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1、阀门流量计算方法如何使用流量系数How to use Cv阀门流量系数(Cv)是表示阀门通过流体能力的数值。Cv 越大，在给定压降下阀门能够通过的流体就越多。Cv 值 1 表示当通过压降为 1 PSI 时，阀门每分钟流过 1 加仑 15 C 的水。Cv 值 350 表示当通过压降为 1PSI 时，阀门每分钟流过 350 加仑 15 C 的水。ooValve coefficient(Cv)is a number which represents a valves ability to pass flow.The biggerthe Cv,the more flow a valve can pas
2、s with a given pressure drop.A Cv of 1 means a valve willpass 1 gallon per minute(gpm)of 60 F water with a pressure drop(dp)of 1 PSI across the valve.A Cv of 350 means a valve will pass 350 gpm of 60 F water with a dp of 1 PSI.oo公式 1FORMULA 1流速：磅/小时(蒸汽或水)FLOW RATE LBS/HR(Steam or Water)在此：Where:dp=压
3、降，单位：PSIdp=pressure drop in PSIF=流速，单位：磅/小时F=flow rate in lbs./hr.=比容积的平方根，单位：立方英尺/磅(阀门下游)=square root of a specific volume in ft/lb.(downstream of valve)3公式 2FORMULA 2流速：加伦/分钟(水或其它液体)FLOW RATE GPM(Water or other liquids)在此：Where:dp=压降，单位：PSIdp=pressure drop in PSISg=比重Sg=specific gravityQ=流速，单位：加伦/
4、分钟Q=flow rate in GPM局限性LIMITATIONS上列公式在下列条件下无效：Above formulas are not valid under the following conditions:a.对于可压缩性流体，如果压降超过进口压力的一半。b.For compressible fluids,where pressure drop exceeds half the inlet pressure.c.对于不可压缩性流体，如果压降产生空穴或闪蒸。d.For non-compressible fluids,where pressure drop causes cavitatio
5、n or flashing.e.对于双相流体，如蒸汽-水混合流体。f.For dual-phase flow such as steam-water mixtures.例子EXAMPLE1.通过DN350,压力等级Class 900的压力密封闸阀，水温400 F，压力为1500 PSIG，流速为5,000,000磅/小时的压降是多少？2.What is the pressure drop through a 14 Class 900 pressure seal gate valve with 400Fwater,1500 PSIG,and 5,000,000 lbs/hr flow rate？
6、3.解：采用公式 14.Solution:Use formula 1.ooF=5,000,000=(从水温为 400 F 的表中得到)=(from chart for water at 400 F)Cv=9150(来自本页)Cv=9150(from page 26)oo2.DN350 x DN300 x DN350，压力等级 Class 900缩喉管压力密封闸阀，其它条件与例 1 相同，求压降。3.What is the pressure drop through a 14x12x14 Class 900 Venturi pressure seal gate valvewith the sam
7、e conditions as example 1.4.解：采用公式 15.Solution:Use formula 1.6.Cv=6285(来自本页)7.Cv=6285(from page 26)8.o9.温度 900 F,压力 1200 PSI，流速 500,000 磅/小时的蒸汽应用中压降小于 5 PSI 的压力等级 Class2500 闸阀的最小通径是多少？10.What is the smallest Class 2500 gate valve that will have less than a 5 PSI pressure dropin 900 F,1200 PSI steam
8、service at a flow rate of 500,000 lbs/hr？11.解：采用公式 112.Solution:Use formula 1.oF=500,000=(来自 900 F,1200 PSIG 蒸汽表)=(from chart for steam at 900 F,1200 PSIG)=oo最接近的、较大的 Cv 是 DN250 压力等级 Class 2500闸阀，其 Cv 是 3130。这里是压降小于 5 PSIG 的最小的阀门。The closest higher Cv is a 10 Class 2500 gate with a Cv of 3130.This i
9、s the smallest valvewith a pressure drop less than 5 PSIG.水和蒸汽的备选特性Selected Properties of Water and Steam水的(下游)For Water(Downstream)温度(F)所有压力等级All100Pressures蒸汽的(下游)200300400500600Temperature(F)ooFor Steam(Downstream)压力PSIGPressurePSIG100200300400500600Sat50060070080090010001100温度(F)Temperature(F)oo
10、7008009001000110012001300140016001800200025003000400050006000阀座端口流速计算Calculating Seat Port Velocity下列公式可以用来计算任何阀门的阀座流速：The following formulas can be used to calculate seat portvelocity in any valve:F(流量(磅/小时):流速:(英尺/秒)=)225AF(Flow(lbs/hr):vel:(fps)=)225A流量(加仑/分钟):流速:(英尺/秒)=AFlow(GPM):vel:(fps)=A在此：W
11、here:F=流量(磅/小时)F=flow(lbs/hr)=比容积的平方根=square root of specific volumeA=阀座端口面积(英寸)A=seat port area(in)Q=流量(加仑/分钟)Q=flow(gpm)22例：DN300 型号 58809(压力等级 Class 900)止回阀，流体介质为温度 500 F，压力 200 PSIG 的蒸汽，流速为 90,000 磅/小时，求阀座端口的流速oExample:What is the seat port velocity in a 12 Figure 58809(Class 900)check valve wit
