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(lan)接頭(tou)的(de)(de)密封失(shi)效形式主要表現(xian)為泄漏。泄漏輕(qing)則造成能(neng)源、原材料的(de)(de)大量浪費，重(zhong)則導致設備報廢、停(ting)工停(ting)產、人員(yuan)傷(shang)亡和嚴重(zhong)的(de)(de)環境污染。隨著(zhu)現(xian)代石油、化(hua)工、原子能(neng)、航天及(ji)(ji)深海技術的(de)(de)迅速發展，對管道(dao)及(ji)(ji)其裝(zhuang)置的(de)(de)密封提出了更(geng)嚴格的(de)(de)要求，因而密封墊片的(de)(de)地位(wei)更(geng)加重(zhong)要。

  在墊(dian)(dian)片(pian)(pian)密(mi)封(feng)的(de)(de)法蘭接(jie)頭中，雖然泄漏無法避免(mian)，但可以控(kong)制在一(yi)定(ding)的(de)(de)范圍內(nei)。墊(dian)(dian)片(pian)(pian)密(mi)封(feng)的(de)(de)可靠性(xing)與(yu)連接(jie)結構的(de)(de)形式、介質特(te)性(xing)、工(gong)況條件等諸(zhu)多因素有(you)關，而(er)且最主要的(de)(de)是與(yu)所采用的(de)(de)密(mi)封(feng)墊(dian)(dian)片(pian)(pian)材料和其結構有(you)關。影響墊(dian)(dian)片(pian)(pian)密(mi)封(feng)的(de)(de)因素很多，至今(jin)還是一(yi)個未能定(ding)量的(de)(de)問(wen)題(ti)，因此(ci)研究墊(dian)(dian)片(pian)(pian)密(mi)封(feng)的(de)(de)工(gong)作，至今(jin)仍(reng)然是工(gong)業界普遍關注的(de)(de)問(wen)題(ti)。

  本篇就墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)基礎知識、墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)結(jie)(jie)構及其標準進(jin)行描(miao)述，共4章組(zu)成，內(nei)容包(bao)括墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)的一般結(jie)(jie)構型(xing)(xing)式、種類、參數和設計選用(yong)；非金(jin)(jin)屬(shu)(shu)平墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)(han)非金(jin)(jin)屬(shu)(shu)軟(ruan)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)及聚四(si)氟乙烯包(bao)覆墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)）；金(jin)(jin)屬(shu)(shu)復(fu)合墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)(han)纏(chan)繞式墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)包(bao)覆墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)沖齒(chi)板柔(rou)性(xing)(xing)石墨(mo)復(fu)合墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、柔(rou)性(xing)(xing)石墨(mo)金(jin)(jin)屬(shu)(shu)波齒(chi)復(fu)合墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)）及金(jin)(jin)屬(shu)(shu)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)(han)金(jin)(jin)屬(shu)(shu)環形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)齒(chi)形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)及R型(xing)(xing)、RX型(xing)(xing)及BX型(xing)(xing)專用(yong)自緊密封金(jin)(jin)屬(shu)(shu)環墊(dian)(dian)(dian)(dian)）等(deng)。