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。

  法蘭接頭的密封(feng)失效形式主要(yao)表(biao)現(xian)(xian)為泄(xie)漏。泄(xie)漏輕(qing)則造成能源(yuan)、原(yuan)材料的大量浪費，重則導致設備(bei)報廢、停工停產、人員傷亡和(he)嚴(yan)重的環境污(wu)染。隨著現(xian)(xian)代石油、化(hua)工、原(yuan)子能、航天及深海技術的迅速發(fa)展(zhan)，對管道及其裝(zhuang)置的密封(feng)提出了更(geng)嚴(yan)格的要(yao)求(qiu)，因而密封(feng)墊(dian)片的地位(wei)更(geng)加重要(yao)。

  在墊(dian)片(pian)(pian)密(mi)封的(de)(de)法蘭接頭(tou)中，雖然泄漏無(wu)法避(bi)免，但可以控制在一定的(de)(de)范圍內。墊(dian)片(pian)(pian)密(mi)封的(de)(de)可靠性與連(lian)接結(jie)構(gou)的(de)(de)形式、介質特(te)性、工況(kuang)條件等諸多因素有(you)關，而且最主要的(de)(de)是(shi)與所采用的(de)(de)密(mi)封墊(dian)片(pian)(pian)材料和其(qi)結(jie)構(gou)有(you)關。影響墊(dian)片(pian)(pian)密(mi)封的(de)(de)因素很多，至(zhi)今(jin)還(huan)是(shi)一個未能定量(liang)的(de)(de)問(wen)題，因此研究墊(dian)片(pian)(pian)密(mi)封的(de)(de)工作(zuo)，至(zhi)今(jin)仍然是(shi)工業(ye)界普(pu)遍關注(zhu)的(de)(de)問(wen)題。

  本篇(pian)就墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)基礎(chu)知識、墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)結構(gou)及(ji)(ji)其標(biao)準進行(xing)描述，共4章組成(cheng)，內容(rong)包括墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)的一般結構(gou)型(xing)(xing)(xing)(xing)式、種類、參(can)數和設(she)計選用；非(fei)(fei)金(jin)(jin)(jin)(jin)屬(shu)(shu)平墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含非(fei)(fei)金(jin)(jin)(jin)(jin)屬(shu)(shu)軟(ruan)墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)及(ji)(ji)聚四氟乙烯包覆墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)）；金(jin)(jin)(jin)(jin)屬(shu)(shu)復(fu)(fu)(fu)合墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含纏繞式墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金(jin)(jin)(jin)(jin)屬(shu)(shu)包覆墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金(jin)(jin)(jin)(jin)屬(shu)(shu)沖齒(chi)板柔性石(shi)墨復(fu)(fu)(fu)合墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、柔性石(shi)墨金(jin)(jin)(jin)(jin)屬(shu)(shu)波(bo)齒(chi)復(fu)(fu)(fu)合墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)）及(ji)(ji)金(jin)(jin)(jin)(jin)屬(shu)(shu)墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)（含金(jin)(jin)(jin)(jin)屬(shu)(shu)環形(xing)墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)、金(jin)(jin)(jin)(jin)屬(shu)(shu)齒(chi)形(xing)墊(dian)(dian)(dian)(dian)(dian)片(pian)(pian)(pian)(pian)及(ji)(ji)R型(xing)(xing)(xing)(xing)、RX型(xing)(xing)(xing)(xing)及(ji)(ji)BX型(xing)(xing)(xing)(xing)專用自緊密封金(jin)(jin)(jin)(jin)屬(shu)(shu)環墊(dian)(dian)(dian)(dian)(dian)）等(deng)。