12、h a flow rateof 90,000 lbs/hr of steam at 500 F and 200 PSIGo解：从蒸汽表得为，从阀座端口面积表 A 得阀座端口面积为 78.5 英寸。2Answer:From the steam tablesis,and from the seat port area table A is 78.5 in.2F(流速:(英尺/秒)=)=290,000=英尺/秒25225AF(Vel(fps)=)=290,000=fps25225A例：DN300 型号 180(压力等级 150)旋启式止回阀，流体介质为温度 500 F，压力 200 PSIG 的蒸汽
13、，流速为 90,000 磅/小时，求阀座端口流速？oExample:What is the seat port velocity in a 12 Figure 180(Class 150)Swing Check Valve with a flowrate of 90,000 lbs/hr of steam at 500 F and 200 PSIGo解：查表得为，A 为 113.1 英寸.3Answer:From the tablesis and A is 113.1 in.3F(流速:(英尺/秒)=)=290,000=英尺/秒25225AF(Vel(fps)=)=290,000=fps252
14、25A局限性LIMITATIONS流速公式在下列条件下无效：Velocity formulas are not valid under the following conditions:a.对于可压缩性流体，如果压降超过进口压力的一半。b.For compressible fluids,where pressure drop exceeds half the inlet pressure.c.对于不可压缩性流体，如果压降产生空穴或闪蒸。d.For non-compressible fluids,where pressure drop causes cavitation or flashing.
15、e.对于双相流体，如蒸汽-水混合流体。f.For dual-phase flow such as steam-water mixtures.注意NOTE在确定止回阀通径时，最适宜的工作流速应该位于这些范围内：When determining sizing for check valves,the optimum operating velocities should fall withinthese ranges:BB 旋启式止回阀：55至 115或 135至 240BB 截止止回阀：40至 120PS 提升式阀瓣止回阀：55至 200PSY 形止回阀：148至 200BB Swing Che
16、ck Valves-55to 115 or 135 to 240BB Stop Check Valves-40to 120PS Tilt Disc Check Valves-55 to 200PS Stop Check Valves-40to 180PS Y-Stop Check Valves-148to 200阀座端口面积“A”(英寸)适用于螺栓阀帽阀门SEAT PORT AREA A FOR BOLTEDBONNET VALVES(in)压力等级阀门通径Valve Size1501/222/234681012141618202430361122Pressure Class300600900
17、1500阀座端口面积(英寸)2适用于压力密封闸阀，截止阀，提升式阀瓣止回阀SEAT PORT AREA FOR PRESSURE SEAL GATE,GLOBE,TILT DISC CHECK VALVES(in)阀门通径Valve Size压力等级Pressure Class26002/2346810121416182024190015002500阀座端口面积(英寸)2适用于压力密封 Y 形截止阀SEAT PORT AREA FOR PRESSURE SEAL Y-GLOBEVALVES(in)压力等级阀门通径Valve Size90081012141618202415002500Press
18、ure Class2螺栓阀帽闸阀全开状态下的流量系数 CvBolted BonnetGate Valves FULL OPEN Cv压力等级阀门通径Valve Size1501/222/23456810121416182024303611Pressure Class300165307490710130031105720893513350162752156027890348405105084765125825图 1螺栓阀帽截止阀Figure 1Bolted BonnetGlobe Valves(1)当开启度小于10%时，不建议用于节流应用。(1)not recommended forthrott
19、ling at less600165307490710130031105540849512800153702917026270321404671075530114250900650122028505025785011475139101500138270400600107016002500437568409980120001653074907101300209031105720893513350162752156028720357605216586235129500than 10%Open.压力密封闸阀全开状态下的流量系数 CvPressure SealGate Valves FULL OPEN
20、 Cv压力等级阀门通径Valve Size6002/23468101214161820241Pressure Class90035045085019253575525075509150119501557519200276751500275415730167529254550657078901032513425168252415025001902754601100197031304535550072109215114501657535052592521503775575086001027513425172002095030850压力密封缩喉管闸阀全开状态下的流量系数 CvPressure Sea
21、lVenturi Gate Valves FULL OPEN Cv压力等级阀门通径Valve Size6008 x 6 x 815709001385150011852500815Pressure Class10 x 8 x 1012 x 10 x 1214 x 12 x 1416 x 14 x 1618 x 16 x 1820 x 18 x 2022 x 20 x 2226 x 24 x 26279544857310900011000142001680025000238540656285720097601218516005230002155345056406270846511120141301
22、430251538554415616579609645螺栓阀盖旋启式止回阀全开状态下的流量系数 CvBolted CapSwing Check Valves FULL OPEN Cv压力等级阀门通径Valve Size1501/222/23468101214161820243011Pressure Class3006316827539274019922340572085441946413800130291627636672546526009713922724649913343359544070459840129121954090035860516232508406963161500111315
