法蘭接頭是由法蘭、密封墊片及連接螺栓三種元件組成的一個承壓管道連接件。在法蘭密封接頭中，墊片是最主要的密封元件。對于非金屬墊片來說，法蘭接頭的密封是通過擰緊螺栓，使法蘭與墊片接觸表面及其墊片內部造成較大的壓緊應力，從而一方面使墊片表面與法蘭表面緊密貼合以填滿法蘭表面的微間隙，另一方面減小墊片材料的孔隙率，即減小被密封流體的泄漏通道，從而實現法蘭接頭的密封。由于任何制造或加工方法都不可能形成絕對光滑的理想表面，也不可能實現密封面間的完全嵌合以及密封件本身孔隙的完全阻塞，所以在相互接觸的密封面間和密封墊片內部總是存在著微小的間隙或通道。因而，對墊片密封來說，泄漏總是不可避免的。當介質以一定的壓力通過螺栓法蘭連接時，總會在密封點處出現泄漏。

  法蘭接頭的(de)密封失效(xiao)形式主要(yao)表(biao)現為(wei)泄漏(lou)。泄漏(lou)輕則造(zao)成(cheng)能(neng)(neng)源、原材料的(de)大量浪費(fei)，重(zhong)則導(dao)致(zhi)設備報廢、停工(gong)停產、人員傷亡和嚴重(zhong)的(de)環境污(wu)染。隨著現代(dai)石油、化工(gong)、原子能(neng)(neng)、航天(tian)及深海技術的(de)迅速發展(zhan)，對管道及其(qi)裝置的(de)密封提出了更(geng)嚴格的(de)要(yao)求，因(yin)而(er)密封墊片(pian)的(de)地位更(geng)加重(zhong)要(yao)。

  在墊(dian)片密封(feng)(feng)的(de)(de)(de)(de)法(fa)蘭接頭中，雖(sui)然泄漏無法(fa)避免，但(dan)可以控(kong)制在一定的(de)(de)(de)(de)范圍內。墊(dian)片密封(feng)(feng)的(de)(de)(de)(de)可靠性與連(lian)接結構的(de)(de)(de)(de)形式、介質特性、工(gong)況條件等(deng)諸多(duo)因(yin)素(su)有關(guan)(guan)，而(er)且最(zui)主要的(de)(de)(de)(de)是(shi)與所采用的(de)(de)(de)(de)密封(feng)(feng)墊(dian)片材料(liao)和其結構有關(guan)(guan)。影響墊(dian)片密封(feng)(feng)的(de)(de)(de)(de)因(yin)素(su)很多(duo)，至今(jin)還是(shi)一個未能(neng)定量(liang)的(de)(de)(de)(de)問題(ti)，因(yin)此(ci)研(yan)究(jiu)墊(dian)片密封(feng)(feng)的(de)(de)(de)(de)工(gong)作，至今(jin)仍然是(shi)工(gong)業界普遍(bian)關(guan)(guan)注的(de)(de)(de)(de)問題(ti)。

  本(ben)篇就墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)基礎知識、墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)結構及(ji)其標準(zhun)進(jin)行描述(shu)，共4章組(zu)成，內容包括(kuo)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)的一(yi)般結構型(xing)(xing)式(shi)、種類、參數和設(she)計選(xuan)用(yong)；非金屬(shu)(shu)(shu)平墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含非金屬(shu)(shu)(shu)軟墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)及(ji)聚四氟(fu)乙烯(xi)包覆墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)）；金屬(shu)(shu)(shu)復(fu)合(he)(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含纏繞式(shi)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金屬(shu)(shu)(shu)包覆墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金屬(shu)(shu)(shu)沖齒板柔(rou)性石(shi)墨復(fu)合(he)(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、柔(rou)性石(shi)墨金屬(shu)(shu)(shu)波齒復(fu)合(he)(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)）及(ji)金屬(shu)(shu)(shu)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含金屬(shu)(shu)(shu)環(huan)形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金屬(shu)(shu)(shu)齒形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)及(ji)R型(xing)(xing)、RX型(xing)(xing)及(ji)BX型(xing)(xing)專(zhuan)用(yong)自(zi)緊密(mi)封金屬(shu)(shu)(shu)環(huan)墊(dian)(dian)(dian)(dian)）等(deng)。