露。工作作用虽然简单，但在实际运行中有许多因素会影响蒸汽疏水阀的工作效果，如选型、安装、使用等。自由浮球式疏水阀:自由浮球式疏水阀的结构简单，内部只有一个活动部件精细研磨的不锈钢空心浮球，既是浮子又是启闭件，无易损零件，使用寿命很长，YQ疏水阀内部带有Y系列自动排空气装置，非常灵敏,能自动排空气，工作质量高。设备刚启动工作时，管道内的空气经过Y系列自动排空气装置排出，低温凝结水进入疏水阀内，凝结水的液位上升，浮球上升，阀门开启，凝结水迅速排出，蒸汽很快进入设备，设备迅速升温，Y系列自动排空气装置的感温液体膨胀，自动排空气装置关闭。疏水阀开始正常工作，浮球随凝结水液位升降，阻汽排水。自由半浮球式疏水阀：自由半浮球式疏水阀只有一个半浮球式的球桶为活动部件，开口朝下，球桶即是启闭件，又是密封件。整个球面都可为密封，使用寿命很长，能抗水锤，没有易损件，无故障，经久耐用，无蒸汽泄漏。背压率大于80%，能排饱和温度凝结水，最小过冷度为0℃，加热设备里不存水，能使加热设备达到最佳换热效率。当装置刚启动时，管道内的空气和低温凝结水经过发射管进入疏水阀内，阀内的双金属片排空元件把球桶弹开，阀门开启，空气和低温凝结水迅速排出。当蒸汽进入球桶内，球桶产生向上浮力，同时阀内的温度升高，双金属片排空元件收缩，球捅漂向阀口，阀门关闭。当球桶内的蒸汽变成凝结水，球桶失去浮力往下沉，阀门开启，凝结水迅速排出。当蒸汽再进入球桶之内，阀门再关闭，间断和连续工作球阀球阀问世于20世纪50年代，随着科学技术的飞速发展，生产工艺及产品结构的的不断改进，在短短的40年时间里，已迅速发展成为一种主要的阀类。在西方国家工业发达的国家，球阀的使用正在逐年不断的上升，在我国，球阀被广泛的应用在石油炼制、长输管线、化工、造纸、制药、水利、电力、市政、钢铁等行业，在国民经济中占有举足轻重的地位球阀主要用于截断或接通管路中的介质，亦可用于流体的调节与控制，其中硬密封V型球阀其V型球芯与堆焊硬质合金的金属阀座之间具有很强的剪切力，特别适用于含纤维、微小固体颗料等介质。而多通球阀在管道上不仅可灵活控制介质的合流、分流、及流向的切换，同时也可关闭任一通道而使另外两个通道相连。本类阀门在管道中一般应当水平安装。球阀球阀它具有旋转90度的动作，旋塞体为球体，有圆形通孔或通道通过其轴线。球阀在管球阀路中主要用来做切断、分配和改变介质的流动方向，它只需要用旋转90度的操作和很小的转动力矩就能关闭严密。球阀最适宜做开关、切断阀使用，但近来的发展已将球阀设计成使它具有节流和控制流量之用，如V型球阀。球阀的主要特点是本身结构紧凑，密封可靠，结构简单，维修方便，密封面与球面常在闭合状态，不易被介质冲蚀，易于操作和维修，适用于水、溶剂、酸和天然气等一般工作介质，而且还适用于工作条件恶劣的介质，如氧气、过氧化氢、甲烷和乙烯等，在各行业得到广泛的应用。球阀阀体可以是整体的，也可以是组合式的.TapsandvalvesAftercompletingthischapterthereadershouldbeableto:1.Describetheworkingprinciplesoftapsandvalvesfordomestichotandcoldwatersupplies.2.Describethemethodsusedtorepairandmaintaintapsandvalvesingoodworkingorder.3.Recognizedifferenttypesoffloatworkingprinciples.4.Specifysuitabletypesofvalvesforspecificpurposes.5.Describenoiseincoldwatersystems.Tapsandvalves-generalrequirementsTheWaterRegulationsrequirethatallfittingsmustbesuitablefortheirpurpose,madeofcorrosion-resistantmaterialshavingsufficientstrengthtoresistnormalandsurgepressures.Theyshouldalsobecapableofworkingatappropriatetemperatures.Sealsandwashersmustbeeasilyaccessibleforrenewalwhennecessary.TapsandfittingsusedforbothhotandcoldwatersuppliesshouldconformtoBS1010Parts1and2andBS5412.High-resistancetapsshouldcomplywithBSEN200andBS6920,theminimuminletpressurebeing0.5bar.Float-operatedvalvesshouldcomplywithBS1212Parts1,2,3and4.Alltapsandvalvesareusuallymadeofbrasspressingsorcastingsandsometapsarechromiumplatedtoimprovetheappearanceandtofacilitateeasycleaning.Morerecentlyathermosettingplasticcalledacetalhasbecomeincreasinglypopularforthemanufactureoftaps.Marketedundervarioustradenames,itisanengineeringplasticwhichishardwearingandcapableofbeingmachinedinasimilarwaytometal.Ithasalowerimpactstrengththanmetal,ismoreeasilydamagedandnotsoresistanttoabrasionasbrass.Itismainlythesefactorswhichhaveatpresentpreventeditbecomingamoreseriouscompetitortometals.Certaincomponentsofmoderntapsandshowermixervalvesaremadeofsyntheticplastic,especiallynylonwhichhasgoodwearingqualities.Itisalsoresistanttoheatandlimescale.Polypropyleneisanotherplasticmaterialthathasbeenusedsuccessfullyforthemanufactureoffloat-operatedvalves,especiallythediaphragmtypewhich,becauseofitsdesign,lendsitselftothelimitationsofthisparticularmaterial.Screw-downtapsPriorto1986onlyscrew-downtapswerepermittedonwatersuppliestakendirectlyfromthemains,asthesearedesignedinsuchawaythattheycannotbeclosedquickly,thusavoidingwaterhammer.Thisisatermusedtodescribenoise,usuallyabangingsoundornoisyvibrationsthroughoutthesystem,whichoccurswhentheflowofhigh-pressurewaterissuddenlyarrested.Notonlyisthisnoisedisconcertingbutwaterhammercanbedamagingtopipe-work,especiallywhereithasbeenweakenedowingtoexposuretofrost.Sincethe1986'WaterBylaws,however,quickclosing,usuallyquarter-turntapsarepermitted,butthereadershouldbeawarethatbyinstallingthemtheymaycausewaterhammer.Toavoidthis,especiallyinareaswherewaterissuppliedbythewaterauthoritiesatveryhighpressure,itmaybenecessarytoprovidepressure-reducingvalvesorwaterhammerarresters.Screw-downtapsaremadeinavarietyofpatternsdependinguponthefittingtheysupply.However,theheadworkofallscrew-downtapsandvalvesisbasicallythesame,incorporatingathreadedspindlewhichhastobeturnedthroughseveralrevolutionstoeffectitsclosure.Manymodemtapsaremadehavingnon-risingspindles.Thisisanadvantageasitreduceswearonthespindleasitpassesthroughthegland.Italsoenablesmanufacturersmorefreedomintheaestheticdesignoftaps(seeFig.6.1).BibtapsThebibtapisatypicalexampleofascrew-downtap,beingdesignedtobefittedintobossesscrewedtothewalloversuchappliancesasbutlers’orcleaners'sinks.Theyarealsousedonstandpipeswhenthebibisthreaded,whichenablesahoseuniontobefitted.Whenbibtapsareprovidedoverasink,alwaysbesurethattheyarefittedhighenoughtoenableabucketorbowltobecomfortablyplacedbeneath.AsectionalelevationofabibtapisshowninFig.6.2(a).Theshroudwhichcoverstheheadworkiscalledaneasy-cleanshieldanditservestopreventthebuildupofdirtandcorrosioninthehead.Thespindle,glandandjumpershownintheillustrationofthebibtaparecommontoalltypesofscrew-downvalves.Whenthecapstanheadisturned,thethreadsonthespindleengagethethreadsinsidethehead,causingthespindletomoveupwardsordownwards,thusopeningorclosingthewatersupply.AnothertypeofbibtapisshowninFig.6.2(b).Usuallyfittedexternallythesetapsarefittedwithauniononthespouttowhichahosecanbeconnected.Becausetheuseofhosesconstitutesoneofthemajorrisksofbacksiphonage,allwatersuppliestothesetapsmustincorporateadouble-checkvalve.Theymaybeinstalledeitherinthepipelineinsidethebuilding,whichispreferable,orinthetapitselfasshown.Becausetheycannotbeeffectivelydrained,theyareverypronetodamageinfrostyweather.ThesubjectofbacksiphonageisdealtwithfullyinBook2ofthisseries.Allscrew-downtapscomplyingwithBS1010havefixedjumpers.Thisisbecausethepressureonsomeindirectsystemsisinsufficienttoliftthejumper.TheonlyexceptionstothisarestopvalvescomplyingwithBS5433.Figure6.3showsadetailoftheusualmethodoffixingjumpers.PillartapsThesearealsoofthescrew-downpattern,butunlikebibtapstheyaredesignedtofitdirectlyintothesanitaryapplianceandbesecuredtoitwithabacknut.Chapter7dealswiththemethodsusedforfixingthesetapstoensureawatertightjoint.Thepillartapillustratedisofmodemdesign,theeasy-cleanshieldbeingmadeinsuchawaythatitalsoservestoturnthetaponoroff.Manyofthesemodemtapsemployacrylicplasticforthemanufactureofthistypeofhead.Pillartapsofasimilardesignbutwithextendedbodiesareusedwithsinkunits.Theupwardsweepoftheoutletenablessufficientclearanceunderthetapforfillingkettlesandculinaryequipment.StopvalvesYetanothermemberofthefamilyofscrew-downvalvesisthestopvalve(seeFig.6.3(a)).Thesearefittedinastraightrunofpipe,theirpurposebeingtocontrolthesupplyofwaterintoabuilding,orcontrolonefittingoragroupoffittingsindependentlyofothersinthesamebuilding.Suchvalvesareintendedforuseasthemaincontrolofthewatersupplyonentryintoabuilding,thedrain-offenablingallthewaterinthepipe-worktobeemptiedasaprecautionwhenthebuildingisleftwithoutheatinperiodsofcoldweather.StopvalvesforusebelowgroundmustcomplywithBS5433.Theyaremadeofcorrosion-resistantmaterialsuchasgunmetalorbronze,havealoosejumperandareofheavierconstructionthanthosecomplyingwithBS1010.AnalternativetovalvescomplyingwithBS5433,whicharenowpermissible,isaquarter-turnvalvehavingworkingprinciplessimilartothoseoftheballvalveshowninFig.6.3.Astheyareusedforcontrolpurposesonly,theywillnotgiverisetopersistentwaterhammer.Anadditionaladvantageisthereislittleornopressuredropthroughballservicevalvesastheyareclassifiedas'fullway',unlikethoseofthescrew-downpattern.Screw-downstopvalvesarestampedwithanarrowindicatingthedirectionofthewaterflow.,itshowsthecorrectinstallationofastopvalveandtheflowofwaterthroughit.LockshieldsThesearefittedtotapsnotintendedforpublicusetopreventinterferencefromunauthorisedpersons.Theyareprovidedonstopvalvesandbibtaps(usedbycleaners,etc.)inschools、hospitalsandpublictoilets.Figure6.4(a)showstheheadofatapfittedwithalockshield.Thespindleterminatesasasquarebelowthetopedgeofthelockshieldwhichisscrewedovertheheadofthetapandsecuredwithasetscrew.Thesetapsareprovidedwithaloosekeywhichshouldbehandedovertoaresponsiblepersonforsafekeepingandusewhenthetapisinstalled.Athree-headedkey,sometimescalledanIsleofMankey,isanessentialtoolforplumberscarryingoutmaintenanceworkinpublicandcommercialbuildings.Athree-headedkey,sometimescalledanIsleofMankey,isanessentialtoolforplumberscarryingoutmaintenanceworkinpublicandcommercialbuildings.Thethreeendsarerecessedwithsquaresofdifferingsizesforoperatinglock-shieldvalvesiftheoriginalisnotavailablewhenrequired.GeramicdisctapsTapsofthistypearequitedifferentinoperationtothescrew-downpatternwhichweredesignedinVictoriantimestoreplacetheplugcockcommonlyinuseatthatperiod.Figure6.5illustratesindiagrammaticformtheworkingprincipleofasimplediscvalve.Unlikescrew-downvalvestheyhavenoseatingorwasher.Thesearereplacedbytwoceramicdiscs,onestatic,beingfixedtothevalvebodysoitcannotrotate;theothercanbeturnedthrough90°,usuallybyalever.Thediscsareprovidedwithwaterwayswhichlineupwhenthetapisturnedon.Likemostmodemtapstheyhavenon-risingspindleswhicheliminateleakagefromglandsanditisclaimedthatdiscs,unlikerubberwashers,willlastthelifetimeofthetap.Theprincipleoftheceramicdiscisalsousedformanytypesofmixingvalvesincludingmonobloc.Theyaremorecomplexthanthesimpleillustrationshownandshoulditbenecessarytodismantlethetap,itisadvisabletorefertothemaker'sinstructions.Ceramicdiscsarealsousedwithcertaintypesoffloat-operationvalves.Non-concussivetapsThesearespecialtapswhicharedesignedtosavewaterinpublicbuildingsandoperateonlywhendownwardpressureisexertedonthehead.Modemnon-concussivetapsarerathermorecomplicated,closurebeingeffectedgraduallybymeansofahydraulicvalveinsidethetap.AetvsafetyvalveSafetyvalveisworkingunderthepressureofthepressuresystemautomaticallyopenandclose,usuallyinstalledintheclosedsystemoftheequipmentorpipelineprotectionsystemsecurity.Whentheequipmentorpipelinepressureexceedssetpressuresafetyvalve,pressurereliefautomaticallyopen,ensuringequipmentandmediumpressurepipelinesunderpressureinthesetting,protectionequipmentandpipework,preventaccidentsandreducelosses.Safetyvalveisworkingunderthepressureofthepressuresystemautomaticallyopenandclose,usuallyinstalledintheclosedsystemoftheequipmentorpipelineprotectionsystemsecurity.Whentheequipmentorpipelinepressureexceedssetpressuresafetyvalve,pressurereliefautomaticallyopen,ensuringequipmentandmediumpressurepipelinesunderpressureinthesetting,protectionequipmentandpipework,preventaccidentsandreducelosses.TheroleofsafetyvalveSafetyvalveplayansecurityroleinthesystem.Whenthesystempressureexceedsthesetvalue,thevalveopens,thepartofthesystemofgasintotheatmosphere,allowingthesystempressuredoesnotexceedtheallowablevalue,thusensuringthesystemisnotanaccidentbecauseofthepressureistoohigh.Safetyvalve,alsoknownasreliefvalve.Iconforthesafetyvalveofsometypicalstructure.Figureasafetyvalveforthepiston,valvecoreisatablet.AirpressureactingonpistonA,whenthepressureexceedsthespringforcetodeterminethesafetyvalue,pistonAisthetopopenpartofthecompressedairfromthevalveportintotheatmosphere;Thevalvesealingsurfaceisclean，whenthegassupplypressureislessthanthesafetyvalue,thespring-drivenpistondown,closingvalveport.Safetyvalvestructurearetwomajorcategories:spring-loadedandthelevertype.Spring-loadedflapvalveissealedwiththevalveseatbyspringforce.Leveragedrelyonleverageandheavyhammerofforce.Withthelargecapacityneeds,butalsoakindofpulse-typesafetyvalve,alsoknownaspilotsafetyvalve,themainvalveandsecondaryvalve.Whenthepipelinepressureexceedsthepressurewithinthemediumvalue,theauxiliaryvalvefirstopens,themediumalongthecatheterintothemainvalveandopenthemainvalvetoreducetheincreasedmediapressure.ButterflyvalveCalledbutterflyflapvalveisasimplecontrolvalve,butalsocanbeusedforlowpressurepipeswitchcontrolmedium.Butterflyvalveisclosedparts(valveflapordisc)todisk,aroundthevalveaxistoachievetheopeningandclosingavalveinthemainpipeandthethrottlecutofffromuse.Butterflyvalveopenandcloseadisk-shapedpiecesofthedisc,thevalvebodyrotatingarounditsownaxis,soastoachievethepurposeofhoistingorregulation.ButterflyvalveButterflyvalvefullyopentofullyclosedisusuallylessthan90°,butterflyvalvesandbutterflybaritselfisnotself-lockingcapability,inordertopositionthedisctoinstallthevalvestemwormreducer.Withwormreducer,notonlytomakethedischasaself-lockingcapability,sothedisctostopatanyposition,butalsotoimprovetheoperabilityofthevalve.Industry-specificcharacteristicsofbutterflyvalvestohightemperatureandhigherappliedpressurerange,thevalvenominaldiameterlargerbodywithcarbonsteel,valveplatetoreplacerubbersealringwithmetalring.Largebutterflyvalvewithhightemperatureofsteelplate,mainlyforhigh-temperaturemediumFlueandgaspipelinesButterflyvalveopeningandflowraterelationshipislinearproportionalchange.Ifusedtocontroltheflow,theflowcharacteristicsanddistributionpipesarealsocloselyrelatedtotheflowresistance,suchastheinstallationoftwopipevalvediameter,form,etc.Allthesame,butdifferentchannellosscoefficient,theflowvalvewillbeverydifferentifthevalveasignificantreductioninthethrottlestate,thevalveplateonthebackpronetocavitation,adamagedvalvemay,generallyusedinthe15°outside.Butterflyvalveintheopening,thevalvebodyanddiscshapeofthefrontopeningformedwiththevalveshaftasthecenter,completedtheformationofdifferentstatesonbothsides,thefrontsideofthediscmovingalongthedirectionofflow,theothersideofthecountercurrentdirectionofwaterThemove,therefore,thesideofthebodyandthevalveplatemayformanozzle-shapedopenings,similartotheothersideofthethrottleholeshapedopening,thenozzlesidefasterthanthethrottleflowrateoverthesideandexpendituresideofthefollowingwouldbethenegativepressurevalveoftenthererubbersealsoff.Valveoperationtorque,andbyopeningthevalveopeningandclosingitsvaluevariesindifferentdirections,horizontalButterfly,especiallylargediametervalves,aswaterdepth,valveshaft,intothewaterheaddifferencegeneratedtorquecannotbeignored.Inaddition,thevalvedeviceelbowimportside,theformationofdrift,torquewillbeincreased.Valveopeninginthemiddle,becausethewaterflowtorquework,organizationsneedtoself-lockingoperation.GatevalvesThegatevalveofopeningandclosingparts,ramdirectionofmotionperpendiculartothedirectionofthefluid,valvecanonlybefullyopenandfullyclosed,cannotbeadjustedandthethrottle.Ramhastwosealingsurface,themostcommonmodeofgatevalvesealingsurfaceformedtwowedge,wedgeanglevarieswiththevalveparameters,usually50,themediumtemperatureisnothighwhen425℃.Wedgegatevalveofthegatecanbemadeintoawhole,calledtherigidgate;alsobemadetoproducemicro-deformationofram,inordertoimproveitsprocessof,tomakeupthesealingsurfaceangledeviationsarisingduringprocessing,suchgateiscalledtheflexiblegate.Valvetypes,accordingtothesealingsurfaceconfigurationcanbedividedintowedgegate-typevalveandparalleltothegate-typevalve,wedgegate-typevalvecanbedividedinto:single-gatetype,dualgateplateandtheflexiblegate-type;parallelslidegatevalvecanbeclassifiedintosingle-ramtypeanddoubleplate.Locationbythestemthreadaredividedintoclearanddarkbarbargatevalvetwo.Valveclosed,sealingsurfacecanonlyrelyonmediapressuretoseal,thatonlyrelyonmediapressuretorampressuretotheothersideofthesealingsurfaceofthevalveseattoensurethesealingsurfaceoftheseal,whichisaself-sealing.Mostofthevalveissealedbyforce,thatthevalveisclosed,torelyonexternalpressuretoforcethegatetotheseat,toensurethesealingsurfaceoftheseal.Thegatevalvestemwithastraightlinewiththe.Usuallyintheliftrodwithtrapezoidalthread,throughthevalvebodyontopofthenutandtheguidegroove,therotarymotionintolinearmotion,thatis,theoperationoftorquethrustintoaction.PlugtapsSometimesreferredtoas'quarter-turn'tapstheseareprobablytheoldesttypeoftapinuse(seeFig.6.12).Untilthe1986WaterBylawstheywerenotpermittedonmainscoldwaterservices,butsincethisdatetheyhavefoundapplicationsasservicevalvesinsomecircumstancesandareusedalmostexclusivelybythegasindustryfordomesticappliances,maincocksongasservicesandcontroltapsongasboilers.Theplugisoperatedbyturningthetaperedvalvewhichistightenedintoacorrespondingcirculartaperingseating,alocknutsecuringthevalveintothebodyofthetap.Plugcocksdonotrequireagreatdealofmaintenanceiftheybecomedifficulttomm,theplugcanberemovedbyundoingthelocknutandapplyingalightsmearofgrease.Plugtapsmaybeprovidedwithasquareheadforwhichasuitablespannerisprovided,andsothatthepositionofthevalvecanbedetermined,i.e.whetheritisintheopenorclosedposition,aslotiscutintothesquare.TrapvalveThebasicroleofthesteamtrapsteamsystemcondensate,airandcarbondioxideemissionsasquicklyaspossible;whilemaximizingautomaticallytopreventleakageofsteam.Workroleissimple,butinrealitytherearemanyfactorsthatwillaffecttheworkofsteamtrapeffects,suchselection,installation,andsoon.Bythefloat-typetraps:

Freefloat-typetrapissimple,andhasonlyonemovingpartfinelygroundstainlesssteelhollowfloat,floatisbothopenandcloseparts,nowearingparts,longlife,YQtrapswithYseriesautomaticinternalrowofairdevices,verysensitive,automaticallyschedulingtheair,highqualitywork.Equipmenthasjuststartedwork,thepipelineoftheairthroughtheYseriesautomaticdischargingexhaustairdevices,lowtemperaturecondensateintothetrap,thecondensatewaterlevelrise,floatup,thevalveopens,therapiddischargecondensate,steamsoonintotheequipment,equipmentrapidwarming,Yseriesautomaticschedulingofairtemperatureofliquidexpansiondevices,automaticschedulingofairdeviceclosed.Trapsstartedwork,withthecondensatelevelfloatdown,wastegasdrainage.Freesemi-floattypesteamtraps:Freehalf-float-typetrapsonlyoneandahalfbarrelsfortheballfloattypemovingparts,openingdown,theballbucketthatisopenandclosecases,butalsoseals.Thespherecanbeaclosed,longservicelife,resistanttowaterhammer,nowearingparts,trouble-free,durable,nosteamleakage.Backpressurehigherthan80%,torowcondensatesaturationtemperature,theminimumundercoolingto0℃,heatingequipmentisnotinstorage,canachievethebestheattransfertheefficiencyofheatingequipment.Whent