23、5641520631422173567161414296157207860104161380013420167083338454556螺栓阀帽截止阀全开状态下的流量系数 CvBolted BonnetGlobe Valves FULL OPEN Cv压力等级Pressure Class150阀门通径Valve Size塞形或球形阀瓣Plug orBallDisc1/222/234568101211300塞形V 形端口阀瓣V-PortDisc或球形阀瓣Plug orBallDisc4092170273405745115023437010018544081012601890214092170405
24、745V 形端口阀瓣V-PortDisc塞形或球形阀瓣600900塞形V 形端口阀瓣V-PortDisc或球形阀瓣Plug orBallDisc409217040590170Plug orBallDisc234370100185440780181023437010018529744081012601890压力密封提升式阀瓣止回阀全开状态下的流量系数 CvPressure SealTilting Disc Check Valves FULL OPEN Cv压力等级阀门通径Valve Size9002/21Pressure Class15008025006095346810121416182024
25、146268627106217222420295539454900627592951322305369401465211025503395436554658060941463556271020142017752355302537055465压力密封缩喉管提升式阀瓣止回阀全开状态下的流量系数 CvPressure SealVenturi Tilting Disc Check Valves FULL OPEN Cv压力等级阀门通径Valve Size1508 x 6 x 810 x 8 x 1012 x 10 x 1214 x 12 x 1416 x 14 x 1618 x 16 x 1820 x
26、 18 x 2022 x 20 x 22球形止回阀，截止止回阀，提升式止回阀的流量特性曲线56595515502175266035504410565030048084513201900229530553930492060032056592012751598212027253335Pressure ClassCharacteristic Flow Curves for Globe Stop,Stop-Check,Lift-Check Valves小于全开状态的估计流量系数 CvEstimating Cv For Less Than Fully Open Valves图 2球形止回阀，截止止回阀和
27、提升式止回阀Figure 2Globe Stop,Stop-Check andLift-Check Valves压力密封 T 形球形止回阀，截止止回阀和提升式止回阀阀全开状态下的流量系数 CvPressure Seal T-Globe Stop,Stop-Check and Lift-Check Valves FULL OPEN Cv压力等级阀门通径Valve Size9002/23461Pressure Class1500659517039525004565105265901051954558101214800125018202205695108515804707501100压力密封 Y 球
28、形止回阀，截止止回阀和提升式止回阀阀全开状态下的流量系数 CvPressure Seal Y-Globe Stop,Stop-Check and Lift-Check Valves FULL OPEN Cv压力等级阀门通径Valve Size60081012141618202420253025460043007650732511800164509001750272538253650600058259125135001500175027253825365060005825912513500250011751875265040753775662562259050Pressure Class表中所列
29、流量系数仅适用于全开状态下的阀门。不是全开状态的流量系数可以采用适用于提升式阀瓣止回阀和截止阀的流量特性曲线进行估算。不建议将闸阀用在节流应用中。The flow coefficient(Cv)listed in the tables apply to fully open valves only.Flow coefficients at other than fully openmay be approximated by use of the characteristic flow curves for tilting disc check and globe valves.Gate va
30、lves are not recommendedfor throttling service.例：DN300，压力等级 Class 900 的美国太平洋压力密封截止阀在开气度为 1/4 时的流量系数是多少？EXAMPLE:What is the Cv of a 12 inch Class 900 Pacific pressure seal globe valve 1/4 open图 3Y 形球形止回阀，截止止回阀和提升式止回阀Figure 3Y-Globe Stop,Stop-Check andLift-Check Valves压力密封缩喉管球形止回阀，截止止回阀和提升式止回阀阀全开状态下的流
31、量系数 CvPressure Seal Venturi Globe Stop,Stop-Check and Lift-Check Valves FULL OPEN Cv压力等级阀门通径Valve Size9008 x 6 x 810 x 8 x 1012 x 10 x 124507701215150039069010552500260465745Pressure Class14 x 12 x 1416 x 14 x 161775212515501070压力密封缩喉管 Y 球形止回阀，截止止回阀和提升式止回阀阀全开状态下的流量系数 CvPressure Seal Venturi Y-Globe
32、Stop,Stop-Check and Lift-Check Valves FULL OPEN Cv压力等级阀门通径Valve Size6008 x 6 x 810 x 8 x 1012 x 10 x 1214 x 12 x 1416 x 14 x 1618 x 16 x 1820 x 18 x 2022 x 20 x 2216 x 24 x 2611001925287543754075725069501120015850900100016752600365034505700552586751282515001000167526003650345057005525867512825250065
33、011251775252538753575630059258600Pressure Class解：从上列流量系数表中得到，DN300，压力等级 Class 900 截止阀在全开状态下的 Cv 是 1820。SOLUTION:From the flow coefficient table above,the fully open Cv for a 12 inch,Class 900 globe valve is 1820.查询图 2，全开状态的 1/4 时阀门的比率是 52%.Consulting Figure 2,the percent of fully open Cv at 1/4 valve open is 52%.因此计算 1/4 全开的流量系数 Cv 为：x 1820=946.The Cv at 1/4 open is then computed as:x 1820=946.