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1、Pipethread管螺紋Twocommonpipethreadsizesexist,thetaperedNationalPipeThread(NPT)andthestraightNationalStandardFree-FittingStraightMechanicalPipeThread(NPSM).Thetaperedthreadsareforjoiningandsealing,thestraightthreadsareonlyforjoining.TheDry-sealthread(NPTF)allowsfo
2、rjoiningwithoutsealants.Threelesscommonthreadsexist,theGardenHoseThread(GHT),FireHoseCoupling(NST)andBritishStandardTaperPipeThread(BSPT).TheNPTandNPTFthreadsareinterchangeablewithsealantssuchasPTFEtape.Noneoftheotherthreadstandardsareinterchangeable.FemaleNPTt
3、hreadscanbedesignatedas"FPT"andmaleNPTthreadscanbedesignatedas"MPT."Pipesizesdonotrefertoanyphysicaldimensions.Theoutsidediameterofeachpipeorfittingmustbemeasuredandcomparedtothetableforsizeidentification.Forexample,a3/4"NPTpipethreadhasanoutsidediameterof1.050
4、inches.Eachthreadsizehasadefinednumberofthreadsperinch(TPI).The3/4"NPTpipethreadhas14threadsperinch.BoththeTPIandODofthethreadarerequiredforpositiveidentificationofthreadsizebecauseseveralsizeshavethesameTPI.NominalPipeSize(NPT)ThreadsPerInchApproximateCaliperM
5、easurement1/8"270.38"1/4"180.55"3/8"180.63"1/2"140.80"3/4"141.00"1"11.51.25"1-1/4"11.51.55"1-1/2"11.51.80"2"11.52.30"DefinitionofpipethreadacronymsNPTNationalPipeThreadFPTFemalePipeThreadMPTMalePipeThreadPTFSAEshorttapepipethreadNPTFAmericanNationaltaperpipethr
6、eadfordrysealpressure-tightjointsNPSMAmericanNationalstraightpipethreadformechanicaljointsNPSIAmericanNationalstraightintermediatepipethread管螺紋的規範及用途 PT(英制管用推拔螺紋) 以癰是使用面直角的螺紋峰,現在將規格統一爲軸直角者.JIS定爲耐密用而組全外螺紋和內螺紋. PT外螺紋除了配合PT內螺紋,有時也配合PS. PS(英制管用推拔螺紋用平行內
7、螺紋) 屬於JIS內PT的規格,舊JIS裹有外螺紋,現在已被取消,對方的外螺紋規定要有用PT.(耐密用) PF(英制管用平行螺紋) JIS所定的機械接合螺紋,外螺紋與內螺紋成一對,許容差之設定與PS不同,採用一般固定螺釘方法,外螺紋在負邊,內螺紋在正邊,成爲無餘隙公差.精度有A級.B級二等級. NPT(美制管用耐密推拔螺紋) 制定在ANSI規格中,稱爲美國標準管用推拔螺紋,有外螺紋與內螺紋.NPT外螺紋不但對NPT內螺紋配合,有時也配合NPSC,這點類似T.紋
8、峰與根切成同形,又因公差,大餘隙.壓緊兩種配合都可用.如用潤滑齊,則變成耐密用,耐密用者另有稱爲幹封閉之如NPTF,NPSF等付有F之一群. NPTF(美制管用耐密推拔螺紋) NPTF外螺紋,像PT.NPT有時也配合NPSF.NPSI(都是內螺紋).因這種螺紋都是峰尖.根淺.峰不是密接於根就是食進.可防止在此部份變成螺旋狀間隙,這是前述
