法蘭接頭是由法蘭、密封(feng)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(fa)蘭接頭(tou)的(de)密(mi)封失效形式(shi)主要(yao)(yao)表現(xian)為泄(xie)漏(lou)。泄(xie)漏(lou)輕(qing)則造成能(neng)源、原(yuan)(yuan)材料的(de)大(da)量浪費(fei)，重(zhong)則導致設備(bei)報(bao)廢(fei)、停工(gong)停產、人員傷亡和嚴(yan)重(zhong)的(de)環境(jing)污染。隨(sui)著現(xian)代石油、化(hua)工(gong)、原(yuan)(yuan)子(zi)能(neng)、航天及深海(hai)技(ji)術的(de)迅速發展，對管道(dao)及其裝置的(de)密(mi)封提出了更(geng)嚴(yan)格(ge)的(de)要(yao)(yao)求，因而密(mi)封墊片的(de)地位更(geng)加重(zhong)要(yao)(yao)。

  在(zai)墊(dian)(dian)(dian)片(pian)(pian)(pian)密封(feng)的(de)(de)法蘭接(jie)頭中，雖然泄(xie)漏(lou)無(wu)法避免(mian)，但可以控制在(zai)一(yi)定的(de)(de)范(fan)圍內。墊(dian)(dian)(dian)片(pian)(pian)(pian)密封(feng)的(de)(de)可靠性與連(lian)接(jie)結(jie)構的(de)(de)形式、介質(zhi)特性、工(gong)況條(tiao)件等(deng)諸多因素(su)有(you)關，而且最主要的(de)(de)是與所采用的(de)(de)密封(feng)墊(dian)(dian)(dian)片(pian)(pian)(pian)材料和其結(jie)構有(you)關。影響(xiang)墊(dian)(dian)(dian)片(pian)(pian)(pian)密封(feng)的(de)(de)因素(su)很(hen)多，至今(jin)(jin)還(huan)是一(yi)個未能定量的(de)(de)問題，因此研究墊(dian)(dian)(dian)片(pian)(pian)(pian)密封(feng)的(de)(de)工(gong)作(zuo)，至今(jin)(jin)仍然是工(gong)業界普遍關注的(de)(de)問題。

  本篇就墊(dian)(dian)(dian)片(pian)(pian)(pian)基礎知識、墊(dian)(dian)(dian)片(pian)(pian)(pian)結(jie)構及(ji)(ji)其標準進行(xing)描述，共4章組(zu)成，內容包括墊(dian)(dian)(dian)片(pian)(pian)(pian)的一(yi)般結(jie)構型(xing)式(shi)、種類、參數和設(she)計選用；非(fei)金(jin)(jin)屬(shu)(shu)(shu)平墊(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)非(fei)金(jin)(jin)屬(shu)(shu)(shu)軟墊(dian)(dian)(dian)片(pian)(pian)(pian)及(ji)(ji)聚(ju)四氟乙烯包覆(fu)墊(dian)(dian)(dian)片(pian)(pian)(pian)）；金(jin)(jin)屬(shu)(shu)(shu)復(fu)(fu)合(he)(he)墊(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)纏繞式(shi)墊(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)包覆(fu)墊(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)沖齒(chi)(chi)板柔性石墨復(fu)(fu)合(he)(he)墊(dian)(dian)(dian)片(pian)(pian)(pian)、柔性石墨金(jin)(jin)屬(shu)(shu)(shu)波齒(chi)(chi)復(fu)(fu)合(he)(he)墊(dian)(dian)(dian)片(pian)(pian)(pian)）及(ji)(ji)金(jin)(jin)屬(shu)(shu)(shu)墊(dian)(dian)(dian)片(pian)(pian)(pian)（含(han)金(jin)(jin)屬(shu)(shu)(shu)環(huan)形(xing)墊(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)齒(chi)(chi)形(xing)墊(dian)(dian)(dian)片(pian)(pian)(pian)及(ji)(ji)R型(xing)、RX型(xing)及(ji)(ji)BX型(xing)專用自(zi)緊(jin)密封金(jin)(jin)屬(shu)(shu)(shu)環(huan)墊(dian)(dian)(dian)）等。